CN117941359A

CN117941359A - Processing video data picture size change request and notification messages

Info

Publication number: CN117941359A
Application number: CN202280061891.4A
Authority: CN
Inventors: Y·何; M·Z·科班
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 2021-09-20
Filing date: 2022-08-16
Publication date: 2024-04-26

Abstract

An example apparatus for requesting reduced resolution for video data includes: a memory configured to store video data; and one or more processors implemented in the circuit and configured to: decoding a first picture sequence of a bitstream, the first picture sequence having a first resolution; in response to determining that the device is to enter a power saving mode, sending a message requesting reduced resolution relative to the first resolution for a second sequence of pictures that follows the first sequence of pictures in coding order; and decoding the second picture sequence of the video data of the bitstream, the second picture sequence having the reduced resolution. The reduced resolution can be a reduced spatial resolution, a reduced temporal resolution (frame rate), or both.

Description

Processing video data picture size change request and notification messages

The present application claims priority from U.S. patent application Ser. No. 17/819,703, filed 8/15, 2022, and U.S. provisional application Ser. No. 63/261,403, filed 9/20, 2021, which are incorporated herein by reference in their entireties. U.S. patent application Ser. No. 17/819,703, filed 8/15 at 2022, claims the benefit of U.S. provisional application No. 63/261,403, filed 9/20 at 2021.

Technical Field

The present disclosure relates to video coding, including video encoding and video decoding.

Background

Digital video capabilities can be incorporated into a wide variety of devices, including digital televisions, digital direct broadcast systems, wireless broadcast systems, personal Digital Assistants (PDAs), laptop or desktop computers, tablet computers, electronic book readers, digital cameras, digital recording devices, digital media players, video gaming devices, video gaming consoles, cellular or satellite radio telephones (so-called "smartphones"), video teleconferencing devices, video streaming devices, and the like. Digital video devices implement video coding techniques such as the standards defined by MPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264/MPEG-4 (part 10, advanced Video Coding (AVC)), ITU-T H.265/High Efficiency Video Coding (HEVC), ITU-T H.266/multifunctional video coding (VVC) and extensions of such standards, as well as proprietary video codecs/formats such as AOMedia Video (AV 1) developed by the open media alliance. By implementing such video coding techniques, video devices may more efficiently transmit, receive, encode, decode, and/or store digital video information.

Video coding techniques include spatial (intra-picture) prediction and/or temporal (inter-picture) prediction to reduce or eliminate redundancy inherent in video sequences. For block-based video coding, a video slice (e.g., a video picture or a portion of a video picture) may be divided into video blocks, which may also be referred to as Coding Tree Units (CTUs), coding Units (CUs), and/or coding nodes. Video blocks in slices of an intra coded (I) picture are encoded using spatial prediction relative to reference samples in neighboring blocks in the same picture. Video blocks in a slice of an inter coded (P or B) picture may use spatial prediction with respect to reference samples in neighboring blocks in the same picture or temporal prediction with respect to reference samples in other reference pictures. A picture may be referred to as a frame and a reference picture may be referred to as a reference frame.

In some cases, the video decoder may send a message to the video encoder to request modifications to the video coding determination. For example, "Codec Control MESSAGES IN THE RTP Audio-Visual Profile with Feedback (AVPF)" (network working group, RFC 5104, month 2008) by Wenger et al describes Codec Control messages for real-time transport protocol (RTP) in conversational multimedia scenes, including full-frame requests (FIR), space-time compromise requests (TSTR) and notifications (TSTN), ITU-T H.271 Video Back Channel Messages (VBCM), temporary maximum media stream bit rate requests (TMMBR) and notifications (TMMBN).

Disclosure of Invention

In general, this disclosure describes techniques by which a video decoder may send a request to change the resolution of a picture to a video encoder. In some examples, the request (referred to herein as a Video Spatial Resolution Request (VSRR)) may be to change the spatial resolution at which the picture is coded. The request may signal an explicit width and height of a coded picture for a particular temporal layer or spatial layer. The request may signal a percentage decrease or an increase in resolution of the original picture size. The request may also be to encode a specific region of a picture or a set of sub-pictures of a temporal or spatial layer. Additionally or alternatively, the video decoder may request a reduced temporal resolution (i.e., frame rate) of the sequence of pictures. Reducing the spatial resolution and/or the temporal resolution of pictures in a sequence of pictures may reduce the power consumed by a video decoder to decode the reduced resolution pictures.

In one example, a method of requesting reduced resolution for video data includes: decoding, by a video decoder of a client device, a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution; in response to determining that the client device is to enter a power saving mode, sending, by the client device, a message requesting reduced resolution relative to the first resolution for a second sequence of pictures that follows the first sequence of pictures in decoding order; and decoding, by the video decoder of the client device, the second picture sequence of the video data of the bitstream, the second picture sequence having the reduced resolution.

In another example, an apparatus for requesting reduced resolution for video data includes: a memory configured to store video data; and one or more processors implemented in the circuit and configured to: decoding a first picture sequence of a bitstream, the first picture sequence having a first resolution; in response to determining that the device is to enter a power saving mode, sending a message requesting reduced resolution relative to the first resolution for a second sequence of pictures that follows the first sequence of pictures in coding order; and decoding the second picture sequence of the video data of the bitstream, the second picture sequence having the reduced resolution.

In another example, a computer-readable storage medium has stored thereon instructions that, when executed, cause a processor of a client device to: decoding a first picture sequence of a bitstream, the first picture sequence having a first resolution; in response to determining that the device is to enter a power saving mode, sending a message requesting reduced resolution relative to the first resolution for a second sequence of pictures that follows the first sequence of pictures in coding order; and decoding the second picture sequence of the video data of the bitstream, the second picture sequence having the reduced resolution.

In another example, an apparatus for requesting reduced resolution for video data, the apparatus comprising: means for decoding a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution; means for sending a message requesting reduced resolution relative to the first resolution for a second sequence of pictures that follows the first sequence of pictures in coding order in response to determining that the client device is to enter a power save mode; and means for decoding the second picture sequence of the video data of the bitstream, the second picture sequence having the reduced resolution.

The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

Drawings

Fig. 1 is a block diagram illustrating an example video encoding and decoding system that may perform the techniques of this disclosure.

Fig. 2 is a conceptual diagram illustrating a specification of resolution for coding a new picture of a video sequence.

Fig. 3 is a conceptual diagram illustrating an example syntax structure for a Video Spatial Resolution Request (VSRR) resolution change message.

Fig. 4 is a conceptual diagram of an example syntax structure for a Video Spatial Resolution Notification (VSRN) message corresponding to a VSRR resolution change message.

Fig. 5 is a conceptual diagram of an example syntax structure for a Video Spatial Resolution Request (VSRR) region coding message.

Fig. 6 is a conceptual diagram of an example syntax structure for a Video Spatial Resolution Notification (VSRN) message corresponding to a VSRR region encoded message.

Fig. 7 is a conceptual diagram of an example syntax structure for a Video Temporal Resolution Request (VTRR) message.

Fig. 8 is a conceptual diagram of an example syntax structure for a video temporal resolution notification (VSRN) message corresponding to VTRR request messages.

Fig. 9 is a block diagram illustrating an example video encoder that may perform video encoding and video decoding (or video reproduction).

Fig. 10 is a block diagram illustrating an example video decoder that may perform video decoding.

Fig. 11 is a flowchart illustrating an example method of requesting new resolution for a picture in accordance with the techniques of this disclosure.

Fig. 12 is a flowchart illustrating an example method of requesting region decoding in accordance with the techniques of this disclosure.

Fig. 13 is a flowchart illustrating an example method of requesting reduced resolution for video data in accordance with the techniques of this disclosure.

Detailed Description

The universal supplemental enhancement information (VSEI) standard (i.e., ITU-T h.274 and ISO/IEC 23002-7) supports picture spatial resolution changes within the Coding Layer Video Sequence (CLVS). Similarly, ITU-T h.266/universal video coding (VVC) allows resolution change requests to be sent in CLVS. ISO/IEC 23001-11 (referred to as "green MPEG") specifies complexity metrics and interactive signaling for energy-efficient media consumption. The client may request a remote decoder power reduction by signaling to the encoder an expected percentage reduction of the local decoding operation. The encoder may disable certain coding tools to reduce decoder power consumption, which may also reduce coding efficiency and introduce visible artifacts. When the decoder power is insufficient to complete the session and/or the transmission bandwidth is low, it may be desirable to explicitly request a resolution change while maintaining proper coding efficiency.

In addition, when transmission bandwidth is limited, encoding smaller size pictures using the same amount of bits may result in better quality than encoding larger size pictures using the same amount of bits. Downsampling a picture prior to encoding may reduce bandwidth and coding complexity while maintaining adequate picture quality. An alternative approach is to encode a portion of the picture (also referred to as a region of interest) to reduce bandwidth and coding complexity.

The temporal resolution or frame rate also affects the decoder power consumption. The decoder may extract certain temporal sub-layers to reduce the frame rate, but the receiver may still consume energy when receiving those frames that are not to be decoded. It may be desirable to instruct an encoder to encode video at a lower frame rate to reduce decoding complexity and also reduce power consumption of a receiver that includes a decoder.

