WO2021068785A1 - Codeur, décodeur et procédés correspondants d'unification de filtre d'interpolation de composantes de luminance et de chrominance - Google Patents

Codeur, décodeur et procédés correspondants d'unification de filtre d'interpolation de composantes de luminance et de chrominance Download PDF

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WO2021068785A1
WO2021068785A1 PCT/CN2020/118422 CN2020118422W WO2021068785A1 WO 2021068785 A1 WO2021068785 A1 WO 2021068785A1 CN 2020118422 W CN2020118422 W CN 2020118422W WO 2021068785 A1 WO2021068785 A1 WO 2021068785A1
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filter
intra prediction
current block
interpolation filter
interpolation
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PCT/CN2020/118422
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English (en)
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Biao Wang
Semih Esenlik
Anand Meher Kotra
Han GAO
Elena Alexandrovna ALSHINA
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Huawei Technologies Co., Ltd.
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    • 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
    • H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
    • H04N19/157—Assigned coding mode, i.e. the coding mode being predefined or preselected to be further used for selection of another element or parameter
    • 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
    • H04N19/117—Filters, e.g. for pre-processing or post-processing
    • 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
    • H04N19/132—Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
    • 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
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
    • H04N19/176—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a block, e.g. a macroblock
    • 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
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/186—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being a colour or a chrominance component
    • 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
    • H04N19/80—Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation
    • H04N19/82—Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation involving filtering within a prediction loop
    • 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
    • H04N19/11—Selection of coding mode or of prediction mode among a plurality of spatial predictive coding modes
    • 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
    • H04N19/593—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving spatial prediction techniques

Definitions

  • Embodiments of the present application generally relate to the field of picture processing and more particularly to filter modification on general intra prediction process Intra Prediction.
  • Video coding (video encoding and decoding) is used in a wide range of digital video applications, for example broadcast digital TV, video transmission over internet and mobile networks, real-time conversational applications such as video chat, video conferencing, DVD and Blu-ray discs, video content acquisition and editing systems, and camcorders of security applications.
  • digital video applications for example broadcast digital TV, video transmission over internet and mobile networks, real-time conversational applications such as video chat, video conferencing, DVD and Blu-ray discs, video content acquisition and editing systems, and camcorders of security applications.
  • video data is generally compressed before being communicated across modern day telecommunications networks.
  • the size of a video could also be an issue when the video is stored on a storage device because memory resources may be limited.
  • Video compression devices often use software and/or hardware at the source to code the video data prior to transmission or storage, thereby decreasing the quantity of data needed to represent digital video images.
  • the compressed data is then received at the destination by a video decompression device that decodes the video data.
  • intra prediction of luma and chroma samples of pictures of video sequences is a very complex issue of video coding and there is an increasing demand for improving the efficiency of the coding process and reducing the complexity of the hardware needed.
  • a current block for example, a coding block
  • a current block for example, a coding block
  • the first intra prediction includes performing, onto reference samples of the luma component of the current block, an interpolation filtering by means of an interpolation filter (for example, a 4-tap filter) ; and
  • one and the same interpolation filter is used for the coding (intra prediction) of the luma and the chroma components of the current block of the picture.
  • the complexity of the intra prediction and the coding process can be significantly reduced as compared to the art.
  • the same processing unit can be used for the interpolation process resulting in sub-pixel accuracy involved in the intra prediction of the luma component and the intra prediction of the chroma component.
  • two different processing units had to be provided for the interpolation of the luma and chroma components.
  • the hardware configuration can, thus, be simplified.
  • the interpolation filter has a set of interpolation filter coefficients (for the taps of the interpolation filter) which are derived on the bases of the intra prediction mode of the luma component of the current block. Examples ard given in Tables 3 and 4 in the detailed description below. Different filter coefficients may be used for each different angular prediction mode or for at least some angular prediction modes.
  • the method further comprises obtaining an interpolation filter type indicator indicating a first interpolation filter or a second interpolation filter as the interpolation filter and wherein the interpolation filtering onto reference samples of the luma component of the current block and the interpolation filtering onto reference samples of the chroma component of the current block are performed based on the interpolation filter type indicator.
  • an interpolation filter type indicator may be a flag (FilterFlag) that can be readily signaled with a low bit amount. For example, a one-bit flag may be used to select an interpolation filter from two available interpolation filters.
  • the first interpolation filter is a DCT-IF filter (a4-tap cubic filter) and the second interpolation filter is a Gaussian filter.
  • a DCT-IF filter or a Gaussian filter may be advantageous with respect to the sub-pixel accuracy of a resulting intra prediction block.
  • the method further comprises obtaining coding information on the color component of the current block, wherein the interpolation filter type indicator is determined based on the obtained coding information on the color component of the current block.
  • Information on the type of the interpolation filter to be used can, thus, be readily obtained as part of the coding information on the color component.
  • Such coding information may further include a flag that indicates whether a reference sample filter is to be used to smooth the reference samples before performing the first intra prediction.
  • the method may further comprise smoothing the reference samples before performing the first intra prediction by the reference sample filter if that flag indicates that a reference sample filter is to be used to smooth the reference samples before performing the first intra prediction. Such smoothing of the reference samples may improve the reliability of the intra prediction process.
  • the interpolation filter is a DCT-IF filter if one or more of the following conditions hold: a) a reference sample filter is to be used to smooth the reference samples before performing the first intra prediction, b) the first intra prediction includes multiple reference line intra prediction and the reference line index to be used for the multiple reference line intra prediction is not equal to zero, and c) intra-sub partition of the current block is allowed. Interpolation filtering using a DCT-IF filter under one or more of such conditions may result in a very accurate intra prediction.
  • a very accurate intra prediction may be achieved when a Gaussian filter is used as the the interpolation filter if a reference sample filter is not to be used to smooth the reference samples before performing the first intra prediction and the minimum of (abs (predModeIntra -50) , abs (predModeIntra -18) ) , where predModeIntra indicates the intra prediction mode of the luma component of the current block, exceeds a predetermined threshold.
  • abs (predModeIntra -50) and abs (predModeIntra -18) the distances to the horitonzal prediction mode (18) and vertical prediction mode (50) , respectively, are measured.
  • the interpolation filter may be a DCT-IF filter if a reference sample filter is to be used to smooth the reference samples before performing the first intra prediction and the minimum of (abs (predModeIntra -50) , abs (predModeIntra -18) ) does not exceed the predetermined threshold.
  • the predetermined threshold may depend on the size of a transform block used during the overall coding of the current block. An example for such a threshold is given in Table 6 of the detailed description below.
  • the used interpolation filter may be specified by interpolation filter coefficients.
  • the interpolation filter is a DCT-IF filter or Gaussian filter and the interpolation filter coefficients of the DCT-IF filter and the interpolation filter coefficients of the Gaussian filter are selected based on the following table in order to provide interpolation filters resulting in an accurate intra prediction on a sub-pixel level.
  • fc denotes the interpolation filter coefficients of the DCT-IF filter and fG denotes the interpolation filter coefficients of the Gaussian filter.
  • the intra prediction mode of the luma component of the current block and the intra prediction mode of the chroma component of the current block may be angular intra prediction modes. If the current block to be coded is a non-square block the intra prediction mode of the luma component of the current block and the intra prediction mode of the chroma component of the current block may be wide angle intra prediction modes. For both angular intra prediction and wide angle intra prediction modes one and the same interpolation filter can be used for coding a luma and a chroma component in order to reduce the overall complexity of the coding process.
  • All of the above-described embodiments of the method of coding a block can be implemented in an encoding device or a decoding device.
  • all of the above-described embodiments of the method of coding a block may be performed by an encoding device or a decoding device.
  • a decoder or an encoder comprising processing circuitry for carrying out the method according to any of the above-described embodiments.
  • a computer program product comprising a program code for performing the method according to any of the above-described embodiments.
  • a non-transitory computer-readable medium carrying a program code which, when executed by a computer device, causes the computer device to perform the method of any of the above-described embodiments.
  • a decoder or an encoder comprises one or more processors; and a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the decoder to carry out the method according to any of the above-described embodiments.
  • a video coding device for coding (encoding or decoding) a current block (for example, a coding block) of a picture of a video sequence according to the following aspects providing the same or similar advantages as the above-described embodiments of the inventive method provided herein. Specifications of features of that method given above may also apply to the video coding device.
  • the video coding device comprises a luma coding unit configured for coding a luma component of the current block using a first intra prediction based on an intra prediction mode of the luma component of the current block, wherein the first intra prediction includes performing, onto reference samples of the luma component of the current block, an interpolation filtering by means of an interpolation filter (for example, a 4-tap interpolation filter) and a chroma coding unit configured for coding a chroma component of the current block using a second intra prediction based on an intra prediction mode of the chroma component of the current block, wherein the second intra prediction includes performing, onto reference samples of the chroma component of the current block, interpolation filtering by means of the interpolation filter.
  • an interpolation filter for example, a 4-tap interpolation filter
  • the interpolation filter may have a set of interpolation filter coefficients which are derived on the bases of the intra prediction mode of the luma component of the current block.
  • the video coding device further comprises:
  • an obtaining unit configured for obtaining an interpolation filter type indicator indicating a first interpolation filter or a second interpolation filter as the interpolation filter, and wherein the luma coding unit is configured for performing, onto the reference samples of the luma component of the current block, the interpolation filtering by means of the interpolation filter indicated by the interpolation filter type indicator;
  • the chroma coding unit is configured for performing, onto the reference samples of the chroma component of the current block, the interpolation filtering by means of the interpolation filter indicated by the interpolation filter type indicator.
  • the first interpolation filter may be a DCT-IF filter (4-tap cubic filter) and the second interpolation filter may be a Gaussian filter.
  • the obtaining unit may be further configured for obtaining coding information on the color component of the current block, and the obtaining unit may be configured to determine the interpolation filter type indicator based on the obtained coding information on the color component of the current block.
  • the coding information on the color component of the current block may include a flag that indicates whether a reference sample filter is to be used to smooth the reference samples before performing the first intra prediction, and further comprising a reference samples filtering unit configured for smoothing the reference samples before performing the first intra prediction by the reference sample filter if the flag indicates that a reference sample filter is to be used to smooth the reference samples before performing the first intra prediction.
  • the interpolation filter is a DCT-IF filter if one or more of the following conditions hold: a) a reference sample filter is to be used to smooth the reference samples before performing the first intra prediction, b) the first intra prediction includes multiple reference line intra prediction and the reference line index to be used for the multiple reference line intra prediction is not equal to zero, and c) intra-sub partition of the current block is allowed.
