WO2017140946A1 - Appareil, procédé et programme informatique de codage et de décodage vidéo - Google Patents

Appareil, procédé et programme informatique de codage et de décodage vidéo Download PDF

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Publication number
WO2017140946A1
WO2017140946A1 PCT/FI2017/050089 FI2017050089W WO2017140946A1 WO 2017140946 A1 WO2017140946 A1 WO 2017140946A1 FI 2017050089 W FI2017050089 W FI 2017050089W WO 2017140946 A1 WO2017140946 A1 WO 2017140946A1
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WIPO (PCT)
Prior art keywords
view
pictures
picture
layer
container
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PCT/FI2017/050089
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English (en)
Inventor
Miska Hannuksela
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Nokia Technologies Oy
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Publication of WO2017140946A1 publication Critical patent/WO2017140946A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/597—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding specially adapted for multi-view video sequence encoding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L65/00—Network arrangements, protocols or services for supporting real-time applications in data packet communication
    • H04L65/60—Network streaming of media packets
    • H04L65/70—Media network packetisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/10—Processing, recording or transmission of stereoscopic or multi-view image signals
    • H04N13/106—Processing image signals
    • H04N13/161—Encoding, multiplexing or demultiplexing different image signal components
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/103—Selection of coding mode or of prediction mode
    • H04N19/107—Selection of coding mode or of prediction mode between spatial and temporal predictive coding, e.g. picture refresh
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/70—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by syntax aspects related to video coding, e.g. related to compression standards
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
    • H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
    • H04N21/234—Processing of video elementary streams, e.g. splicing of video streams, manipulating MPEG-4 scene graphs
    • H04N21/2343—Processing of video elementary streams, e.g. splicing of video streams, manipulating MPEG-4 scene graphs involving reformatting operations of video signals for distribution or compliance with end-user requests or end-user device requirements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
    • H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
    • H04N21/234—Processing of video elementary streams, e.g. splicing of video streams, manipulating MPEG-4 scene graphs
    • H04N21/2343—Processing of video elementary streams, e.g. splicing of video streams, manipulating MPEG-4 scene graphs involving reformatting operations of video signals for distribution or compliance with end-user requests or end-user device requirements
    • H04N21/23439—Processing of video elementary streams, e.g. splicing of video streams, manipulating MPEG-4 scene graphs involving reformatting operations of video signals for distribution or compliance with end-user requests or end-user device requirements for generating different versions
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/44—Processing of video elementary streams, e.g. splicing a video clip retrieved from local storage with an incoming video stream, rendering scenes according to MPEG-4 scene graphs
    • H04N21/4402—Processing of video elementary streams, e.g. splicing a video clip retrieved from local storage with an incoming video stream, rendering scenes according to MPEG-4 scene graphs involving reformatting operations of video signals for household redistribution, storage or real-time display
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/80—Generation or processing of content or additional data by content creator independently of the distribution process; Content per se
    • H04N21/81—Monomedia components thereof
    • H04N21/816—Monomedia components thereof involving special video data, e.g 3D video
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/80—Generation or processing of content or additional data by content creator independently of the distribution process; Content per se
    • H04N21/83—Generation or processing of protective or descriptive data associated with content; Content structuring
    • H04N21/84—Generation or processing of descriptive data, e.g. content descriptors
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/80—Generation or processing of content or additional data by content creator independently of the distribution process; Content per se
    • H04N21/83—Generation or processing of protective or descriptive data associated with content; Content structuring
    • H04N21/845—Structuring of content, e.g. decomposing content into time segments
    • H04N21/8456—Structuring of content, e.g. decomposing content into time segments by decomposing the content in the time domain, e.g. in time segments
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/80—Generation or processing of content or additional data by content creator independently of the distribution process; Content per se
    • H04N21/85—Assembly of content; Generation of multimedia applications
    • H04N21/854—Content authoring
    • H04N21/85406—Content authoring involving a specific file format, e.g. MP4 format

Definitions

  • the present invention relates to an apparatus, a method and a computer program video coding and decoding.
  • a view may be defined as a sequence of pictures representing one camera or viewpoint.
  • the pictures representing a view may also be called view components.
  • a view component may be defined as a coded representation of a view in a single access unit.
  • multiview video coding more than one view is coded in a bitstream. Since views are typically intended to be displayed on stereoscopic or multiview
  • autostrereoscopic display or to be used for other 3D arrangements they typically represent the same scene and are content-wise partly overlapping although representing different viewpoints to the content.
  • inter-view prediction may be utilized in multiview video coding to take advantage of inter- view correlation and improve compression efficiency.
  • Enabling inter- view prediction can provide a significant compression gain.
  • inter- view prediction is enabled only in codec extensions, such as the MVC extension of H.264/AVC or the MV-HEVC extension of HEVC in which the Multiview Main profile is specified.
  • codec extensions might not be commonly supported in decoding, particularly when considering hardware decoder implementations.
  • the decoded total picture rate increases when several hardware decoding instances are used.
  • a method comprises writing, into a first container, a first track comprising coded pictures of a first view, wherein the coded pictures of the first view comprise one or more intra random access point (IRAP) pictures and are independent of coded picture of any other view; writing, into a second container, a second track comprising in-line coded pictures of a second view and comprising, by reference, fully or partially coded data of at least one of said IRAP pictures, wherein at least one of the coded pictures of the second view uses the at least one of said IRAP pictures as a reference for prediction; and indicating, in the second container or a description associated with the second container and/or the second view, that the second track complies with single-view decoding.
  • IRAP intra random access point
  • the first container and the second container are one of the following:
  • the first container and the second container are the same media file
  • the first container and the second container are the same media segment
  • the first container and the second container are the same media subsegment.
  • the first container and the second container are one of the following:
  • the first container is a first media file and the second container is a second media file that is different from the first media file;
  • the first container is a first media segment of a first Representation and the second container is a second media segment of a second Representation;
  • the first container is a first media subsegment of a first Representation and the second container is a second media subsegment of a second Representation.
  • the first container is a first level of a media subsegment and the second container is a second level of the same media subsegment.
  • the method further comprises receiving the first view and the second view in a single-view bitstream wherein pictures of the first view are temporally interleaved with pictures of the second view.
  • the method further comprises receiving the first view and an original second view in a multiview bitstream wherein the original second view is indicated to be predicted from the first view; and modifying pictures of the original second view to become in-line coded pictures of a second view.
  • said modification comprises one or more of the following:
  • a method according to a second aspect comprises writing, into a first container, a first track comprising coded pictures of a first view, wherein the coded pictures of the first view comprise one or more intra random access point (IRAP) pictures and are independent of coded picture of any other view; writing, into a second container, a second track comprising in-line coded pictures of a predicted view wherein at least one of the coded pictures of the predicted view uses the at least one of said IRAP pictures as a reference for prediction;
  • IRAP intra random access point
  • a third track comprising a third view comprising, by reference, coded pictures of a predicted view and comprising, by reference, fully or partially coded data of at least one of said IRAP pictures, wherein at least one of the coded pictures of the third view uses the at least one of said IRAP pictures as a reference for prediction; and indicating, in the third container or a description associated with the third container and/or the third view, that the third track complies with single- view decoding.
  • a method comprises writing, into a first container, a first track comprising coded pictures comprising one or more elementary units, each preceded by a start code; and writing, into a second container, a second track comprising, by reference, elementary units of the first track excluding start codes.
  • the method further comprises including, in an elementary unit contained in-line in the second container, a constructor instructing to include, by reference, an elementary unit of the first track excluding a start code into the second track.
  • a method comprises parsing a first track from a first container, said parsing resulting into coded pictures of a first view, wherein the coded pictures of the first view comprise one or more intra random access point (IRAP) pictures and are independent of coded picture of any other view; parsing a second track from a second container, said parsing resulting into coded pictures of a second view, and said parsing comprising: including coded pictures present in-line in the second track into the coded pictures of the second view; and including coded pictures included by reference in the second track into the coded pictures of the second view, wherein the coded pictures included by reference include fully or partially coded data of at least one of said IRAP pictures, wherein at least one of the coded pictures of the second view uses the at least one of said IRAP pictures as a reference for prediction.
  • IRAP intra random access point
  • the method further comprises parsing from the second container or a description associated with the second container and/or the second view, that the second track complies with single- view decoding.
  • the method further comprises decoding the coded pictures of the second view using single-view decoding.
  • Figure 1 shows schematically an electronic device employing embodiments of the invention
  • Figure 2 shows schematically a user equipment suitable for employing
  • FIG. 3 further shows schematically electronic devices employing embodiments of the invention connected using wireless and wired network connections;
  • Figure 4 shows schematically an encoder suitable for implementing embodiments of the invention
  • Figure 5 shows an example of a hierarchical data model used in DASH
  • Figure 6 shows a flow chart of generating a bitstream according to an embodiment of the invention
  • Figure 7 shows an overall view of the phases according to various embodiments of the invention.
  • Figures 8a and 8b show an example of track generation from a MV-HEVC prediction structure according to an embodiment of the invention
  • Figures 9a and 9b show an example of a file structure and a constructor operator according to an embodiment of the invention
  • Figure 10 shows an example of the phases of the method according to an embodiment of the invention implementing the file structure of Figure 9a;
  • Figure 11 shows an example of creating a pre-constructed second view from a multiview bitstream according to an embodiment of the invention
  • Figure 12 an example of the phases of the method according to an embodiment of the invention implementing the bitstreams of Figure 11;
  • Figure 13 shows an example of a file structure according to an embodiment of the invention
  • Figures 14a and 14b show an example of a temporal interleaved frame packing bitstream according to an embodiment of the invention
  • Figure 15 shows an example of coding a base view and a predicted view with motion-constrained tile sets according to an embodiment of the invention
  • Figure 16 shows a schematic diagram of a decoder suitable for implementing embodiments of the invention.
  • Figure 17 shows a schematic diagram of an example multimedia communication system within which various embodiments may be implemented.
  • Figure 1 shows a block diagram of a video coding system according to an example embodiment as a schematic block diagram of an exemplary apparatus or electronic device 50, which may incorporate a codec according to an embodiment of the invention.
  • Figure 2 shows a layout of an apparatus according to an example embodiment. The elements of Figs. 1 and 2 will be explained next.
  • the electronic device 50 may for example be a mobile terminal or user equipment of a wireless communication system. However, it would be appreciated that embodiments of the invention may be implemented within any electronic device or apparatus which may require encoding and decoding or encoding or decoding video images.
  • the apparatus 50 may comprise a housing 30 for incorporating and protecting the device.
  • the apparatus 50 further may comprise a display 32 in the form of a liquid crystal display.
  • the display may be any suitable display technology suitable to display an image or video.
  • the apparatus 50 may further comprise a keypad 34.
  • any suitable data or user interface mechanism may be employed.
  • the user interface may be implemented as a virtual keyboard or data entry system as part of a touch-sensitive display.
  • the apparatus may comprise a microphone 36 or any suitable audio input which may be a digital or analogue signal input.
  • the apparatus 50 may further comprise an audio output device which in embodiments of the invention may be any one of: an earpiece 38, speaker, or an analogue audio or digital audio output connection.
  • the apparatus 50 may also comprise a battery 40 (or in other embodiments of the invention the device may be powered by any suitable mobile energy device such as solar cell, fuel cell or clockwork generator).
  • the apparatus may further comprise a camera 42 capable of recording or capturing images and/or video.
  • the apparatus 50 may further comprise an infrared port for short range line of sight communication to other devices. In other embodiments the apparatus 50 may further comprise any suitable short range communication solution such as for example a Bluetooth wireless connection or a USB/firewire wired connection.
  • the apparatus 50 may comprise a controller 56 or processor for controlling the apparatus 50.
  • the controller 56 may be connected to memory 58 which in embodiments of the invention may store both data in the form of image and audio data and/or may also store instructions for implementation on the controller 56.
  • the controller 56 may further be connected to codec circuitry 54 suitable for carrying out coding and decoding of audio and/or video data or assisting in coding and decoding carried out by the controller.
  • the apparatus 50 may further comprise a card reader 48 and a smart card 46, for example a UICC and UICC reader for providing user information and being suitable for providing authentication information for authentication and authorization of the user at a network.
  • a card reader 48 and a smart card 46 for example a UICC and UICC reader for providing user information and being suitable for providing authentication information for authentication and authorization of the user at a network.
  • the apparatus 50 may comprise radio interface circuitry 52 connected to the controller and suitable for generating wireless communication signals for example for communication with a cellular communications network, a wireless communications system or a wireless local area network.
  • the apparatus 50 may further comprise an antenna 44 connected to the radio interface circuitry 52 for transmitting radio frequency signals generated at the radio interface circuitry 52 to other apparatus(es) and for receiving radio frequency signals from other apparatus(es).
  • the apparatus 50 may comprise a camera capable of recording or detecting individual frames which are then passed to the codec 54 or the controller for processing.
  • the apparatus may receive the video image data for processing from another device prior to transmission and/or storage.
  • the apparatus 50 may also receive either wirelessly or by a wired connection the image for coding/decoding.
  • the system 10 comprises multiple communication devices which can communicate through one or more networks.
  • the system 10 may comprise any combination of wired or wireless networks including, but not limited to a wireless cellular telephone network (such as a GSM, UMTS, CDMA network etc), a wireless local area network (WLAN) such as defined by any of the IEEE 802.x standards, a Bluetooth personal area network, an Ethernet local area network, a token ring local area network, a wide area network, and the Internet.
  • a wireless cellular telephone network such as a GSM, UMTS, CDMA network etc
  • WLAN wireless local area network
  • the system 10 may include both wired and wireless communication devices and/or apparatus 50 suitable for implementing embodiments of the invention.
  • the system shown in Figure 3 shows a mobile telephone network 11 and a representation of the internet 28.
  • Connectivity to the internet 28 may include, but is not limited to, long range wireless connections, short range wireless connections, and various wired connections including, but not limited to, telephone lines, cable lines, power lines, and similar communication pathways.
  • the example communication devices shown in the system 10 may include, but are not limited to, an electronic device or apparatus 50, a combination of a personal digital assistant (PDA) and a mobile telephone 14, a PDA 16, an integrated messaging device (IMD) 18, a desktop computer 20, a notebook computer 22.
  • PDA personal digital assistant
  • IMD integrated messaging device
  • the apparatus 50 may be stationary or mobile when carried by an individual who is moving.
  • the apparatus 50 may also be located in a mode of transport including, but not limited to, a car, a truck, a taxi, a bus, a train, a boat, an airplane, a bicycle, a motorcycle or any similar suitable mode of transport.
  • the embodiments may also be implemented in a set-top box; i.e. a digital TV receiver, which may/may not have a display or wireless capabilities, in tablets or (laptop) personal computers (PC), which have hardware or software or combination of the
  • encoder/decoder implementations in various operating systems, and in chipsets, processors, DSPs and/or embedded systems offering hardware/software based coding.
  • Some or further apparatus may send and receive calls and messages and communicate with service providers through a wireless connection 25 to a base station 24.
  • the base station 24 may be connected to a network server 26 that allows communication between the mobile telephone network 11 and the internet 28.
  • the system may include additional communication devices and communication devices of various types.
  • the communication devices may communicate using various transmission technologies including, but not limited to, code division multiple access (CDMA), global systems for mobile communications (GSM), universal mobile telecommunications system (UMTS), time divisional multiple access (TDMA), frequency division multiple access
  • CDMA code division multiple access
  • GSM global systems for mobile communications
  • UMTS universal mobile telecommunications system
  • TDMA time divisional multiple access
  • CDMA code division multiple access
  • GSM global systems for mobile communications
  • UMTS universal mobile telecommunications system
  • TDMA time divisional multiple access
  • frequency division multiple access frequency division multiple access
  • FDMA transmission control protocol-internet protocol
  • TCP-IP transmission control protocol-internet protocol
  • SMS short messaging service
  • MMS multimedia messaging service
  • email instant messaging service
  • IMS instant messaging service
  • Bluetooth IEEE 802.11 and any similar wireless communication technology.
  • communications device involved in implementing various embodiments of the present invention may communicate using various media including, but not limited to, radio, infrared, laser, cable connections, and any suitable connection.
  • RTP Real-time Transport Protocol
  • UDP User Datagram Protocol
  • IP Internet Protocol
  • RTP is specified in Internet Engineering Task Force (IETF) Request for Comments (RFC) 3550, available from www.ietf.org/rfc/rfc3550.txt.
  • IETF Internet Engineering Task Force
  • RTC Request for Comments
  • media data is encapsulated into RTP packets.
  • each media type or media coding format has a dedicated RTP payload format.
  • An RTP session is an association among a group of participants communicating with RTP. It is a group communications channel which can potentially carry a number of RTP streams.
  • An RTP stream is a stream of RTP packets comprising media data.
  • An RTP stream is identified by an SSRC belonging to a particular RTP session.
  • SSRC refers to either a synchronization source or a synchronization source identifier that is the 32-bit SSRC field in the RTP packet header.
  • a synchronization source is characterized in that all packets from the synchronization source form part of the same timing and sequence number space, so a receiver may group packets by synchronization source for playback. Examples of
  • synchronization sources include the sender of a stream of packets derived from a signal source such as a microphone or a camera, or an RTP mixer.
  • a signal source such as a microphone or a camera
  • RTP mixer Each RTP stream is identified by a SSRC that is unique within the RTP session.
  • An MPEG-2 transport stream (TS), specified in ISO/IEC 13818-1 or equivalently in ITU-T Recommendation H.222.0, is a format for carrying audio, video, and other media as well as program metadata or other metadata, in a multiplexed stream.
  • a packet identifier (PID) is used to identify an elementary stream (a.k.a. packetized elementary stream) within the TS.
  • Available media file format standards include ISO base media file format (ISO/IEC 14496-12, which may be abbreviated ISOBMFF), MPEG-4 file format (ISO/IEC 14496-14, also known as the MP4 format), file format for NAL unit structured video (ISO/IEC 14496- 15) and 3 GPP file format (3 GPP TS 26.244, also known as the 3GP format).
  • ISOBMFF is the base for derivation of all the above mentioned file formats (excluding the ISOBMFF itself).
  • ISOBMFF Some concepts, structures, and specifications of ISOBMFF are described below as an example of a container file format, based on which the embodiments may be implemented. The aspects of the invention are not limited to ISOBMFF, but rather the description is given for one possible basis on top of which the invention may be partly or fully realized.
  • One building block in the ISOBMFF is called a box. Each box may have a header and a payload. The box header indicates the type of the box and the size of the box in terms of bytes. A box may enclose other boxes, and the ISO file format specifies which box types are allowed within a box of a certain type. Furthermore, the presence of some boxes may be mandatory in each file, while the presence of other boxes may be optional.
  • the ISOBMFF may be considered to specify a hierarchical structure of boxes.
  • Each box of the ISO base media file may be identified by a four-character code (4CC, fourCC).
  • a four- character code may interchangeably be represented by a 32-bit unsigned integer (by assuming a certain conversion of characters to 8-bit values, a certain bit endianness, and a certain byte endianness).
  • the header may provide information about the type and size of the box.
  • a file may include media data and metadata that may be enclosed in separate boxes.
  • the media data may be provided in a media data (mdat) box and the movie (moov) box (a.k.a. MovieBox) may be used to enclose the metadata.
  • the movie (moov) box may include one or more tracks, and each track may reside in one corresponding track (trak) box.
  • Each track is associated with a handler, identified by a four-character code, specifying the track type.
  • Video, audio, and image sequence tracks can be collectively called media tracks, and they contain an elementary media stream.