In accordance with the techniques of this disclosure, a video decoder may send a Video Spatial Resolution Request (VSRR) to request a video encoder to change its coding resolution. The request may signal an explicit width and height of a coded picture for a particular temporal layer or spatial layer. The request may signal a percentage decrease or an increase in resolution of the original picture size. The request may also request that a specific region of a picture or a set of sub-pictures of a temporal or spatial layer be encoded. The video encoder may reply with a Video Spatial Resolution Notification (VSRN) message that represents the actual resolution, which may be the same as or different from the requested resolution (or picture size).

In this way, a client device including a video decoder may request reduced resolution (e.g., spatial resolution, temporal resolution, or both) for a sequence of pictures of video data from a source device including a video encoder. The video decoder may consume less power when fewer pictures are decoded (e.g., video data with reduced temporal resolution/frame rate) over a period of time and/or when pictures have reduced spatial resolution. Accordingly, the techniques of this disclosure may reduce power consumption of a video decoder, thereby increasing battery life and reducing resources required to charge or maintain battery charge. Furthermore, reducing the spatial resolution and/or the temporal resolution of the pictures of the video data may reduce the bandwidth consumed by a network device between and including the source device and the client device. Furthermore, reducing spatial resolution and/or temporal resolution may reduce the processing that needs to be performed by the video encoder to encode the video data. In this way, these techniques may improve the fields of video coding and video transmission, as well as the performance of devices operating within those fields.

Fig. 1 is a block diagram illustrating an example video encoding and decoding system 100 that may perform the techniques of this disclosure. The techniques of this disclosure generally relate to coding (encoding and/or decoding) video data. Generally, video data includes any data used to process video. Thus, video data may include raw uncoded video, encoded video, decoded (e.g., reconstructed) video, and video metadata, such as signaling data.

As shown in fig. 1, in this example, system 100 includes a source device 102 that provides encoded video data to be decoded and displayed by a destination device 116. Specifically, the source device 102 provides video data to the destination device 116 via the computer readable medium 110. Source device 102 and destination device 116 may comprise any of a wide range of devices including desktop computers, notebook (i.e., laptop) computers, mobile devices, tablet computers, set-top boxes, hand-held phones such as smartphones, televisions, cameras, display devices, digital media players, video game consoles, video streaming devices, broadcast receiver devices, and the like. In some cases, the source device 102 and the destination device 116 may be equipped for wireless communication, and thus may be referred to as wireless communication devices.

In the example of fig. 1, source device 102 includes video source 104, memory 106, video encoder 200, and communication interface 108. Destination device 116 includes communication interface 122, battery 124, power sensor 126, charging interface 128, video decoder 300, memory 120, and display device 118. The source device 102 represents an example of a video encoding device and the destination device 116 represents an example of a video decoding device. In other examples, the source device and the destination device may include other components or arrangements. For example, the source device 102 may receive video data from an external video source, such as an external camera. Likewise, the destination device 116 may interface with an external display device instead of including an integrated display device.

The system 100 as shown in fig. 1 is only one example. In general, any digital video encoding and/or decoding device may perform techniques for processing requests to change the resolution of a picture. Source device 102 and destination device 116 are merely examples of such transcoding devices, wherein source device 102 generates transcoded video data for transmission to destination device 116. The present disclosure refers to a "decoding" device as a device that performs decoding (e.g., encoding and/or decoding) of data. Thus, the video encoder 200 and the video decoder 300 represent examples of decoding apparatuses, specifically, a video encoder and a video decoder, respectively. In some examples, source device 102 and destination device 116 may operate in a substantially symmetrical manner such that each of source device 102 and destination device 116 includes video encoding and decoding components. Thus, the system 100 may support unidirectional or bidirectional video transmission between the source device 102 and the destination device 116, for example, for video streaming, video playback, video broadcasting, or video telephony.

In general, video source 104 represents a source of video data (i.e., raw, uncoded video data) and provides a series of consecutive pictures (also referred to as "frames") of video data to video encoder 200, which encodes the data for the pictures. The video source 104 of the source device 102 may include a video capture device such as a video camera, a video archive containing previously captured raw video, and/or a video feed interface for receiving video from a video content provider. As further alternatives, the video source 104 may generate computer graphics-based data as the source video, or a combination of real-time video, archived video, and computer-generated video. In each case, the video encoder 200 encodes captured, pre-captured, or computer-generated video data. Video encoder 200 may rearrange pictures from the received order (sometimes referred to as the "display order") to a coding order for coding. The video encoder 200 may generate a bitstream comprising encoded video data. The source device 102 may then output the encoded video data onto the computer readable medium 110 via the communication interface 108 for receipt and/or retrieval by the communication interface 122, e.g., the destination device 116.

The memory 106 of the source device 102 and the memory 120 of the destination device 116 represent general purpose memory. In some examples, the memories 106, 120 may store raw video data, e.g., raw video from the video source 104 and raw decoded video data from the video decoder 300. Additionally or alternatively, the memories 106, 120 may store software instructions that are executable by, for example, the video encoder 200 and the video decoder 300, respectively. Although memory 106 and memory 120 are shown separate from video encoder 200 and video decoder 300 in this example, it should be understood that video encoder 200 and video decoder 300 may also include internal memory for functionally similar or equivalent purposes. Further, the memories 106, 120 may store encoded video data, for example, output from the video encoder 200 and input to the video decoder 300. In some examples, portions of the memory 106, 120 may be allocated as one or more video buffers, e.g., to store raw decoded and/or encoded video data.

Computer-readable medium 110 may represent any type of communication medium capable of transmitting encoded video data from source device 102 to destination device 116. In one example, the computer-readable medium 110 represents a communication medium that enables the source device 102 to transmit encoded video data directly to the destination device 116 in real-time, e.g., via a radio frequency network or a computer-based network. According to a communication standard, such as a wireless communication protocol, communication interface 108 may modulate a transmission signal including encoded video data, and communication interface 122 may demodulate a received transmission signal. The communication medium may include any wireless or wired communication medium such as a Radio Frequency (RF) spectrum or one or more physical transmission lines. The communication medium may form part of a packet-based network such as: a local area network, a wide area network, or a global network such as the internet. The communication medium may include a router, switch, base station, or any other equipment that may be useful for facilitating communication from the source device 102 to the destination device 116.

Communication interface 108 and communication interface 122 may represent a wireless transmitter/receiver, a modem, a wired networking component (e.g., an ethernet card), a wireless communication component operating according to any of a variety of IEEE802.11 standards, or other physical components. In examples where communication interface 108 and communication interface 122 include wireless components, communication interface 108 and communication interface 122 may be configured to transmit data (such as encoded video data) according to a cellular communication standard, such as 4G, 4G-LTE (long term evolution), LTE-advanced, 5G, and the like. In some examples where communication interface 108 includes a wireless transmitter, communication interface 108 and communication interface 122 may be configured to communicate data (such as encoded video data) in accordance with other wireless standards, such as the IEEE802.11 specification, the IEEE 802.15 specification (e.g., the ZigBee ^TM)、Bluetooth^TM standard, etc.), in some examples, source device 102 and/or destination device 116 may include respective system-on-chip (SoC) devices.

The techniques of this disclosure may be applied to video coding to support any of a variety of multimedia applications, such as over-the-air television broadcasting, cable television transmission, satellite television transmission, internet streaming video transmission (such as dynamic adaptive streaming over HTTP (DASH)), digital video encoded onto a data storage medium, decoding of digital video stored on a data storage medium, or other applications.

The communication interface 122 of the destination device 116 receives the encoded video bitstream from the computer readable medium 110 (e.g., a communication medium). The encoded video bitstream may include signaling information defined by the video encoder 200 and also used by the video decoder 300, such as syntax elements having values describing characteristics and/or processing of video blocks or other coding units (e.g., slices, pictures, groups of pictures, sequences, etc.). The display device 118 displays the decoded pictures of the decoded video data to a user. Display device 118 may represent any of a variety of display devices, such as a Liquid Crystal Display (LCD), a plasma display, an Organic Light Emitting Diode (OLED) display, or another type of display device.

Although not shown in fig. 1, in some examples, both the video encoder 200 and the video decoder 300 may be integrated with an audio encoder and/or an audio decoder, and may include appropriate MUX-DEMUX units or other hardware and/or software to process multiplexed streams that include both audio and video in a common data stream.

Video encoder 200 and video decoder 300 may each be implemented as any of a variety of suitable encoder and/or decoder circuits, such as one or more microprocessors, digital Signal Processors (DSPs), application Specific Integrated Circuits (ASICs), field Programmable Gate Arrays (FPGAs), discrete logic, software, hardware, firmware, or any combinations thereof. When the techniques are implemented in part in software, the apparatus may store instructions for the software in a suitable non-transitory computer-readable medium and execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Each of the video encoder 200 and the video decoder 300 may be included in one or more encoders or decoders, either of which may be integrated as part of a combined encoder/decoder (codec) in the respective device. Devices including video encoder 200 and/or video decoder 300 may include integrated circuits, microprocessors, and/or wireless communication devices (such as cellular telephones).

Video encoder 200 and video decoder 300 may operate in accordance with a video coding standard, such as ITU-T h.265 (also known as High Efficiency Video Coding (HEVC)) or an extension thereto, such as a multiview and/or scalable video coding extension. Alternatively, the video encoder 200 and video decoder 300 may operate in accordance with other proprietary or industry standards, such as ITU-T h.266, also known as multi-function video coding (VVC). In other examples, the video encoder 200 and video decoder 300 may operate in accordance with a proprietary video codec/format, such as AOMedia Video (AV 1), an extension of AV1, and/or a subsequent version of AV1 (e.g., AV 2). In other examples, video encoder 200 and video decoder 300 may operate according to other proprietary formats or industry standards. However, the techniques of this disclosure are not limited to any particular coding standard or format. In general, video encoder 200 and video decoder 300 may be configured to perform the techniques of this disclosure in connection with any video coding technique that includes processing a request to change a picture resolution.