  • the interpolation filter is a Gaussian filter if a reference sample filter is not to be used to smooth the reference samples before performing the first intra prediction and the minimum of (abs (predModeIntra -50) , abs (predModeIntra -18) ) , where predModeIntra indicates the intra prediction mode of the luma component of the current block, exceeds a predetermined threshold.
  • the interpolation filter is a DCT-IF filter if a reference sample filter is to be used to smooth the reference samples before performing the first intra prediction and the minimum of (abs (predModeIntra -50) , abs (predModeIntra -18) ) does not exceed the predetermined threshold.
  • the interpolation filter is a DCT-IF filter or Gaussian filter and the interpolation filter coefficients of the DCT-IF filter and the interpolation filter coefficients of the Gaussian filter are selected based on a table:
  • fc denotes the interpolation filter coefficients of the DCT-IF filter and fG denotes the interpolation filter coefficients of the Gaussian filter.
  • the intra prediction mode of the luma component of the current block used for the first intra prediction carried out be the luma coding unit and the intra prediction mode of the chroma component of the current block used for the second intra prediction carried out be the chrom coding unit are angular intra prediction modes.
  • the intra prediction mode of the luma component of the current block and the intra prediction mode of the chroma component of the current block may be wide angle intra prediction modes.
  • FIG. 1A is a block diagram showing an example of a video coding system configured to implement embodiments of the invention
  • FIG. 1B is a block diagram showing another example of a video coding system configured to implement embodiments of the invention.
  • FIG. 2 is a block diagram showing an example of a video encoder configured to implement embodiments of the invention
  • FIG. 3 is a block diagram showing an example structure of a video decoder configured to implement embodiments of the invention
  • FIG. 4 is a block diagram illustrating an example of an encoding apparatus or a decoding apparatus
  • FIG. 5 is a block diagram illustrating another example of an encoding apparatus or a decoding apparatus
  • FIG. 6 illustrates iIntra prediction modes in VVC
  • FIG. 7 illustrates intra mode mapping in wide angle intra prediction
  • FIG. 8 illustrates multiple reference line intra prediction
  • FIG. 9 illustrates reference sample smoothing for a block with intra planar mode
  • FIG. 10 illustrates coordinates of reference samples and intra prediction samples
  • FIG. 11 is a flow chart illustrating a method of encoding a current block of a picture of a video sequence according to an embodiment of the present invention
  • FIG. 12 shows a configuration of a video coding device comprising a luma coding unit and a chroma coding unit according to an embodiment of the present invention
  • FIG. 13 shows a configuration of a video coding device comprising a luma coding unit and a chroma coding unit according to another embodiment of the present invention.
  • FIG. 14 shows a configuration of a video coding device comprising a luma coding unit and a chroma coding unit according to another embodiment of the present invention.
  • a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa.
  • a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method steps (e.g. one unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps) , even if such one or more units are not explicitly described or illustrated in the figures.
  • a specific apparatus is described based on one or a plurality of units, e.g.
  • a corresponding method may include one step to perform the functionality of the one or plurality of units (e.g. one step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units) , even if such one or plurality of steps are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments and/or aspects described herein may be combined with each other, unless specifically noted otherwise.
  • Video coding typically refers to the processing of a sequence of pictures, which form the video or video sequence. Instead of the term “picture” the term “frame” or “image” may be used as synonyms in the field of video coding.
  • Video coding (or coding in general) comprises two parts video encoding and video decoding. Video encoding is performed at the source side, typically comprising processing (e.g. by compression) the original video pictures to reduce the amount of data required for representing the video pictures (for more efficient storage and/or transmission) . Video decoding is performed at the destination side and typically comprises the inverse processing compared to the encoder to reconstruct the video pictures.
  • Embodiments referring to “coding” of video pictures shall be understood to relate to “encoding” or “decoding” of video pictures or respective video sequences.
  • the combination of the encoding part and the decoding part is also referred to as CODEC (Coding and Decoding) .
  • the original video pictures can be reconstructed, i.e. the reconstructed video pictures have the same quality as the original video pictures (assuming no transmission loss or other data loss during storage or transmission) .
  • further compression e.g. by quantization, is performed, to reduce the amount of data representing the video pictures, which cannot be completely reconstructed at the decoder, i.e. the quality of the reconstructed video pictures is lower or worse compared to the quality of the original video pictures.
  • Video coding standards belong to the group of “lossy hybrid video codecs” (i.e. combine spatial and temporal prediction in the sample domain and 2D transform coding for applying quantization in the transform domain) .
  • Each picture of a video sequence is typically partitioned into a set of non-overlapping blocks and the coding is typically performed on a block level.
  • the video is typically processed, i.e. encoded, on a block (video block) level, e.g.
  • the encoder duplicates the decoder processing loop such that both will generate identical predictions (e.g. intra-and inter predictions) and/or re-constructions for processing, i.e. coding, the subsequent blocks.
  • a video encoder 20 and a video decoder 30 are described based on Figs. 1 to 3.
  • Fig. 1A is a schematic block diagram illustrating an example coding system 10, e.g. a video coding system 10 (or short coding system 10) that may utilize techniques of this present application.
  • Video encoder 20 (or short encoder 20) and video decoder 30 (or short decoder 30) of video coding system 10 represent examples of devices that may be configured to perform techniques in accordance with various examples described in the present application.
  • the coding system 10 comprises a source device 12 configured to provide encoded picture data 21 e.g. to a destination device 14 for decoding the encoded picture data 13.
  • the source device 12 comprises an encoder 20, and may additionally, i.e. optionally, comprise a picture source 16, a pre-processor (or pre-processing unit) 18, e.g. a picture pre-processor 18, and a communication interface or communication unit 22.
  • the picture source 16 may comprise or be any kind of picture capturing device, for example a camera for capturing a real-world picture, and/or any kind of a picture generating device, for example a computer-graphics processor for generating a computer animated picture, or any kind of other device for obtaining and/or providing a real-world picture, a computer generated picture (e.g. a screen content, a virtual reality (VR) picture) and/or any combination thereof (e.g. an augmented reality (AR) picture) .
  • the picture source may be any kind of memory or storage storing any of the aforementioned pictures.
  • the picture or picture data 17 may also be referred to as raw picture or raw picture data 17.
  • Pre-processor 18 is configured to receive the (raw) picture data 17 and to perform pre-processing on the picture data 17 to obtain a pre-processed picture 19 or pre-processed picture data 19.
  • Pre-processing performed by the pre-processor 18 may, e.g., comprise trimming, color format conversion (e.g. from RGB to YCbCr) , color correction, or de-noising. It can be understood that the pre-processing unit 18 may be optional component.
  • the video encoder 20 is configured to receive the pre-processed picture data 19 and provide encoded picture data 21 (further details will be described below, e.g., based on Fig. 2) .
  • Communication interface 22 of the source device 12 may be configured to receive the encoded picture data 21 and to transmit the encoded picture data 21 (or any further processed version thereof) over communication channel 13 to another device, e.g. the destination device 14 or any other device, for storage or direct reconstruction.
  • the destination device 14 comprises a decoder 30 (e.g. a video decoder 30) , and may additionally, i.e. optionally, comprise a communication interface or communication unit 28, a post-processor 32 (or post-processing unit 32) and a display device 34.
  • a decoder 30 e.g. a video decoder 30
  • the communication interface 28 of the destination device 14 is configured receive the encoded picture data 21 (or any further processed version thereof) , e.g. directly from the source device 12 or from any other source, e.g. a storage device, e.g. an encoded picture data storage device, and provide the encoded picture data 21 to the decoder 30.
  • a storage device e.g. an encoded picture data storage device
  • the communication interface 22 and the communication interface 28 may be configured to transmit or receive the encoded picture data 21 or encoded data 13 via a direct communication link between the source device 12 and the destination device 14, e.g. a direct wired or wireless connection, or via any kind of network, e.g. a wired or wireless network or any combination thereof, or any kind of private and public network, or any kind of combination thereof.
  • the communication interface 22 may be, e.g., configured to package the encoded picture data 21 into an appropriate format, e.g. packets, and/or process the encoded picture data using any kind of transmission encoding or processing for transmission over a communication link or communication network.
  • the communication interface 28, forming the counterpart of the communication interface 22, may be, e.g., configured to receive the transmitted data and process the transmission data using any kind of corresponding transmission decoding or processing and/or de-packaging to obtain the encoded picture data 21.
  • Both, communication interface 22 and communication interface 28 may be configured as unidirectional communication interfaces as indicated by the arrow for the communication channel 13 in Fig. 1A pointing from the source device 12 to the destination device 14, or bi-directional communication interfaces, and may be configured, e.g. to send and receive messages, e.g. to set up a connection, to acknowledge and exchange any other information related to the communication link and/or data transmission, e.g. encoded picture data transmission.
  • the decoder 30 is configured to receive the encoded picture data 21 and provide decoded picture data 31 or a decoded picture 31 (further details will be described below, e.g., based on Fig. 3 or Fig. 5) .
  • the post-processor 32 of destination device 14 is configured to post-process the decoded picture data 31 (also called reconstructed picture data) , e.g. the decoded picture 31, to obtain post-processed picture data 33, e.g. a post-processed picture 33.
  • the post-processing performed by the post-processing unit 32 may comprise, e.g. color format conversion (e.g. from YCbCr to RGB) , color correction, trimming, or re-sampling, or any other processing, e.g. for preparing the decoded picture data 31 for display, e.g. by display device 34.
  • the display device 34 of the destination device 14 is configured to receive the post-processed picture data 33 for displaying the picture, e.g. to a user or viewer.
  • the display device 34 may be or comprise any kind of display for representing the reconstructed picture, e.g. an integrated or external display or monitor.
  • the displays may, e.g. comprise liquid crystal displays (LCD) , organic light emitting diodes (OLED) displays, plasma displays, projectors , micro LED displays, liquid crystal on silicon (LCoS) , digital light processor (DLP) or any kind of other display.
  • FIG. 1A depicts the source device 12 and the destination device 14 as separate devices
  • embodiments of devices may also comprise both or both functionalities, the source device 12 or corresponding functionality and the destination device 14 or corresponding functionality.
  • the source device 12 or corresponding functionality and the destination device 14 or corresponding functionality may be implemented using the same hardware and/or software or by separate hardware and/or software or any combination thereof.
  • the encoder 20 (e.g. a video encoder 20) or the decoder 30 (e.g. a video decoder 30) or both encoder 20 and decoder 30 may be implemented via processing circuitry as shown in Fig. 1B, such as one or more microprocessors, digital signal processors (DSPs) , application-specific integrated circuits (ASICs) , field-programmable gate arrays (FPGAs) , discrete logic, hardware, video coding dedicated or any combinations thereof.
  • the encoder 20 may be implemented via processing circuitry 46 to embody the various modules as discussed with respect to encoder 20of FIG. 2 and/or any other encoder system or subsystem described herein.