  • Tracks comprise samples, such as audio or video frames.
  • a media track refers to samples (which may also be referred to as media samples) formatted according to a media compression format (and its encapsulation to the ISOBMFF).
  • a hint track refers to hint samples, containing cookbook instructions for constructing packets for transmission over an indicated communication protocol.
  • the cookbook instructions may include guidance for packet header construction and may include packet payload construction.
  • data residing in other tracks or items may be referenced.
  • data residing in other tracks or items may be indicated by a reference as to which piece of data in a particular track or item is instructed to be copied into a packet during the packet construction process.
  • a timed metadata track may refer to samples describing referred media and/or hint samples. For the presentation of one media type, one media track may be selected.
  • the 'trak' box contains a Sample Table box.
  • the Sample Table box comprises e.g. all the time and data indexing of the media samples in a track.
  • the Sample Table box is required to contain a Sample Description box.
  • the Sample Description box includes an entry count field, specifying the number of sample entries included in the box.
  • Description box is required to contain at least one sample entry.
  • the sample entry format depends on the handler type for the track. Sample entries give detailed information about the coding type used and any initialization information needed for that coding.
  • Composition times are specific to their track, i.e. they appear on the media timeline of the track.
  • a content author may determine and indicate the mapping of the media timeline of the track to the movie timeline, e.g. for synchronization of the tracks relative to each other, through edits in Edit List boxes ("elst") in each track. If no edits are present the media timeline is directly mapped to the movie timeline.
  • the movie fragment feature may enable splitting the metadata that otherwise might reside in the movie box into multiple pieces. Each piece may correspond to a certain period of time of a track.
  • the movie fragment feature may enable interleaving file metadata and media data. Consequently, the size of the movie box may be limited and the use cases mentioned above be realized.
  • the media samples for the movie fragments may reside in an mdat box.
  • a moof box may be provided.
  • the moof box may include the information for a certain duration of playback time that would previously have been in the moov box.
  • the moov box may still represent a valid movie on its own, but in addition, it may include an mvex box indicating that movie fragments will follow in the same file.
  • the movie fragments may extend the presentation that is associated to the moov box in time.
  • the movie fragment there may be a set of track fragments, including anywhere from zero to a plurality per track.
  • the track fragments may in turn include anywhere from zero to a plurality of track runs, each of which document is a contiguous run of samples for that track (and hence are similar to chunks).
  • many fields are optional and can be defaulted.
  • the metadata that may be included in the moof box may be limited to a subset of the metadata that may be included in a moov box and may be coded differently in some cases. Details regarding the boxes that can be included in a moof box may be found from the ISOBMFF specification.
  • a self-contained movie fragment may be defined to consist of a moof box and an mdat box that are consecutive in the file order and where the mdat box contains the samples of the movie fragment (for which the moof box provides the metadata) and does not contain samples of any other movie fragment (i.e. any other moof box).
  • a sample grouping in the ISOBMFF and its derivatives may be defined as an assignment of each sample in a track to be a member of one sample group, based on a grouping criterion.
  • a sample group in a sample grouping is not limited to being contiguous samples and may contain non-adjacent samples. As there may be more than one sample grouping for the samples in a track, each sample grouping may have a type field to indicate the type of grouping.
  • Sample groupings may be represented by two linked data structures: (1) a
  • SampleToGroup box represents the assignment of samples to sample groups; and (2) a SampleGroupDescription box (sgpd box) contains a sample group entry for each sample group describing the properties of the group. There may be multiple instances of the
  • SampleToGroup and SampleGroupDescription boxes based on different grouping criteria. These may be distinguished by a type field used to indicate the type of grouping.
  • the 'sbgp' and the 'sgpd' boxes may be linked using the value of grouping type and, in some versions of the boxes, also the value of grouping_type_parameter.
  • the 'sbgp' box indicates the index of the sample group description entry that a particular sample belongs to.
  • the Matroska file format is capable of (but not limited to) storing any of video, audio, picture, or subtitle tracks in one file.
  • Matroska file extensions include .mkv for video (with subtitles and audio), .mk3d for stereoscopic video, .mka for audio-only files, and .mks for subtitles only.
  • Matroska may be used as a basis format for derived file formats, such as WebM.
  • Matroska uses Extensible Binary Meta Language (EBML) as basis.
  • EBML specifies a binary and octet (byte) aligned format inspired by the principle of XML.
  • EBML itself is a generalized description of the technique of binary markup.
  • a Matroska file consists of Elements that make up an EBML "document.” Elements incorporate an Element ID, a descriptor for the size of the element, and the binary data itself. Elements can be nested.
  • a Segment Element of Matroska is a container for other top-level (level 1) elements.
  • a Matroska file may comprise (but is not limited to be composed of) one Segment.
  • Multimedia data in Matroska files is organized in Clusters (or Cluster Elements), each containing typically a few seconds of multimedia data.
  • a Cluster comprises BlockGroup elements, which in turn comprise Block Elements.
  • a Cues Element comprises metadata which may assist in random access or seeking and may include file pointers or respective timestamps for seek points.
  • Video codec consists of an encoder that transforms the input video into a compressed representation suited for storage/transmission and a decoder that can uncompress the compressed video representation back into a viewable form.
  • a video encoder and/or a video decoder may also be separate from each other, i.e. need not form a codec. Typically encoder discards some information in the original video sequence in order to represent the video in a more compact form (that is, at lower bitrate).
  • a video encoder may be used to encode an image sequence, as defined subsequently, and a video decoder may be used to decode a coded image sequence.
  • a video encoder or an intra coding part of a video encoder or an image encoder may be used to encode an image, and a video decoder or an inter decoding part of a video decoder or an image decoder may be used to decode a coded image.
  • Typical hybrid video encoders for example many encoder implementations of ITU- T H.263 and H.264, encode the video information in two phases. Firstly pixel values in a certain picture area (or "block") are predicted for example by motion compensation means (finding and indicating an area in one of the previously coded video frames that corresponds closely to the block being coded) or by spatial means (using the pixel values around the block to be coded in a specified manner). Secondly the prediction error, i.e. the difference between the predicted block of pixels and the original block of pixels, is coded. This is typically done by transforming the difference in pixel values using a specified transform (e.g.
  • DCT Discrete Cosine Transform
  • Inter prediction which may also be referred to as temporal prediction, motion compensation, or motion-compensated prediction, reduces temporal redundancy.
  • inter prediction the sources of prediction are previously decoded pictures.
  • Intra prediction utilizes the fact that adjacent pixels within the same picture are likely to be correlated.
  • Intra prediction can be performed in spatial or transform domain, i.e., either sample values or transform coefficients can be predicted. Intra prediction is typically exploited in intra coding, where no inter prediction is applied.
  • One outcome of the coding procedure is a set of coding parameters, such as motion vectors and quantized transform coefficients. Many parameters can be entropy-coded more efficiently if they are predicted first from spatially or temporally neighboring parameters. For example, a motion vector may be predicted from spatially adjacent motion vectors and only the difference relative to the motion vector predictor may be coded. Prediction of coding parameters and intra prediction may be collectively referred to as in-picture prediction.
  • Figure 4 shows a block diagram of a video encoder suitable for employing embodiments of the invention.
  • Figure 4 presents an encoder for two layers, but it would be appreciated that presented encoder could be similarly simplified to encode only one layer or extended to encode more than two layers.
  • Figure 4 illustrates an embodiment of a video encoder comprising a first encoder section 500 for a base layer and a second encoder section 502 for an enhancement layer.
  • Each of the first encoder section 500 and the second encoder section 502 may comprise similar elements for encoding incoming pictures.
  • the encoder sections 500, 502 may comprise a pixel predictor 302, 402, prediction error encoder 303, 403 and prediction error decoder 304, 404.
  • Figure 4 also shows an embodiment of the pixel predictor 302, 402 as comprising an inter-predictor 306, 406, an intra-predictor 308, 408, a mode selector 310, 410, a filter 316, 416, and a reference frame memory 318, 418.
  • the pixel predictor 302 of the first encoder section 500 receives 300 base layer images of a video stream to be encoded at both the inter-predictor 306 (which determines the difference between the image and a motion compensated reference frame 318) and the intra-predictor 308 (which determines a prediction for an image block based only on the already processed parts of current frame or picture).
  • the output of both the inter-predictor and the intra-predictor are passed to the mode selector 310.
  • the intra-predictor 308 may have more than one intra- prediction modes. Hence, each mode may perform the intra-prediction and provide the predicted signal to the mode selector 310.
  • the mode selector 310 also receives a copy of the base layer picture 300.
  • the pixel predictor 402 of the second encoder section 502 receives 400 enhancement layer images of a video stream to be encoded at both the inter- predictor 406 (which determines the difference between the image and a motion compensated reference frame 418) and the intra-predictor 408 (which determines a prediction for an image block based only on the already processed parts of current frame or picture).
  • the output of both the inter-predictor and the intra-predictor are passed to the mode selector 410.
  • the intra- predictor 408 may have more than one intra-prediction modes. Hence, each mode may perform the intra-prediction and provide the predicted signal to the mode selector 410.
  • the mode selector 410 also receives a copy of the enhancement layer picture 400.
  • the output of the inter-predictor 306, 406 or the output of one of the optional intra-predictor modes or the output of a surface encoder within the mode selector is passed to the output of the mode selector 310, 410.
  • the output of the mode selector is passed to a first summing device 321, 421.
  • the first summing device may subtract the output of the pixel predictor 302,
  • the pixel predictor 302, 402 further receives from a preliminary reconstructor 339, 439 the combination of the prediction representation of the image block 312, 412 and the output 338, 438 of the prediction error decoder 304, 404.
  • the preliminary reconstructed image 314, 414 may be passed to the intra-predictor 308, 408 and to a filter 316, 416.
  • the filter 316, 416 receiving the preliminary representation may filter the preliminary
  • the reference frame memory 318 may be connected to the inter-predictor 306 to be used as the reference image against which a future base layer picture 300 is compared in inter-prediction operations.
  • the reference frame memory 318 may also be connected to the inter-predictor 406 to be used as the reference image against which a future enhancement layer pictures 400 is compared in inter-prediction operations.
  • the reference frame memory 418 may be connected to the inter- predictor 406 to be used as the reference image against which a future enhancement layer picture 400 is compared in inter-prediction operations.
  • Filtering parameters from the filter 316 of the first encoder section 500 may be provided to the second encoder section 502 subject to the base layer being selected and indicated to be source for predicting the filtering parameters of the enhancement layer according to some embodiments.
  • the prediction error encoder 303, 403 comprises a transform unit 342, 442 and a quantizer 344, 444.
  • the transform unit 342, 442 transforms the first prediction error signal 320, 420 to a transform domain.
  • the transform is, for example, the DCT transform.
  • the quantizer 344, 444 quantizes the transform domain signal, e.g. the DCT coefficients, to form quantized coefficients.
  • the prediction error decoder 304, 404 receives the output from the prediction error encoder 303, 403 and performs the opposite processes of the prediction error encoder 303,
  • the prediction error decoder may be considered to comprise a dequantizer 361, 461, which dequantizes the quantized coefficient values, e.g. DCT coefficients, to reconstruct the transform signal and an inverse transformation unit 363, 463, which performs the inverse transformation to the reconstructed transform signal wherein the output of the inverse transformation unit 363, 463 contains reconstructed block(s).
  • the prediction error decoder may also comprise a block filter which may filter the reconstructed block(s) according to further decoded information and filter parameters.
  • the entropy encoder 330, 430 receives the output of the prediction error encoder 303, 403 and may perform a suitable entropy encoding/variable length encoding on the signal to provide error detection and correction capability.
  • the outputs of the entropy encoders 330, 430 may be inserted into a bitstream e.g. by a multiplexer 508.
  • the H.264/AVC standard was developed by the Joint Video Team (JVT) of the Video Coding Experts Group (VCEG) of the Telecommunications Standardization Sector of International Telecommunication Union (ITU-T) and the Moving Picture Experts Group (MPEG) of International Organisation for Standardization (ISO) / International
  • H.264/AVC Electrotechnical Commission
  • ISO/IEC International Standard 14496-10 also known as MPEG-4 Part 10 Advanced Video Coding (AVC).
  • AVC MPEG-4 Part 10 Advanced Video Coding
  • SVC Scalable Video Coding
  • MVC Multiview Video Coding
  • H.265/HEVC a.k.a. HEVC High Efficiency Video Coding
  • JCT-VC Joint Collaborative Team - Video Coding
  • the standard was published by both parent standardization organizations, and it is referred to as ITU-T Recommendation H.265 and ISO/IEC International Standard 23008-2, also known as MPEG-H Part 2 High Efficiency Video Coding (HEVC).
  • H.265/HEVC a.k.a. HEVC High Efficiency Video Coding
  • H.265/HEVC included scalable, multiview, and fidelity range extensions, which may be abbreviated SHVC, MV-HEVC, and REXT, respectively. Version 2 of H.265/HEVC was published as ITU-T Recommendation H.265 (10/2014) and as Edition 2 of ISO/IEC 23008-2. There are currently ongoing standardization projects to develop further extensions to
  • H.265/HEVC including three-dimensional and screen content coding extensions, which may be abbreviated 3D-HEVC and SCC, respectively.
  • SHVC, MV-HEVC, and 3D-HEVC use a common basis specification, specified in Annex F of the version 2 of the HEVC standard.
  • This common basis comprises for example high-level syntax and semantics e.g. specifying some of the characteristics of the layers of the bitstream, such as inter-layer dependencies, as well as decoding processes, such as reference picture list construction including inter-layer reference pictures and picture order count derivation for multi-layer bitstream.
  • Annex F may also be used in potential subsequent multilayer extensions of HEVC.
  • a video encoder a video decoder, encoding methods, decoding methods, bitstream structures, and/or embodiments may be described in the following with reference to specific extensions, such as SHVC and/or MV-HEVC, they are generally applicable to any multi- layer extensions of HEVC, and even more generally to any multi-layer video coding scheme.
  • H.264/AVC and HEVC Some key definitions, bitstream and coding structures, and concepts of H.264/AVC and HEVC are described in this section as an example of a video encoder, decoder, encoding method, decoding method, and a bitstream structure, wherein the embodiments may be implemented.
  • Some of the key definitions, bitstream and coding structures, and concepts of H.264/AVC are the same as in HEVC - hence, they are described below jointly.
  • the aspects of the invention are not limited to H.264/AVC or HEVC, but rather the description is given for one possible basis on top of which the invention may be partly or fully realized.
  • bitstream syntax and semantics as well as the decoding process for error-free bitstreams are specified in
  • HRD Hypothetical Reference Decoder
  • a syntax element may be defined as an element of data represented in the bitstream.
  • a syntax structure may be defined as zero or more syntax elements present together in the bitstream in a specified order.
  • a phrase "by external means” or "through external means” may be used.
  • an entity such as a syntax structure or a value of a variable used in the decoding process, may be provided "by external means" to the decoding process.
  • the phrase "by external means” may indicate that the entity is not included in the bitstream created by the encoder, but rather conveyed externally from the bitstream for example using a control protocol. It may alternatively or additionally mean that the entity is not created by the encoder, but may be created for example in the player or decoding control logic or alike that is using the decoder.
  • the decoder may have an interface for inputting the external means, such as variable values.
  • the elementary unit for the input to an H.264/AVC or HEVC encoder and the output of an H.264/AVC or HEVC decoder, respectively, is a picture.
  • a picture given as an input to an encoder may also referred to as a source picture, and a picture decoded by a decoded may be referred to as a decoded picture.
  • the source and decoded pictures are each comprised of one or more sample arrays, such as one of the following sets of sample arrays:
  • RGB Green, Blue and Red
  • these arrays may be referred to as luma (or L or Y) and chroma, where the two chroma arrays may be referred to as Cb and Cr; regardless of the actual color representation method in use.
  • the actual color representation method in use can be indicated e.g. in a coded bitstream e.g. using the Video Usability Information (VUI) syntax of
  • a component may be defined as an array or single sample from one of the three sample arrays arrays (luma and two chroma) or the array or a single sample of the array that compose a picture in monochrome format.
  • a picture may either be a frame or a field.
  • a frame comprises a matrix of luma samples and possibly the corresponding chroma samples.
  • a field is a set of alternate sample rows of a frame and may be used as encoder input, when the source signal is interlaced.
  • Chroma sample arrays may be absent (and hence monochrome sampling may be in use) or chroma sample arrays may be subsampled when compared to luma sample arrays.
  • Chroma formats may be summarized as follows:
  • each of the two chroma arrays has half the height and half the width of the luma array.
  • each of the two chroma arrays has the same height and half the width of the luma array.
  • each of the two chroma arrays has the same height and width as the luma array.
  • H.264/AVC and HEVC it is possible to code sample arrays as separate color planes into the bitstream and respectively decode separately coded color planes from the bitstream.
  • each one of them is separately processed (by the encoder and/or the decoder) as a picture with monochrome sampling.
  • a partitioning may be defined as a division of a set into subsets such that each element of the set is in exactly one of the subsets.
  • a macroblock is a 16x16 block of luma samples and the
  • a macroblock contains one 8x8 block of chroma samples per each chroma component.
  • a picture is partitioned to one or more slice groups, and a slice group contains one or more slices.
  • a slice consists of an integer number of macroblocks ordered consecutively in the raster scan within a particular slice group.
  • a coding block may be defined as an NxN block of samples for some value of N such that the division of a coding tree block into coding blocks is a partitioning.
  • a coding tree block may be defined as an NxN block of samples for some value of N such that the division of a component into coding tree blocks is a partitioning.
  • a coding tree unit may be defined as a coding tree block of luma samples, two corresponding coding tree blocks of chroma samples of a picture that has three sample arrays, or a coding tree block of samples of a monochrome picture or a picture that is coded using three separate color planes and syntax structures used to code the samples.
  • a coding unit may be defined as a coding block of luma samples, two corresponding coding blocks of chroma samples of a picture that has three sample arrays, or a coding block of samples of a monochrome picture or a picture that is coded using three separate color planes and syntax structures used to code the samples.
  • video pictures are divided into coding units (CU) covering the area of the picture.
  • a CU consists of one or more prediction units (PU) defining the prediction process for the samples within the CU and one or more transform units (TU) defining the prediction error coding process for the samples in the said CU.
  • PU prediction units
  • TU transform units
  • a CU consists of a square block of samples with a size selectable from a predefined set of possible CU sizes.
  • a CU with the maximum allowed size may be named as LCU (largest coding unit) or coding tree unit (CTU) and the video picture is divided into non-overlapping LCUs.
  • LCU largest coding unit
  • CTU coding tree unit
  • An LCU can be further split into a combination of smaller CUs, e.g. by recursively splitting the LCU and resultant CUs.
  • Each resulting CU typically has at least one PU and at least one TU associated with it.
  • Each PU and TU can be further split into smaller PUs and TUs in order to increase granularity of the prediction and prediction error coding processes, respectively.
  • Each PU has prediction information associated with it defining what kind of a prediction is to be applied for the pixels within that PU (e.g. motion vector information for inter predicted PUs and intra prediction directionality information for intra predicted PUs).
  • Each TU can be associated with information describing the prediction error decoding process for the samples within the said TU (including e.g. DCT coefficient information). It is typically signalled at CU level whether prediction error coding is applied or not for each CU. In the case there is no prediction error residual associated with the CU, it can be considered there are no TUs for the said CU.
  • the division of the image into CUs, and division of CUs into PUs and TUs is typically signalled in the bitstream allowing the decoder to reproduce the intended structure of these units.