In general, video encoder 200 and video decoder 300 may perform block-based coding of pictures. The term "block" generally refers to a structure that includes data to be processed (e.g., to be encoded, decoded, or otherwise used in an encoding and/or decoding process). For example, a block may comprise a two-dimensional matrix of samples of luminance and/or chrominance data. In general, video encoder 200 and video decoder 300 may decode video data represented in YUV (e.g., Y, cb, cr) format. That is, instead of coding red, green, and blue (RGB) data for samples of a picture, the video encoder 200 and the video decoder 300 may code luminance and chrominance components, wherein the chrominance components may include both red-hue chrominance components and blue-hue chrominance components. In some examples, the video encoder 200 converts the received RGB formatted data to a YUV representation prior to encoding, and the video decoder 300 converts the YUV representation to RGB format. Alternatively, a preprocessing and post-processing unit (not shown) may perform these conversions.

The present disclosure may generally refer to the coding (e.g., encoding and decoding) of a picture to include the process of encoding or decoding data of the picture. Similarly, the present disclosure may refer to coding a block of a picture to include a process of encoding or decoding (e.g., prediction and/or residual coding) data for the block. The encoded video bitstream typically includes a series of values for syntax elements that represent coding decisions (e.g., coding modes) and picture-to-block partitioning. Thus, references to coding of a picture or block should generally be understood as coding values of syntax elements forming the picture or block.

HEVC defines various blocks, including Coding Units (CUs), prediction Units (PUs), and Transform Units (TUs). According to HEVC, a video coder, such as video encoder 200, partitions Coding Tree Units (CTUs) into CUs according to a quadtree structure. That is, the video coder divides the CTUs and CUs into four equal, non-overlapping squares, and each node of the quadtree has zero or four child nodes. A node without child nodes may be referred to as a "leaf node," and a CU of such a leaf node may include one or more PUs and/or one or more TUs. The video coder may further divide the PU and the TU. For example, in HEVC, a Residual Quadtree (RQT) represents the partitioning of TUs. In HEVC, PUs represent inter prediction data, while TUs represent residual data. The intra-predicted CU includes intra-prediction information, such as an intra-mode indication.

As another example, the video encoder 200 and the video decoder 300 may be configured to operate according to VVC. According to VVC, a video coder, such as video encoder 200, divides a picture into a plurality of Coding Tree Units (CTUs). The video encoder 200 may divide the CTUs according to a tree structure, such as a quadtree-binary tree (QTBT) structure or a multi-type tree (MTT) structure. The QTBT structure removes the concept of multiple partition types, such as the separation between CUs, PUs, and TUs of HEVC. The QTBT structure includes two levels: a first level partitioned according to the quadtree partitioning, and a second level partitioned according to the binary tree partitioning. The root node of QTBT structure corresponds to the CTU. Leaf nodes of the binary tree correspond to Coding Units (CUs).

In the MTT partition structure, the blocks may be partitioned using a Quadtree (QT) partition, a Binary Tree (BT) partition, and one or more types of Trigeminal Tree (TT) (also referred to as Ternary Tree (TT)) partitions. A trigeminal or ternary tree partition is a partition in which a block is divided into three sub-blocks. In some examples, a trigeminal or ternary tree partition divides a block into three sub-blocks, rather than dividing the original block through the center. The partition types (e.g., QT, BT, and TT) in the MTT may be symmetrical or asymmetrical.

When operating according to the AV1 codec, the video encoder 200 and the video decoder 300 may be configured to code video data in block units. In AV1, the largest decoding block that can be processed is called a super block. In AV1, the superblock may be 128x128 luma samples or 64x64 luma samples. However, in a subsequent video coding format (e.g., AV 2), the super block may be defined by a different (e.g., larger) luma sample size. In some examples, the superblock is the top level of the block quadtree. Video encoder 200 may further divide the super block into smaller coding blocks. Video encoder 200 may divide super blocks and other coding blocks into smaller blocks using square or non-square partitions. Non-square blocks may include N/2xN, nxN/2, N/4xN, and NxN/4 blocks. The video encoder 200 and the video decoder 300 may perform separate prediction and transform processes for each coding block.

AV1 also defines tiles of video data. A tile is a rectangular array of super blocks that may be coded independently of other tiles. That is, the video encoder 200 and the video decoder 300 may encode and decode, respectively, the coding blocks within a tile without using video data from other tiles. However, the video encoder 200 and video decoder 300 may perform filtering across tile boundaries. The size of the tiles may be uniform or non-uniform. Tile-based coding may enable parallel processing and/or multithreading implemented by the encoder and decoder.

In some examples, video encoder 200 and video decoder 300 may use a single QTBT or MTT structure to represent each of the luma component and the chroma component, while in other examples, video encoder 200 and video decoder 300 may use two or more QTBT or MTT structures, such as one QTBT/MTT structure for the luma component and another QTBT/MTT structure for the two chroma components (or two QTBT/MTT structures for the respective chroma components).

Video encoder 200 and video decoder 300 may be configured to use quadtree partitioning, QTBT partitioning, MTT partitioning, superblock partitioning, or other partitioning structures.

In some examples, the CTUs include a Coding Tree Block (CTB) of luma samples, two corresponding CTBs of chroma samples of a picture having three sample arrays, or CTBs of monochrome pictures or samples of pictures coded using three separate color planes and syntax structures for coding the samples. CTBs may be blocks of NxN samples of some value of N such that one partition is to divide a component into CTBs. The component may be an array or a single sample from one of three arrays (luminance and two chromaticities) for a picture in a 4:2:0, 4:2:2 or 4:4:4 color format, or an array or a single sample of the array for a picture in a monochrome format. In some examples, the coding block is a block of MxN samples of some M and N values such that one partition is dividing CTBs into coding blocks.

Blocks (e.g., CTUs or CUs) may be grouped in pictures in various ways. As one example, a brick (brick) may refer to a rectangular region of CTU rows within a particular tile in a picture. A tile may be a rectangular region of CTUs within a particular tile column and a particular tile row in a picture. A tile column refers to a rectangular region of CTU having a height equal to the height of a picture and a width specified by a syntax element (e.g., such as in a picture parameter set). A tile line refers to a rectangular region of a CTU having a height specified by a syntax element (e.g., such as in a picture parameter set) and a width equal to the width of a picture.

In some examples, a tile may be divided into a plurality of bricks, each of which may include one or more rows of CTUs within the tile. A tile that is not divided into a plurality of bricks may also be referred to as a brick. However, bricks that are a true subset of tiles may not be referred to as tiles. The bricks in the picture may also be arranged in the slice. A slice may be an integer number of tiles of a picture, which may be uniquely contained in a single Network Abstraction Layer (NAL) unit. In some examples, a slice includes a continuous sequence of complete tiles of multiple complete tiles or just one tile.

The present disclosure may use "NxN" and "N by N" interchangeably to refer to the sample size of a block (such as a CU or other video block) in both the vertical and horizontal dimensions, e.g., 16x16 samples or 16 by 16 samples. Typically, a 16x16 CU will have 16 samples in the vertical direction (y=16) and 16 samples in the horizontal direction (x=16). Likewise, an NxN CU typically has N samples in the vertical direction and N samples in the horizontal direction, where N represents a non-negative integer value. Samples in a CU may be arranged in rows and columns. Furthermore, a CU does not necessarily need to have the same number of samples in the horizontal direction as in the vertical direction. For example, a CU may include NxM samples, where M is not necessarily equal to N.

The video encoder 200 encodes video data representing prediction and/or residual information and other information for the CU. The prediction information indicates how the CU is to be predicted in order to form a prediction block of the CU. Residual information generally represents a sample-by-sample difference between samples of a CU before encoding and a prediction block.

To predict a CU, video encoder 200 may typically form a prediction block of the CU by inter-prediction or intra-prediction. Inter-prediction generally refers to predicting a CU from data of a previously coded picture, while intra-prediction generally refers to predicting a CU from previously coded data of the same picture. To perform inter prediction, video encoder 200 may use one or more motion vectors to generate a prediction block. Video encoder 200 may typically perform a motion search to identify reference blocks that closely match the CU, e.g., according to differences between the CU and the reference blocks. The video encoder 200 may calculate a difference metric using a Sum of Absolute Differences (SAD), a Sum of Squared Differences (SSD), a Mean Absolute Difference (MAD), a Mean Squared Difference (MSD), or other such difference calculation to determine whether the reference block closely matches the current CU. In some examples, video encoder 200 may use unidirectional prediction or bi-directional prediction to predict the current CU.

Some examples of VVCs also provide affine motion compensation modes, which may be considered inter prediction modes. In affine motion compensation mode, the video encoder 200 may determine two or more motion vectors representing non-translational motion (such as zoom in or out, rotation, perspective motion, or other irregular motion types).

To perform intra prediction, the video encoder 200 may select an intra prediction mode to generate a prediction block. Some examples of VVCs provide sixty-seven intra-prediction modes, including various directional modes, as well as planar modes and DC modes. In general, the video encoder 200 selects an intra prediction mode that describes neighboring samples of a current block (e.g., a block of a CU) from which to predict samples of the current block. Assuming that video encoder 200 codes CTUs and CUs in raster scan order (left to right, top to bottom), such samples may typically be above, above left, or to the left of the current block in the same picture as the current block.