  • the decoder 30 may be implemented via processing circuitry 46 to embody the various modules as discussed with respect to decoder 30 of FIG. 3 and/or any other decoder system or subsystem described herein.
  • the processing circuitry may be configured to perform the various operations as discussed later.
  • a device may store instructions for the software in a suitable, non-transitory computer-readable storage medium and may execute the instructions in hardware using one or more processors to perform the techniques of this disclosure.
  • Either of video encoder 20 and video decoder 30 may be integrated as part of a combined encoder/decoder (CODEC) in a single device, for example, as shown in Fig. 1B.
  • CDEC combined encoder/decoder
  • Source device 12 and destination device 14 may comprise any of a wide range of devices, including any kind of handheld or stationary devices, e.g. notebook or laptop computers, mobile phones, smart phones, tablets or tablet computers, cameras, desktop computers, set-top boxes, televisions, display devices, digital media players, video gaming consoles, video streaming devices (such as content services servers or content delivery servers) , broadcast receiver device, broadcast transmitter device, or the like and may use no or any kind of operating system.
  • the source device 12 and the destination device 14 may be equipped for wireless communication.
  • the source device 12 and the destination device 14 may be wireless communication devices.
  • video coding system 10 illustrated in Fig. 1A is merely an example and the techniques of the present application may apply to video coding settings (e.g., video encoding or video decoding) that do not necessarily include any data communication between the encoding and decoding devices.
  • data is retrieved from a local memory, streamed over a network, or the like.
  • a video encoding device may encode and store data to memory, and/or a video decoding device may retrieve and decode data from memory.
  • the encoding and decoding is performed by devices that do not communicate with one another, but simply encode data to memory and/or retrieve and decode data from memory.
  • HEVC High-Efficiency Video Coding
  • VVC Versatile Video coding
  • JCT-VC Joint Collaboration Team on Video Coding
  • VCEG ITU-T Video Coding Experts Group
  • MPEG ISO/IEC Motion Picture Experts Group
  • Fig. 2 shows a schematic block diagram of an example video encoder 20 that is configured to implement the techniques of the present application.
  • the video encoder 20 comprises an input 201 (or input interface 201) , a residual calculation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, and inverse transform processing unit 212, a reconstruction unit 214, a loop filter unit 220, a decoded picture buffer (DPB) 230, a mode selection unit 260, an entropy encoding unit 270 and an output 272 (or output interface 272) .
  • the mode selection unit 260 may include an inter prediction unit 244, an intra prediction unit 254 and a partitioning unit 262.
  • Inter prediction unit 244 may include a motion estimation unit and a motion compensation unit (not shown) .
  • a video encoder 20 as shown in Fig. 2 may also be referred to as hybrid video encoder or a video encoder according to a hybrid video codec.
  • the residual calculation unit 204, the transform processing unit 206, the quantization unit 208, the mode selection unit 260 may be referred to as forming a forward signal path of the encoder 20, whereas the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the buffer 216, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244 and the intra-prediction unit 254 may be referred to as forming a backward signal path of the video encoder 20, wherein the backward signal path of the video encoder 20 corresponds to the signal path of the decoder (see video decoder 30 in Fig. 3) .
  • the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the loop filter 220, the decoded picture buffer (DPB) 230, the inter prediction unit 244 and the intra-prediction unit 254 are also referred to forming the “built-in decoder” of video encoder 20.
  • the encoder 20 may be configured to receive, e.g. via input 201, a picture 17 (or picture data 17) , e.g. picture of a sequence of pictures forming a video or video sequence.
  • the received picture or picture data may also be a pre-processed picture 19 (or pre-processed picture data 19) .
  • the picture 17 may also be referred to as current picture or picture to be coded (in particular in video coding to distinguish the current picture from other pictures, e.g. previously encoded and/or decoded pictures of the same video sequence, i.e. the video sequence which also comprises the current picture) .
  • a (digital) picture is or can be regarded as a two-dimensional array or matrix of samples with intensity values.
  • a sample in the array may also be referred to as pixel (short form of picture element) or a pel.
  • the number of samples in horizontal and vertical direction (or axis) of the array or picture define the size and/or resolution of the picture.
  • typically three color components are employed, i.e. the picture may be represented or include three sample arrays.
  • RBG format or color space a picture comprises a corresponding red, green and blue sample array.
  • each pixel is typically represented in a luminance and chrominance format or color space, e.g.
  • YCbCr which comprises a luminance component indicated by Y (sometimes also L is used instead) and two chrominance components indicated by Cb and Cr.
  • the luminance (or short luma) component Y represents the brightness or grey level intensity (e.g. like in a grey-scale picture)
  • the two chrominance (or short chroma) components Cb and Cr represent the chromaticity or color information components.
  • a picture in YCbCr format comprises a luminance sample array of luminance sample values (Y) , and two chrominance sample arrays of chrominance values (Cb and Cr) .
  • a picture in RGB format may be converted or transformed into YCbCr format and vice versa, the process is also known as color transformation or conversion.
  • a picture is monochrome, the picture may comprise only a luminance sample array. Accordingly, a picture may be, for example, an array of luma samples in monochrome format or an array of luma samples and two corresponding arrays of chroma samples in 4: 2: 0, 4: 2: 2, and 4: 4: 4 colour format.
  • Embodiments of the video encoder 20 may comprise a picture partitioning unit (not depicted in Fig. 2) configured to partition the picture 17 into a plurality of (typically non-overlapping) picture blocks 203. These blocks may also be referred to as root blocks, macro blocks (H.264/AVC) or coding tree blocks (CTB) or coding tree units (CTU) (H. 265/HEVC and VVC) .
  • the picture partitioning unit may be configured to use the same block size for all pictures of a video sequence and the corresponding grid defining the block size, or to change the block size between pictures or subsets or groups of pictures, and partition each picture into the corresponding blocks.
  • the video encoder may be configured to receive directly a block 203 of the picture 17, e.g. one, several or all blocks forming the picture 17.
  • the picture block 203 may also be referred to as current picture block or picture block to be coded.
  • the picture block 203 again is or can be regarded as a two-dimensional array or matrix of samples with intensity values (sample values) , although of smaller dimension than the picture 17.
  • the block 203 may comprise, e.g., one sample array (e.g. a luma array in case of a monochrome picture 17, or a luma or chroma array in case of a color picture) or three sample arrays (e.g. a luma and two chroma arrays in case of a color picture 17) or any other number and/or kind of arrays depending on the color format applied.
  • the number of samples in horizontal and vertical direction (or axis) of the block 203 define the size of block 203.
  • a block may, for example, an MxN (M-column by N-row) array of samples, or an MxN array of transform coefficients.
  • Embodiments of the video encoder 20 as shown in Fig. 2 may be configured to encode the picture 17 block by block, e.g. the encoding and prediction is performed per block 203.
  • Embodiments of the video encoder 20 as shown in Fig. 2 may be further configured to partition and/or encode the picture by using slices (also referred to as video slices) , wherein a picture may be partitioned into or encoded using one or more slices (typically non-overlapping) , and each slice may comprise one or more blocks (e.g. CTUs) .
  • slices also referred to as video slices
  • each slice may comprise one or more blocks (e.g. CTUs) .
  • Embodiments of the video encoder 20 as shown in Fig. 2 may be further configured to partition and/or encode the picture by using tile groups (also referred to as video tile groups) and/or tiles (also referred to as video tiles) , wherein a picture may be partitioned into or encoded using one or more tile groups (typically non-overlapping) , and each tile group may comprise, e.g. one or more blocks (e.g. CTUs) or one or more tiles, wherein each tile, e.g. may be of rectangular shape and may comprise one or more blocks (e.g. CTUs) , e.g. complete or fractional blocks.
  • tile groups also referred to as video tile groups
  • tiles also referred to as video tiles
  • each tile group may comprise, e.g. one or more blocks (e.g. CTUs) or one or more tiles, wherein each tile, e.g. may be of rectangular shape and may comprise one or more blocks (e.g. CTUs) , e.g.
  • the residual calculation unit 204 may be configured to calculate a residual block 205 (also referred to as residual 205) based on the picture block 203 and a prediction block 265 (further details about the prediction block 265 are provided later) , e.g. by subtracting sample values of the prediction block 265 from sample values of the picture block 203, sample by sample (pixel by pixel) to obtain the residual block 205 in the sample domain.
  • a residual block 205 also referred to as residual 205
  • a prediction block 265 further details about the prediction block 265 are provided later
  • the transform processing unit 206 may be configured to apply a transform, e.g. a discrete cosine transform (DCT) or discrete sine transform (DST) , on the sample values of the residual block 205 to obtain transform coefficients 207 in a transform domain.
  • a transform e.g. a discrete cosine transform (DCT) or discrete sine transform (DST)
  • DCT discrete cosine transform
  • DST discrete sine transform
  • the transform processing unit 206 may be configured to apply integer approximations of DCT/DST, such as the transforms specified for H. 265/HEVC. Compared to an orthogonal DCT transform, such integer approximations are typically scaled by a certain factor. In order to preserve the norm of the residual block which is processed by forward and inverse transforms, additional scaling factors are applied as part of the transform process.
  • the scaling factors are typically chosen based on certain constraints like scaling factors being a power of two for shift operations, bit depth of the transform coefficients, tradeoff between accuracy and implementation costs, etc. Specific scaling factors are, for example, specified for the inverse transform, e.g. by inverse transform processing unit 212 (and the corresponding inverse transform, e.g. by inverse transform processing unit 312 at video decoder 30) and corresponding scaling factors for the forward transform, e.g. by transform processing unit 206, at an encoder 20 may be specified accordingly.
  • Embodiments of the video encoder 20 may be configured to output transform parameters, e.g. a type of transform or transforms, e.g. directly or encoded or compressed via the entropy encoding unit 270, so that, e.g., the video decoder 30 may receive and use the transform parameters for decoding.
  • transform parameters e.g. a type of transform or transforms, e.g. directly or encoded or compressed via the entropy encoding unit 270, so that, e.g., the video decoder 30 may receive and use the transform parameters for decoding.
  • the quantization unit 208 may be configured to quantize the transform coefficients 207 to obtain quantized coefficients 209, e.g. by applying scalar quantization or vector quantization.
  • the quantized coefficients 209 may also be referred to as quantized transform coefficients 209 or quantized residual coefficients 209.
  • the quantization process may reduce the bit depth associated with some or all of the transform coefficients 207. For example, an n-bit transform coefficient may be rounded down to an m-bit Transform coefficient during quantization, where n is greater than m.
  • the degree of quantization may be modified by adjusting a quantization parameter (QP) .