  • a picture can be partitioned in tiles, which are rectangular and contain an integer number of LCUs.
  • the partitioning to tiles forms a tile grid comprising one or more tile columns and one or more tile rows.
  • a coded tile is byte-aligned, which may be achieved by adding byte-alignment bits at the end of the coded tile.
  • a slice is defined to be an integer number of coding tree units contained in one independent slice segment and all subsequent dependent slice segments (if any) that precede the next independent slice segment (if any) within the same access unit.
  • a slice segment is defined to be an integer number of coding tree units ordered consecutively in the tile scan and contained in a single NAL unit. The division of each picture into slice segments is a partitioning.
  • an independent slice segment is defined to be a slice segment for which the values of the syntax elements of the slice segment header are not inferred from the values for a preceding slice segment
  • a dependent slice segment is defined to be a slice segment for which the values of some syntax elements of the slice segment header are inferred from the values for the preceding independent slice segment in decoding order.
  • a slice header is defined to be the slice segment header of the independent slice segment that is a current slice segment or is the independent slice segment that precedes a current dependent slice segment
  • a slice segment header is defined to be a part of a coded slice segment containing the data elements pertaining to the first or all coding tree units represented in the slice segment.
  • a tile contains an integer number of coding tree units, and may consist of coding tree units contained in more than one slice.
  • a slice may consist of coding tree units contained in more than one tile.
  • all coding tree units in a slice belong to the same tile and/or all coding tree units in a tile belong to the same slice.
  • all coding tree units in a slice segment belong to the same tile and/or all coding tree units in a tile belong to the same slice segment.
  • a motion-constrained tile set is such that the inter prediction process is constrained in encoding such that no sample value outside the motion-constrained tile set, and no sample value at a fractional sample position that is derived using one or more sample values outside the motion-constrained tile set, is used for inter prediction of any sample within the motion- constrained tile set.
  • sample locations used in inter prediction are saturated so that a location that would be outside the picture otherwise is saturated to point to the corresponding boundary sample of the picture.
  • motion vectors may effectively cross that boundary or a motion vector may effectively cause fractional sample interpolation that would refer to a location outside that boundary, since the sample locations are saturated onto the boundary.
  • the temporal motion-constrained tile sets SEI message of HEVC can be used to indicate the presence of motion-constrained tile sets in the bitstream.
  • An inter- layer constrained tile set is such that the inter- layer prediction process is constrained in encoding such that no sample value outside each associated reference tile set, and no sample value at a fractional sample position that is derived using one or more sample values outside each associated reference tile set, is used for inter-layer prediction of any sample within the inter-layer constrained tile set.
  • the inter-layer constrained tile sets SEI message of HEVC can be used to indicate the presence of inter- layer constrained tile sets in the bitstream.
  • the decoder reconstructs the output video by applying prediction means similar to the encoder to form a predicted representation of the pixel blocks (using the motion or spatial information created by the encoder and stored in the compressed representation) and prediction error decoding (inverse operation of the prediction error coding recovering the quantized prediction error signal in spatial pixel domain). After applying prediction and prediction error decoding means the decoder sums up the prediction and prediction error signals (pixel values) to form the output video frame.
  • the decoder (and encoder) can also apply additional filtering means to improve the quality of the output video before passing it for display and/or storing it as prediction reference for the forthcoming frames in the video sequence.
  • the filtering may for example include one more of the following: deblocking, sample adaptive offset (SAO), and/or adaptive loop filtering (ALF).
  • deblocking sample adaptive offset (SAO)
  • ALF adaptive loop filtering
  • H.264/AVC includes a deblocking
  • HEVC includes both deblocking and SAO.
  • the motion information is indicated with motion vectors associated with each motion compensated image block, such as a prediction unit.
  • Each of these motion vectors represents the displacement of the image block in the picture to be coded (in the encoder side) or decoded (in the decoder side) and the prediction source block in one of the previously coded or decoded pictures.
  • those are typically coded differentially with respect to block specific predicted motion vectors.
  • the predicted motion vectors are created in a predefined way, for example calculating the median of the encoded or decoded motion vectors of the adjacent blocks.
  • Another way to create motion vector predictions is to generate a list of candidate predictions from adjacent blocks and/or co-located blocks in temporal reference pictures and signalling the chosen candidate as the motion vector predictor.
  • it can be predicted which reference picture(s) are used for motion- compensated prediction and this prediction information may be represented for example by a reference index of previously coded/decoded picture.
  • the reference index is typically predicted from adjacent blocks and/or co-located blocks in temporal reference picture.
  • typical high efficiency video codecs employ an additional motion information coding/decoding mechanism, often called merging/merge mode, where all the motion field information, which includes motion vector and corresponding reference picture index for each available reference picture list, is predicted and used without any modification/correction.
  • predicting the motion field information is carried out using the motion field information of adjacent blocks and/or co-located blocks in temporal reference pictures and the used motion field information is signalled among a list of motion field candidate list filled with motion field information of available adjacent/co-located blocks.
  • Typical video codecs enable the use of uni-prediction, where a single prediction block is used for a block being (de)coded, and bi-prediction, where two prediction blocks are combined to form the prediction for a block being (de)coded.
  • Some video codecs enable weighted prediction, where the sample values of the prediction blocks are weighted prior to adding residual information. For example, multiplicative weighting factor and an additive offset which can be applied.
  • a weighting factor and offset may be coded for example in the slice header for each allowable reference picture index.
  • the weighting factors and/or offsets are not coded but are derived e.g. based on the relative picture order count (POC) distances of the reference pictures.
  • POC picture order count
  • Typical video encoders utilize Lagrangian cost functions to find optimal coding modes, e.g. the desired Macroblock mode and associated motion vectors.
  • C the Lagrangian cost to be minimized
  • D the image distortion (e.g. Mean Squared Error) with the mode and motion vectors considered
  • R the number of bits needed to represent the required data to reconstruct the image block in the decoder (including the amount of data to represent the candidate motion vectors).
  • Video coding standards and specifications may allow encoders to divide a coded picture to coded slices or alike and/or tiles or alike.
  • In-picture prediction is typically disabled across slice boundaries and tile boundaries.
  • slices and tiles can be regarded as a way to split a coded picture to independently decodable pieces.
  • in-picture prediction may be disabled across slice boundaries
  • HEVC in-picture prediction may be disable across tile boundaries.
  • slices can be regarded as a way to split a coded picture into independently decodable pieces, and slices are therefore often regarded as elementary units for transmission and can also be used as elementary units for parallelization.
  • Tiles can be regarded as elementary units for parallelization in encoding and/or decoding.
  • encoders may indicate in the bitstream which types of in-picture prediction are turned off across slice boundaries or tile boundaries (separately or jointly for slice and tile boundaries), and the decoder operation takes this information into account for example when concluding which prediction sources are available. For example, samples from a neighboring macroblock or CU may be regarded as unavailable for intra prediction, if the neighboring macroblock or CU resides in a different slice.
  • NAL Network Abstraction Layer
  • a NAL unit may be defined as a syntax structure containing an indication of the type of data to follow and bytes containing that data in the form of an RBSP interspersed as necessary with start code emulation prevention bytes.
  • a raw byte sequence payload (RBSP) may be defined as a syntax structure containing an integer number of bytes that is encapsulated in a NAL unit.
  • An RBSP is either empty or has the form of a string of data bits containing syntax elements followed by an RBSP stop bit and followed by zero or more subsequent bits equal to 0.
  • NAL units consist of a header and payload.
  • a two-byte NAL unit header is used for all specified NAL unit types.
  • the NAL unit header contains one reserved bit, a six-bit NAL unit type indication, a three-bit nuh_temporal_id_plusl indication for temporal level (may be required to be greater than or equal to 1) and a six-bit nuh layer id syntax element.
  • temporal_id_plusl is required to be non-zero in order to avoid start code emulation involving the two NAL unit header bytes.
  • the bitstream created by excluding all VCL NAL units having a Temporalld greater than or equal to a selected value and including all other VCL NAL units remains conforming.
  • a sub-layer or a temporal sublayer may be defined to be a temporal scalable layer of a temporal scalable bitstream, consisting of VCL NAL units with a particular value of the Temporalld variable and the associated non-VCL NAL units, nuh layer id can be understood as a scalability layer identifier.
  • NAL units can be categorized into Video Coding Layer (VCL) NAL units and non- VCL NAL units.
  • VCLNAL units contain syntax elements representing one or more CU.
  • a coded slice NAL unit can be indicated to be one of the following types:
  • TRAIL Temporal Sub-layer Access
  • STSA Step-wise Temporal Sub-layer Access
  • RDL Random Access Decodable Leading
  • RASL Random Access Skipped Leading
  • BLA Broken Link Access
  • IDR Instantaneous Decoding Refresh
  • CRA Clean Random Access
  • a Random Access Point (RAP) picture which may also be referred to as an intra random access point (IRAP) picture, is a picture where each slice or slice segment has nal unit type in the range of 16 to 23, inclusive.
  • a IRAP picture in an independent layer contains only intra-coded slices.
  • An IRAP picture belonging to a predicted layer with nuh layer id value currLayerld may contain P, B, and I slices, cannot use inter prediction from other pictures with nuh layer id equal to currLayerld, and may use inter-layer prediction from its direct reference layers.
  • an IRAP picture may be a BLA picture, a CRA picture or an IDR picture.
  • the first picture in a bitstream containing a base layer is an IRAP picture at the base layer.
  • an IRAP picture at an independent layer and all subsequent non-RASL pictures at the independent layer in decoding order can be correctly decoded without performing the decoding process of any pictures that precede the IRAP picture in decoding order.
  • the IRAP picture belonging to a predicted layer with nuh layer id value currLayerld and all subsequent non-RASL pictures with nuh layer id equal to currLayerld in decoding order can be correctly decoded without performing the decoding process of any pictures with nuh layer id equal to currLayerld that precede the IRAP picture in decoding order, when the necessary parameter sets are available when they need to be activated and when the decoding of each direct reference layer of the layer with nuh layer id equal to currLayerld has been initialized (i.e.
  • a CRA picture may be the first picture in the bitstream in decoding order, or may appear later in the bitstream.
  • CRA pictures in HEVC allow so-called leading pictures that follow the CRA picture in decoding order but precede it in output order.
  • Some of the leading pictures, so-called RASL pictures may use pictures decoded before the CRA picture as a reference.
  • Pictures that follow a CRA picture in both decoding and output order are decodable if random access is performed at the CRA picture, and hence clean random access is achieved similarly to the clean random access functionality of an IDR picture.
  • a CRA picture may have associated RADL or RASL pictures.
  • the CRA picture is the first picture in the bitstream in decoding order
  • the CRA picture is the first picture of a coded video sequence in decoding order
  • any associated RASL pictures are not output by the decoder and may not be decodable, as they may contain references to pictures that are not present in the bitstream.
  • a leading picture is a picture that precedes the associated RAP picture in output order.
  • the associated RAP picture is the previous RAP picture in decoding order (if present).
  • a leading picture is either a RADL picture or a RASL picture.
  • All RASL pictures are leading pictures of an associated BLA or CRA picture.
  • the RASL picture is not output and may not be correctly decodable, as the RASL picture may contain references to pictures that are not present in the bitstream.
  • a RASL picture can be correctly decoded if the decoding had started from a RAP picture before the associated RAP picture of the RASL picture.
  • RASL pictures are not used as reference pictures for the decoding process of non-RASL pictures. When present, all RASL pictures precede, in decoding order, all trailing pictures of the same associated RAP picture. In some drafts of the HEVC standard, a RASL picture was referred to a Tagged for Discard (TFD) picture.
  • TDD Tagged for Discard
  • All RADL pictures are leading pictures. RADL pictures are not used as reference pictures for the decoding process of trailing pictures of the same associated RAP picture.
  • RADL pictures When present, all RADL pictures precede, in decoding order, all trailing pictures of the same associated RAP picture. RADL pictures do not refer to any picture preceding the associated RAP picture in decoding order and can therefore be correctly decoded when the decoding starts from the associated RAP picture.
  • the RASL pictures associated with the CRA picture might not be correctly decodable, because some of their reference pictures might not be present in the combined bitstream.
  • the NAL unit type of the CRA picture can be changed to indicate that it is a BLA picture.
  • the RASL pictures associated with a BLA picture may not be correctly decodable hence are not be output/displayed.
  • the RASL pictures associated with a BLA picture may be omitted from decoding.
  • a BLA picture may be the first picture in the bitstream in decoding order, or may appear later in the bitstream. Each BLA picture begins a new coded video sequence, and has similar effect on the decoding process as an IDR picture. However, a BLA picture contains syntax elements that specify a non-empty reference picture set. When a BLA picture has nal unit type equal to BLA W LP, it may have associated RASL pictures, which are not output by the decoder and may not be decodable, as they may contain references to pictures that are not present in the bitstream. When a BLA picture has nal unit type equal to
  • BLA W LP it may also have associated RADL pictures, which are specified to be decoded.
  • BLA picture has nal unit type equal to BLA W RADL, it does not have associated RASL pictures but may have associated RADL pictures, which are specified to be decoded.
  • BLA picture has nal unit type equal to BLA N LP, it does not have any associated leading pictures.
  • An IDR picture having nal unit type equal to IDR N LP does not have associated leading pictures present in the bitstream.
  • An IDR picture having nal unit type equal to IDR W LP does not have associated RASL pictures present in the bitstream, but may have associated RADL pictures in the bitstream.
  • nal unit type is equal to TRAIL N, TSA_N, STSA_N,
  • the decoded picture is not used as a reference for any other picture of the same temporal sub-layer. That is, in HEVC, when the value of nal unit type is equal to TRAIL N, TSA_N, STSA_N,
  • the decoded picture is not included in any of RefPicSetStCurrBefore, RefPicSetStCurrAfter and
  • a coded picture with nal unit type equal to TRAIL N, TSA N, STSA N, RADL N, RASL N, RSV VCL N10, RSV VCL N12, or RSV VCL N14 may be discarded without affecting the decodability of other pictures with the same value of Temporalld.
  • These types of pictures are sub-layer non- reference (SLNR) pictures, and may be indicated by the _N postfix in the picture type abbreviation.
  • a SLNR picture may be defined as a picture that contains samples that cannot be used for inter prediction in the decoding process of subsequent pictures of the same sublayer in decoding order.
  • a sub-layer reference picture may be indicated by the _R postfix in the picture type abbreviation.
  • a sub-layer reference picture may be defined as a picture that contains samples that may be used for inter prediction in the decoding process of subsequent pictures of the same sub-layer in decoding order.
  • a trailing picture may be defined as a picture that follows the associated RAP picture in output order. Any picture that is a trailing picture does not have nal unit type equal to RADL N, RADL R, RASL N or RASL R. Any picture that is a leading picture may be constrained to precede, in decoding order, all trailing pictures that are associated with the same RAP picture. No RASL pictures are present in the bitstream that are associated with a BLA picture having nal unit type equal to BLA W RADL or BLA N LP. No RADL pictures are present in the bitstream that are associated with a BLA picture having
  • Any RASL picture associated with a CRA or BLA picture may be constrained to precede any RADL picture associated with the CRA or BLA picture in output order.
  • Any RASL picture associated with a CRA picture may be constrained to follow, in output order, any other RAP picture that precedes the CRA picture in decoding order.
  • the TSA and STSA picture types that can be used to indicate temporal sub-layer switching points. If temporal sub-layers with Temporalld up to N had been decoded until the TSA or STSA picture (exclusive) and the TSA or STSA picture has Temporalld equal to N+l, the TSA or STSA picture enables decoding of all subsequent pictures (in decoding order) having Temporalld equal to N+l .
  • the TSA picture type may impose restrictions on the TSA picture itself and all pictures in the same sub-layer that follow the TSA picture in decoding order. None of these pictures is allowed to use inter prediction from any picture in the same sub-layer that precedes the TSA picture in decoding order.
  • the TSA definition may further impose restrictions on the pictures in higher sub-layers that follow the TSA picture in decoding order. None of these pictures is allowed to refer a picture that precedes the TSA picture in decoding order if that picture belongs to the same or higher sub-layer as the TSA picture. TSA pictures have Temporalld greater than 0.
  • the STSA is similar to the TSA picture but does not impose restrictions on the pictures in higher sublayers that follow the STSA picture in decoding order and hence enable up-switching only onto the sub-layer where the STSA picture resides.
  • a non-VCL NAL unit may be for example one of the following types: a sequence parameter set, a picture parameter set, a supplemental enhancement information (SEI) NAL unit, an access unit delimiter, an end of sequence NAL unit, an end of bitstream NAL unit, or a filler data NAL unit.
  • SEI Supplemental Enhancement Information
  • Parameter sets may be needed for the reconstruction of decoded pictures, whereas many of the other non-VCL NAL units are not necessary for the reconstruction of decoded sample values.
  • Parameters that remain unchanged through a coded video sequence may be included in a sequence parameter set.
  • the sequence parameter set may optionally contain video usability information (VUI), which includes parameters that may be important for buffering, picture output timing, rendering, and resource reservation.
  • VUI video usability information
  • a sequence parameter set RBSP includes parameters that can be referred to by one or more picture parameter set RBSPs or one or more SEI NAL units containing a buffering period SEI message.
  • a picture parameter set contains such parameters that are likely to be unchanged in several coded pictures.
  • a picture parameter set RBSP may include parameters that can be referred to by the coded slice NAL units of one or more coded pictures.
  • a video parameter set may be defined as a syntax structure containing syntax elements that apply to zero or more entire coded video sequences as determined by the content of a syntax element found in the SPS referred to by a syntax element found in the PPS referred to by a syntax element found in each slice segment header.
  • a video parameter set RBSP may include parameters that can be referred to by one or more sequence parameter set RBSPs.
  • VPS resides one level above SPS in the parameter set hierarchy and in the context of scalability and/or 3D video.
  • VPS may include parameters that are common for all slices across all (scalability or view) layers in the entire coded video sequence.
  • SPS includes the parameters that are common for all slices in a particular (scalability or view) layer in the entire coded video sequence, and may be shared by multiple (scalability or view) layers.
  • PPS includes the parameters that are common for all slices in a particular layer representation (the
  • VPS may provide information about the dependency relationships of the layers in a bitstream, as well as many other information that are applicable to all slices across all
  • VPS may be considered to comprise two parts, the base VPS and a VPS extension, where the VPS extension may be optionally present.
  • the base VPS may be considered to comprise the
  • the video_parameter_set_rbsp( ) syntax structure was primarily specified already for HEVC version 1 and includes syntax elements which may be of use for base layer decoding.
  • the VPS extension may be considered to comprise the vps_extension( ) syntax structure.
  • the vps_extension( ) syntax structure was specified in HEVC version 2 primarily for multi-layer extensions and comprises syntax elements which may be of use for decoding of one or more non-base layers, such as syntax elements indicating layer dependency relations.
  • the VPS extension may comprise VPS VUI, which comprises parameters relating to multi-layer properties of the bitstream.
  • the syntax element max_tid_il_ref_pics_plusl in the VPS extension can be used to indicate that non-IRAP pictures are not used a reference for inter- layer prediction and, if not so, which temporal sub-layers are not used as a reference for inter-layer prediction:
  • max_tid_il_ref_pics_plusl [ i ][ j ] 0 specifies that non-IRAP pictures with nuh layer id equal to layer_id_in_nuh[ i ] are not used as source pictures for inter-layer prediction for pictures with nuh layer id equal to layer_id_in_nuh[ j ].