The video encoder 200 encodes data representing a prediction mode of the current block. For example, for inter prediction modes, video encoder 200 may encode data representing which of the various available inter prediction modes to use, as well as motion information for the corresponding modes. For example, for unidirectional or bi-directional inter prediction, the video encoder 200 may encode the motion vectors using Advanced Motion Vector Prediction (AMVP) or merge mode. The video encoder 200 may use a similar mode to encode the motion vectors for the affine motion compensation mode.

AV1 includes two general techniques for encoding and decoding coding blocks of video data. These two general techniques are intra-prediction (e.g., intra-prediction or spatial prediction) and inter-prediction (e.g., inter-prediction or temporal prediction). In the content of AV1, when the block of the current frame of video data is predicted using the intra prediction mode, the video encoder 200 and the video decoder 300 do not use video data from other frames of video data. For most intra-prediction modes, the video encoder 200 encodes a block of the current frame based on the difference between the sample values in the current block and the prediction values generated from the reference samples in the same frame. The video encoder 200 determines a prediction value generated from the reference samples based on the intra prediction mode.

After prediction (such as intra-prediction or inter-prediction of a block), video encoder 200 may calculate residual data for the block. Residual data, such as a residual block, represents a sample-by-sample difference between the block and a prediction block for the block, which is formed using a corresponding prediction mode. The video encoder 200 may apply one or more transforms to the residual block to produce transformed data in the transform domain instead of in the sample domain. For example, video encoder 200 may apply a Discrete Cosine Transform (DCT), an integer transform, a wavelet transform, or a conceptually similar transform to the residual video data. Additionally, the video encoder 200 may apply a secondary transform, such as a mode dependent inseparable secondary transform (MDNSST), a signal dependent transform, a Karhunen-Loeve transform (KLT), or the like, after the first transform. The video encoder 200 generates transform coefficients after applying one or more transforms.

As noted above, after generating any transform of the transform coefficients, the video encoder 200 may perform quantization of the transform coefficients. Quantization generally refers to the process of: wherein the transform coefficients are quantized to possibly reduce the amount of data representing the transform coefficients, thereby providing further compression. By performing the quantization process, the video encoder 200 may reduce the bit depth associated with some or all of the transform coefficients. For example, the video encoder 200 may round n-bit values down to m-bit values during quantization, where n is greater than m. In some examples, to perform quantization, the video encoder 200 may perform a bit-wise right-shift of the value to be quantized.

After quantization, the video encoder 200 may scan the transform coefficients to generate a one-dimensional vector from a two-dimensional matrix comprising quantized transform coefficients. The scan may be designed to place higher energy (and thus lower frequency) transform coefficients in front of the vector and lower energy (and thus higher frequency) transform coefficients in back of the vector. In some examples, video encoder 200 may scan quantized transform coefficients using a predefined scan order to generate a serialized vector, and then entropy encode the quantized transform coefficients of the vector. In other examples, video encoder 200 may perform adaptive scanning. After scanning the quantized transform coefficients to form a one-dimensional vector, video encoder 200 may entropy encode the one-dimensional vector, e.g., according to context-adaptive binary arithmetic coding (CABAC). The video encoder 200 may also entropy encode values of syntax elements that describe metadata associated with the encoded video data that was used by the video decoder 300 in decoding the video data.

To perform CABAC, the video encoder 200 may assign contexts within the context model to symbols to be transmitted. The context may relate to, for example, whether the adjacent value of the symbol is a zero value. The probability determination may be based on the context assigned to the symbol.

The video encoder 200 may further generate syntax data, such as block-based syntax data, picture-based syntax data, and sequence-based syntax data, or other syntax data, such as a Sequence Parameter Set (SPS), picture Parameter Set (PPS), or Video Parameter Set (VPS), to the video decoder 300, for example, in a picture header, a block header, a slice header. The video decoder 300 may also decode such syntax data to determine how to decode the corresponding video data.

In this way, the video encoder 200 may generate a bitstream including encoded video data, e.g., syntax elements describing the partitioning of pictures into blocks (e.g., CUs) and prediction and/or residual information for the blocks. Finally, the video decoder 300 may receive the bitstream and decode the encoded video data.

In general, the video decoder 300 performs a process inverse to that performed by the video encoder 200 to decode encoded video data of a bitstream. For example, the video decoder 300 may use CABAC to decode values of syntax elements for the bitstream in a substantially similar, but opposite manner to the CABAC encoding process of the video encoder 200. The syntax element may define partition information for dividing a picture into CTUs and dividing each CTU according to a corresponding partition structure such as QTBT structures to define CUs of the CTUs. Syntax elements may further define prediction and residual information for a block of video data (e.g., a CU).

The residual information may be represented by, for example, quantized transform coefficients. The video decoder 300 may inverse quantize and inverse transform the quantized transform coefficients of the block to reproduce a residual block for the block. The video decoder 300 uses the signaled prediction mode (intra prediction or inter prediction) and related prediction information (e.g., motion information for inter prediction) to form a prediction block for a block. The video decoder 300 may then combine the prediction block and the residual block (on a sample-by-sample basis) to reproduce the original block. The video decoder 300 may perform additional processing, such as performing a deblocking process to reduce visual artifacts along the boundaries of the blocks.

The present disclosure may refer generally to "signaling" certain information (such as syntax elements). The term "signaling" may generally refer to the communication of values of syntax elements and/or other data used to decode encoded video data. That is, the video encoder 200 may signal the value of the syntax element in the bitstream. Typically, signaling refers to generating a value in the bitstream. As noted above, the source device 102 may transmit the bit stream to the destination device 116 in substantially real-time.

In accordance with the techniques of this disclosure, destination device 116 and/or video decoder 300 may be configured to generate a request and send the request to source device 102 to change the picture resolution of the decoded video data. For example, the battery 124 of the destination device 116 may provide power to the display device 118, the memory 120, the video decoder 300, the communication interface 122, and the power sensor 126, as well as other components of the destination device 116 (not shown in fig. 1).

In general, processing (e.g., decoding, rendering, and displaying) high resolution video data may consume a greater amount of power than processing lower resolution video data. The term "resolution" may refer to the spatial resolution (e.g., width and height) and/or the temporal resolution (e.g., frame rate) of a picture. In some examples, the charge sensor 126 may be configured with a battery level threshold. When the current power of the battery 124 is above the battery level threshold, the video data may be processed at a relatively high resolution. However, in some examples, when the charge sensor 126 detects that the charge of the battery 124 is below a battery level threshold, the charge sensor 126 may determine that the destination device 116 should enter the power saving mode. Accordingly, the power sensor 126 may inform the communication interface 122 and/or the video decoder 300, either of which may request lower resolution (spatial and/or temporal) video data from the source device 102 and/or the video encoder 200. In other examples, the battery level threshold and the power sensor need not be provided, but instead, the user of the destination device 116 may determine that a power save mode should be performed in which lower resolution (spatial and/or temporal) video data is requested.

In particular, destination device 116 may send a request for reduced resolution video data to source device 102 via computer-readable medium 110. For example, video decoder 300 may construct a Video Spatial Resolution Request (VSRR) message specifying a resolution change and send the VSRR message to video encoder 200 via communication interface 122. If video encoder 200 can adjust its encoded picture or region resolution, it may consider the received VSRR message for coding of future pictures. The destination device 116 may include the VSRR message in a payload-specific Feedback message, such as a real-time transport control protocol (RTCP) Feedback message (e.g., as specified in Ott et al, "Extended RTP Profile for Real-time Transport Control Protocol (RTCP) -based Feedback (RTP/AVPF)" (network working group, RFC 4585, month 7 2006).

The destination device 116 may form a VSRR message to include the contents of syntax elements or fields to indicate the suitability of the requested picture resolution change and update according to the discussion below. The syntax element or field may indicate the VSRR type, for example, as follows: resolution or resolution change for pictures of one or more layers; resolution or resolution change of a picture for one or more temporal layers of a particular layer; and/or resolution change for pictures of a particular temporal layer across all layers. The VSRR message may include a syntax element or field to indicate the number of resolution changes specified in the VSRR message.

The VSRR message may include a syntax element or field to request cancellation of the resolution change request of any previous VSRR message. The VSRR message may include a syntax element or field to request that the original picture resolution be restored when no picture resolution is present in the message. For example, if destination device 116 determines that a power source has been coupled to charging interface 128 (e.g., a Universal Serial Bus (USB) interface), destination device 116 may determine that normal power mode may be restored and thus send a VSRR message indicating that higher resolution (e.g., previous resolution) video data may be restored.

In general, the reaction time of video encoder 200 may be significantly longer than a typical picture duration. The video encoder 200 may determine whether and to what extent a request from the destination device 116 causes a change in resolution or area. The video encoder 200 may return a Video Spatial Resolution Notification (VSRN) message to indicate the changes that it will use thereafter.

Fig. 2 is a conceptual diagram illustrating a specification of resolution for coding a new picture of a video sequence. Specifically, fig. 2 depicts an original picture 130, a requested new picture 131, a left offset 132, a top offset 134, a right offset 136, and a bottom offset 138. Destination device 116 may request video encoder 200 to encode the region of original picture 130 as a new picture. Destination device 116 may form a VSRR message to include syntax elements to indicate left offset 132, top offset 134, right offset 136, and bottom offset 138 to original picture 130 to form new picture 131. For a sub-picture based encoding process, destination device 116 may form a VSRR message to include a syntax element to indicate a sub-picture Identifier (ID) and request video encoder 200 to encode a particular sub-picture instead of the entire picture.