  • QP quantization parameter
  • different scaling may be applied to achieve finer or coarser quantization. Smaller quantization step sizes correspond to finer quantization, whereas larger quantization step sizes correspond to coarser quantization.
  • the applicable quantization step size may be indicated by a quantization parameter (QP) .
  • the quantization parameter may for example be an index to a predefined set of applicable quantization step sizes.
  • small quantization parameters may correspond to fine quantization (small quantization step sizes) and large quantization parameters may correspond to coarse quantization (large quantization step sizes) or vice versa.
  • the quantization may include division by a quantization step size and a corresponding and/or the inverse dequantization, e.g. by inverse quantization unit 210, may include multiplication by the quantization step size.
  • Embodiments according to some standards, e.g. HEVC may be configured to use a quantization parameter to determine the quantization step size.
  • the quantization step size may be calculated based on a quantization parameter using a fixed point approximation of an equation including division.
  • Additional scaling factors may be introduced for quantization and dequantization to restore the norm of the residual block, which might get modified because of the scaling used in the fixed point approximation of the equation for quantization step size and quantization parameter.
  • the scaling of the inverse transform and dequantization might be combined.
  • customized quantization tables may be used and signaled from an encoder to a decoder, e.g. in a bitstream.
  • the quantization is a lossy operation, wherein the loss increases with increasing quantization step sizes.
  • Embodiments of the video encoder 20 may be configured to output quantization parameters (QP) , e.g. directly or encoded via the entropy encoding unit 270, so that, e.g., the video decoder 30 may receive and apply the quantization parameters for decoding.
  • QP quantization parameters
  • the inverse quantization unit 210 is configured to apply the inverse quantization of the quantization unit 208 on the quantized coefficients to obtain dequantized coefficients 211, e.g. by applying the inverse of the quantization scheme applied by the quantization unit 208 based on or using the same quantization step size as the quantization unit 208.
  • the dequantized coefficients 211 may also be referred to as dequantized residual coefficients 211 and correspond -although typically not identical to the transform coefficients due to the loss by quantization -to the transform coefficients 207.
  • the inverse transform processing unit 212 is configured to apply the inverse transform of the transform applied by the transform processing unit 206, e.g. an inverse discrete cosine transform (DCT) or inverse discrete sine transform (DST) or other inverse transforms, to obtain a reconstructed residual block 213 (or corresponding dequantized coefficients 213) in the sample domain.
  • the reconstructed residual block 213 may also be referred to as transform block 213.
  • the reconstruction unit 214 (e.g. adder or summer 214) is configured to add the transform block 213 (i.e. reconstructed residual block 213) to the prediction block 265 to obtain a reconstructed block 215 in the sample domain, e.g. by adding –sample by sample -the sample values of the reconstructed residual block 213 and the sample values of the prediction block 265.
  • the loop filter unit 220 (or short “loop filter” 220) , is configured to filter the reconstructed block 215 to obtain a filtered block 221, or in general, to filter reconstructed samples to obtain filtered samples.
  • the loop filter unit is, e.g., configured to smooth pixel transitions, or otherwise improve the video quality.
  • the loop filter unit 220 may comprise one or more loop filters such as a de-blocking filter, a sample-adaptive offset (SAO) filter or one or more other filters, e.g. a bilateral filter, an adaptive loop filter (ALF) , a sharpening, a smoothing filters or a collaborative filters, or any combination thereof.
  • the loop filter unit 220 is shown in FIG. 2 as being an in loop filter, in other configurations, the loop filter unit 220 may be implemented as a post loop filter.
  • the filtered block 221 may also be referred to as filtered reconstructed block 221.
  • Embodiments of the video encoder 20 may be configured to output loop filter parameters (such as sample adaptive offset information) , e.g. directly or encoded via the entropy encoding unit 270, so that, e.g., a decoder 30 may receive and apply the same loop filter parameters or respective loop filters for decoding.
  • loop filter parameters such as sample adaptive offset information
  • the decoded picture buffer (DPB) 230 may be a memory that stores reference pictures, or in general reference picture data, for encoding video data by video encoder 20.
  • the DPB 230 may be formed by any of a variety of memory devices, such as dynamic random access memory (DRAM) , including synchronous DRAM (SDRAM) , magnetoresistive RAM (MRAM) , resistive RAM (RRAM) , or other types of memory devices.
  • DRAM dynamic random access memory
  • SDRAM synchronous DRAM
  • MRAM magnetoresistive RAM
  • RRAM resistive RAM
  • the decoded picture buffer (DPB) 230 may be configured to store one or more filtered blocks 221.
  • the decoded picture buffer 230 may be further configured to store other previously filtered blocks, e.g. previously reconstructed and filtered blocks 221, of the same current picture or of different pictures, e.g.
  • the decoded picture buffer (DPB) 230 may be also configured to store one or more unfiltered reconstructed blocks 215, or in general unfiltered reconstructed samples, e.g. if the reconstructed block 215 is not filtered by loop filter unit 220, or any other further processed version of the reconstructed blocks or samples.
  • the mode selection unit 260 comprises partitioning unit 262, inter-prediction unit 244 and intra-prediction unit 254, and is configured to receive or obtain original picture data, e.g. an original block 203 (current block 203 of the current picture 17) , and reconstructed picture data, e.g. filtered and/or unfiltered reconstructed samples or blocks of the same (current) picture and/or from one or a plurality of previously decoded pictures, e.g. from decoded picture buffer 230 or other buffers (e.g. line buffer, not shown) .
  • the reconstructed picture data is used as reference picture data for prediction, e.g. inter-prediction or intra-prediction, to obtain a prediction block 265 or predictor 265.
  • Mode selection unit 260 may be configured to determine or select a partitioning for a current block prediction mode (including no partitioning) and a prediction mode (e.g. an intra or inter prediction mode) and generate a corresponding prediction block 265, which is used for the calculation of the residual block 205 and for the reconstruction of the reconstructed block 215.
  • a prediction mode e.g. an intra or inter prediction mode
  • Embodiments of the mode selection unit 260 may be configured to select the partitioning and the prediction mode (e.g. from those supported by or available for mode selection unit 260) , which provide the best match or in other words the minimum residual (minimum residual means better compression for transmission or storage) , or a minimum signaling overhead (minimum signaling overhead means better compression for transmission or storage) , or which considers or balances both.
  • the mode selection unit 260 may be configured to determine the partitioning and prediction mode based on rate distortion optimization (RDO) , i.e. select the prediction mode which provides a minimum rate distortion. Terms like “best” , “minimum” , “optimum” etc.
  • the partitioning unit 262 may be configured to partition the block 203 into smaller block partitions or sub-blocks (which form again blocks) , e.g. iteratively using quad-tree-partitioning (QT) , binary partitioning (BT) or triple-tree-partitioning (TT) or any combination thereof, and to perform, e.g., the prediction for each of the block partitions or sub-blocks, wherein the mode selection comprises the selection of the tree-structure of the partitioned block 203 and the prediction modes are applied to each of the block partitions or sub-blocks.
  • QT quad-tree-partitioning
  • BT binary partitioning
  • TT triple-tree-partitioning
  • partitioning e.g. by partitioning unit 260
  • prediction processing by inter-prediction unit 244 and intra-prediction unit 254
  • the partitioning unit 262 may partition (or split) a current block 203 into smaller partitions, e.g. smaller blocks of square or rectangular size. These smaller blocks (which may also be referred to as sub-blocks) may be further partitioned into even smaller partitions.
  • This is also referred to tree-partitioning or hierarchical tree-partitioning, wherein a root block, e.g. at root tree-level 0 (hierarchy-level 0, depth 0) , may be recursively partitioned, e.g. partitioned into two or more blocks of a next lower tree-level, e.g.
  • nodes at tree-level 1 (hierarchy-level 1, depth 1) , wherein these blocks may be again partitioned into two or more blocks of a next lower level, e.g. tree-level 2 (hierarchy-level 2, depth 2) , etc. until the partitioning is terminated, e.g. because a termination criterion is fulfilled, e.g. a maximum tree depth or minimum block size is reached.
  • Blocks which are not further partitioned are also referred to as leaf-blocks or leaf nodes of the tree.
  • a tree using partitioning into two partitions is referred to as binary-tree (BT)
  • BT binary-tree
  • TT ternary-tree
  • QT quad-tree
  • the term “block” as used herein may be a portion, in particular a square or rectangular portion, of a picture.
  • the block may be or correspond to a coding tree unit (CTU) , a coding unit (CU) , prediction unit (PU) , and transform unit (TU) and/or to the corresponding blocks, e.g. a coding tree block (CTB) , a coding block (CB) , a transform block (TB) or prediction block (PB) .
  • CTU coding tree unit
  • CU coding unit
  • PU prediction unit
  • TU transform unit
  • a coding tree unit may be or comprise a CTB of luma samples, two corresponding CTBs of chroma samples of a picture that has three sample arrays, or a CTB of samples of a monochrome picture or a picture that is coded using three separate colour planes and syntax structures used to code the samples.
  • a coding tree block may be an NxN block of samples for some value of N such that the division of a component into CTBs is a partitioning.
  • a coding unit may be or comprise 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 colour planes and syntax structures used to code the samples.
  • a coding block may be an MxN block of samples for some values of M and N such that the division of a CTB into coding blocks is a partitioning.
  • a coding tree unit may be split into CUs by using a quad-tree structure denoted as coding tree.
  • the decision whether to code a picture area using inter-picture (temporal) or intra-picture (spatial) prediction is made at the CU level.
  • Each CU can be further split into one, two or four PUs according to the PU splitting type. Inside one PU, the same prediction process is applied and the relevant information is transmitted to the decoder on a PU basis.
  • a CU can be partitioned into transform units (TUs) according to another quadtree structure similar to the coding tree for the CU.
  • a combined Quad-tree and binary tree (QTBT) partitioning is for example used to partition a coding block.
  • a CU can have either a square or rectangular shape.
  • a coding tree unit (CTU) is first partitioned by a quadtree structure.
  • the quadtree leaf nodes are further partitioned by a binary tree or ternary (or triple) tree structure.
  • the partitioning tree leaf nodes are called coding units (CUs) , and that segmentation is used for prediction and transform processing without any further partitioning.
  • CUs coding units
  • multiple partition for example, triple tree partition may be used together with the QTBT block structure.
  • the mode selection unit 260 of video encoder 20 may be configured to perform any combination of the partitioning techniques described herein.
  • the video encoder 20 is configured to determine or select the best or an optimum prediction mode from a set of (e.g. pre-determined) prediction modes.
  • the set of prediction modes may comprise, e.g., intra-prediction modes and/or inter-prediction modes.