  • max_tid_il_ref_pics_plusl [ i ][ j ] greater than 0 specifies that pictures with nuh layer id equal to layer_id_in_nuh[ i ] and Temporalld greater than max_tid_il_ref_pics_plusl [ i ][ j ] - 1 are not used as source pictures for inter-layer prediction for pictures with nuh layer id equal to layer_id_in_nuh[ j ].
  • the value of max_tid_il_ref_pics_plusl [ i ][ j ] is inferred to be equal to 7.
  • H.264/AVC and HEVC syntax allows many instances of parameter sets, and each instance is identified with a unique identifier. In order to limit the memory usage needed for parameter sets, the value range for parameter set identifiers has been limited.
  • each slice header includes the identifier of the picture parameter set that is active for the decoding of the picture that contains the slice, and each picture parameter set contains the identifier of the active sequence parameter set. Consequently, the transmission of picture and sequence parameter sets does not have to be accurately synchronized with the
  • parameter sets can be included as a parameter in the session description for Real-time Transport Protocol (RTP) sessions. If parameter sets are transmitted in-band, they can be repeated to improve error robustness.
  • RTP Real-time Transport Protocol
  • Out-of-band transmission, signaling or storage can additionally or alternatively be used for other purposes than tolerance against transmission errors, such as ease of access or session negotiation. For example, a sample entry of a track in a file conforming to the
  • ISOBMFF may comprise parameter sets, while the coded data in the bitstream is stored elsewhere in the file or in another file.
  • the phrase along the bitstream (e.g. indicating along the bitstream) may be used in claims and described embodiments to refer to out-of-band transmission, signaling, or storage in a manner that the out-of-band data is associated with the bitstream.
  • the phrase decoding along the bitstream or alike may refer to decoding the referred out-of-band data (which may be obtained from out-of-band transmission, signaling, or storage) that is associated with the bitstream.
  • a coded picture is a coded representation of a picture.
  • a coded picture may be defined as a coded representation of a picture containing all coding tree units of the picture.
  • an access unit (AU) may be defined as a set of NAL units that are associated with each other according to a specified classification rule, are consecutive in decoding order, and contain at most one picture with any specific value of nuh layer id.
  • an access unit may also contain non-VCL NAL units.
  • coded pictures may appear in certain order within an access unit. For example a coded picture with nuh layer id equal to nuhLayerldA may be required to precede, in decoding order, all coded pictures with nuh layer id greater than nuhLayerldA in the same access unit.
  • An AU typically contains all the coded pictures that represent the same output time and/or capturing time.
  • a bitstream may be defined as a sequence of bits, in the form of a NAL unit stream or a byte stream, that forms the representation of coded pictures and associated data forming one or more coded video sequences.
  • a first bitstream may be followed by a second bitstream in the same logical channel, such as in the same file or in the same connection of a communication protocol.
  • An elementary stream (in the context of video coding) may be defined as a sequence of one or more bitstreams.
  • the end of the first bitstream may be indicated by a specific NAL unit, which may be referred to as the end of bitstream (EOB) NAL unit and which is the last NAL unit of the bitstream.
  • EOB NAL unit In HEVC and its current draft extensions, the EOB NAL unit is required to have nuh layer id equal to 0.
  • a byte stream format has been specified in H.264/AVC and HEVC for transmission or storage environments that do not provide framing structures.
  • the byte stream format separates NAL units from each other by attaching a start code in front of each NAL unit.
  • encoders run a byte-oriented start code emulation prevention algorithm, which adds an emulation prevention byte to the NAL unit payload if a start code would have occurred otherwise.
  • start code emulation prevention may always be performed regardless of whether the byte stream format is in use or not.
  • the bit order for the byte stream format may be specified to start with the most significant bit (MSB) of the first byte, proceed to the least significant bit (LSB) of the first byte, followed by the MSB of the second byte, etc.
  • the byte stream format may be considered to consist of a sequence of byte stream NAL unit syntax structures. Each byte stream NAL unit syntax structure may be considered to contain one start code prefix followed by one NAL unit syntax structure, i.e. the nal_unit( NumBytesInNalUnit ) syntax structure if syntax element names are referred to.
  • a byte stream NAL unit may also contain an additional zero byte syntax element. It may also contain one or more additional trailing_zero_8bits syntax elements. When a byte stream NAL unit is the first byte stream NAL unit in the bitstream, it may also contain one or more additional leading_zero_8bits syntax elements.
  • the syntax of a byte stream NAL unit may be specified as follows:
  • the order of byte stream NAL units in the byte stream may be required to follow the decoding order of the NAL units contained in the byte stream NAL units.
  • the semantics of syntax elements may be specified as follows. leading_zero_8bits is a byte equal to 0x00.
  • leading_zero_8bits syntax element can only be present in the first byte stream NAL unit of the bitstream, because any bytes equal to 0x00 that follow a NAL unit syntax structure and precede the four-byte sequence 0x00000001 (which is to be interpreted as a zero byte followed by a start_code_prefix_one_3 bytes) will be considered to be trailing_zero_8bits syntax elements that are part of the preceding byte stream NAL unit.
  • zero_byte is a single byte equal to 0x00.
  • start_code_prefix_one_3 bytes is a fixed- value sequence of 3 bytes equal to 0x000001. This syntax element may be called a start code prefix (or simply a start code).
  • trailing_zero_8bits is a byte equal to 0x00.
  • a NAL unit may be defined as a syntax structure containing an indication of the type of data to follow and bytes containing that data in the form of an RBSP interspersed as necessary with emulation prevention bytes.
  • a raw byte sequence payload (RBSP) may be defined as a syntax structure containing an integer number of bytes that is encapsulated in a NAL unit.
  • An RBSP is either empty or has the form of a string of data bits containing syntax elements followed by an RBSP stop bit and followed by zero or more subsequent bits equal to 0.
  • NAL units consist of a header and payload.
  • the NAL unit header indicates the type of the NAL unit.
  • HEVC syntax of the nal_unit( NumBytesInNalUnit ) syntax structure are provided next as an example of a syntax of NAL unit.
  • a coded video sequence may be defined, for example, as a sequence of access units that consists, in decoding order, of an IRAP access unit with
  • NoRaslOutputFlag 1 , followed by zero or more access units that are not IRAP access units with NoRaslOutputFlag equal to 1 , including all subsequent access units up to but not including any subsequent access unit that is an IRAP access unit with NoRaslOutputFlag equal to 1.
  • An IRAP access unit may be defined as an access unit in which the base layer picture is an IRAP picture.
  • the value of NoRaslOutputFlag is equal to 1 for each IDR picture, each BLA picture, and each IRAP picture that is the first picture in that particular layer in the bitstream in decoding order, is the first IRAP picture that follows an end of sequence NAL unit having the same value of nuh layer id in decoding order.
  • NoRaslOutputFlag is equal to 1 for each IRAP picture when its nuh layer id is such that LayerInitializedFlag[ nuh layer id ] is equal to 0 and LayerInitializedFlag[ refLayerld ] is equal to 1 for all values of refLayerld equal to IdDirectRefLayerf nuh layer id ][ j ], where j is in the range of 0 to NumDirectRefLayers[ nuh layer id ] - 1, inclusive. Otherwise, the value of NoRaslOutputFlag is equal to HandleCraAsBlaFlag. NoRaslOutputFlag equal to 1 has an impact that the RASL pictures associated with the IRAP picture for which the
  • NoRaslOutputFlag is set are not output by the decoder.
  • HandleCraAsBlaFlag may be set to 1 for example by a player that seeks to a new position in a bitstream or tunes into a broadcast and starts decoding and then starts decoding from a CRA picture.
  • HandleCraAsBlaFlag is equal to 1 for a CRA picture, the CRA picture is handled and decoded as if it were a BLA picture.
  • a coded video sequence may additionally or alternatively (to the specification above) be specified to end, when a specific NAL unit, which may be referred to as an end of sequence (EOS) NAL unit, appears in the bitstream and has nuh layer id equal to O.
  • EOS end of sequence
  • a group of pictures (GOP) and its characteristics may be defined as follows.
  • a GOP can be decoded regardless of whether any previous pictures were decoded.
  • An open GOP is such a group of pictures in which pictures preceding the initial intra picture in output order might not be correctly decodable when the decoding starts from the initial intra picture of the open GOP.
  • pictures of an open GOP may refer (in inter prediction) to pictures belonging to a previous GOP.
  • An HEVC decoder can recognize an intra picture starting an open GOP, because a specific NAL unit type, CRA NAL unit type, may be used for its coded slices.
  • a closed GOP is such a group of pictures in which all pictures can be correctly decoded when the decoding starts from the initial intra picture of the closed GOP. In other words, no picture in a closed GOP refers to any pictures in previous GOPs.
  • a closed GOP may start from an IDR picture.
  • a closed GOP may also start from a BLA W RADL or a BLA N LP picture.
  • An open GOP coding structure is potentially more efficient in the compression compared to a closed GOP coding structure, due to a larger flexibility in selection of reference pictures.
  • a Structure of Pictures may be defined as one or more coded pictures consecutive in decoding order, in which the first coded picture in decoding order is a reference picture at the lowest temporal sub-layer and no coded picture except potentially the first coded picture in decoding order is a RAP picture. All pictures in the previous SOP precede in decoding order all pictures in the current SOP and all pictures in the next SOP succeed in decoding order all pictures in the current SOP.
  • a SOP may represent a hierarchical and repetitive inter prediction structure.
  • the term group of pictures may sometimes be used interchangeably with the term SOP and having the same semantics as the semantics of SOP.
  • bitstream syntax of H.264/AVC and HEVC indicates whether a particular picture is a reference picture for inter prediction of any other picture.
  • Pictures of any coding type (I, P, B) can be reference pictures or non-reference pictures in H.264/AVC and HEVC.
  • H.264/AVC and HEVC include a concept of picture order count (POC).
  • a value of POC is derived for each picture and is non-decreasing with increasing picture position in output order. POC therefore indicates the output order of pictures.
  • POC may be used in the decoding process for example for implicit scaling of motion vectors in the temporal direct mode of bi-predictive slices, for implicitly derived weights in weighted prediction, and for reference picture list initialization. Furthermore, POC may be used in the verification of output order conformance. In H.264/AVC, POC is specified relative to the previous IDR picture or a picture containing a memory management control operation marking all pictures as "unused for reference".
  • a reference picture set valid or active for a picture includes all the reference pictures used as reference for the picture and all the reference pictures that are kept marked as "used for reference” for any subsequent pictures in decoding order.
  • RefPicSetStCurrBefore RefPicSetStCurrl (a.k.a. RefPicSetStCurrAfter), RefPicSetStFollO, RefPicSetStFolll, RefPicSetLtCurr, and RefPicSetLtFoll. RefPicSetStFollO and
  • RefPicSetStFolll may also be considered to form jointly one subset RefPicSetStFoll.
  • the notation of the six subsets is as follows.
  • “Curr” refers to reference pictures that are included in the reference picture lists of the current picture and hence may be used as inter prediction reference for the current picture.
  • “Foil” refers to reference pictures that are not included in the reference picture lists of the current picture but may be used in subsequent pictures in decoding order as reference pictures.
  • St refers to short-term reference pictures, which may generally be identified through a certain number of least significant bits of their POC value.
  • Lt refers to long-term reference pictures, which are specifically identified and generally have a greater difference of POC values relative to the current picture than what can be represented by the mentioned certain number of least significant bits. "0” refers to those reference pictures that have a smaller POC value than that of the current picture. “1” refers to those reference pictures that have a greater POC value than that of the current picture.
  • RefPicSetStCurrO, RefPicSetStCurrl, RefPicSetStFollO and RefPicSetStFolll are collectively referred to as the short-term subset of the reference picture set.
  • RefPicSetLtFoll are collectively referred to as the long-term subset of the reference picture set.
  • a reference picture set may be specified in a sequence parameter set and taken into use in the slice header through an index to the reference picture set.
  • a reference picture set may also be specified in a slice header.
  • a reference picture set may be coded independently or may be predicted from another reference picture set (known as inter-RPS prediction).
  • inter-RPS prediction a flag (used_by_curr_pic_X_flag) is additionally sent for each reference picture indicating whether the reference picture is used for reference by the current picture (included in a *Curr list) or not (included in a *Foll list).
  • Pictures that are included in the reference picture set used by the current slice are marked as "used for reference", and pictures that are not in the reference picture set used by the current slice are marked as "unused for reference”. If the current picture is an IDR picture,
  • RefPicSetStCurrO, RefPicSetStCurrl, RefPicSetStFollO, RefPicSetStFolll, RefPicSetLtCurr, and RefPicSetLtFoll are all set to empty.
  • a Decoded Picture Buffer may be used in the encoder and/or in the decoder. There are two reasons to buffer decoded pictures, for references in inter prediction and for reordering decoded pictures into output order. As H.264/AVC and HEVC provide a great deal of flexibility for both reference picture marking and output reordering, separate buffers for reference picture buffering and output picture buffering may waste memory resources. Hence, the DPB may include a unified decoded picture buffering process for reference pictures and output reordering. A decoded picture may be removed from the DPB when it is no longer used as a reference and is not needed for output.
  • the reference picture for inter prediction is indicated with an index to a reference picture list.
  • the index may be coded with variable length coding, which usually causes a smaller index to have a shorter value for the corresponding syntax element.
  • variable length coding usually causes a smaller index to have a shorter value for the corresponding syntax element.
  • reference picture list 0 and reference picture list 1 are generated for each bi-predictive (B) slice, and one reference picture list (reference picture list 0) is formed for each inter-coded (P) slice.
  • a reference picture list such as reference picture list 0 and reference picture list 1, is typically constructed in two steps: First, an initial reference picture list is generated.
  • the initial reference picture list may be generated for example on the basis of frame num, POC, temporal id (or Temporalld or alike), or information on the prediction hierarchy such as GOP structure, or any combination thereof.
  • the initial reference picture list may be reordered by reference picture list reordering (RPLR) commands, also known as reference picture list modification syntax structure, which may be contained in slice headers.
  • RPLR reference picture list reordering
  • the reference picture list 0 may be initialized to contain RefPicSetStCurrO first, followed by RefPicSetStCurrl, followed by RefPicSetLtCurr.
  • Reference picture list 1 may be initialized to contain RefPicSetStCurrl first, followed by RefPicSetStCurrO.
  • the initial reference picture lists may be modified through the reference picture list modification syntax structure, where pictures in the initial reference picture lists may be identified through an entry index to the list.
  • reference picture list modification is encoded into a syntax structure comprising a loop over each entry in the final reference picture list, where each loop entry is a fixed-length coded index to the initial reference picture list and indicates the picture in ascending position order in the final reference picture list.
  • a reference picture index may be coded by an encoder into the bitstream is some inter coding modes or it may be derived (by an encoder and a decoder) for example using neighboring blocks in some other inter coding modes.
  • motion vectors may be coded differentially with respect to a block-specific predicted motion vector.
  • the predicted motion vectors are created in a predefined way, for example by calculating the median of the encoded or decoded motion vectors of the adjacent blocks.
  • AVP advanced motion vector prediction
  • Another way to create motion vector predictions is to generate a list of candidate predictions from adjacent blocks and/or co-located blocks in temporal reference pictures and signalling the chosen candidate as the motion vector predictor.
  • the reference index of previously coded/decoded picture can be predicted.
  • the reference index is typically predicted from adjacent blocks and/or co-located blocks in temporal reference picture.
  • Differential coding of motion vectors is typically disabled across slice boundaries.
  • Scalable video coding may refer to coding structure where one bitstream can contain multiple representations of the content, for example, at different bitrates, resolutions or frame rates.
  • the receiver can extract the desired representation depending on its characteristics (e.g. resolution that matches best the display device).
  • a server or a network element can extract the portions of the bitstream to be transmitted to the receiver depending on e.g. the network characteristics or processing capabilities of the receiver.
  • a meaningful decoded representation can be produced by decoding only certain parts of a scalable bit stream.
  • a scalable bitstream typically consists of a "base layer" providing the lowest quality video available and one or more enhancement layers that enhance the video quality when received and decoded together with the lower layers.
  • the coded representation of that layer typically depends on the lower layers.
  • the motion and mode information of the enhancement layer can be predicted from lower layers.
  • the pixel data of the lower layers can be used to create prediction for the enhancement layer.
  • a video signal can be encoded into a base layer and one or more enhancement layers.
  • An enhancement layer may enhance, for example, the temporal resolution (i.e., the frame rate), the spatial resolution, or simply the quality of the video content represented by another layer or part thereof.
  • Each layer together with all its dependent layers is one representation of the video signal, for example, at a certain spatial resolution, temporal resolution and quality level.
  • a scalable layer together with all of its dependent layers as a "scalable layer representation”.
  • the portion of a scalable bitstream corresponding to a scalable layer representation can be extracted and decoded to produce a representation of the original signal at certain fidelity.
  • Scalability modes or scalability dimensions may include but are not limited to the following:
  • Base layer pictures are coded at a lower quality than enhancement layer pictures, which may be achieved for example using a greater quantization parameter value (i.e., a greater quantization step size for transform coefficient quantization) in the base layer than in the enhancement layer.
  • a greater quantization parameter value i.e., a greater quantization step size for transform coefficient quantization
  • Spatial scalability Base layer pictures are coded at a lower resolution (i.e. have fewer samples) than enhancement layer pictures. Spatial scalability and quality scalability, particularly its coarse-grain scalability type, may sometimes be considered the same type of scalability.
  • Bit-depth scalability Base layer pictures are coded at lower bit-depth (e.g. 8 bits) than enhancement layer pictures (e.g. 10 or 12 bits).
  • Dynamic range scalability Scalable layers represent a different dynamic range and/or images obtained using a different tone mapping function and/or a different optical transfer function.
  • Chroma format scalability Base layer pictures provide lower spatial resolution in chroma sample arrays (e.g. coded in 4:2:0 chroma format) than enhancement layer pictures (e.g. 4:4:4 format).
  • enhancement layer pictures have a richer/broader color representation range than that of the base layer pictures - for example the enhancement layer may have UHDTV (ITU-R BT.2020) color gamut and the base layer may have the ITU-R BT.709 color gamut.
  • UHDTV ITU-R BT.2020
  • the base layer represents a base view
  • a predicted layer represents a predicted view
  • Depth scalability which may also be referred to as depth-enhanced coding.
  • a layer or some layers of a bitstream may represent texture view(s), while other layer or layers may represent depth view(s).
  • Interlaced-to-progressive scalability also known as field-to-frame scalability: coded interlaced source content material of the base layer is enhanced with an enhancement layer to represent progressive source content.
  • Hybrid codec scalability also known as coding standard scalability
  • bitstream syntax, semantics and decoding process of the base layer and the enhancement layer are specified in different video coding standards.
  • base layer pictures are coded according to a different coding standard or format than enhancement layer pictures.
  • the base layer may be coded with
  • H.264/AVC and an enhancement layer may be coded with an HEVC multi-layer extension.
  • the term layer may be used in context of any type of scalability, including view scalability and depth enhancements.
  • An enhancement layer may refer to any type of an enhancement, such as SNR, spatial, multiview, depth, bit-depth, chroma format, and/or color gamut enhancement.
  • a base layer may refer to any type of a base video sequence, such as a base view, a base layer for SNR/spatial scalability, or a texture base view for depth-enhanced video coding.
  • a view may be defined as a sequence of pictures representing one camera or viewpoint.
  • the pictures representing a view may also be called view components.
  • a view component may be defined as a coded representation of a view in a single access unit.