Fig. 3 is a conceptual diagram illustrating an example syntax structure for a Video Spatial Resolution Request (VSRR) resolution change message 140. In this example, VSRR resolution change message 140 includes a Synchronization Source (SSRC) field 141, a sequence number (sequence num.) field 142, a layer identifier (layer ID.) field 143, a time identifier (t.id) field 144, padding fields 145A, 145B, a picture width field 146, and a picture height field 147. The picture width field 146 and the picture height field 147 may be referred to as the payload of the VSRR resolution change message 140.

In this example, SSRC field 141 may represent a synchronization source of a Video Spatial Resolution Request (VSRR) that originated the request. The payload of VSRR resolution change message 140 carries data representing the requested picture width (in picture width field 146) and picture height (in picture height field 147) of the picture applicable to the particular temporal layer (specified in layer ID field 143) and temporal layer (specified in temporal ID field 144). The VSRR resolution change message 140 can contain a Field Control Information (FCI) field containing one or more VSRR FCI entries.

Sequence number field 142 may be an 8-bit field that includes the sequence number of the requested packet. Layer ID field 143 includes an identifier of the video layer (e.g., for multi-layer video coding, such as scalable video coding or multiview video coding). When the value of layer ID field 143 is equal to 0x3F, the associated resolution change may be applicable to all layers (e.g., all scalability layers or all views). The temporal ID field 144 may indicate an identifier of the corresponding temporal layer. When the value of the temporal ID field 144 is equal to 0x7, the associated resolution change is applicable to all temporal layers.

The picture width field 146 and the picture height field 147 may be respective 14-bit fields. These fields may have values indicating target picture resolutions applied to the associated scalability layer, view, and/or temporal layer.

In particular, the video decoder 300 may form the VSRR resolution change message 140 to request a new spatial resolution for a subsequent picture of the video bitstream. Video decoder 300 may specify a particular spatial or scalable layer or view in layer ID field 143 or a temporal layer in t.id field 144, a picture width in picture width field 146, and a picture height in picture height field 147. The video decoder 300 may form FCI including a plurality of such VSRR resolution change messages for different spatial/scalability layers and/or temporal layers to request different resolutions for the various spatial/scalability layers and/or temporal layers.

The video encoder 200 may determine a request width for a subsequently encoded picture according to the value of the picture width field 146 and a request height for the subsequently encoded picture according to the picture height field 147. Similarly, video encoder 200 may determine the requested subsequent encoded picture to be in a particular spatial layer and/or a scalable layer, view, and/or temporal layer (or all such layers) based on the values of layer ID field 143 and t.id 144. In some examples, video encoder 200 may receive a plurality of VSSR resolution change messages that include different resolution change requests for different sets of spatial/scalability layers and/or temporal layers. The video encoder 200 may thus determine whether to modify the resolution for the various layers (or all layers) as requested. In response to determining the modified resolution, video encoder 200 may encode a subsequent picture according to the requested resolution change.

The pad fields 145A, 145B may include all zeros used to pad to produce a double word alignment for the VSRR resolution change message 140. The video decoder 300 may set the value of the pad fields 145A, 145B to zero. The video encoder 200 may ignore the values of the pad fields 145A, 145B.

Fig. 4 is a conceptual diagram of an example syntax structure for a Video Spatial Resolution Notification (VSRN) message 150 corresponding to a VSRR resolution change message, such as VSRR resolution change message 140. The video encoder 200 and/or the source device 102 may prepare VSRN the message 150 in response to receiving the VSRR resolution change message 140 from the destination device 116/video decoder 300. The video encoder 200/source device 102 may prepare VSRN a message 150 to indicate that the resolution video encoder 200 is to be used for one or more subsequent pictures of the bitstream. The video encoder 200/source device 102 may prepare an FCI field that includes one or more VSRN FCI entries. VSRN message 150 represents example content of FCI entries (i.e., VSRN FCI entries) for VSRN messages.

In the example of fig. 4, VSRN message 150 includes a Synchronization Source (SSRC) field 151, a sequence number (sequence num.) field 152, a layer identifier (layer ID.) field 153, a time identifier (t.id) field 154, padding fields 155A, 155B, a picture width field 156, and a picture height field 157. In this example, SSRC field 151 is a 32-bit field specifying the SSRC of the source of the Video Spatial Resolution Notification (VSRN) that generated VSRN message 150. In this example, sequence number (num.) field 152 is an eight-bit field that specifies a sequence number value from the VSRR being acknowledged (e.g., a sequence number specified in sequence num. Field 142 of the corresponding VSRR resolution change message 140).

In this example, the layer identifier (layer ID) field 153 is a six-bit field that specifies an identifier of a layer associated with a resolution change. A value of 0x3F for the layer ID field 153 equal to 0x3F (i.e., binary 111111) may indicate that the resolution change applies to all layers (e.g., all spatial layers and/or scalable layers, and/or views for multi-view video data) of the corresponding bitstream. The temporal ID (t.id) field 154 is a three-bit field that includes an identifier of a temporal layer associated with a resolution change. A value of t.id field 154 equal to 0x7 (i.e., binary 111) may indicate that the resolution change is applicable to all temporal layers.

The pad fields 155A, 155B may include all zeros used to pad to produce a double word alignment for VSRN messages 150. The video encoder 200 may set the value of the pad fields 155A, 155B to zero. The video decoder 300 may ignore the values of the pad fields 155A, 155B.

The picture width field 156 and the picture height field 157 may specify the size (width and height, respectively) of the picture corresponding to the layer indicated in the layer ID field 153 and the temporal ID field 154. That is, video encoder 200 may specify the size of pictures in these layers using VSRN message 150, for example, in response to VSRR resolution change message 140 from video decoder 300. In turn, video decoder 300 may determine the size of the picture in the layer indicated in layer ID field 153 and temporal ID field 154 from the values of picture width field 156 and picture height field 157.

Fig. 5 is a conceptual diagram of an example syntax structure for a Video Spatial Resolution Request (VSRR) region coding message. In this example, VSRR region coded message 160 includes a Synchronization Source (SSRC) field 161, a sequence number (sequence num.) field 162, a layer identifier (layer ID.) field 163, a time identifier (t.id) field 164, padding fields 165A-165C (padding field 165), a left offset field 166, a right offset field 167, a top offset field 168, and a bottom offset field 169.

In this example, SSRC field 161 may represent the synchronization source of the Video Spatial Resolution Request (VSRR) that originated the request. The payload of VSRR region coded message 160 carries data representing the requested picture width (in left offset field 166 and right offset field 167) and picture height (in top offset field 168 and bottom offset field 169) for the pictures of the particular temporal layer (specified in layer ID field 163) and temporal layer (specified in temporal ID field 164). The Field Control Information (FCI) field may contain one or more VSRR FCI entries corresponding to the VSRR region encoded message 160.

Sequence number field 162 may be an 8-bit field that includes the sequence number of the requested packet. Layer ID field 163 includes an identifier of the video layer (e.g., for multi-layer video coding, such as scalable video coding or multiview video coding). When the value of layer ID field 163 is equal to 0x3F, the associated region encoding may be applicable to all layers (e.g., all scalability layers or all views). The temporal ID field 164 may indicate an identifier of the corresponding temporal layer. When the value of the temporal ID field 164 is equal to 0x7, the associated region coding may be applicable to all temporal layers.

The pad field 165 may include all zeros used to pad to produce a double word alignment for the VSRR region encoded message 160. Video decoder 300 may set the value of pad field 165 to zero. The video encoder 200 may ignore the value of the pad field 165.

In this example, left offset field 166, right offset field 167, top offset field 168, and bottom offset field 169 are 14-bit fields that specify respective left offset, right offset, top offset, and bottom offset to indicate the region of the subsequent picture to be encoded relative to the previous picture. For example, the previous picture may correspond to the original picture 130 of fig. 2, and the subsequent picture may correspond to the requested new picture 131 of fig. 2. The requested new picture 131 may be specified using an offset relative to the original picture 130. For example, a value for left offset 132 may be specified in left offset field 166, a value for right offset 136 may be specified in right offset field 167, a value for top offset 134 may be specified in top offset field 168, and a value for bottom offset 138 may be specified in bottom offset field 169. VSRR region encoding message 160 may request region encoding of pictures for all pictures or only for a particular spatial layer/scalable layer, view and/or temporal layer.

In particular, video decoder 300 may form VSRR region encoding message 160 to specify regions of one or more subsequent pictures to be encoded by video encoder 200 (of a specified layer) relative to a previous picture. In turn, the video encoder 200 may use the VSRR region encoding message 160 to determine the requested region to be encoded. Thus, instead of encoding the entire picture, video encoder 200 may instead encode only the requested region for the specified layer. For example, the video decoder 300 may specify a region of interest to be encoded in a subsequent picture of the specified layer.

Fig. 6 is a conceptual diagram of an example syntax structure for a Video Spatial Resolution Notification (VSRN) message 170 corresponding to a VSRR region encoded message. The video encoder 200 and/or the source device 102 may prepare VSRN the message 170 in response to receiving the VSRR region encoded message 160 from the destination device 116/video decoder 300. The video encoder 200/source device 102 may prepare VSRN a message 170 to indicate the region of a picture (relative to the original picture) that the video encoder 200 is to encode for one or more subsequent pictures of the bitstream. The video encoder 200/source device 102 may prepare an FCI field that includes one or more VSRN FCI entries. VSRN message 170 represents example content of FCI entries (i.e., VSRN FCI entries) for VSRN messages.