  • the set of intra-prediction modes may comprise 35 different intra-prediction modes, e.g. non-directional modes like DC (or mean) mode and planar mode, or directional modes, e.g. as defined in HEVC, or may comprise 67 different intra-prediction modes, e.g. non-directional modes like DC (or mean) mode and planar mode, or directional modes, e.g. as defined for VVC.
  • intra-prediction modes e.g. non-directional modes like DC (or mean) mode and planar mode
  • directional modes e.g. as defined for VVC.
  • the intra-prediction unit 254 is configured to use reconstructed samples of neighboring blocks of the same current picture to generate an intra-prediction block 265 according to an intra-prediction mode of the set of intra-prediction modes.
  • the intra prediction unit 254 (or in general the mode selection unit 260) is further configured to output intra-prediction parameters (or in general information indicative of the selected intra prediction mode for the block) to the entropy encoding unit 270 in form of syntax elements 266 for inclusion into the encoded picture data 21, so that, e.g., the video decoder 30 may receive and use the prediction parameters for decoding.
  • the set of (or possible) inter-prediction modes depends on the available reference pictures (i.e. previous at least partially decoded pictures, e.g. stored in DBP 230) and other inter-prediction parameters, e.g. whether the whole reference picture or only a part, e.g. a search window area around the area of the current block, of the reference picture is used for searching for a best matching reference block, and/or e.g. whether pixel interpolation is applied, e.g. half/semi-pel and/or quarter-pel interpolation, or not.
  • other inter-prediction parameters e.g. whether the whole reference picture or only a part, e.g. a search window area around the area of the current block, of the reference picture is used for searching for a best matching reference block, and/or e.g. whether pixel interpolation is applied, e.g. half/semi-pel and/or quarter-pel interpolation, or not.
  • skip mode and/or direct mode may be applied.
  • the inter prediction unit 244 may include a motion estimation (ME) unit and a motion compensation (MC) unit (both not shown in Fig. 2) .
  • the motion estimation unit may be configured to receive or obtain the picture block 203 (current picture block 203 of the current picture 17) and a decoded picture 231, or at least one or a plurality of previously reconstructed blocks, e.g. reconstructed blocks of one or a plurality of other/different previously decoded pictures 231, for motion estimation.
  • a video sequence may comprise the current picture and the previously decoded pictures 231, or in other words, the current picture and the previously decoded pictures 231 may be part of or form a sequence of pictures forming a video sequence.
  • the encoder 20 may, e.g., be configured to select a reference block from a plurality of reference blocks of the same or different pictures of the plurality of other pictures and provide a reference picture (or reference picture index) and/or an offset (spatial offset) between the position (x, y coordinates) of the reference block and the position of the current block as inter prediction parameters to the motion estimation unit.
  • This offset is also called motion vector (MV) .
  • the motion compensation unit is configured to obtain, e.g. receive, an inter prediction parameter and to perform inter prediction based on or using the inter prediction parameter to obtain an inter prediction block 265.
  • Motion compensation performed by the motion compensation unit, may involve fetching or generating the prediction block based on the motion/block vector determined by motion estimation, possibly performing interpolations to sub-pixel precision. Interpolation filtering may generate additional pixel samples from known pixel samples, thus potentially increasing the number of candidate prediction blocks that may be used to code a picture block.
  • the motion compensation unit may locate the prediction block to which the motion vector points in one of the reference picture lists.
  • the motion compensation unit may also generate syntax elements associated with the blocks and video slices for use by video decoder 30 in decoding the picture blocks of the video slice.
  • syntax elements associated with the blocks and video slices for use by video decoder 30 in decoding the picture blocks of the video slice.
  • tile groups and/or tiles and respective syntax elements may be generated or used.
  • the entropy encoding unit 270 is configured to apply, for example, an entropy encoding algorithm or scheme (e.g. a variable length coding (VLC) scheme, an context adaptive VLC scheme (CAVLC) , an arithmetic coding scheme, a binarization, a context adaptive binary arithmetic coding (CABAC) , syntax-based context-adaptive binary arithmetic coding (SBAC) , probability interval partitioning entropy (PIPE) coding or another entropy encoding methodology or technique) or bypass (no compression) on the quantized coefficients 209, inter prediction parameters, intra prediction parameters, loop filter parameters and/or other syntax elements to obtain encoded picture data 21 which can be output via the output 272, e.g.
  • an entropy encoding algorithm or scheme e.g. a variable length coding (VLC) scheme, an context adaptive VLC scheme (CAVLC) , an arithmetic coding scheme, a binarization
  • the encoded bitstream 21 may be transmitted to video decoder 30, or stored in a memory for later transmission or retrieval by video decoder 30.
  • a non-transform based encoder 20 can quantize the residual signal directly without the transform processing unit 206 for certain blocks or frames.
  • an encoder 20 can have the quantization unit 208 and the inverse quantization unit 210 combined into a single unit.
  • Fig. 3 shows an example of a video decoder 30 that is configured to implement the techniques of this present application.
  • the video decoder 30 is configured to receive encoded picture data 21 (e.g. encoded bitstream 21) , e.g. encoded by encoder 20, to obtain a decoded picture 331.
  • the encoded picture data or bitstream comprises information for decoding the encoded picture data, e.g. data that represents picture blocks of an encoded video slice (and/or tile groups or tiles) and associated syntax elements.
  • the decoder 30 comprises an entropy decoding unit 304, an inverse quantization unit 310, an inverse transform processing unit 312, a reconstruction unit 314 (e.g. a summer 314) , a loop filter 320, a decoded picture buffer (DBP) 330, a mode application unit 360, an inter prediction unit 344 and an intra prediction unit 354.
  • Inter prediction unit 344 may be or include a motion compensation unit.
  • Video decoder 30 may, in some examples, perform a decoding pass generally reciprocal to the encoding pass described with respect to video encoder 100 from FIG. 2.
  • the inverse quantization unit 210 may be identical in function to the inverse quantization unit 110
  • the inverse transform processing unit 312 may be identical in function to the inverse transform processing unit 212
  • the reconstruction unit 314 may be identical in function to reconstruction unit 214
  • the loop filter 320 may be identical in function to the loop filter 220
  • the decoded picture buffer 330 may be identical in function to the decoded picture buffer 230. Therefore, the explanations provided for the respective units and functions of the video 20 encoder apply correspondingly to the respective units and functions of the video decoder 30.
  • the entropy decoding unit 304 is configured to parse the bitstream 21 (or in general encoded picture data 21) and perform, for example, entropy decoding to the encoded picture data 21 to obtain, e.g., quantized coefficients 309 and/or decoded coding parameters (not shown in Fig. 3) , e.g. any or all of inter prediction parameters (e.g. reference picture index and motion vector) , intra prediction parameter (e.g. intra prediction mode or index) , transform parameters, quantization parameters, loop filter parameters, and/or other syntax elements.
  • Entropy decoding unit 304 maybe configured to apply the decoding algorithms or schemes corresponding to the encoding schemes as described with regard to the entropy encoding unit 270 of the encoder 20.
  • Entropy decoding unit 304 may be further configured to provide inter prediction parameters, intra prediction parameter and/or other syntax elements to the mode application unit 360 and other parameters to other units of the decoder 30.
  • Video decoder 30 may receive the syntax elements at the video slice level and/or the video block level. In addition or as an alternative to slices and respective syntax elements, tile groups and/or tiles and respective syntax elements may be received and/or used.
  • the inverse quantization unit 310 may be configured to receive quantization parameters (QP) (or in general information related to the inverse quantization) and quantized coefficients from the encoded picture data 21 (e.g. by parsing and/or decoding, e.g. by entropy decoding unit 304) and to apply based on the quantization parameters an inverse quantization on the decoded quantized coefficients 309 to obtain dequantized coefficients 311, which may also be referred to as transform coefficients 311.
  • the inverse quantization process may include use of a quantization parameter determined by video encoder 20 for each video block in the video slice (or tile or tile group) to determine a degree of quantization and, likewise, a degree of inverse quantization that should be applied.
  • Inverse transform processing unit 312 may be configured to receive dequantized coefficients 311, also referred to as transform coefficients 311, and to apply a transform to the dequantized coefficients 311 in order to obtain reconstructed residual blocks 213 in the sample domain.
  • the reconstructed residual blocks 213 may also be referred to as transform blocks 313.
  • the transform may be an inverse transform, e.g., an inverse DCT, an inverse DST, an inverse integer transform, or a conceptually similar inverse transform process.
  • the inverse transform processing unit 312 may be further configured to receive transform parameters or corresponding information from the encoded picture data 21 (e.g. by parsing and/or decoding, e.g. by entropy decoding unit 304) to determine the transform to be applied to the dequantized coefficients 311.
  • the reconstruction unit 314 (e.g. adder or summer 314) may be configured to add the reconstructed residual block 313 to the prediction block 365 to obtain a reconstructed block 315 in the sample domain, e.g. by adding the sample values of the reconstructed residual block 313 and the sample values of the prediction block 365.
  • the loop filter unit 320 (either in the coding loop or after the coding loop) is configured to filter the reconstructed block 315 to obtain a filtered block 321, e.g. to smooth pixel transitions, or otherwise improve the video quality.
  • the loop filter unit 320 may comprise one or more loop filters such as a de-blocking filter, a sample-adaptive offset (SAO) filter or one or more other filters, e.g. a bilateral filter, an adaptive loop filter (ALF) , a sharpening, a smoothing filters or a collaborative filters, or any combination thereof.
  • the loop filter unit 320 is shown in FIG. 3 as being an in loop filter, in other configurations, the loop filter unit 320 may be implemented as a post loop filter.
  • decoded video blocks 321 of a picture are then stored in decoded picture buffer 330, which stores the decoded pictures 331 as reference pictures for subsequent motion compensation for other pictures and/or for output respectively display.
  • the decoder 30 is configured to output the decoded picture 311, e.g. via output 312, for presentation or viewing to a user.
  • the inter prediction unit 344 may be identical to the inter prediction unit 244 (in particular to the motion compensation unit) and the intra prediction unit 354 may be identical to the intra prediction unit 254 in function, and performs split or partitioning decisions and prediction based on the partitioning and/or prediction parameters or respective information received from the encoded picture data 21 (e.g. by parsing and/or decoding, e.g. by entropy decoding unit 304) .
  • Mode application unit 360 may be configured to perform the prediction (intra or inter prediction) per block based on reconstructed pictures, blocks or respective samples (filtered or unfiltered) to obtain the prediction block 365.
  • intra prediction unit 354 of mode application unit 360 is configured to generate prediction block 365 for a picture block of the current video slice based on a signaled intra prediction mode and data from previously decoded blocks of the current picture.
  • inter prediction unit 344 e.g. motion compensation unit
  • the prediction blocks may be produced from one of the reference pictures within one of the reference picture lists.