  • multiview video coding more than one view is coded in a bitstream. Since views are typically intended to be displayed on stereoscopic or multiview autostrereoscopic display or to be used for other 3D arrangements, they typically represent the same scene and are content-wise partly overlapping although representing different viewpoints to the content. Hence, inter- view prediction may be utilized in multiview video coding to take advantage of inter- view correlation and improve compression efficiency.
  • One way to realize inter- view prediction is to include one or more decoded pictures of one or more other views in the reference picture list(s) of a picture being coded or decoded residing within a first view.
  • View scalability may refer to such multiview video coding or multiview video bitstreams, which enable removal or omission of one or more coded views, while the resulting bitstream remains conforming and represents video with a smaller number of views than originally.
  • Region of Interest (ROI) coding may be defined to refer to coding a particular region within a video at a higher fidelity.
  • ROI scalability may be defined as a type of scalability wherein an enhancement layer enhances only part of a reference- layer picture e.g. spatially, quality-wise, in bit-depth, and/or along other scalability dimensions.
  • an enhancement layer can be transmitted to enhance the quality and/or a resolution of a region in the base layer.
  • a decoder receiving both enhancement and base layer bitstream might decode both layers and overlay the decoded pictures on top of each other and display the final picture.
  • the spatial correspondence of a reference- layer picture and an enhancement-layer picture may be inferred or may be indicated with one or more types of so-called reference layer location offsets.
  • reference layer location offsets may be included in the PPS by the encoder and decoded from the PPS by the decoder.
  • Reference layer location offsets may be used for but are not limited to achieving ROI scalability.
  • Reference layer location offsets may comprise one or more of scaled reference layer offsets, reference region offsets, and resampling phase sets.
  • Scaled reference layer offsets may be considered to specify the horizontal and vertical offsets between the sample in the current picture that is collocated with the top-left luma sample of the reference region in a decoded picture in a reference layer and the horizontal and vertical offsets between the sample in the current picture that is collocated with the bottom-right luma sample of the reference region in a decoded picture in a reference layer. Another way is to consider scaled reference layer offsets to specify the positions of the corner samples of the upsampled reference region relative to the respective corner samples of the enhancement layer picture.
  • the scaled reference layer offset values may be signed.
  • Reference region offsets may be considered to specify the horizontal and vertical offsets between the top-left luma sample of the reference region in the decoded picture in a reference layer and the top-left luma sample of the same decoded picture as well as the horizontal and vertical offsets between the bottom-right luma sample of the reference region in the decoded picture in a reference layer and the bottom-right luma sample of the same decoded picture.
  • the reference region offset values may be signed.
  • a resampling phase set may be considered to specify the phase offsets used in resampling process of a source picture for inter-layer prediction. Different phase offsets may be provided for luma and chroma components.
  • a spatial packing of a stereo pair into a single frame is performed at the encoder side as a pre-processing step for encoding and then the frame-packed frames are encoded with a conventional 2D video coding scheme.
  • the output frames produced by the decoder contain constituent frames of a stereo pair.
  • the spatial resolution of the original frames of each view and the packaged single frame have the same resolution.
  • the encoder downsamples the two views of the stereoscopic video before the packing operation.
  • the spatial packing may use for example a side-by-side or top-bottom format, and the
  • Frame packing may be preferred over multiview video coding (e.g. MVC extension of H.264/AVC or MV-HEVC extension of H.265/HEVC) for example due to the following reasons:
  • the post-production workflows might be tailored for a single video signal. Some post- production tools might not be able to handle two separate picture sequences and/or might not be able to keep the separate picture sequences in synchrony with each other.
  • the distribution system such as transmission protocols, might be such that support single coded sequence only and/or might not be able to keep separate coded sequences in synchrony with each other and/or may require more buffering or latency to keep the separate coded sequences in synchrony with each other.
  • the decoding of bitstreams with multiview video coding tools may require support of specific coding modes, which might not be available in players. For example, many smartphones support H.265/HEVC Main profile decoding but are not able to handle H.265/HEVC Multiview Main profile decoding even though it only requires high- level additions compared to the Main profile.
  • Some scalable video coding schemes may require IRAP pictures to be aligned across layers in a manner that either all pictures in an access unit are IRAP pictures or no picture in an access unit is an IRAP picture.
  • Other scalable video coding schemes such as the multi-layer extensions of HEVC, may allow IRAP pictures that are not aligned, i.e. that one or more pictures in an access unit are IRAP pictures, while one or more other pictures in an access unit are not IRAP pictures.
  • Scalable bitstreams with IRAP pictures or similar that are not aligned across layers may be used for example for providing more frequent IRAP pictures in the base layer, where they may have a smaller coded size due to e.g. a smaller spatial resolution.
  • a process or mechanism for layer- wise start-up of the decoding may be included in a video decoding scheme.
  • Decoders may hence start decoding of a bitstream when a base layer contains an IRAP picture and step-wise start decoding other layers when they contain IRAP pictures.
  • decoders progressively increase the number of decoded layers (where layers may represent an enhancement in spatial resolution, quality level, views, additional components such as depth, or a combination) as subsequent pictures from additional enhancement layers are decoded in the decoding process.
  • the progressive increase of the number of decoded layers may be perceived for example as a progressive improvement of picture quality (in case of quality and spatial scalability).
  • a layer- wise start-up mechanism may generate unavailable pictures for the reference pictures of the first picture in decoding order in a particular enhancement layer.
  • a decoder may omit the decoding of pictures preceding, in decoding order, the IRAP picture from which the decoding of a layer can be started.
  • These pictures that may be omitted may be specifically labeled by the encoder or another entity within the bitstream. For example, one or more specific NAL unit types may be used for them.
  • These pictures, regardless of whether they are specifically marked with a NAL unit type or inferred e.g. by the decoder, may be referred to as cross-layer random access skip (CL-RAS) pictures.
  • the decoder may omit the output of the generated unavailable pictures and the decoded CL-RAS pictures.
  • Scalability may be enabled in two basic ways. Either by introducing new coding modes for performing prediction of pixel values or syntax from lower layers of the scalable representation or by placing the lower layer pictures to a reference picture buffer (e.g. a decoded picture buffer, DPB) of the higher layer.
  • the first approach may be more flexible and thus may provide better coding efficiency in most cases.
  • the second, reference frame based scalability, approach may be implemented efficiently with minimal changes to single layer codecs while still achieving majority of the coding efficiency gains available.
  • a reference frame based scalability codec may be implemented by utilizing the same hardware or software implementation for all the layers, just taking care of the DPB management by external means.
  • a scalable video encoder for quality scalability also known as Signal-to-Noise or SNR
  • SNR Signal-to-Noise
  • spatial scalability may be implemented as follows.
  • a base layer a conventional non-scalable video encoder and decoder may be used.
  • the reconstructed/decoded pictures of the base layer are included in the reference picture buffer and/or reference picture lists for an enhancement layer.
  • the reconstructed/decoded base-layer picture may be upsampled prior to its insertion into the reference picture lists for an enhancement-layer picture.
  • the base layer decoded pictures may be inserted into a reference picture list(s) for coding/decoding of an enhancement layer picture similarly to the decoded reference pictures of the enhancement layer. Consequently, the encoder may choose a base-layer reference picture as an inter prediction reference and indicate its use with a reference picture index in the coded bitstream.
  • the decoder decodes from the bitstream, for example from a reference picture index, that a base-layer picture is used as an inter prediction reference for the enhancement layer.
  • a base-layer picture is used as an inter prediction reference for the enhancement layer.
  • a second enhancement layer may depend on a first enhancement layer in encoding and/or decoding processes, and the first enhancement layer may therefore be regarded as the base layer for the encoding and/or decoding of the second enhancement layer.
  • inter-layer reference pictures from more than one layer in a reference picture buffer or reference picture lists of an enhancement layer, and each of these inter-layer reference pictures may be considered to reside in a base layer or a reference layer for the enhancement layer being encoded and/or decoded.
  • bit-depth of the samples of the reference- layer picture may be converted to the bit-depth of the enhancement layer and/or the sample values may undergo a mapping from the color space of the reference layer to the color space of the enhancement layer.
  • a scalable video coding and/or decoding scheme may use multi-loop coding and/or decoding, which may be characterized as follows.
  • a base layer picture may be reconstructed/decoded to be used as a motion-compensation reference picture for subsequent pictures, in coding/decoding order, within the same layer or as a reference for inter-layer (or inter-view or inter-component) prediction.
  • the reconstructed/decoded base layer picture may be stored in the DPB.
  • An enhancement layer picture may likewise be reconstructed/decoded to be used as a motion-compensation reference picture for subsequent pictures, in coding/decoding order, within the same layer or as reference for inter-layer (or inter-view or inter-component) prediction for higher enhancement layers, if any.
  • syntax element values of the base/reference layer or variables derived from the syntax element values of the base/reference layer may be used in the inter-layer/inter-component/inter-view prediction.
  • Inter- layer prediction may be defined as prediction in a manner that is dependent on data elements (e.g., sample values or motion vectors) of reference pictures from a different layer than the layer of the current picture (being encoded or decoded).
  • data elements e.g., sample values or motion vectors
  • the available types of inter-layer prediction may for example depend on the coding profile according to which the bitstream or a particular layer within the bitstream is being encoded or, when decoding, the coding profile that the bitstream or a particular layer within the bitstream is indicated to conform to.
  • the available types of inter-layer prediction may depend on the types of scalability or the type of an scalable codec or video coding standard amendment (e.g. SHVC, MV-HEVC, or 3D-HEVC) being used.
  • inter-layer prediction may comprise, but are not limited to, one or more of the following: inter-layer sample prediction, inter-layer motion prediction, inter-layer residual prediction.
  • inter-layer sample prediction at least a subset of the reconstructed sample values of a source picture for inter-layer prediction are used as a reference for predicting sample values of the current picture.
  • inter-layer motion prediction at least a subset of the motion vectors of a source picture for inter-layer prediction are used as a reference for predicting motion vectors of the current picture.
  • predicting information on which reference pictures are associated with the motion vectors is also included in inter-layer motion prediction.
  • the reference indices of reference pictures for the motion vectors may be inter-layer predicted and/or the picture order count or any other identification of a reference picture may be inter-layer predicted.
  • inter- layer motion prediction may also comprise prediction of block coding mode, header information, block partitioning, and/or other similar parameters.
  • coding parameter prediction such as inter-layer prediction of block partitioning, may be regarded as another type of inter-layer prediction.
  • inter-layer residual prediction the prediction error or residual of selected blocks of a source picture for inter-layer prediction is used for predicting the current picture.
  • cross-component inter-layer prediction may be applied, in which a picture of a first type, such as a depth picture, may affect the inter-layer prediction of a picture of a second type, such as a conventional texture picture.
  • a picture of a first type such as a depth picture
  • a second type such as a conventional texture picture.
  • disparity-compensated inter-layer sample value and/or motion prediction may be applied, where the disparity may be at least partially derived from a depth picture.
  • a direct reference layer may be defined as a layer that may be used for inter- layer prediction of another layer for which the layer is the direct reference layer.
  • a direct predicted layer may be defined as a layer for which another layer is a direct reference layer.
  • An indirect reference layer may be defined as a layer that is not a direct reference layer of a second layer but is a direct reference layer of a third layer that is a direct reference layer or indirect reference layer of a direct reference layer of the second layer for which the layer is the indirect reference layer.
  • An indirect predicted layer may be defined as a layer for which another layer is an indirect reference layer.
  • An independent layer may be defined as a layer that does not have direct reference layers. In other words, an independent layer is not predicted using inter-layer prediction.
  • a non-base layer may be defined as any other layer than the base layer, and the base layer may be defined as the lowest layer in the bitstream.
  • An independent non-base layer may be defined as a layer that is both an independent layer and a non-base layer.
  • a source picture for inter-layer prediction may be defined as a decoded picture that either is, or is used in deriving, an inter-layer reference picture that may be used as a reference picture for prediction of the current picture.
  • an inter-layer reference picture is included in an inter-layer reference picture set of the current picture.
  • An inter-layer reference picture may be defined as a reference picture that may be used for inter- layer prediction of the current picture.
  • the inter-layer reference pictures may be treated as long term reference pictures.
  • a source picture for inter- layer prediction may be required to be in the same access unit as the current picture.
  • the source picture for inter-layer prediction and the respective inter-layer reference picture may be identical.
  • inter-layer processing is applied to derive an inter-layer reference picture from the source picture for inter-layer prediction. Examples of such inter-layer processing are described in the next paragraphs.
  • Inter- layer sample prediction may be comprise resampling of the sample array(s) of the source picture for inter-layer prediction.
  • the encoder and/or the decoder may derive a horizontal scale factor (e.g. stored in variable ScaleFactorX) and a vertical scale factor (e.g. stored in variable ScaleF actor Y) for a pair of an enhancement layer and its reference layer for example based on the reference layer location offsets for the pair. If either or both scale factors are not equal to 1 , the source picture for inter-layer prediction may be resampled to generate an inter- layer reference picture for predicting the enhancement layer picture.
  • a horizontal scale factor e.g. stored in variable ScaleFactorX
  • a vertical scale factor e.g. stored in variable ScaleF actor Y
  • the process and/or the filter used for resampling may be pre-defined for example in a coding standard and/or indicated by the encoder in the bitstream (e.g. as an index among pre-defined resampling processes or filters) and/or decoded by the decoder from the bitstream.
  • a different resampling process may be indicated by the encoder and/or decoded by the decoder and/or inferred by the encoder and/or the decoder depending on the values of the scale factor. For example, when both scale factors are less than 1 , a pre-defined downsampling process may be inferred; and when both scale factors are greater than 1 , a pre-defined upsampling process may be inferred.
  • a different resampling process may be indicated by the encoder and/or decoded by the decoder and/or inferred by the encoder and/or the decoder depending on which sample array is processed. For example, a first resampling process may be inferred to be used for luma sample arrays and a second resampling process may be inferred to be used for chroma sample arrays.
  • SHVC enables the use of weighted prediction or a color-mapping process based on a 3D lookup table (LUT) for (but not limited to) color gamut scalability.
  • the 3D LUT approach may be described as follows. The sample value range of each color components may be first split into two ranges, forming up to 2x2x2 octants, and then the luma ranges can be further split up to four parts, resulting into up to 8x2x2 octants. Within each octant, a cross color component linear model is applied to perform color mapping.
  • Color mapping may be considered to involve three steps: First, the octant to which a given reference- layer sample triplet (Y, Cb, Cr) belongs is determined. Second, the sample locations of luma and chroma may be aligned through applying a color component adjustment process. Third, the linear mapping specified for the determined octant is applied. The mapping may have cross-component nature, i.e. an input value of one color component may affect the mapped value of another color component.
  • the input to the resampling process is the picture that has been color-mapped.
  • the color-mapping may (but needs not to) map samples of a first bit-depth to samples of another bit-depth.
  • Inter-layer motion prediction may be realized as follows.
  • a temporal motion vector prediction process such as TMVP of H.265/HEVC, may be used to exploit the redundancy of motion data between different layers. This may be done as follows: when the decoded base- layer picture is upsampled, the motion data of the base-layer picture is also mapped to the resolution of an enhancement layer. If the enhancement layer picture utilizes motion vector prediction from the base layer picture e.g. with a temporal motion vector prediction mechanism such as TMVP of H.265/HEVC, the corresponding motion vector predictor is originated from the mapped base-layer motion field. This way the correlation between the motion data of different layers may be exploited to improve the coding efficiency of a scalable video coder.
  • inter-layer motion prediction may be performed by setting the inter-layer reference picture as the collocated reference picture for TMVP derivation.
  • inter- view reference pictures can be included in the reference picture list(s) of the current picture being coded or decoded.
  • SHVC uses multi- loop decoding operation (unlike the SVC extension of H.264/AVC).
  • SHVC may be considered to use a reference index based approach, i.e. an inter-layer reference picture can be included in a one or more reference picture lists of the current picture being coded or decoded (as described above).
  • the concepts and coding tools of HEVC base layer may be used in SHVC, MV-HEVC, and/or alike.
  • the additional inter-layer prediction tools which employ already coded data (including reconstructed picture samples and motion parameters a.k.a motion information) in reference layer for efficiently coding an enhancement layer, may be integrated to SHVC, MV-HEVC, and/or alike codec.
  • a coding standard or system may refer to a term operation point or alike, which may indicate the scalable layers and/or sub-layers under which the decoding operates and/or may be associated with a sub-bitstream that includes the scalable layers and/or sub-layers being decoded.
  • an operation point is defined as bitstream created from another bitstream by operation of the sub-bitstream extraction process with the another bitstream, a target highest Temporalld, and a target layer identifier list as inputs.
  • the VPS of HEVC specifies layer sets and HRD parameters for these layer sets.
  • a layer set may be used as the target layer identifier list in the sub-bitstream extraction process.
  • a layer set may be defined as set of layers represented within a bitstream created from another bitstream by operation of the sub-bitstream extraction process with the another bitstream, the target highest Temporalld equal to 6, and the target layer identifier list equal to the layer identifier list associated with the layer set as inputs.
  • An output layer may be defined as a layer whose decoded pictures are output by the decoding process.
  • the output layers may depend on which subset of the multi-layer bitstream is decoded.
  • the pictures output by the decoding process may be further processed, e.g. a color space conversion from the YUV color space to RGB may be performed, and they may be displayed. However, further processing and/or displaying may be considered to be processes external of the decoder and/or the decoding process and might not take place.
  • an operation point definition may include a consideration a target output layer set.
  • an operation point may be defined as a bitstream that is created from another bitstream by operation of the sub-bitstream extraction process with the another bitstream, a target highest temporal sub-layer (e.g. a target highest
  • an output operation point may be defined as a bitstream that is created from an input bitstream by operation of the sub-bitstream extraction process with the input bitstream, a target highest Temporalld, and a target layer identifier list as inputs, and that is associated with a set of output layers.
  • An output layer set may be defined as a set of layers consisting of the layers of one of the specified layer sets, where one or more layers in the set of layers are indicated to be output layers.
  • An output layer may be defined as a layer of an output layer set that is output when the decoder and/or the HRD operates using the output layer set as the target output layer set.
  • the variable TargetOlsIdx may specify which output layer set is the target output layer set by setting TargetOlsIdx equal to the index of the output layer set that is the target output layer set.
  • a target output layer set may be defined as the output layer set for which the index is equal to TargetOlsIdx.
  • TargetOlsIdx may be set for example by the HRD and/or may be set by external means, for example by a player or alike through an interface provided by the decoder.
  • an output layer may be defined as a layer of an output layer set that is output when TargetOlsIdx is equal to the index of the output layer set.
  • a sender, a gateway, a client, or alike may select the transmitted layers and/or sublayers of a scalable video bitstream.
  • Terms layer extraction, extraction of layers, or layer down-switching may refer to transmitting fewer layers than what is available in the bitstream received by the sender, gateway, client, or alike.
  • Layer up-switching may refer to transmitting additional layer(s) compared to those transmitted prior to the layer up-switching by the sender, gateway, client, or alike, i.e. restarting the transmission of one or more layers whose transmission was ceased earlier in layer down-switching.
  • the sender, gateway, client, or alike may perform down- and/or up- switching of temporal sub-layers.
  • the sender, gateway client, or alike may also perform both layer and sub-layer down-switching and/or up-switching.
  • Layer and sub-layer down- switching and/or up-switching may be carried out in the same access unit or alike (i.e.
  • encoders can specify the use of alternative output layers within the bitstream and in response to the specified use of alternative output layers decoders output a decoded picture from an alternative output layer in the absence of a picture in an output layer within the same access unit.