In the example of fig. 6, VSRN message 170 includes a Synchronization Source (SSRC) field 171, a sequence number (sequence num.) field 172, a layer identifier (layer ID.) field 173, a time identifier (t.id) field 174, padding fields 175A-175C (padding field 175), a left offset field 176, a right offset field 177, a top offset field 178, and a bottom offset field 179. In this example, SSRC field 171 is a 32-bit field specifying the SSRC of the source of the Video Spatial Resolution Notification (VSRN) that generated VSRN message 170. In this example, sequence number (num.) field 172 is an eight-bit field that specifies a sequence number value from the VSRR being acknowledged (e.g., a sequence number specified in sequence num. Field 162 of the corresponding VSRR region coded message 160).

In this example, layer identifier (layer ID) field 173 is a six-bit field specifying an identifier of a layer associated with a resolution change. A value of 0x3F for layer ID field 173 equal to 0x3F (i.e., binary 111111) may indicate that the resolution change applies to all layers (e.g., all spatial layers and/or scalable layers, and/or views for multi-view video data) of the corresponding bitstream. The temporal ID (t.id) field 174 is a three-bit field that includes an identifier of a temporal layer associated with a resolution change. A value of the t.id field 174 equal to 0x7 (i.e., binary 111) may indicate that the resolution change is applicable to all temporal layers.

The pad field 175 may include all zeros used to pad to produce a double word alignment for VSRN messages 170. The video encoder 200 may set the value of the padding field 175 to zero. The video decoder 300 may ignore the value of the padding field 175.

In this example, left offset field 176, right offset field 177, top offset field 178, and bottom offset field 179 are 14-bit fields that specify respective left offset, right offset, top offset, and bottom offset to indicate the region of a subsequent picture to be encoded relative to a previous picture. For example, the previous picture may correspond to the original picture 130 of fig. 2, and the subsequent picture may correspond to the requested new picture 131 of fig. 2. The requested new picture 131 may be specified using an offset relative to the original picture 130. For example, a value for left offset 132 may be specified in left offset field 176, a value for right offset 136 may be specified in right offset field 177, a value for top offset 134 may be specified in top offset field 178, and a value for bottom offset 138 may be specified in bottom offset field 179.

In particular, video encoder 300 may form VSRN message 170 to specify a region of one or more subsequent pictures relative to a previous picture to be encoded by video encoder 200 for the corresponding specified layer. The video decoder 300 may in turn use VSRN the message 170 to determine the region of the specified layer to be encoded. Accordingly, the video decoder 300 may receive the encoded picture corresponding to the designated region. The video decoder 300 may decode a picture and construct an entire decoded picture, for example, by copying a portion of the original picture outside the encoded region and updating the designated region by using the decoded data of the picture. In this way, the video encoder 200 and the video decoder 300 may encode/decode only a specified region of a specified layer, instead of encoding and decoding the entire picture.

The video encoder 200 may use VSRN the message 170 to acknowledge receipt of the VSRR region encoded message 160 from the video decoder 300. For each VSRR region encoded message received at and targeted to a session participant, the video encoder 200 may send a corresponding VSRN FCI entry in the VSRN feedback message. A single VSRN message may use multiple FCI entries to acknowledge multiple requests. VSRN message content may be different from the corresponding VSRR message. For example, the video encoder 200 may not be able to adjust the resolution of a particular spatial layer or temporal layer, or may use pre-recorded content.

Fig. 7 is a conceptual diagram of an example syntax structure for a Video Temporal Resolution Request (VTRR) message 180. In this example, VTRR message 180 includes a Synchronization Source (SSRC) field 181, a sequence number (sequence num.) field 182, a layer identifier (layer ID.) field 183, a frame rate field 184, and a padding field 185.SSRC field 181 may represent the synchronization source of the space-time compromise request (TSTR) that originated the request. The payload of VTRR region-coded message 180 carries data representing the requested frame rate in frame rate field 184 of the picture applicable to the particular temporal layer (specified in layer ID field 183). The Field Control Information (FCI) field may contain one or more VTRR FCI entries corresponding to VTRR region-coded message 180.

The pad field 185 may be a 6-bit field set to an all-zero value. That is, the video decoder 300 may form VTRR the message 180 to include six zero value bits in the pad field 185. The video encoder 200 may ignore the value of the pad field 185.

Video decoder 300 may use VTRR message 180 to command or request video encoder 200 to change the decoding frame rate of the video encoder. Video decoder 300 may explicitly signal the requested frame rate of coded pictures for a particular temporal or spatial layer (e.g., specified in layer ID field 183) in VTRR message 180. Alternatively, the video decoder 300 may express a percentage decrease or increase in the frame rate of the original frame rate in VTRR messages 180.

The video decoder 300 may suggest a frame rate change by sending VTRR a message 180 to the video encoder 200. If video encoder 200 may adjust its coding frame rate, video encoder 200 may consider received VTRR message 180 for future coding of the picture. In general, the video encoder 200 reaction time may be significantly longer than a typical picture duration.

FIG. 7 depicts example VTRR content of an FCI entry. The payload of VTRR message 180 carries the picture frame rate (in frame rate field 184) for the picture of the particular temporal layer or scalable layer (in layer ID field 183). The FCI field may contain one or more VTRR FCI entries.

In some examples, video decoder 300 or destination device 116 may add fields similar to layer ID field 183 and frame rate field 184 to VSRR message 140 of fig. 3 and/or to VSRR region encoded message 160. In this way, the video decoder 300 or the destination device 116 may construct a single message to request both reduced spatial resolution and reduced temporal resolution (frame rate). Alternatively, the video decoder 300 or the destination device 116 may send two separate messages to reduce both the frame rate and the spatial resolution.

Fig. 8 is a conceptual diagram of an example syntax structure for a Video Temporal Resolution Notification (VTRN) message 190 corresponding to VTRR messages, such as VTRR message 180 of fig. 7. The video encoder 200 may return VTRN a message 190 in response to VTRR the message 180 to indicate the changed frame rate that the video encoder 200 will use thereafter. The video encoder 200 may determine VTRN whether the request of the message 190 caused a change in the frame rate to what extent the change was caused.

In this example, VTRN message 190 includes a Synchronization Source (SSRC) field 191, a sequence number (sequence num.) field 192, a layer identifier (layer ID.) field 193, a frame rate field 194, and a padding field 195. In this example, SSRC field 191 is a 32-bit field that specifies the SSRC of the source of the Video Temporal Resolution Request (VTRR) that generated VTRN message 190. In this example, sequence number (num.) field 192 is an eight-bit field that specifies a sequence number value from VTRR being acknowledged (e.g., the sequence number specified in sequence num. Field 182 of corresponding VTRR message 180).

Layer ID field 193 may be a six bit field that indicates an identifier of a layer. When the value of the layer ID field 193 is equal to 0x3F (i.e., 111111), the associated frame rate specified in the frame rate field 194 may be applicable to all scalable layers (or all temporal layers).

The frame rate field 194 indicates a target picture frame rate applied to one or more associated layers (e.g., a scalable layer, a spatial layer, a view, or a temporal layer). That is, the video encoder 200 may set the value of the frame rate field 194 to indicate the picture frame rate of the corresponding layer. Accordingly, the video decoder 300 may determine a frame rate for the corresponding layer according to the frame rate field 194.

The pad field 195 may be an all zero six bit field. The video encoder 200 may set the value of the pad field 195 to all zeros. The video decoder 300 may ignore the value of the pad field 195.

In some examples, for example, where the video decoder 300 or the destination device 118 requests both reduced spatial resolution and reduced temporal resolution (frame rate), the video encoder or the source device 102 may send a single message including both spatial resolution information (e.g., spatial resolution information similar to VSRN message 150 or VSRN message 170) and VTRN message 190. In other examples, where the video decoder 300 or the destination device 118 requests both reduced spatial resolution and reduced temporal resolution (frame rate), the video encoder or the source device 102 may send separate VSRN and VTRN messages indicating the new reduced spatial resolution and temporal resolution, respectively.

Fig. 9 is a block diagram illustrating an example video encoder 200 that may perform the techniques of this disclosure. Fig. 9 is provided for purposes of explanation and should not be considered limiting of the techniques broadly illustrated and described in this disclosure. For purposes of explanation, this disclosure describes a video encoder 200 according to techniques of VVC (ITU-T h.266) and HEVC (ITU-T h.265). However, the techniques of this disclosure may be performed by video encoding devices configured in accordance with other video coding standards and video coding formats (such as AV1 and subsequent formats to the AV1 video coding format).

In the example of fig. 9, the video encoder 200 includes a video data memory 230, a reduction (DS) unit 228, a mode selection unit 202, a residual generation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a filter unit 216, a Decoded Picture Buffer (DPB) 218, and an entropy encoding unit 220. Any or all of video data memory 230, mode selection unit 202, residual generation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, filter unit 216, DPB 218, and entropy encoding unit 220 may be implemented in one or more processors or in processing circuitry. For example, the elements of video encoder 200 may be implemented as one or more circuits or logic elements as part of a hardware circuit or as part of a processor, ASIC, or FPGA. Furthermore, the video encoder 200 may include additional or alternative processors or processing circuits to perform these and other functions.