  • Video decoder 30 may construct the reference frame lists, List 0 and List 1, using default construction techniques based on reference pictures stored in DPB 330.
  • the same or similar may be applied for or by embodiments using tile groups (e.g. video tile groups) and/or tiles (e.g. video tiles) in addition or alternatively to slices (e.g. video slices) , e.g. a video may be coded using I, P or B tile groups and /or tiles.
  • Mode application unit 360 is configured to determine the prediction information for a video block of the current video slice by parsing the motion vectors or related information and other syntax elements, and uses the prediction information to produce the prediction blocks for the current video block being decoded. For example, the mode application unit 360 uses some of the received syntax elements to determine a prediction mode (e.g., intra or inter prediction) used to code the video blocks of the video slice, an inter prediction slice type (e.g., B slice, P slice, or GPB slice) , construction information for one or more of the reference picture lists for the slice, motion vectors for each inter encoded video block of the slice, inter prediction status for each inter coded video block of the slice, and other information to decode the video blocks in the current video slice.
  • a prediction mode e.g., intra or inter prediction
  • an inter prediction slice type e.g., B slice, P slice, or GPB slice
  • tile groups e.g. video tile groups
  • tiles e.g. video tiles
  • slices e.g. video slices
  • a video may be coded using I, P or B tile groups and/or tiles.
  • Embodiments of the video decoder 30 as shown in Fig. 3 may be configured to partition and/or decode the picture by using slices (also referred to as video slices) , wherein a picture may be partitioned into or decoded using one or more slices (typically non-overlapping) , and each slice may comprise one or more blocks (e.g. CTUs) .
  • slices also referred to as video slices
  • each slice may comprise one or more blocks (e.g. CTUs) .
  • Embodiments of the video decoder 30 as shown in Fig. 3 may be configured to partition and/or decode the picture by using tile groups (also referred to as video tile groups) and/or tiles (also referred to as video tiles) , wherein a picture may be partitioned into or decoded using one or more tile groups (typically non-overlapping) , and each tile group may comprise, e.g. one or more blocks (e.g. CTUs) or one or more tiles, wherein each tile, e.g. may be of rectangular shape and may comprise one or more blocks (e.g. CTUs) , e.g. complete or fractional blocks.
  • tile groups also referred to as video tile groups
  • tiles also referred to as video tiles
  • each tile group may comprise, e.g. one or more blocks (e.g. CTUs) or one or more tiles, wherein each tile, e.g. may be of rectangular shape and may comprise one or more blocks (e.g. CTUs) , e.
  • the video decoder 30 can be used to decode the encoded picture data 21.
  • the decoder 30 can produce the output video stream without the loop filtering unit 320.
  • a non-transform based decoder 30 can inverse-quantize the residual signal directly without the inverse-transform processing unit 312 for certain blocks or frames.
  • the video decoder 30 can have the inverse-quantization unit 310 and the inverse-transform processing unit 312 combined into a single unit.
  • a processing result of a current step may be further processed and then output to the next step.
  • a further operation such as Clip or shift, may be performed on the processing result of the interpolation filtering, motion vector derivation or loop filtering.
  • the value of motion vector is constrained to a predefined range according to its representing bit. If the representing bit of motion vector is bitDepth, then the range is -2 ⁇ (bitDepth-1) ⁇ 2 ⁇ (bitDepth-1) -1, where “ ⁇ ” means exponentiation. For example, if bitDepth is set equal to 16, the range is -32768 ⁇ 32767; if bitDepth is set equal to 18, the range is -131072 ⁇ 131071.
  • the value of the derived motion vector (e.g. the MVs of four 4x4 sub-blocks within one 8x8 block) is constrained such that the max difference between integer parts of the four 4x4 sub-block MVs is no more than N pixels, such as no more than 1 pixel.
  • N pixels such as no more than 1 pixel.
  • ux (mvx+2 bitDepth ) %2 bitDepth (1)
  • mvx is a horizontal component of a motion vector of an image block or a sub-block
  • mvy is a vertical component of a motion vector of an image block or a sub-block
  • ux and uy indicates an intermediate value
  • decimal numbers are stored as two’s complement.
  • the two’s complement of -32769 is 1, 0111, 1111, 1111, 1111 (17 bits) , then the MSB is discarded, so the resulting two’s complement is 0111, 1111, 1111, 1111 (decimal number is 32767) , which is same as the output by applying formula (1) and (2) .
  • ux (mvpx + mvdx +2 bitDepth ) %2 bitDepth (5)
  • the operations may be applied during the sum of mvp and mvd, as shown in formula (5) to (8) .
  • vx Clip3 (-2 bitDepth-1 , 2 bitDepth-1 -1, vx)
  • vy Clip3 (-2 bitDepth-1 , 2 bitDepth-1 -1, vy)
  • vx is a horizontal component of a motion vector of an image block or a sub-block
  • vy is a vertical component of a motion vector of an image block or a sub-block
  • x, y and z respectively correspond to three input value of the MV clipping process, and the definition of function Clip3 is as follow:
  • FIG. 4 is a schematic diagram of a video coding device 400 according to an embodiment of the disclosure.
  • the video coding device 400 is suitable for implementing the disclosed embodiments as described herein.
  • the video coding device 400 may be a decoder such as video decoder 30 of FIG. 1A or an encoder such as video encoder 20 of FIG. 1A.
  • the video coding device 400 comprises ingress ports 410 (or input ports 410) and receiver units (Rx) 420 for receiving data; a processor, logic unit, or central processing unit (CPU) 430 to process the data; transmitter units (Tx) 440 and egress ports 450 (or output ports 450) for transmitting the data; and a memory 460 for storing the data.
  • the video coding device 400 may also comprise optical-to-electrical (OE) components and electrical-to-optical (EO) components coupled to the ingress ports 410, the receiver units 420, the transmitter units 440, and the egress ports 450 for egress or ingress of optical or electrical signals.
  • OE optical-to-electrical
  • EO electrical-to-optical
  • the processor 430 is implemented by hardware and software.
  • the processor 430 may be implemented as one or more CPU chips, cores (e.g., as a multi-core processor) , FPGAs, ASICs, and DSPs.
  • the processor 430 is in communication with the ingress ports 410, receiver units 420, transmitter units 440, egress ports 450, and memory 460.
  • the processor 430 comprises a coding module 470.
  • the coding module 470 implements the disclosed embodiments described above. For instance, the coding module 470 implements, processes, prepares, or provides the various coding operations. The inclusion of the coding module 470 therefore provides a substantial improvement to the functionality of the video coding device 400 and effects a transformation of the video coding device 400 to a different state.
  • the coding module 470 is implemented as instructions stored in the memory 460 and executed by the processor 430.
  • the memory 460 may comprise one or more disks, tape drives, and solid-state drives and may be used as an over-flow data storage device, to store programs when such programs are selected for execution, and to store instructions and data that are read during program execution.
  • the memory 460 may be, for example, volatile and/or non-volatile and may be a read-only memory (ROM) , random access memory (RAM) , ternary content-addressable memory (TCAM) , and/or static random-access memory (SRAM) .
  • Fig. 5 is a simplified block diagram of an apparatus 500 that may be used as either or both of the source device 12 and the destination device 14 from Fig. 1 according to an exemplary embodiment.
  • a processor 502 in the apparatus 500 can be a central processing unit.
  • the processor 502 can be any other type of device, or multiple devices, capable of manipulating or processing information now-existing or hereafter developed.
  • the disclosed implementations can be practiced with a single processor as shown, e.g., the processor 502, advantages in speed and efficiency can be achieved using more than one processor.
  • a memory 504 in the apparatus 500 can be a read only memory (ROM) de vice or a random access memory (RAM) device in an implementation. Any other suitable type of storage device can be used as the memory 504.
  • the memory 504 can include code and data 506 that is accessed by the processor 502 using a bus 512.
  • the memory 504 can further include an operating system 508 and application programs 510, the application programs 510 including at least one program that permits the processor 502 to perform the methods described here.
  • the application programs 510 can include applications 1 through N, which further include a video coding application that performs the methods described here.
  • the apparatus 500 can also include one or more output devices, such as a display 518.
  • the display 518 may be, in one example, a touch sensitive display that combines a display with a touch sensitive element that is operable to sense touch inputs.
  • the display 518 can be coupled to the processor 502 via the bus 512.
  • the bus 512 of the apparatus 500 can be composed of multiple buses.
  • the secondary storage 514 can be directly coupled to the other components of the apparatus 500 or can be accessed via a network and can comprise a single integrated unit such as a memory card or multiple units such as multiple memory cards.
  • the apparatus 500 can thus be implemented in a wide variety of configurations.
  • the number of directional intra modes in VTM6 is extended from 33, as used in HEVC, to 65.
  • the new directional modes not in HEVC are depicted as dotted arrows in Figure 6, and the planar and DC modes remain the same.
  • These denser directional intra prediction modes apply for all block sizes and for both luma and chroma intra predictions. Specifically, the values of all intra prediction modes are defined in Table 1:
  • Conventional angular intra prediction directions are defined from 45 degrees to -135 degrees in clockwise direction.
  • VTM6 several conventional angular intra prediction modes are adaptively replaced with wide-angle intra prediction modes for the non-square blocks.
  • width/height ratio is 1/2
  • the modes from 61 to 66 is mapped to -6 to -1, respectively.
  • the modes from 61 to 66 will refer to the reference samples from down left side instead of up-right edges.
  • mapping rule is defined as the following process, with the input nW as the width of the block, nH as the height of the block, and predModeIntra as the input angle mode:
  • the variable whRatio is set equal to Abs (Log2 (nW /nH) ) .
  • the intra prediction mode predModeIntra is modified as follows:
  • predModeIntra is set equal to (predModeIntra + 65) .
  • nH is greater than nH
  • predModeIntra is greater than or equal to 2
  • predModeIntra is less than (whRatio > 1) ? (8 + 2 *whRatio) : 8.
  • predModeIntra is set equal to (predModeIntra -67) .
  • nW is greater than nW
  • predModeIntra is less than or equal to 66
  • predModeIntra is greater than (whRatio > 1) ? (60 -2 *whRatio) : 60.
  • predModeIntra modes 61 to 66 would be mapped to -6 to -1. as it meets the following conditions:
  • nW is greater than nW
  • predModeIntra is less than or equal to 66
  • Intra sub-partition (ISP) coding mode is a tool applied for luma intra prediction modes.
  • the applied intra-prediction are divided vertically or horizontally into 2 or 4 sub-partitions, depending on the block size dimensions, as shown in Table 2. Note, vertically the width of sub-prediction-partition is not allowed to be smaller than 4 luma samples. All sub-prediction-partition shared a same intra prediction mode.