  • the alternative output layer set mechanism may be constrained to be used only for output layer sets containing only one output layer, and an output-layer-set-wise flag (alt_output_layer_flag[ olsldx ] in HEVC) may be used for specifying that any direct or indirect reference layer of the output layer may serve as an alternative output layer for the output layer of the output layer set.
  • an output-layer-set-wise flag (alt_output_layer_flag[ olsldx ] in HEVC) may be used for specifying that any direct or indirect reference layer of the output layer may serve as an alternative output layer for the output layer of the output layer set.
  • an output-layer-set-wise flag (alt_output_layer_flag[ olsldx ] in HEVC) may be used for specifying that any direct or indirect reference layer of the output layer may serve as an alternative output layer for the output layer of the output layer set.
  • a sample in according to the sample entry codes defined presently in ISO/IEC 14496-15 (e.g. 'hvcl', 'hevl') consists of a sequence of NAL units without start code, each prefixed by their byte count. The length of the byte count field can be indicated in the sample entry.
  • Internet media types also known as MIME (Multipurpose Internet Mail Extension) types, are used by various applications to identify the type of a resource or a file.
  • MIME types consist of a media type, a subtype, and zero or more optional parameters.
  • MIME is an extension to an email protocol which makes it possible to transmit and receive different kinds of data files on the Internet, for example video and audio, images, software, etc.
  • An internet media type is an identifier used on the Internet to indicate the type of data that a file contains. Such internet media types may also be called as content types.
  • MIME type/subtype combinations exist that can indicate different media formats.
  • Content type information may be included by a transmitting entity in a MIME header at the beginning of a media transmission. A receiving entity thus may need to examine the details of such media content to determine if the specific elements can be rendered given an available set of codecs.
  • the codecs parameter may be considered to comprise a comma-separated list of one or more list items.
  • the list item may comprise a four-character code of the sample entry of the track.
  • a list item may additionally indicate the coding profile (e.g. HEVC Main profile) to which the bitstream contained by the samples of the track conform.
  • the profiles MIME parameter can provide an overall indication, to the receiver, of the specifications with which the content complies. This is an indication of the compatibility of the container format and its contents to some specification.
  • the receiver may be able to work out the extent to which it can handle and render the content by examining to see which of the declared profiles it supports, and what they mean.
  • ISOBMFF file may be specified to comprise a list of the compatible brands included in the file.
  • a uniform resource identifier may be defined as a string of characters used to identify a name of a resource. Such identification enables interaction with representations of the resource over a network, using specific protocols.
  • a URI is defined through a scheme specifying a concrete syntax and associated protocol for the URI.
  • the uniform resource locator (URL) and the uniform resource name (URN) are forms of URI.
  • a URL may be defined as a URI that identifies a web resource and specifies the means of acting upon or obtaining the representation of the resource, specifying both its primary access mechanism and network location.
  • a URN may be defined as a URI that identifies a resource by name in a particular namespace. A URN may be used for identifying a resource without implying its location or how to access it.
  • Hypertext Transfer Protocol has been widely used for the delivery of realtime multimedia content over the Internet, such as in video streaming applications.
  • HTTP Hypertext Transfer Protocol
  • Adaptive HTTP streaming was first standardized in Release 9 of 3rd Generation Partnership Project (3GPP) packet-switched streaming (PSS) service (3GPP TS 26.234
  • the multimedia content may be stored on an HTTP server and may be delivered using HTTP.
  • the content may be stored on the server in two parts:
  • MPD Presentation Description
  • the MDP provides the necessary information for clients to establish a dynamic adaptive streaming over HTTP.
  • the MPD contains information describing media presentation, such as an HTTP- uniform resource locator (URL) of each Segment to make GET Segment request.
  • URL uniform resource locator
  • the DASH client may obtain the MPD e.g. by using HTTP, email, thumb drive, broadcast, or other transport methods.
  • the DASH client may become aware of the program timing, media-content availability, media types, resolutions, minimum and maximum bandwidths, and the existence of various encoded alternatives of multimedia components, accessibility features and required digital rights management (DRM), media-component locations on the network, and other content characteristics. Using this information, the DASH client may select the appropriate encoded alternative and start streaming the content by fetching the segments using e.g. HTTP GET requests. After appropriate buffering to allow for network throughput variations, the client may continue fetching the subsequent segments and also monitor the network bandwidth fluctuations. The client may decide how to adapt to the available bandwidth by fetching segments of different alternatives (with lower or higher bitrates) to maintain an adequate buffer.
  • DRM digital rights management
  • a media presentation consists of a sequence of one or more Periods, each Period contains one or more Groups, each Group contains one or more Adaptation Sets, each
  • Adaptation Sets contains one or more Representations, each Representation consists of one or more Segments.
  • a Representation is one of the alternative choices of the media content or a subset thereof typically differing by the encoding choice, e.g. by bitrate, resolution, language, codec, etc.
  • the Segment contains certain duration of media data, and metadata to decode and present the included media content.
  • a Segment is identified by a URI and can typically be requested by a HTTP GET request.
  • a Segment may be defined as a unit of data associated with an HTTP-URL and optionally a byte range that are specified by an MPD.
  • the DASH MPD complies with Extensible Markup Language (XML) and is therefore specified through elements and attribute as defined in XML.
  • the MPD may be specified using the following conventions: Elements in an XML document may be identified by an upper-case first letter and may appear in bold face as Element. To express that an element Elementl is contained in another element Element2, one may write
  • Element2.Elementl If an element's name consists of two or more combined words, camel- casing may be used, e.g. ImportantElement. Elements may be present either exactly once, or the minimum and maximum occurrence may be defined by ⁇ minOccurs> ... ⁇ maxOccurs>. Attributes in an XML document may be identified by a lower-case first letter as well as they may be preceded by a '@'-sign, e.g. @attribute. To point to a specific attribute @attribute contained in an element Element, one may write Element@attribute. If an attribute's name consists of two or more combined words, camel-casing may be used after the first word, e.g. @veryImportant Attribute. Attributes may have assigned a status in the XML as mandatory (M), optional (O), optional with default value (OD) and conditionally mandatory (CM).
  • M mandatory
  • O optional
  • OD optional with default value
  • an independent representation may be defined as a representation that can be processed independently of any other representations.
  • An independent representation may be understood to comprise an independent bitstream or an independent layer of a bitstream.
  • a dependent representation may be defined as a representation for which Segments from its complementary representations are necessary for presentation and/or decoding of the contained media content components.
  • a dependent representation may be understood to comprise e.g. a predicted layer of a scalable bitstream.
  • a complementary representation may be defined as a representation which complements at least one dependent representation.
  • a complementary representation may be an independent representation or a dependent representation.
  • Dependent Representations may be described by a Representation element that contains a @dependencyld attribute.
  • Dependent Representations can be regarded as regular Representations except that they depend on a set of complementary Representations for decoding and/or presentation.
  • the @dependencyld contains the values of the @id attribute of all the complementary Representations, i.e. Representations that are necessary to present and/or decode the media content components contained in this dependent
  • a media content component or a media component may be defined as one continuous component of the media content with an assigned media component type that can be encoded individually into a media stream.
  • Media content may be defined as one media content period or a contiguous sequence of media content periods.
  • Media content component type may be defined as a single type of media content such as audio, video, or text.
  • a media stream may be defined as an encoded version of a media content component.
  • An Initialization Segment may be defined as a Segment containing metadata that is necessary to present the media streams encapsulated in Media Segments.
  • an Initialization Segment may comprise the Movie Box ('moov') which might not include metadata for any samples, i.e. any metadata for samples is provided in 'moof boxes.
  • a Media Segment contains certain duration of media data for playback at a normal speed, such duration is referred as Media Segment duration or Segment duration.
  • the content producer or service provider may select the Segment duration according to the desired characteristics of the service. For example, a relatively short Segment duration may be used in a live service to achieve a short end-to-end latency. The reason is that Segment duration is typically a lower bound on the end-to-end latency perceived by a DASH client since a Segment is a discrete unit of generating media data for DASH. Content generation is typically done such a manner that a whole Segment of media data is made available for a server.
  • a Segment may be further partitioned into Subsegments e.g. to enable downloading segments in multiple parts. Subsegments may be required to contain complete access units. Subsegments may be indexed by Segment Index box, which contains information to map presentation time range and byte range for each Subsegment.
  • the Segment Index box may also describe subsegments and stream access points in the segment by signaling their durations and byte offsets.
  • a DASH client may use the information obtained from Segment Index box(es) to make a HTTP GET request for a specific Subsegment using byte range HTTP request. If relatively long Segment duration is used, then Subsegments may be used to keep the size of HTTP responses reasonable and flexible for bitrate adaptation.
  • the indexing information of a segment may be put in the single box at the beginning of that segment, or spread among many indexing boxes in the segment. Different methods of spreading are possible, such as hierarchical, daisy chain, and hybrid. This technique may avoid adding a large box at the beginning of the segment and therefore may prevent a possible initial download delay.
  • Sub-Representations are embedded in regular Representations and are described by the SubRepresentation element.
  • SubRepresentation elements are contained in a
  • the SubRepresentation element describes properties of one or several media content components that are embedded in the Representation. It may for example describe the exact properties of an embedded audio component (e.g., codec, sampling rate, etc.), an embedded sub-title (e.g., codec) or it may describe some embedded lower quality video layer (e.g. some lower frame rate, etc.). Sub-Representations and
  • Sub-Representations provide the ability for accessing a lower quality version of the Representation in which they are contained.
  • Sub-Representations for example allow extracting the audio track in a multiplexed Representation or may allow for efficient fast-forward or rewind operations if provided with lower frame rate;
  • the Initialization Segment and/or the Media Segments and/or the Index Segments shall provide sufficient information such that the data can be easily accessed through HTTP partial GET requests. The details on providing such information are defined by the media format in use.
  • the Initialization Segment contains the Level Assignment box.
  • the Subsegment Index box ('ssix') is present for each Subsegment.
  • the attribute @level specifies the level to which the described Sub- Representation is associated to in the Subsegment Index.
  • the information in Representation, Sub-Representation and in the Level Assignment ('leva') box contains information on the assignment of media data to levels. o Media data should have an order such that each level provides an enhancement compared to the lower levels.
  • the SubRepresentation element is solely used to provide a more detailed description for media streams that are embedded in the
  • the ISOBMFF includes the so-called level mechanism to specify subsets of the file.
  • levels can be specified according to temporal sub-layer (e.g., temporal id of SVC or MVC or Temporalld of HEVC).
  • Levels may be announced in the Level Assignment ('leva') box contained in the Movie Extends ('mvex') box. Levels cannot be specified for the initial movie. When the Level Assignment box is present, it applies to all movie fragments subsequent to the initial movie.
  • a fraction is defined to consist of one or more Movie Fragment boxes and the associated Media Data boxes, possibly including only an initial part of the last Media Data Box.
  • data for each level appears contiguously.
  • Data for levels within a fraction appears in increasing order of level value. All data in a fraction shall be assigned to levels.
  • the Level Assignment box provides a mapping from features, such as scalability layers or temporal sublayers, to levels.
  • a feature can be specified through a track, a sub-track within a track, or a sample grouping of a track.
  • the Temporal Level sample grouping may be used to indicate a mapping of the pictures to temporal levels, which are equivalent to temporal sublayers in HEVC. That is, HEVC pictures of a certain Temporalld value may be mapped to the a particular temporal level using the Temporal Level sample grouping (and the same can be repeated for all Temporalld values).
  • the Level Assignment box can then refer to the
  • the Level Assignment box includes the syntax element padding flag.
  • padding flag is equal to 1 indicates that a conforming fraction can be formed by concatenating any positive integer number of levels within a fraction and padding the last Media Data box by zero bytes up to the full size that is indicated in the header of the last Media Data box.
  • padding flag can be set equal to 1 when each fraction contains two or more AVC, SVC, or MVC tracks of the same video bitstream, the samples for each track of a fraction are contiguous and in decoding order in a Media Data box, and the samples of the first AVC, SVC, or MVC level contain extractor NAL units for including the video coding NAL units from the other levels of the same fraction.
  • the Subsegment Index box ('ssix') provides a mapping from levels (as specified by the Level Assignment box) to byte ranges of the indexed subsegment.
  • this box provides a compact index for how the data in a subsegment is ordered according to levels into partial subsegments. It enables a client to easily access data for partial subsegments by downloading ranges of data in the subsegment.
  • each byte in the subsegment is assigned to a level. If the range is not associated with any information in the level assignment, then any level that is not included in the level assignment may be used.
  • Subsegment Index boxes present per each Segment Index box that indexes only leaf subsegments, i.e. that only indexes subsegments but no segment indexes.
  • a Subsegment Index box if any, is the next box after the associated Segment Index box.
  • a Subsegment Index box documents the subsegment that is indicated in the immediately preceding Segment Index box.
  • Each level may be assigned to exactly one partial subsegment, i.e. byte ranges for one level are contiguous.
  • Levels of partial subsegments are assigned by increasing numbers within a subsegment, i.e., samples of a partial subsegment may depend on any samples of preceding partial subsegments in the same subsegment, but not the other way around. For example, each partial subsegment contains samples having an identical temporal sub-layer and partial subsegments appear in increasing temporal sub-layer order within the subsegment.
  • the final Media Data box may be incomplete, that is, less data is accessed than the length indication of the Media Data Box indicates is present.
  • the length of the Media Data box may need adjusting, or padding may be used.
  • the padding flag in the Level Assignment Box indicates whether this missing data can be replaced by zeros. If not, the sample data for samples assigned to levels that are not accessed is not present, and care should be taken
  • Subsegments of the dependent Representations each being preceded by the corresponding Subsegment of each of the complementary Representations in order as provided in the @dependencyld attribute shall represent a conforming Subsegment sequence conforming to the media format as specified in the @mimeType attribute for this dependent Representation.
  • MPEG-DASH defines segment-container formats for both ISOBMFF and MPEG-2 Transport Streams. Other specifications may specify segment formats based on other container formats. For example, a segment format based on Matroska container file format has been proposed and may be summarized as follows. When Matroska files are carried as DASH segments or alike, the association of DASH units and Matroska units may be specified as follows. A subsegment (of DASH) may be are defined as one or more consecutive Clusters of Matroska-encapsulated content. An Initialization Segment of DASH may be required to comprise the EBML header, Segment header (of Matroska), Segment Information (of
  • a Segment Index of DASH may comprise a Cues Element of Matroska.
  • a specific projection for mapping a panoramic image covering 360-degree field-of- view horizontally and 180-degree field-of-view vertically (hence representing a sphere) to a rectangular two-dimensional image plane is known as equirectangular projection.
  • the horizontal coordinate may be considered equivalent to a longitude
  • the vertical coordinate may be considered equivalent to a latitude, with no transformation or scaling applied.
  • panoramic content with 360-degree horizontal field-of-view but with less than 180-degree vertical field-of-view may be considered special cases of equirectangular projection, where the polar areas of the sphere have not been mapped onto the two- dimensional image plane.
  • panoramic may have less than 360-degree horizontal field-of-view and up to 180-degree vertical field-of-view, while otherwise have the characteristics of equirectangular projection format.
  • a panorama such as an equirectangular panorama
  • a stereoscopic panorama format one panorama picture may represent the left view and the other parorama picture (of the same time instant or access unit) may represent the right view.
  • a stereoscopic panorama is displayed on a stereoscopic display arrangement, such as as a virtual reality headset
  • the left- view panorama may be displayed in appropriate viewing angle and field of view to the left eye
  • the right-view panorama may be similarly displayed to the right eye.
  • the stereoscopic viewing may be assumed to happen towards the equator (i.e.
  • cubemap projection format spherical video is projected onto the six faces (a.k.a. sides) of a cube.
  • the cubemap may be generated e.g. by first rendering the spherical scene six times from a viewpoint, with the views defined by an 90 degree view frustum representing each cube face.
  • the cube sides may be frame-packed into the same frame or each cube side may be treated individually (e.g. in encoding). There are many possible orders of locating cube sides onto a frame and/or cube sides may be rotated or mirrored.
  • the frame width and height for frame-packing may be selected to fit the cube sides "tightly" e.g. at 3x2 cube side grid, or may include unused constituent frames e.g. at 4x3 cube side grid.
  • a cubemap can be stereoscopic.
  • a stereoscopic cubemap can e.g. be reached by re- projecting each view of a stereoscopic panorama to the cubemap format.
  • a first track is written (600) into a first container, the first track comprising coded pictures of a first view, wherein the coded pictures of the first view comprise one or more intra random access point (IRAP) pictures.
  • a second track is written (602) into a second container, the second track comprising in-line coded pictures of a second view and comprising, by reference, fully or partially coded data of at least one of said IRAP pictures, wherein at least one of the coded pictures of the second view uses the at least one of said IRAP pictures as a reference for prediction.
  • the second track complies with single-view decoding.
  • Figure 7 depicts an overall characterization of the method, from where it may be concluded that the approach comprises three phases, which may be used together or individually.
  • the phases may be called: i) content encapsulation, ii) transmission/storage, and iii) content decapsulation, decoding, and playback.
  • content encapsulation a coded video bitstream comprising two views is encapsulated into container(s), which may be for example media file(s) or media (sub)segment(s) intended for DASH delivery or alike.
  • container(s) may be for example media file(s) or media (sub)segment(s) intended for DASH delivery or alike.
  • the container(s) are transmitted or made available to a player.
  • the player comprises content decapsulation, decoding, and playback steps.
  • a base- view bitstream is extracted from the container(s) and a pre-constructed second-view bitstream is constructed from the container(s).
  • Two single- view decoding processes such as HEVC Main profile decoding, are then separately used to decode the bitstreams.
  • the output of the decoding may be displayed. Further details of the phases are described below.
  • the content encapsulation phase obtains a coded video bitstream that comprises coded data of a first view (e.g., the left view of a stereoscopic video) and a second view (e.g., the right view of a stereoscopic video).
  • the first view may also be referred to as a base view in the bitstream.
  • the second view is a predicted view in the bitstream, utilizing prediction from the base view in its coding.
  • the coded pictures of the base view are independent of other pictures in the bitstream.
  • the coded pictures of the predicted view may be predicted from a subset of the base-view pictures.
  • the subset of the base-view pictures may, for example, consist of the IRAP pictures or alike of the base view.
  • the subset and all additional base- view pictures needed for decoding the subset are referred to as the inter- view- reference subset of the base view.
  • the inter-layer-reference subset is at least one picture of the base view but does not comprise the base view in its entirety.
  • the coded base-view pictures are encapsulated in a base-view track. I.e., the coded base-view pictures are included in-line in samples of the base-view track.
  • a second- view track is generated by including base-view data by reference into the second- view track.
  • This data included by reference comprises fully or partially the inter- view- reference subset of the base- view pictures from which coded pictures of the predicted view may be predicted.
  • the second-view track also includes, in-line (in some embodiments) or by reference (in other embodiments), coded data of the predicted view.
  • Samples of the second- view track may comprise constructors, such as extractors and in-line constructors.
  • the second- view track is indicated to comply with a single-view decoding process, such as HEVC Main profile decoding.
  • pictures of the inter-view-reference subset are represented by samples of the second-view track that are separate from samples of the predicted view.
  • the timestamps of the second-view track are generated in a manner that a picture (or a sample) of the second- view track that is originally in the same access unit as a picture (or a sample) of the base-view track have identical playback time.
  • the timestamp alignment may be done by decoding timestamps in the container(s), and/or by output timestamps in the container(s), and/or by edit lists or alike in the
  • the second view track is indicated to comply with a single- view format and decoding.