Video data memory 230 may store video data to be encoded by components of video encoder 200. Video encoder 200 may receive video data stored in video data store 230 from, for example, video source 104 (fig. 1). DPB 218 may serve as a reference picture memory that stores reference video data for use in predicting subsequent video data by video encoder 200. Video data memory 230 and DPB 218 may be formed from 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. Video data memory 230 and DPB 218 may be provided by the same memory device or separate memory devices. In various examples, video data memory 230 may be on-chip (as shown) with other components of video encoder 200, or off-chip with respect to those components.

In this disclosure, references to video data memory 230 should not be construed as limited to memory internal to video encoder 200 (unless specifically stated) or memory external to video encoder 200 (unless specifically stated). Conversely, references to video data memory 230 should be understood as reference memory storing video data received by video encoder 200 for encoding (e.g., video data for a current block to be encoded). The memory 106 of fig. 1 may also provide temporary storage of the output from the various units of the video encoder 200.

The various elements of fig. 9 are illustrated to aid in understanding the operations performed by video encoder 200. The units may be implemented as fixed function circuits, programmable circuits or a combination thereof. A fixed function circuit refers to a circuit that provides a specific function and presets executable operations. Programmable circuitry refers to circuitry that can be programmed to perform various tasks and provide flexible functionality in the operations that can be performed. For example, the programmable circuit may execute software or firmware that causes the programmable circuit to operate in a manner defined by instructions of the software or firmware. Fixed function circuitry may execute software instructions (e.g., to receive parameters or output parameters) but the type of operation that fixed function circuitry performs is typically not variable. In some examples, one or more of the units may be different circuit blocks (fixed function or programmable), and in some examples, one or more of the units may be an integrated circuit.

The video encoder 200 may include an Arithmetic Logic Unit (ALU), a basic functional unit (EFU), digital circuitry, analog circuitry, and/or a programmable core formed from programmable circuitry. In examples where the operations of video encoder 200 are performed using software executed by programmable circuitry, memory 106 (fig. 1) may store instructions (e.g., object code) of the software received and executed by video encoder 200, or another memory within video encoder 200 (not shown) may store such instructions.

The video data memory 230 is configured to store received video data. The video encoder 200 may retrieve pictures of the video data from the video data store 230 and provide the video data to the residual generation unit 204 and the mode selection unit 202. The video data in the video data memory 230 may be raw video data to be encoded.

In accordance with the techniques of this disclosure, video encoder 200 may receive data indicating that video data is to be encoded at a reduced resolution relative to an original resolution of the original video data stored in video data store 230. The reduced resolution may be a reduced spatial resolution, a reduced temporal resolution, or both. The Downscaling (DS) unit 228 may perform spatial downscaling and/or temporal downscaling of video data. For example, DS unit 228 may perform one or more decimation filters to reduce the spatial resolution of the original picture to be encoded. As another example, DS unit 228 may extract a particular region of interest of the original picture to be encoded, e.g., as discussed above with respect to fig. 2.

Additionally or alternatively, the DS unit 228 may determine a temporal layer identifier of a picture to be omitted from encoding. In general, a temporal layer identifier for a picture indicates that pictures of the corresponding temporal layer and lower temporal layers are needed to code the pictures of the corresponding temporal layer. Thus, if the requested temporal layer is layer 3, pictures of temporal layers 0, 1,2, and 3 will be provided. The various temporal layers may correspond to various frame rates, such as 15 frames per second (fps), 30fps, 60fps, and 120fps for layers 0, 1,2, and 3, respectively. Thus, if the original video data can meet 120fps at temporal layer 3 and the client device requests a reduced frame rate of 30fps, the DS unit may omit encoding the pictures at temporal layers 2 and 3, but instead pass only the pictures at temporal layers 0 and 1 for encoding. In the case where full resolution encoding is to be performed, DS unit 228 may pass all pictures at full spatial resolution from video data store 230 for encoding.

In some examples, mode selection unit 202 may determine the temporal layer to which the original picture is assigned and provide information to DS unit 228 indicating to which temporal layer the picture is to be assigned. For example, mode selection unit 202 may determine that a scene change has occurred at a particular picture, and thus the picture should be encoded as an I-frame and assigned to temporal layer 0. Mode selection unit 202 may also assign other pictures following the I frame to other temporal layers according to a picture coding mode (e.g., IPBB, IPPP, etc.).

The mode selection unit 202 comprises a motion estimation unit 222, a motion compensation unit 224 and an intra prediction unit 226. The mode selection unit 202 may include additional functional units that perform video prediction according to other prediction modes. As an example, mode selection unit 202 may include a palette unit, an intra-block copy unit (which may be part of motion estimation unit 222 and/or motion compensation unit 224), an affine unit, a Linear Model (LM) unit, and the like.

Mode selection unit 202 typically coordinates multiple encoding channels to test combinations of encoding parameters and resulting rate-distortion values for such combinations. The coding parameters may include a partition of CTUs to CUs, a prediction mode for CUs, a transform type for residual data of CUs, quantization parameters for residual data of CUs, and the like. The mode selection unit 202 may finally select a combination of coding parameters having better rate-distortion values than other tested combinations.

Video encoder 200 may divide a picture retrieved from video data storage 230 into a series of CTUs and encapsulate one or more CTUs within a slice. The mode selection unit 202 may divide CTUs of pictures according to a tree structure such as an MTT structure, QTBT structure, super block structure, or the above quadtree structure. As described above, the video encoder 200 may form one or more CUs by dividing CTUs according to a tree structure. Such CUs may also be commonly referred to as "video blocks" or "blocks.

Typically, mode selection unit 202 also controls its components (e.g., motion estimation unit 222, motion compensation unit 224, and intra prediction unit 226) to generate a prediction block for the current block (e.g., the current CU, or in HEVC, the overlapping portion of PU and TU). To inter-predict the current block, motion estimation unit 222 may perform a motion search to identify one or more closely matching reference blocks in one or more reference pictures (e.g., one or more previously coded pictures stored in DPB 218). Specifically, the motion estimation unit 222 may calculate a value indicating the degree to which the potential reference block will be similar to the current block, for example, from the Sum of Absolute Differences (SAD), the Sum of Squared Differences (SSD), the Mean Absolute Difference (MAD), the Mean Squared Difference (MSD), and the like. The motion estimation unit 222 may typically perform these calculations using the sample-by-sample difference between the current block and the reference block under consideration. The motion estimation unit 222 may identify the reference block with the lowest value resulting from these calculations to indicate the reference block that best matches the current block.

The motion estimation unit 222 may form one or more Motion Vectors (MVs) defining a position of the reference block in the reference picture relative to a position of the current block in the current picture. The motion estimation unit 222 may then provide the motion vectors to the motion compensation unit 224. For example, for unidirectional inter prediction, motion estimation unit 222 may provide a single motion vector, while for bi-directional inter prediction, motion estimation unit 222 may provide two motion vectors. The motion compensation unit 224 may then generate a prediction block using the motion vector. For example, the motion compensation unit 224 may retrieve data of the reference block using the motion vector. As another example, if the motion vector has fractional sample precision, the motion compensation unit 224 may interpolate the values of the prediction block according to one or more interpolation filters. Furthermore, for bi-directional inter prediction, the motion compensation unit 224 may retrieve data of two reference blocks identified by respective motion vectors and combine the retrieved data, e.g. by sample-wise averaging or weighted averaging.

When operating in accordance with the AV1 video coding format, motion estimation unit 222 and motion compensation unit 224 may be configured to encode coding blocks of video data (e.g., both luma coding blocks and chroma coding blocks) using translational motion compensation, affine motion compensation, overlapped Block Motion Compensation (OBMC), and/or composite inter-intra prediction.

As another example, for intra prediction or intra prediction coding, intra prediction unit 226 may generate a prediction block from samples adjacent to the current block. For example, for directional modes, intra-prediction unit 226 may typically mathematically combine the values of adjacent samples and populate these calculated values in defined directions across the current block to produce a prediction block. As another example, for DC mode, the intra prediction unit 226 may calculate an average of neighboring samples of the current block and generate a prediction block to include the resulting average of each sample of the prediction block.

When operating in accordance with the AV1 video coding format, the intra prediction unit 226 may be configured to encode coded blocks of video data (e.g., both luma coded blocks and chroma coded blocks) using directional intra prediction, non-directional intra prediction, recursive filter intra prediction, chroma (CFL) prediction from luma, intra copy (IBC), and/or palette modes. The mode selection unit 202 may include additional functional units that perform video prediction according to other prediction modes.

The mode selection unit 202 supplies the prediction block to the residual generation unit 204. The residual generation unit 204 receives the original, non-coded version of the current block from the video data store 230 and the prediction block from the mode selection unit 202. The residual generation unit 204 calculates a sample-by-sample difference between the current block and the prediction block. The resulting sample-by-sample difference defines the residual block of the current block. In some examples, residual generation unit 204 may also determine differences between sample values in the residual block to generate the residual block using Residual Differential Pulse Code Modulation (RDPCM). In some examples, residual generation unit 204 may be formed using one or more subtractor circuits that perform binary subtraction.