  • Multiple reference line (MRL) intra prediction uses more reference lines for intra prediction.
  • FIG 8 an example of 4 reference lines is depicted, where the samples of segments A and F are not fetched from reconstructed neighbouring samples but padded with the closest samples from Segment B and E, respectively.
  • intra-picture prediction uses the nearest reference line (i.e., reference line 0) .
  • reference line 0 the nearest reference line
  • 2 additional lines reference line 1 and reference line 2 can be used.
  • reference line 1 and reference line 2 can be used.
  • MRL When MRL is enable, a reference line index is signaled or inferred from bitstream to indicate which reference line is selected.
  • the angular intra prediction (not Matrix-based Intra Prediction, i.e. MIP) for luma and chroma components are different.
  • MIP Matrix-based Intra Prediction
  • For the luma component samples either a 4-tap cubic filter (sometimes it is also called a DCT-IF filter) or a 4-tap Gaussian filter could be applied.
  • For the chroma component samples a bilinear filter is applied.
  • the filter coefficients of DCT-IF filter and Gaussian filter are defined in the Table 3 in the current VVC Spec., as follows:
  • coefficients fc [p] [x] and fg [p] [x] with x equal to 0 to 3 corresponds to the coefficients of DCT-IF and Gaussian filter, respectively.
  • the fraction (sometimes it is also called phase) p used to index the coefficient group is derived as follows:
  • ⁇ y presents the vertical position of the desired prediction sample.
  • the desirable prediction sample p (0, 1) has a value of y equals to 1.
  • ⁇ refIdx represents the reference line index. It refers to which reference line is used for intra prediction, as shown in Figure 8. Allowed reference line are reference line 0, 1, 2.
  • intraPredAngle is defined according to Table 5
  • the condition using DCT-IF or Gaussian filter is determined by a flag FilterFlag.
  • the filterFlag When the filterFlag is 0, it means using DCT-IF filter coefficients.
  • the filterFlag When the filterFlag is 1, it means using Gaussian filter coefficients.
  • variable filterFlag is derived as follows:
  • filterFlag is set equal to 0.
  • IntraSubPartitionsSplitType is not equal to ISP_NO_SPLIT
  • nTbS is set equal to (Log2 (nTbW) + Log2 (nTbH) ) >> 1.
  • MinDistVerHor Min(Abs (predModeIntra -50) , Abs (predModeIntra -18) ) .
  • variable filterFlag is derived as follows:
  • filterFlag is set equal to 1.
  • filterFlag is set equal to 0.
  • the above process means, when MRL is enabled (i.e. refIdx is not equal to 0) or ISP is enabled (i.e. IntraSubPartitionsSplitType is not equal to ISP_NO_SPLIT) or a reference sample filter is enabled (i.e. refFilterFlag is equal to 1) filterFlag is set equal to 0, i.e. DCT-IF Filter is used.
  • the reference sample filter is used to smooth the reference samples before the actual prediction is performed, the flag refFilterFlag equal to 1 means it is enabled, 0 disabled.
  • variable refFilterFlag is derived as follows:
  • predModeIntra (after wide angle mode mapping) is equal to one of the following values: 0, -14, -12, -10, -6, 2, 34, 66, 72, 76, 78, 80, then refFilterFlag is set equal to 1.
  • refFilterFlag is set equal to 0.
  • variable filterFlag is further dependent on the intra prediction mode and block sizes. i.e. the following process:
  • nTbS is set equal to (Log2 (nTbW) + Log2 (nTbH) ) >> 1.
  • MinDistVerHor is set equal to Min (Abs (predModeIntra -50) , Abs (predModeIntra -18) ) .
  • variable filterFlag is derived as follows:
  • filterFlag is set equal to 1.
  • filterFlag is set equal to 0.
  • nTbW and nTbH are the prediction block width and height, respectively.
  • minDistVerHor represents whether the prediction mode is cloesr to Horitonzal prediction mode (18) or vertical prediction mode (50) . If the distance to mode horizontal or vertical is larger than a predefined parameter and reference sample filter is not applied (i.e. refFilterFlag is equal to 0) , then Gaussian filter is used (i.e. filterFlag is set equal to 1) , otherwise, DCT-IF filter is used.
  • the luma or chroma prediction is defined as follows:
  • index variable iIdx and the multiplication factor iFact are derived as follows:
  • iIdx ( ( (y + 1 + refIdx) *intraPredAngle) >> 5) + refIdx
  • fT [j] filterFlag ? fG [iFact] [j] : fC [iFact] [j]
  • the output predSamples is a 4-tap filtered value with fT [j] and the corresponding reference sample ref [x+iIdx+i] as the input.
  • a bi-linear filter 32-iFact, iFact is applied when iFact is not equal to zero. Otherwise (iFact is equal to 0) , the reference sample ref [x+iIdx+1] is copied as the output sample.
  • Chroma use a different filter than luma. It is proposed to apply the same 4-tap filters for the chroma component.
  • condition switch between DCT-IF filter and Gaussian Filter can also be the same for the luma and chroma.
  • the intra prediction process is defined as follows, as a comparison to the related art, deletion is noted as strikethrough, and addition is highlighted:
  • index variable iIdx and the multiplication factor iFact are derived as follows:
  • iIdx ( ( (y + 1 + refIdx) *intraPredAngle) >> 5) + refIdx
  • fT [j] filterFlag ? fG [iFact] [j] : fC [iFact] [j]
  • the filtering processes for the luma component and the chroma component can be unified by using the same filter, which can reduce the complexity significantly as compared to the method used in the current VVC draft.
  • the following embodiments are considered to adapt the different sampling ratio, for example, for 4: 4: 4 or 4: 2: 0, 4: 2: 2.
  • the unified derivation process for FilterFlag is defined as follows:
  • variable filterFlag is derived as follows:
  • filterFlag is set equal to 0.
  • IntraSubPartitionsSplitType is not equal to ISP_NO_SPLIT
  • nTbS is set equal to (Log2 (nTbW) + Log2 (nTbH) ) >> 1.
  • MinDistVerHor is set equal to Min (Abs (predModeIntra -50) , Abs (predModeIntra -18) ) .
  • variable filterFlag is derived as follows:
  • filterFlag is set equal to 1.
  • filterFlag is set equal to 0.
  • the unified derivation process for FilterFlag is defined as follows:
  • variable filterFlag is derived as follows:
  • filterFlag is set equal to 0.
  • IntraSubPartitionsSplitType is not equal to ISP_NO_SPLIT
  • MinDistVerHor is set equal to Min (Abs (predModeIntra -50) , Abs (predModeIntra -18) ) .
  • variable filterFlag is derived as follows:
  • filterFlag is set equal to 1.
  • filterFlag is set equal to 0.
  • the unified derivation process for FilterFlag is defined as follows:
  • variable filterFlag is derived as follows:
  • filterFlag is set equal to 0.
  • IntraSubPartitionsSplitType is not equal to ISP_NO_SPLIT
  • MinDistVerHor is set equal to Min (Abs (predModeIntra -50) , Abs (predModeIntra -18) ) .
  • variable filterFlag is derived as follows:
  • filterFlag is set equal to 1.
  • filterFlag is set equal to 0.
  • cIdx represents the color component of the current block
  • cIdx equal to 0 indicates current block is a luma block
  • cIdx equal to 1 indicates a chroma Cb block
  • cIdx equal to 2 indicates a chroma Cr block.
  • a method of coding (encoding or decoding) a current block (for example, a prediction block) of a picture of a video sequence wherein coding a luma component and coding a chroma component comprises intra prediction processing including interpolation filtering in order to achieve sub-pixel accuracy wherein the interpolation filtering is performed for the chroma component with the same interpolation filter that is used for the interpolation filtering of the luma component.
  • An embodiment of such a method is illustrated in Figure 11.
  • the method comprises coding 1110 a luma component of the current block using a first intra prediction based on an intra prediction mode of the luma component of the current block (for example, an angular intra prediction mode or wide-angle intra prediction mode) , wherein the first intra prediction includes performing, onto reference samples of the luma component of the current block, an interpolation filtering by means of an interpolation filter.
  • the interpolation filter may be a 4-tap filter.
  • the interpolation filter used in step 1110 of Figure 11 may be a Gaussian filter or a DCT-IF filter or another 4-tap interpolation filter.
  • the method illustrated in Figure 11 comprises coding 1120 a chroma component of the current block using a second intra prediction based on an intra prediction mode of the chroma component of the current block, wherein the second intra prediction includes performing, onto reference samples of the chroma component of the current block, interpolation filtering by means of the same interpolation filter that is used for the interpolation filtering comprised in step 1110 of coding the luma component.
  • the intra prediction mode of the chroma component may be the same as the intra prediction mode of the luma component.
  • the interpolation filtering of both the luma component and the chroma component is based on the same interpolation filter the logical and physical complexity of the overall interpolation filtering and coding may be reduced as compared to the art.
  • the interpolation can be performed by the same single interpolation unit of the processing hardware architecture.
  • An interpolation filter type indicator indicating a particular interpolation filter (for example, one of two filters) that is to be used as the interpolation filter may be provided.
  • the method illustrated in Figure 11 may comprise the step of obtaining coding information on the color component of the current block, and wherein the interpolation filter type indicator is determined based on the obtained coding information on the color component of the current block.
  • the method illustrated in Figure 11 can be readily implemented in the apparatuses described above with reference to Figures 1a, 1b, 4 and 5. Particularly, the method illustrated in Figure 11 may be carried out by the encoder 20 shown in Figures 1A, 1B and Figure 2.
  • the intra prediction may be carried out by the intra-prediction unit 254 of the encoder 20 shown in Figure 2 or the intra-prediction unit 354 of the decoder 20 shown in Figure 3.
  • FIG. 12 A configuration of a video coding device 1200 according to an embodiment is shown in Figure 12.
  • the method illustrated in Figure 11 may be implemented in the video coding device 1200.
  • the video coding device 1200 comprises a luma coding unit 1210 and a chroma coding unit 1220.
  • the luma coding unit 1210 according to this embodiment is configured for coding a luma component of the current block using a first intra prediction based on an intra prediction mode of the luma component of the current block, wherein the first intra prediction includes performing, onto reference samples of the luma component of the current block, an interpolation filtering by means of an interpolation filter.
  • the chroma coding unit 1220 makes use of the same interpolation filter (for example, a 4-tap interpolation filter, particularly a DCT-IF filter or Gaussian filter) that is used by the luma coding unit 1210.
  • the chroma coding unit 1220 is configured for coding a chroma component of the current block using a second intra prediction based on an intra prediction mode of the chroma component of the current block, wherein the second intra prediction includes performing, onto reference samples of the chroma component of the current block, interpolation filtering by means of the same interpolation filter used by the luma coding unit 1210.