  • the second view is encapsulated and announced to be available for streaming delivery, e.g. for DASH, in a manner that a player perceives it to comply with a single- view format and decoding, such as with HEVC Main profile.
  • the second view may be encapsulated for streaming delivery in a manner that the player can adaptively, e.g. (sub)segment-wise, choose whether the second view is received.
  • Parsing the second- view track comprises resolving the constructors contained in the samples of the second- view track.
  • the parsing of the second- view track results into a pre- constructed bitstream complying with a single- view format and decoding, such as HEVC Main profile.
  • the pre-constructed bitstream can be decoded with one single- view decoding instance.
  • the base-view track is parsed to extract a base- view bitstream, which can be decoded with another single- view decoding instance.
  • the output of the decoding instances may be synchronized for displaying and other display-related processing may also be done, such as color space conversion.
  • Figure 8a illustrates the prediction structure of an MV-HEVC bitstream with two views.
  • the boxes illustrate coded pictures and include the picture type (or equivalent ly the NAL unit type of VCL NAL units of the coded picture) and a relative decoding order (pictures are decoded in increasing order of the value within the box).
  • the output order of the pictures is from left to right.
  • the IRAP pictures are aligned across layers in a manner that whenever there is an IRAP picture in the base layer (a.k.a. base view), there is an IRAP picture in the predicted view too.
  • Pictures with the label IDR may be understood to be of picture type IDR N LP.
  • the predicted view (a.k.a. predicted layer) uses inter-layer prediction only at IRAP pictures.
  • Inter-view prediction (a.k.a. inter-layer prediction in MV- HEVC) is enabled only when the base layer contains an IRAP picture and disabled at other access units.
  • Figure 8b illustrates how the second-view track is generated.
  • the IDR picture from the base view is included by reference into the second- view track (illustrated by the dash-dot line).
  • the picture type of the IDR picture in the predicted view is changed to a trailing picture, for example by using an in-line constructor.
  • the slice segment headers of the pictures in the second- view track may be modified from those in the original MV-HEVC bitstream for example by using an in-line constructor.
  • the slice data of the pictures in the second- view track may be included in-line or by reference to samples of a track containing the predicted view of the original MV-HEVC bitstream. As a result the parsing of the second- view track results into a single-view compliant bitstream, i.e. into an HEVC Main profile bitstream in this case.
  • the embodiments may be used with (but are not limited to) the following prediction structures:
  • IRAP pictures are aligned across views in a manner that if one view contains an IRAP picture in an access unit, the other view also contains an IRAP picture in the same access unit. Alignment of the picture across layers may be indicated by the
  • Inter-view prediction is enabled only in IRAP access units and disabled at other access units, which can be indicated with the syntax element max_tid_il_ref_pics_plusl .
  • the inter- view-reference subset consists of the IRAP pictures of the base layer.
  • - IRAP pictures are aligned across layers in a manner that whenever there is an IRAP picture in the base view, there is an IRAP picture in the predicted view too.
  • Inter-view prediction is enabled in access units with an IRAP picture in the base view and disabled at other access units, which can be indicated with the syntax element max_tid_il_ref_pics_plusl .
  • the inter- view-reference subset consists of the IRAP pictures of the base layer.
  • Inter-view prediction is enabled in access units having Temporalld less than or equal to a certain (but not the highest) Temporalld value and disabled at other Temporalld values, which can be indicated with the syntax element max_tid_il_ref_pics_plusl .
  • the inter-view-reference subset consists of the pictures of the base layer having Temporalld less than or equal to that certain Temporalld value.
  • the encoding of the inter-view-reference subset in the base view may be performed in a manner that each picture in the inter- view-reference subset marks the previous picture in the inter- view- reference subset as a long-term reference picture, e.g. by including it in the long-term subset of the reference picture set.
  • a bitstream comprising a plurality of views is encoded, and inter-view prediction is used in a subset of access units as described above.
  • Signalling from the encoding process e.g. within the encoded bitstream and/or as metadata external from the bitstream is provided.
  • the signalling may be provided in supplemental enhancement information.
  • the signalling may include a coding property characterizing the pre-constructed second-view bitstream.
  • the coding property may comprise, for example, one or more of the following: a coding format, a profile of a standard, a level of a standard, profile compatibility information, at least one resource usage constraint, and/or at least one hypothetical reference decoder parameter (such as the number of picture storage buffers in the decoded picture buffer).
  • the content encapsulation phase parses the signalling described above.
  • the content encapsulation phase creates syntax structures, such as parameter sets, to be included in-line in the second- view track, at least partially based on the signalling.
  • inter-layer prediction provides a significant compression gain.
  • the MV-HEVC compression as described in Figures 8a and 8b provided from 8.1 % to 29.5 % bitrate reduction (and on average about 20.2 % bitrate reduction) compared to frame packing (when about 1 -second IDR picture interval was used) for a stereoscopic equirectangular panorama test set.
  • the use of inter-layer prediction only at IRAP pictures enables the decoding using H.265/HEVC Main profile decoders.
  • a constructor is a set of instructions that, when executed, results into a valid piece of sample data according to the underlying sample format.
  • An extractor is a constructor that, when executed, copies the sample data of an indicated byte range of an indicated sample of an indicated track. Inclusion by reference may be defined as an extractor or alike that, when executed, copies the sample data of an indicated byte range of an indicated sample of an indicated track.
  • An in-line constructor is a constructor that, when executed, returns the sample data that it contains.
  • an in-line constructor may comprise a set of instructions for rewriting a new slice header.
  • the phrase in-line may be used to indicate coded data that is included in the sample of a track.
  • a NAL-unit-like structure refers to a structure with the properties of a NAL unit except that start code emulation prevention is not performed.
  • a pre-constructed bitstream may be defined as a bitstream that has been constructed from another bitstream.
  • a pre-constructed view may be defined as a coded view that has been constructed from a view of another bitstream.
  • a pre-constructed second- view bitstream in embodiments is a view that has been be constructed from a predicted view of a multiview bitstream and conforms to a single- view coding format and/or coding profile.
  • a pre- constructed track may be defined as a track comprising samples of a pre-constructed bitstream or a pre-constructed view.
  • the extractor structure is meant for extracting one or more entire NAL units.
  • extracting partial (not entire) NAL unit(s) may be needed, which may be achieved by an extractor constructor, as defined above.
  • a NAL-unit-like structure may be defined to comprise constructors whose execution results into one or more entire NAL units.. This feature can be achieved with the following changes in the extractor structure of ISO/IEC 14496-15, but it needs to be understood that embodiments are not limited to this syntax or semantics:
  • track ref index indicates the track from where data is extracted
  • sample offset indicates the sample from where data is extracted
  • data offset indicates an offset within the sample starting from which the data is extracted
  • data length indicates the number of bytes to be extracted.
  • the NALUnitHeader structure contains a NAL unit header.
  • InlineNALUnitData structure contains the data bytes to be included in the constructed NAL unit.
  • length is the number of bytes to be included in the constructed NAL unit
  • inline data is the data bytes to be included in the constructed NAL unit.
  • extractors of HEVC are re-defined so that they can be constructed from more than one extent.
  • An extent can either be ExtractorPayload or InlineNALUnitData..
  • the syntax may be as the following:
  • NALUnitConstructor structure is specified. Resolving NALUnitConstructor results into one or more entire NAL units.
  • NALUnitHeader The semantics of NALUnitHeader are identical to those of Extractor except that another nal unit type value is used, e.g. nal unit type equal to 50 is used.
  • the cost of the change caused by the first option compared to conventional use of extractors that extract one or more entire NAL units is one additional byte. Since this cost is moderate, the first option may be preferred over the second option of a separate
  • nal unit extent type 0 specifies that the next extent is ExtractorPayload.
  • nal unit extent type 1 specifies that the extent is
  • InlineNALUnitData Values greater than 1 are reserved.
  • the resolving of the proposed extractor or NAL unit constructor structure may be required to be supported in players supporting certain sample entry four-character code(s), such as 'hvc2' and 'hev2'.
  • a second- view track is generated including proposed extractor or NAL unit constructor structure(s), which selectively extract a coded data of the inter-view- reference subset from the base-view track (e.g. with sample entry code 'hvcl' or 'hevl').
  • the second-view track may have a sample entry code, such as 'hvc2' or 'hev2', that indicates the underlying coding format, such as HEVC, and the use of extractor or NAL unit constructor structure.
  • a player determines to parse, decode and play a second-view track, e.g. marked with 'hvc2' or 'hev2' sample entry code.
  • the player resolves or executes the constructors included in the samples of the track to obtain a bitstream compliant with single- view decoding.
  • the player then decodes bitstream with a single- view decoding process, such as the HEVC Main profile decoding process.
  • the base view is included in-line in the base- view track and the predicted view is also included in-line in the base- view track. Coded data of the inter-view- reference subset of the base view and the predicted view are included by reference into the second-view track.
  • the base view is included in-line in the base- view track and the predicted view is included in-line in another track, referred to as the predicted-view track. Coded data of the inter- view-reference subset of the base view and the predicted view are included by reference into the second- view track.
  • FIG. 9a This file structure is illustrated in Figure 9a, where the first sample of the second- view track obtains a reference from the IDR picture of the base- view track and the following samples of the second- view track obtain reference from the pictures of the predicted- view track.
  • the picture of the second- view track are provided with instruction sets, i.e. a constructor operator ("Constr"), for obtaining the sample data of each picture.
  • Figure 9b shows an example of a constructor operator.
  • the predicted-view track and the second-view track are indicated to be alternatives to each other, i.e. indicated to represent the same content.
  • this can be done by assigning the tracks with the same alternate group value in the
  • TrackHeaderBox In DASH, this can be done e.g. by forming a first Representation from the predicted- view track and a second Representation from the second- view track, both including a majority of the coded data of the predicted view in-line, and by including the first
  • Figure 10 presents a block diagram that corresponds to the encapsulation embodiments above.
  • Figure shows the generation of the base-view track and the second- view track from an input bitstream, which in this case is a constrained MV-HEVC bitstream in which inter-view prediction may have been constrained e.g. as illustrated in Figure 8a.
  • the generation of a predicted- view track or the inclusion of the predicted view into the base- view track is not illustrated in Figure 10.
  • the tracks are included in a bitstream as a container file.
  • container file could be generalized to any type of container(s), including media (sub)segment(s).
  • the base-view is extracted and the pre- constructed second- view is parsed by resolving the constructors of the second- view track.
  • Both the base- view bitstream and the pre-constructed second- view bitstream are decodable by a HEVC Main profile decoder instance.
  • the base view and the predicted view are in the base- view track.
  • the base- view track and the second- view track are contained in the same Representation.
  • the data in MediaDataBoxes of each (sub)segment is ordered in track order (base-view track, followed by second- view track).
  • Sub-representation and levels are used to indicate a MIME type separately to the second-view track.
  • the base- view track contains the base view and the predicted- view track contains the predicted view.
  • the base- view track can be contained in a first Representation.
  • the predicted- view track and the second- view track are contained in a second Representation.
  • Representation is ordered in track order (predicted- view track, followed by the second- view track). Sub-representation and levels are used to indicate a MIME type separately to the second-view track.
  • the MIME type of the second Representation can indicate the HEVC Main profile, e.g. for broader support in players compared to the Multiview Main profile.
  • the second Representation can be indicated to depend on the first Representation, e.g. by using the @dependencyld attribute of MPEG-DASH.
  • the second-view can be pre-constructed for example in one of the following ways:
  • the uncompressed second view is encoded so that the encoder output is the pre- constructed second view.
  • the encoder may input the decoded interview-reference subset, or may input and decode the coded inter- view-reference subset, or may reproduce inter-view-reference subset identically compared to the base view coding.
  • the encoder may use an identical input configuration for the inter- view-reference subset when coding the second view bitstream than when coding the base view bitstream.
  • a container including a second- view track, as described above, is parsed into a pre- constructed second view.
  • a multiview bitstream is processed with a process similar to second-view track
  • the pre-constructed second- view bitstream is provided as input to content encapsulation.
  • This input bitstream may either include the inter- view-reference subset, may include references to the inter- view-reference subset, or may implicitly assume the
  • the inter-view reference subset e.g. for pictures with certain picture type, e.g. IRAP pictures, and/or for pictures with certain Temporalld.
  • the base- view bitstream or the original multiview bitstream is given as input for content encapsulation.
  • Figure 12 illustrates the above embodiment.
  • the base- view bitstream is encapsulated into the base- view track as described in other embodiments.
  • the second- view track is created by including in-line the coded pictures belonging to the second view.
  • the inter-view-reference subset is included by reference into the second- view track.
  • the parsing of the container(s) is performed similarly to other embodiments.
  • the second- view bitstream is constructed by parsing the second- view track. This includes including the inter-view-reference subset into the second- view bitstream as instructed by the constructors of the second- view track.
  • a predicted-view track is constructed from the second-view track. Coded data of the second view is included by reference into the predicted- view track. This is illustrated in Figure 13, which also illustrates the second- view track as described in embodiments above. Compared to the file structure of Figure 9a, herein the samples of the predicted- view track obtain reference starting from the second picture of the second- view track (IDR picture excluded).
  • the predicted- view track may be indicated to conform to a multi-view coding profile, such as the Multiview Main profile of HEVC.
  • Frame packing arrangement SEI messages have been defined for H.264/AVC and HEVC.
  • frame_packing_arrangement_type equal to 5 in the frame packing arrangement SEI message of H.264/AVC and HEVC indicates a temporal frame packing (a.k.a. temporal interleaving frame arrangement) wherein every other coded picture is from a sequence of first constituent pictures (e.g. a first view) and the remaining coded pictures are from a sequence of second constituent pictures (e.g. a second view).
  • the frame packing arrangement SEI message also contains indications whether the first constituent pictures are self-contained and whether the second constituent pictures are self-contained.
  • first or second constituent picture are not self-contained in temporal frame packing, there are no indications in the frame packing arrangement SEI message of H.264/AVC or HEVC whether or how the prediction from first constituent picture to second constituent pictures and/or vice versa is constrained.
  • the pre-constructed second view is obtained from a temporal interleaved frame packing bitstream.
  • a temporal interleaved frame packing bitstream is presented in Figure 14a. It is noted that all the coded pictures of the bitstream belong to the same layer, even though for illustration purposes pictures of different views are in different vertical clusters. As earlier, the decoding output order runs from left to right, and the value within the boxes indicates the decoding order.
  • the first view is coded independently of the second view so that the first view sub- bitstream can be extracted from the bitstream containing both views.
  • the second view may be predicted from an inter-view-reference subset of the first view.
  • prediction from the first view (which may be regarded as the base view) to the second view (which may be regarded as the predicted view) may take place only when the first view has an IRAP picture and is disabled otherwise.
  • Other constraints for predicting between views may alternatively be used, as described earlier.
  • an inter-view-reference subset is concluded. From a coded bitstream this conclusion may be done for example by investigating structure of pictures (SOP) SEI message(s) of HEVC, if any, or reference picture sets in use.
  • the inter-view-reference subset may be provided as configuration input or alike to the content encapsulation.
  • the base- view bitstream to be encapsulated into the base-view track is considered to contain only the first view pictures.
  • the embodiment may follow any embodiment disclosed as options for encapsulation of a pre-constructed second view.
  • a full-sequence track instead of an embodiment to construct a predicted- view track, there may be an embodiment for a full-sequence track.
  • the full-sequence track is constructed by reference from the base-view track and from the second- view track. Coded data of the base-track and the second- view track is included by reference into the full-picture track.
  • the full-picture track represents the original temporal interleaved frame packing bitstream.
  • Figure 14b illustrates the samples in the second- view track, where the IDR picture of first (base)-view track has been constructed to the beginning of the second-view track.
  • temporal interleaved frame packing As described above.
  • the base view can be streamed separately from the predicted view, hence giving more capability for bitrate adaptation.
  • the temporal interleaved framed packing is indicated with an SEI message, which are optional for decoders to process.
  • some legacy players may display the decoding output without consideration of the frame packing, which will cause rapidly flickering picture content (i.e. useless displayed sequence).
  • legacy 2D players can in any case play the base-view track, i.e. the 2D content.
  • higher picture rates may be achieved in decoding, particularly with hardware decoding.
  • embodiments can be similarly realized with other types of temporal interleaving patterns.
  • more than two views can be temporally interleaved into a bitstream used as input to the method.
  • N pictures of a first view can be consecutive in a bitstream, followed by N pictures of a second view, and this pattern may be repeated in the bitstream used as input to the method.
  • the method may be applied to type of temporal interleaving as long as the mapping of a coded picture to a view can be concluded e.g. based on indications included in the bitstream.
  • the parameter sets of the second-view track are included in-line. Parameter sets may be included e.g. in the sample entry or entries of the second-view track and/or in sample(s) of the second view track.
  • the second-view is generated with in-line constructors for NAL unit headers for VCL NAL units of the pictures of the predicted view.
  • the NAL unit header may otherwise be the same as in the corresponding NAL unit header in the predicted view, but nuh layer id is set equal to 0 and nal unit type indicating an IRAP picture may be changed to indicate a trailing picture.
  • the slice segment headers of a picture following, in decoding order, a picture in the inter-view-reference subset in the second- view track are included in- line in the second- view track.
  • the slice segment header(s) may be modified compared to the corresponding slice segment header(s) of the predicted view to mark the preceding picture as a long-term reference picture.
  • the marking of the preceding picture as a long-term picture causes its handling similarly to an inter-layer reference picture in MV-HEVC.
  • the marking can be done by including the preceding picture, originating from the base view, in the long- term subset RefPicSetLtCurr in the slice segment header(s) of the second- view track picture.
  • the slice segment header(s) can be modified to contain num_long_term_pics equal to 1 , poc_lsb_lt[ 0 ] equal to 0 (since the POC of the IDR picture is 0), used_by_curr_pic_lt_flag[ 0 ] equal to 1, and delta_poc_msb_present_flag[ 0 ] equal to 0.
  • the SPS(s) can be modified to contain a long-term reference picture set with equivalent information.
  • pictures of the inter- view-reference subset in the second- view track are marked not to be output. This may be done through file format means and/or through video coding bitstream means.
  • marking a sample of a track as hidden or non-output sample may be done by assigning it a composition timestamp that is less than the smallest composition timestamp used for displaying.
  • output_flag_present_flag 1 may be included and used in the second- view track.
  • output flag may be set equal to 0 in each slice segment header of each picture of the inter-view-reference subset in the second- view track.
  • the picture order count values coded in slice segment header(s) of the second-view track and/or in the constructed predicted-view track may be changed compared to their original values. This may be done to obey constraints on POC values, e.g. as specified in a coding standard such as HEVC.
  • FIG. 15 Another embodiment is illustrated in Figure 15 .
  • a base view e.g. the left view
  • a predicted view is like-wise coded with motion- constrained tile sets.
  • the boundaries of the motion-constrained tile sets may be aligned between the views as illustrated in the figure (but generally need not be aligned).
  • the tile sets in the predicted view are also inter-layer constrained so that inter-layer prediction uses sample values only within the respective tile set of the base view.
  • the white rectangles illustrate the tile boundaries and encoding has been done in a manner that each tile forms its own motion-constrained tile set.
  • Inter-view prediction is constrained as in other embodiments, e.g. inter-view prediction may only take place from an IRAP picture of the base view.
  • instructions may be included in tile set tracks for extracting a motion-constrained tile set.
  • instructions on tile set tracks may be combined with the instructions on the second- view track. That enables creation of a track that extracts a motion-constrained tile set from both views of a multiview bitstream and creates a single- view bitstream out of the multiview tile set bitstream.
  • a constructed tile set track is tile set track, e.g. a track according to ISOBMFF, containing constructors that, when executed, result into a tile set bitstream.
  • bitstream ⁇ is a tile set ⁇ track
  • optionB ⁇ illustrates alternatives, i.e. either optionA or optionB, which is selected consistently in all selections.
  • a full-picture-compliant tile set track can be played as with any full-picture track using the parsing and decoding process of full-picture tracks.
  • a full-picture-compliant bitstream can be decoded as with any full-picture bitstream using the decoding process of full- picture bitstreams.
  • a full-picture track is a track representing an original bitstream (including all its tiles).
  • a pre-constructed tile set track is a tile set track containing the sample data in-line.
  • a tile set bitstream is a bitstream that contains a tile set of an original bitstream but not representing the entire original bitstream.
  • a tile set track is a track representing a tile set of an original bitstream but not representing the entire original bitstream.
  • tile set track/bitstream construction phase one or more tile set tracks or bitstreams are constructed from the base view.
  • One or more tile set tracks or bitstreams are constructed from the predicted view.
  • the resulting tile set tracks and bitstream are full-picture-compliant. For example, when the base view complies with HEVC Main profile and the predicted view complies with HEVC Multiview Main profile, the base and predicted views in the resulting tile set tracks and bitstream also comply with HEVC Main profile and HEVC Multiview Main profile, respectively.
  • the base view part of the tile set track or bitstream are extracted unless already done in the previous phase.
  • the constructed tile set track or bitstream of the predicted view is processed to be single- view profile compliant as described in other embodiments.
  • the outputs of the embodiment are a base- view full-picture-compliant tile set track or bitstream and a second- view full-picture-compliant tile set track or bitstream. Both full- picture-compliant tile set tracks or bitstreams are decodable, as such, by a standard video decoder, such as H.265/HEVC decoder. Alternatively, the output may be instructions to construct base-view and second- view full-picture-compliant tile set tracks or bitstreams.
  • the phases of the embodiment may be performed in opposite order, meaning that the order of tile set track/bitstream construction and rewriting the predicted layer to be a single- view profile bitstream may be reversed.
  • first a single- view bitstream (of full pictures) may be generated and then a single-view tile set bitstream may be generated.
  • the phases of the embodiment may be combined essentially into one operation.
  • a same track may be generated to extract tile sets of a predicted view and to include inter- view reference subset by reference.
  • the same track or sample(s) may perform both constructing a tile set and rewriting a multiview bitstream to be single-view bitstream.
  • start code emulation and start code emulation prevention handling may need to be taken into account in some embodiments.
  • start code emulation may occur.
  • start code emulation may occur.
  • a false start code emulation prevention syntax element may occur. For example, when constructing a tile set bitstream from tiles that are non-consecutive in the full-picture bitstream or when adding data into the tile set bitstream that was not present in the full-picture bitstream (e.g. adding slice segment headers), a false start code emulation prevention syntax element may occur. When a sequence of three bytes in the tile set bitstream contains bytes from different origin (e.g.
  • a decoder falsely concludes that the last byte of the three bytes is an emulation prevention byte. Hence, care should be taken to avoid false start code emulation prevention means in these cases.
  • start code emulation prevention syntax elements e.g.
  • emulation_prevention_three_byte syntax elements in HEVC are removed from the coded video data (e.g. VCL NAL units in HEVC) of an input bitstream, resulting into a processed input bitstream.
  • An intermediate bitstream is then constructed from the processed input bitstream, e.g. as described in other embodiments. Start code emulation prevention syntax elements are added to the intermediate bitstream to form an output bitstream or view according some embodiments.
  • start code emulation prevention syntax that is needed to be added in the output bitstream, as concluded by above embodiment(s), is included in-line in a track representing the output bitstream.
  • a coded video bitstream comprises one or more views or layers and is encapsulated in a content encapsulation phase into a track, here referred to as a byte stream track, comprising samples where the byte stream format is in use rather than length-prefixed NAL units.
  • a second track conforming to a sample format comprising length-prefixed NAL units is formed.
  • coded data from the byte stream track is included by reference, excluding start codes.
  • Allowing start codes in the file makes creation of a file from MPEG-2 TS or other stream-oriented formats easier. It is convenient to store a bitstream as such in the byte stream format (e.g. Annex B of HEVC) within a MediaDataBox or in an external file rather than requiring the removal of start codes and the addition of length-prefixing, which can cause a large number of byte-range copying or moving operations. Moreover, byte stream oriented hypothetical reference decoder parameters may be indicated for the byte stream track.
  • the byte stream format e.g. Annex B of HEVC
  • a specific four-character code such as 'hesl', is defined for start- code-prefixed sample format in the byte stream track.
  • the specifications of and implied by the specific four-character code are identical to those of the respective sample format for length- prefixed NAL units, e.g. 'hevl' in case of HEVC, except that NAL units in the sample format are start-code-prefixed rather than length-prefixed. It may be required that aggregators and extractors are disallowed in byte stream tracks.
  • a coded video bitstream comprises a base layer and an independent non-base layer.
  • a first track is written into a first container, the first track comprising coded pictures of the base layer.
  • a second track is written into a second container, the second track comprising coded pictures of the non-base layer.
  • a third track is written into a third container, the third track comprising in-line elementary unit headers (NAL unit headers) and comprising, by reference, fully or partially coded data of the second track.
  • NAL unit headers in-line elementary unit headers
  • the in-line elementary unit headers may be identical to those of the independent non-base layer, but the layer identifier may indicate a base layer (e.g.
  • nuh layer id 0 in HEVC
  • data included by reference may comprise the NAL unit payloads.
  • the third track may be indicated to conform to a single-layer coding profile, such as HEVC Main profile.
  • the first, second, and third container may for example be the same file.
  • a coded video bitstream comprises a base layer and an independent non-base layer.
  • a first track is written into a first container, the first track comprising coded pictures of the base layer.
  • a third track is written into a third container, the third track comprising in-line elementary unit headers (NAL unit headers) and comprising, also in-line, fully or partially coded data, such as NAL unit payloads, of the independent non-base layer.
  • NAL unit headers in-line elementary unit headers
  • the in-line elementary unit headers may be identical to those of the independent non-base layer, but the layer identifier may indicate a base layer (e.g.
  • the third track may be indicated to conform to a single- layer coding profile, such as HEVC Main profile.
  • a second track may be written into a second container, including in-line elementary unit headers, such as NAL unit headers, of the independent non-base layer, and including by reference fully or partially coded data of the third track, such as the NAL unit payloads.
  • the first, second, and third container may for example be the same file.
  • Figure 16 shows a block diagram of a video decoder suitable for employing embodiments of the invention.
  • Figure 15 depicts a structure of a two-layer decoder, but it would be appreciated that the decoding operations may similarly be employed in a single- layer decoder.
  • the video decoder 550 comprises a first decoder section 552 for base view components and a second decoder section 554 for non-base view components.
  • Block 556 illustrates a demultiplexer for delivering information regarding base view components to the first decoder section 552 and for delivering information regarding non-base view components to the second decoder section 554.
  • Reference P'n stands for a predicted representation of an image block.
  • Reference D'n stands for a reconstructed prediction error signal.
  • Blocks 704, 804 illustrate preliminary reconstructed images (I'n).
  • Reference R'n stands for a final reconstructed image.
  • Blocks 703, 803 illustrate inverse transform ( 1 ).
  • Blocks 702, 802 illustrate inverse quantization (Q 1 ).
  • Blocks 701, 801 illustrate entropy decoding (E 1 ).
  • Blocks 705, 805 illustrate a reference frame memory (RFM).
  • Blocks 706, 806 illustrate prediction (P) (either inter prediction or intra prediction).
  • Blocks 707, 807 illustrate filtering (F).
  • Blocks 708, 808 may be used to combine decoded prediction error information with predicted base view/non-base view components to obtain the preliminary reconstructed images (I'n).
  • Preliminary reconstructed and filtered base view images may be output 709 from the first decoder section 552 and preliminary reconstructed and filtered base view images may be output 809 from the first decoder section 554.
  • FIG. 17 is a graphical representation of an example multimedia communication system within which various embodiments may be implemented.
  • a data source 1510 provides a source signal in an analog, uncompressed digital, or compressed digital format, or any combination of these formats.
  • An encoder 1520 may include or be connected with a pre- processing, such as data format conversion and/or filtering of the source signal. The encoder 1520 encodes the source signal into a coded media bitstream.
  • bitstream to be decoded may be received directly or indirectly from a remote device located within virtually any type of network. Additionally, the bitstream may be received from local hardware or software.
  • the encoder 1520 may be capable of encoding more than one media type, such as audio and video, or more than one encoder 1520 may be required to code different media types of the source signal.
  • the encoder 1520 may also get synthetically produced input, such as graphics and text, or it may be capable of producing coded bitstreams of synthetic media. In the following, only processing of one coded media bitstream of one media type is considered to simplify the description. It should be noted, however, that typically real-time broadcast services comprise several streams (typically at least one audio, video and text sub-titling stream).
  • the system may include many encoders, but in the figure only one encoder 1520 is represented to simplify the description without a lack of generality. It should be further understood that, although text and examples contained herein may specifically describe an encoding process, one skilled in the art would understand that the same concepts and principles also apply to the corresponding decoding process and vice versa.
  • the coded media bitstream may be transferred to a storage 1530.
  • the storage 1530 may comprise any type of mass memory to store the coded media bitstream.
  • the format of the coded media bitstream in the storage 1530 may be an elementary self-contained bitstream format, or one or more coded media bitstreams may be encapsulated into a container file, or the coded media bitstream may be encapsulated into a Segment format suitable for DASH (or a similar streaming system) and stored as a sequence of Segments. If one or more media bitstreams are encapsulated in a container file, a file generator (not shown in the figure) may be used to store the one more media bitstreams in the file and create file format metadata, which may also be stored in the file.
  • the encoder 1520 or the storage 1530 may comprise the file generator, or the file generator is operationally attached to either the encoder 1520 or the storage 1530.
  • Some systems operate "live", i.e. omit storage and transfer coded media bitstream from the encoder 1520 directly to the sender 1540.
  • the coded media bitstream may then be transferred to the sender 1540, also referred to as the server, on a need basis.
  • the format used in the transmission may be an elementary self-contained bitstream format, a packet stream format, a Segment format suitable for DASH (or a similar streaming system), or one or more coded media bitstreams may be encapsulated into a container file.
  • the encoder 1520, the storage 1530, and the server 1540 may reside in the same physical device or they may be included in separate devices.
  • the encoder 1520 and server 1540 may operate with live real-time content, in which case the coded media bitstream is typically not stored
  • the server 1540 sends the coded media bitstream using a communication protocol stack.
  • the stack may include but is not limited to one or more of Real-Time Transport Protocol (RTP), User Datagram Protocol (UDP), Hypertext Transfer Protocol (HTTP), Transmission Control Protocol (TCP), and Internet Protocol (IP).
  • RTP Real-Time Transport Protocol
  • UDP User Datagram Protocol
  • HTTP Hypertext Transfer Protocol
  • TCP Transmission Control Protocol
  • IP Internet Protocol
  • the server 1540 encapsulates the coded media bitstream into packets.
  • RTP Real-Time Transport Protocol
  • UDP User Datagram Protocol
  • HTTP Hypertext Transfer Protocol
  • TCP Transmission Control Protocol
  • IP Internet Protocol
  • the sender 1540 may comprise or be operationally attached to a "sending file parser" (not shown in the figure).
  • a sending file parser locates appropriate parts of the coded media bitstream to be conveyed over the communication protocol.
  • the sending file parser may also help in creating the correct format for the communication protocol, such as packet headers and payloads.
  • the multimedia container file may contain encapsulation instructions, such as hint tracks in the ISOBMFF, for
  • the server 1540 may or may not be connected to a gateway 1550 through a communication network, which may e.g. be a combination of a CDN, the Internet and/or one or more access networks.
  • the gateway may also or alternatively be referred to as a middle- box.
  • the gateway may be an edge server (of a CDN) or a web proxy. It is noted that the system may generally comprise any number gateways or alike, but for the sake of simplicity, the following description only considers one gateway 1550.
  • the gateway 1550 may perform different types of functions, such as translation of a packet stream according to one communication protocol stack to another communication protocol stack, merging and forking of data streams, and manipulation of data stream according to the downlink and/or receiver capabilities, such as controlling the bit rate of the forwarded stream according to prevailing downlink network conditions.
  • the system includes one or more receivers 1560, typically capable of receiving, demodulating, and de-capsulating the transmitted signal into a coded media bitstream.
  • the coded media bitstream may be transferred to a recording storage 1570.
  • the recording storage 1570 may comprise any type of mass memory to store the coded media bitstream.
  • the recording storage 1570 may alternatively or additively comprise computation memory, such as random access memory.
  • the format of the coded media bitstream in the recording storage 1570 may be an elementary self-contained bitstream format, or one or more coded media bitstreams may be encapsulated into a container file.
  • a container file is typically used and the receiver 1560 comprises or is attached to a container file generator producing a container file from input streams.
  • Some systems operate "live,” i.e. omit the recording storage 1570 and transfer coded media bitstream from the receiver 1560 directly to the decoder 1580. In some systems, only the most recent part of the recorded stream, e.g., the most recent 10-minute excerption of the recorded stream, is maintained in the recording storage 1570, while any earlier recorded data is discarded from the recording storage 1570.
  • the coded media bitstream may be transferred from the recording storage 1570 to the decoder 1580. If there are many coded media bitstreams, such as an audio stream and a video stream, associated with each other and encapsulated into a container file or a single media bitstream is encapsulated in a container file e.g. for easier access, a file parser (not shown in the figure) is used to decapsulate each coded media bitstream from the container file.
  • the recording storage 1570 or a decoder 1580 may comprise the file parser, or the file parser is attached to either recording storage 1570 or the decoder 1580. It should also be noted that the system may include many decoders, but here only one decoder 1570 is discussed to simplify the description without a lack of generality
  • the coded media bitstream may be processed further by a decoder 1570, whose output is one or more uncompressed media streams.
  • a renderer 1590 may reproduce the uncompressed media streams with a loudspeaker or a display, for example.
  • recording storage 1570, decoder 1570, and renderer 1590 may reside in the same physical device or they may be included in separate devices.
  • a sender 1540 and/or a gateway 1550 may be configured to perform switching between different representations e.g. for view switching, bitrate adaptation and/or fast startup, and/or a sender 1540 and/or a gateway 1550 may be configured to select the transmitted representation(s). Switching between different representations may take place for multiple reasons, such as to respond to requests of the receiver 1560 or prevailing conditions, such as throughput, of the network over which the bitstream is conveyed.
  • a request from the receiver can be, e.g., a request for a Segment or a Subsegment from a different representation than earlier, a request for a change of transmitted scalability layers and/or sub-layers, or a change of a rendering device having different capabilities compared to the previous one.
  • a request for a Segment may be an HTTP GET request.
  • a request for a Subsegment may be an HTTP GET request with a byte range.
  • bitrate adjustment or bitrate adaptation may be used for example for providing so-called fast start-up in streaming services, where the bitrate of the transmitted stream is lower than the channel bitrate after starting or random-accessing the streaming in order to start playback immediately and to achieve a buffer occupancy level that tolerates occasional packet delays and/or
  • Bitrate adaptation may include multiple representation or layer up-switching and representation or layer down-switching operations taking place in various orders.
  • a decoder 1580 may be configured to perform switching between different representations e.g. for view switching, bitrate adaptation and/or fast start-up, and/or a decoder 1580 may be configured to select the transmitted representation(s). Switching between different representations may take place for multiple reasons, such as to achieve faster decoding operation or to adapt the transmitted bitstream, e.g. in terms of bitrate, to prevailing conditions, such as throughput, of the network over which the bitstream is conveyed. Faster decoding operation might be needed for example if the device including the decoder 580 is multi-tasking and uses computing resources for other purposes than decoding the scalable video bitstream.
  • faster decoding operation might be needed when content is played back at a faster pace than the normal playback speed, e.g. twice or three times faster than conventional real-time playback rate.
  • the speed of decoder operation may be changed during the decoding or playback for example as response to changing from a fast-forward play from normal playback rate or vice versa, and consequently multiple layer up-switching and layer down- switching operations may take place in various orders.
  • slice segment has been described with reference to the term slice segment. It needs to be understood that embodiments apply similarly to other similar picture partitioning units.
  • some coding schemes may not include the concept of slice segments but may have the concept of slices, as defined in video coding standards including H.264/AVC and HEVC, in which case embodiments apply to slices.
  • a multiview coded video bitstream comprises a base view, a first predicted view that may be predicted from the base view, and a second predicted view that may be predicted from the first predicted view.
  • the selection of picture types has been constrained in encoding in a manner that IRAP pictures are aligned across layers.
  • the inter- view prediction has been constrained so that it may only take place between IRAP pictures.
  • a third-view track that has similar properties as the second- view track in embodiments above can be generated in the content encapsulation phase by including by reference the coded data of the IRAP pictures of the first predicted view and the base view (when they are used as reference for inter-view prediction) and the coded data of the third view either in-line or by reference to a track containing the third view.
  • embodiments have been described in relation to inter-view prediction. It needs to be understood that embodiments similarly apply to quality scalability, where a coded video bitstream comprises a base layer and a predicted layer. The predicted layer enhances the picture quality compared to the base layer, e.g. by using a finer quantization of transform coefficients.
  • Embodiments can generally be applied by replacing inter-view prediction with inter-layer prediction, a base view with a base layer, and a predicted view with a predicted layer.
  • user equipment may comprise a video codec such as those described in embodiments of the invention above. It shall be appreciated that the term user equipment is intended to cover any suitable type of wireless user equipment, such as mobile telephones, portable data processing devices or portable web browsers.
  • elements of a public land mobile network may also comprise video codecs as described above.
  • the various embodiments of the invention may be implemented in hardware or special purpose circuits, software, logic or any combination thereof.
  • some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto.
  • firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto.
  • While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.
  • the embodiments of this invention may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware.
  • any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions.
  • the software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD.
  • the memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.
  • the data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multi-core processor architecture, as non-limiting examples.
  • Embodiments of the inventions may be practiced in various components such as integrated circuit modules.
  • the design of integrated circuits is by and large a highly automated process.
  • Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.
  • Programs such as those provided by Synopsys, Inc. of Mountain View, California and Cadence Design, of San Jose, California automatically route conductors and locate components on a semiconductor chip using well established rules of design as well as libraries of pre-stored design modules.
  • the resultant design in a standardized electronic format (e.g., Opus, GDSII, or the like) may be transmitted to a semiconductor fabrication facility or "fab" for fabrication.

Abstract

L'invention concerne un procédé consistant : à écrire, dans un premier conteneur, une première piste comprenant des images codées d'une première vue, les images codées de la première vue comprenant une ou plusieurs images intrapoints d'accès aléatoires (IRAP) et étant indépendantes d'images codées de toute autre vue ; à écrire, dans un deuxième conteneur, une deuxième piste comprenant des images codées en ligne d'une deuxième vue et comprenant, en référence, des données complètement ou partiellement codées d'au moins une des images IRAP, au moins une des images codées de la deuxième vue utilisant l'image ou les images IRAP en tant que référence de prédiction ; et à indiquer, dans le deuxième conteneur ou dans une description associée au deuxième conteneur et/ou à la deuxième vue, que la deuxième piste est conforme à un décodage de vue unique.
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