  • the video coding device 1300 comprises an obtaining unit 1301.
  • the obtaining unit 1301 is configured for obtaining an interpolation filter type indicator indicating an interpolation filter to be used for interpolation filtering.
  • the obtaining unit 1301 may be further configured for obtaining coding information on the color component of a current block to be coded, and the obtaining unit may be configured to determine the interpolation filter type indicator based on the obtained coding information on the color component of the current block.
  • the video coding device 1300 comprises a luma coding unit 1310 configured for coding a luma component of the current block using a first intra prediction based on an intra prediction mode of the luma component of the current block, wherein the first intra prediction includes performing, onto reference samples of the luma component of the current block, an interpolation filtering by means of the interpolation filter indicated by the the interpolation filter type indicator obtained by the obtaining unit 1301.
  • the luma coding unit 1310 comprises a corresponding luma intra prediction unit 1315 for carrying out the first intra prediction.
  • the video coding device 1300 comprises a chroma coding unit 1320 configured for coding a chroma component of the current block using a second intra prediction based on an intra prediction mode of the chroma component of the current block, wherein the second intra prediction includes performing, onto reference samples of the chroma component of the current block, interpolation filtering by means of the same interpolation filter used by the luma coding unit 1310.
  • the chroma coding unit 1320 comprises a corresponding chroma intra prediction unit 1325 for carrying out the second intra prediction.
  • a configuration of a video coding device 1400 employing a DCT-IF filter or Gaussian filter is shown in Figure 14.
  • the video coding device 1400 comprises a luma coding unit 1310 and a chroma coding unit 1420.
  • the luma coding unit 1410 Similar to the video coding device 1200 shown in Figure 12 and the video coding device 1300 shown in Figure 13, the luma coding unit 1410 according to this embodiment is configured for coding a luma component of the current block using a first intra prediction based on an intra prediction mode of the luma component of the current block, wherein the first intra prediction includes performing, onto reference samples of the luma component of the current block, an interpolation filtering by means of an interpolation filter.
  • the chroma coding unit 1420 is configured for coding a chroma component of the current block using a second intra prediction based on an intra prediction mode of the chroma component of the current block, wherein the second intra prediction includes performing, onto reference samples of the chroma component of the current block, interpolation filtering by means of the interpolation filter used by the luma coding unit 1410.
  • Both the luma coding unit 1410 and the chroma coding unit 1420 have access to the DCT-IF filter or Gaussian filter as it is shown in Figure 14.
  • the chroma coding unit 1420 also makes use of the DCT-IF filter.
  • the chroma coding unit 1420 also makes use of the Gaussian filter. Since the luma coding unit 1410 and the chroma coding unit 1420 use the same interpolation filter they may share an interpolation unit 1430 used for the interpolation filtering process.
  • the video coding devices 1200, 1300 and 1400 shown in Figures 12, 13 and 14 may be comprised in the video coding device 400 shown in Figure 4 and/or may be part of the apparatus 500 shown in Figure 5.
  • the video coding device 1200, the video coding device 1300 and the video coding device 1400 may represent the video encoder 20 of the video coding system 40 shown in Figure 1B or the video decoder 30 of the video coding system 40 shown in Figure 1B, for example.
  • a method of coding implemented by a coding device comprising:
  • the second intra prediction includes performing, onto reference samples of the chroma component of the current block, the same interpolation filtering (filtering method) as included in the first intra prediction.
  • interpolation filtering has a set of interpolation filter coefficients which are derived on the bases of intra prediction mode of the luma component of the current block.
  • the filtering type indicator is determined based on coding information of the component of the current block, indicated by a variable of cIdx.
  • cIdx represents the color component of the current block
  • cIdx 0 indicates current block is a luma block
  • cIdx 1 indicates a chroma Cb block
  • cIdx 2 indicates a chroma Cr block.
  • the coding information includes any one or any combination of the following parameters: refFilterFlag, refIdx, IntraSubPartitionsSplitType, nTbS, minDistVerHor, wherein the refFilterFlag indicates if a reference sample filter is used to smooth the reference samples before the actual prediction.
  • IntraSubPartitionsSplitType is not equal to ISP_NO_SPLIT.
  • the filtering type indicator is set equal to the second value (1) if minDistVerHor is greater than intraHorVerDistThres [nTbS] and refFilterFlag is equal to 0, otherwise the filtering type indicator is set to the first value.
  • the fC interpolation filter coefficients specify the coefficients of the first filter
  • the fG interpolation filter coefficients specify the ccoefficeints of the second filter
  • a decoder (30) comprising processing circuitry for carrying out the method according to any one of embodiments 1 to 9.
  • a computer program product comprising a program code for performing the method according to any one of embodiments 1 to 9.
  • a decoder comprising:
  • a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the decoder to carry out the method according to any one of embodiments 1 to 9.
  • An encoder comprising:
  • a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the encoder to carry out the method according to any one of embodiments 1 to 9.
  • na When a relational operator is applied to a syntax element or variable that has been assigned the value "na” (not applicable) , the value “na” is treated as a distinct value for the syntax element or variable. The value “na” is considered not to be equal to any other value.
  • Bit-wise "or” When operating on integer arguments, operates on a two's complement representation of the integer value. When operating on a binary argument that contains fewer bits than another argument, the shorter argument is extended by adding more significant bits equal to 0.
  • x y Arithmetic right shift of a two's complement integer representation of x by y binary digits. This function is defined only for non-negative integer values of y.Bits shifted into the most significant bits (MSBs) as a result of the right shift have a value equal to the MSB of x prior to the shift operation.
  • MSBs most significant bits
  • x y.. z x takes on integer values starting from y to z, inclusive, with x, y, and z being integer numbers and z being greater than y.
  • Asin (x) the trigonometric inverse sine function, operating on an argument x that is in the range of -1.0 to 1.0, inclusive, with an output value in the range of - ⁇ 2 to ⁇ 2, inclusive, in units of radians
  • Atan (x) the trigonometric inverse tangent function, operating on an argument x, with an output value in the range of - ⁇ 2 to ⁇ 2, inclusive, in units of radians
  • Ceil (x) the smallest integer greater than or equal to x.
  • Clip1 Y (x) Clip3 (0, (1 ⁇ BitDepth Y ) -1, x)
  • Clip1 C (x) Clip3 (0, (1 ⁇ BitDepth C ) -1, x)
  • Cos (x) the trigonometric cosine function operating on an argument x in units of radians.
  • Tan (x) the trigonometric tangent function operating on an argument x in units of radians
  • the table below specifies the precedence of operations from highest to lowest; a higher position in the table indicates a higher precedence.
  • statement 1 If one or more of the following conditions are true, statement 1:
  • embodiments of the invention have been primarily described based on video coding, it should be noted that embodiments of the coding system 10, encoder 20 and decoder 30 (and correspondingly the system 10) and the other embodiments described herein may also be configured for still picture processing or coding, i.e. the processing or coding of an individual picture independent of any preceding or consecutive picture as in video coding.
  • inter-prediction units 244 (encoder) and 344 (decoder) may not be available in case the picture processing coding is limited to a single picture 17. All other functionalities (also referred to as tools or technologies) of the video encoder 20 and video decoder 30 may equally be used for still picture processing, e.g.
  • residual calculation 204/304 transform 206, quantization 208, inverse quantization 210/310, (inverse) transform 212/312, partitioning 262/362, intra-prediction 254/354, and/or loop filtering 220, 320, and entropy coding 270 and entropy decoding 304.
  • Embodiments, e.g. of the encoder 20 and the decoder 30, and functions described herein, e.g. with reference to the encoder 20 and the decoder 30, may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on a computer-readable medium or transmitted over communication media as one or more instructions or code and executed by a hardware-based processing unit.
  • Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol.
  • computer-readable media generally may correspond to (1) tangible computer-readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave.
  • Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and/or data structures for implementation of the techniques described in this disclosure.
  • a computer program product may include a computer-readable medium.
  • Such computer-readable storage media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium.
  • coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) , or wireless technologies such as infrared, radio, and microwave are included in the definition of medium.
  • DSL digital subscriber line
  • computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but are instead directed to non-transitory, tangible storage media.
  • Disk and disc includes compact disc (CD) , laser disc, optical disc, digital versatile disc (DVD) , floppy disk and Blu-ray disc, where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
  • processors such as one or more digital signal processors (DSPs) , general purpose microprocessors, application specific integrated circuits (ASICs) , field programmable logic arrays (FPGAs) , or other equivalent integrated or discrete logic circuitry.
  • DSPs digital signal processors
  • ASICs application specific integrated circuits
  • FPGAs field programmable logic arrays
  • processors may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein.
  • the functionality described herein may be provided within dedicated hardware and/or software modules configured for encoding and decoding, or incorporated in a combined codec. Also, the techniques could be fully implemented in one or more circuits or logic elements.
  • the techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC) or a set of ICs (e.g., a chip set) .
  • IC integrated circuit
  • a set of ICs e.g., a chip set
  • Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as described above, various units may be combined in a codec hardware unit or provided by a collection of interoperative hardware units, including one or more processors as described above, in conjunction with suitable software and/or firmware.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Compression Or Coding Systems Of Tv Signals (AREA)

Abstract

L'invention concerne un procédé de codage d'un bloc d'une image, le même filtre d'interpolation intervenant dans le codage d'une composante de luminance et dans le codage d'une composante de chrominance. Le procédé est mis en œuvre par un dispositif de codage et consiste à coder une composante de luminance du bloc courant à l'aide d'une première prédiction intra sur la base d'un mode de prédiction intra de la composante de luminance du bloc courant, la première prédiction intra comprenant l'application, à des échantillons de référence de la composante de luminance du bloc courant, d'un filtrage d'interpolation au moyen d'un filtre d'interpolation et à coder une composante de chrominance du bloc courant à l'aide d'une seconde prédiction intra sur la base d'un mode de prédiction intra de la composante de chrominance du bloc courant, la seconde prédiction intra comprenant l'application, à des échantillons de référence de la composante de chrominance du bloc courant, d'un filtrage d'interpolation au moyen du filtre d'interpolation.
PCT/CN2020/118422 2019-10-06 2020-09-28 Codeur, décodeur et procédés correspondants d'unification de filtre d'interpolation de composantes de luminance et de chrominance WO2021068785A1 (fr)

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Citations (3)

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CN105379266A (zh) * 2013-07-19 2016-03-02 高通股份有限公司 停用帧内预测滤波
CN109196867A (zh) * 2016-06-08 2019-01-11 高通股份有限公司 在帧内预测中使用的参考线索引的隐式译码
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