In examples in which mode selection unit 202 divides a CU into PUs, each PU may be associated with a luma prediction unit and a corresponding chroma prediction unit. Video encoder 200 and video decoder 300 may support PUs having various sizes. As noted above, the size of a CU may refer to the size of the luma coding block of the CU, while the size of a PU may refer to the size of the luma prediction unit of the PU. Assuming that the size of a particular CU is 2Nx2N, video encoder 200 may support PU sizes of 2Nx2N or NxN for intra prediction, and symmetric PU sizes of 2Nx2N, 2NxN, nx2N, nxN, or the like for inter prediction. The video encoder 200 and the video decoder 300 may also support asymmetric partitioning for PU sizes of 2NxnU, 2NxnD, nLx2N, and nRx2N for inter prediction.

In examples in which mode selection unit 202 does not further divide the CUs into PUs, each CU may be associated with a luma coding block and a corresponding chroma coding block. As above, the size of a CU may refer to the size of the luma coding block of the CU. The video encoder 200 and the video decoder 300 may support CU sizes of 2Nx2N, 2NxN, or Nx 2N.

For other video coding techniques, such as intra-block copy mode coding, affine mode coding, and Linear Model (LM) mode coding, as some examples, mode selection unit 202 generates a prediction block of the current block being encoded via a respective unit associated with the coding technique. In some examples (such as palette mode coding), mode selection unit 202 may not generate a prediction block, but instead generate a syntax element indicating the manner in which it reconstructs the block based on the selected palette. In such modes, mode selection unit 202 may provide these syntax elements to entropy encoding unit 220 for encoding.

As described above, the residual generation unit 204 receives video data for the current block and the corresponding prediction block. Then, the residual generating unit 204 generates a residual block for the current block. To generate the residual block, the residual generation unit 204 calculates a sample-by-sample difference between the prediction block and the current block.

The transform processing unit 206 applies one or more transforms to the residual block to generate a block of transform coefficients (referred to herein as a "block of transform coefficients"). The transform processing unit 206 may apply various transforms to the residual block to form a block of transform coefficients. For example, transform processing unit 206 may apply a Discrete Cosine Transform (DCT), a direction transform, a Karhunen-Loeve transform (KLT), or a conceptually similar transform to the residual block. In some examples, transform processing unit 206 may perform a variety of transforms on the residual block, e.g., a primary transform and a secondary transform (such as a rotation transform). In some examples, transform processing unit 206 does not apply a transform to the residual block.

When operating in accordance with AV1, the transform processing unit 206 may apply one or more transforms to the residual block to generate a block of transform coefficients (referred to herein as a "block of transform coefficients"). The transform processing unit 206 may apply various transforms to the residual block to form a block of transform coefficients. For example, transform processing unit 206 may apply a horizontal/vertical transform combination, which may include a Discrete Cosine Transform (DCT), an Asymmetric Discrete Sine Transform (ADST), a flipped ADST (e.g., ADST in reverse order), and an identity transform (IDTX). When an identity transform is used, the transform is skipped in one of the vertical or horizontal directions. In some examples, the transformation process may be skipped.

The quantization unit 208 may quantize the transform coefficients in the block of transform coefficients to generate a block of quantized transform coefficients. The quantization unit 208 may quantize transform coefficients of the block of transform coefficients according to a Quantization Parameter (QP) value associated with the current block. The video encoder 200 (e.g., via the mode selection unit 202) may adjust the degree of quantization applied to the transform coefficient block associated with the current block by adjusting the QP value associated with the CU. Quantization may cause information loss and, therefore, the quantized transform coefficients may have lower precision than the original transform coefficients generated by the transform processing unit 206.

The inverse quantization unit 210 and the inverse transform processing unit 212 may apply inverse quantization and inverse transform, respectively, to the quantized transform coefficient block to reconstruct a residual block from the transform coefficient block. The reconstruction unit 214 may generate a reconstructed block corresponding to the current block (although potentially with some degree of distortion) based on the reconstructed residual block and the prediction block generated by the mode selection unit 202. For example, the reconstruction unit 214 may add samples of the reconstructed residual block to corresponding samples from the prediction block generated by the mode selection unit 202 to generate a reconstructed block.

The filter unit 216 may perform one or more filtering operations on the reconstructed block. For example, filter unit 216 may perform deblocking operations to reduce blocking artifacts along edges of CUs. In some examples, the operation of the filter unit 216 may be skipped.

When operating in accordance with AV1, the filter unit 216 may perform one or more filtering operations on the reconstructed block. For example, filter unit 216 may perform deblocking operations to reduce blocking artifacts along edges of CUs. In other examples, filter unit 216 may apply a Constrained Direction Enhancement Filter (CDEF), which may be applied after deblocking, and may include application of an inseparable, nonlinear, low pass direction filter based on the estimated edge direction. The filter unit 216 may also include a loop recovery filter applied after CDEF and may include a separable symmetric normalized wiener filter or a double self-guide filter.

Video encoder 200 stores the reconstructed block in DPB 218. For example, in an example where the operation of filter unit 216 is not performed, reconstruction unit 214 may store the reconstructed block to DPB 218. In an example of performing the operation of filter unit 216, filter unit 216 may store the filtered reconstructed block to DPB 218. Motion estimation unit 222 and motion compensation unit 224 may retrieve a reference picture formed from the reconstructed (and potentially filtered) block from DPB 218 to inter-predict a block of a subsequently encoded picture. In addition, intra-prediction unit 226 may use the reconstructed block of the current picture in DPB 218 to intra-predict other blocks in the current picture.

In general, entropy encoding unit 220 may entropy encode syntax elements received from other functional components of video encoder 200. For example, entropy encoding unit 220 may entropy encode the quantized transform coefficient block from quantization unit 208. As another example, the entropy encoding unit 220 may entropy encode a prediction syntax element (e.g., motion information for inter prediction or intra mode information for intra prediction) from the mode selection unit 202. The entropy encoding unit 220 may perform one or more entropy encoding operations on syntax elements (which are another example of video data) to generate entropy encoded data. For example, the entropy encoding unit 220 may perform a Context Adaptive Variable Length Coding (CAVLC) operation, a CABAC operation, a variable-variable (V2V) length coding operation, a syntax-based context adaptive binary arithmetic coding (SBAC) operation, a Probability Interval Partitioning Entropy (PIPE) coding operation, an exponential golomb coding operation, or another type of entropy encoding operation on the data. In some examples, entropy encoding unit 220 may operate in bypass mode where syntax elements are not entropy encoded.

The video encoder 200 may output a bitstream including entropy encoded syntax elements required to reconstruct blocks of slices or pictures. In particular, the entropy encoding unit 220 may output a bitstream.

According to AV1, the entropy encoding unit 220 may be configured as a symbol-to-symbol adaptive multi-symbol arithmetic decoder. The syntax element in AV1 contains an alphabet of N elements, and the context (e.g., probability model) contains a set of N probabilities. The entropy encoding unit 220 may store the probabilities as an n-bit (e.g., 15-bit) Cumulative Distribution Function (CDF). Entropy encoding unit 22 may perform recursive scaling using an update factor based on the alphabet size to update the context.

The operations described above are described with respect to blocks. Such descriptions should be understood as operations for luma coding blocks and/or chroma coding blocks. As described above, in some examples, the luma and chroma coding blocks are the luma and chroma components of a CU. In some examples, the luma and chroma coding blocks are luma and chroma components of the PU.

In some examples, the operations performed on the luma coded block need not be repeated for the chroma coded block. As one example, the operation of identifying a Motion Vector (MV) and a reference picture of a luma coding block does not require repetition of the MV and reference pictures for identifying chroma blocks. Conversely, MVs for luma coding blocks may be scaled to determine MVs for chroma blocks, and reference pictures may be the same. As another example, the intra prediction process may be the same for both luma and chroma coded blocks.

Fig. 10 is a block diagram illustrating an example video decoder 300 that may perform the techniques of this disclosure. Fig. 10 is provided for purposes of explanation and is not a limitation on the techniques broadly illustrated and described in this disclosure. For purposes of explanation, this disclosure describes a video decoder 300 according to techniques of VVC (ITU-t h.266) and HEVC (ITU-t h.265). However, the techniques of this disclosure may be performed by video coding devices configured as other video coding standards.

In the example of fig. 10, video decoder 300 includes Coded Picture Buffer (CPB) memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and Decoded Picture Buffer (DPB) 314. Any or all of CPB memory 320, entropy decoding unit 302, prediction processing unit 304, inverse quantization unit 306, inverse transform processing unit 308, reconstruction unit 310, filter unit 312, and DPB 314 may be implemented in one or more processors or in processing circuitry. For example, the elements of video decoder 300 may be implemented as one or more circuits or logic elements as part of a hardware circuit or as part of a processor, ASIC, or FPGA. Furthermore, the video decoder 300 may include additional or alternative processors or processing circuits to perform these and other functions.

The prediction processing unit 304 includes a motion compensation unit 316 and an intra prediction unit 318. The prediction processing unit 304 may include additional units that perform prediction according to other prediction modes. As an example, prediction processing unit 304 may include a palette unit, an intra-block copy unit (which may form part of motion compensation unit 316), an affine unit, a Linear Model (LM) unit, and so forth. In other examples, video decoder 300 may include more, fewer, or different functional components.

As described above, when operating in accordance with AV1, compensation unit 316 may be configured to decode coded blocks of video data (e.g., both luma coded blocks and chroma coded blocks) using translational motion compensation, affine motion compensation, OBMC, and/or complex inter-frame intra prediction. As described above, intra-prediction unit 318 may be configured to decode coded blocks (e.g., both luma and chroma coded blocks) of video data using directional intra-prediction, non-directional intra-prediction, recursive filter intra-prediction, CFL, intra-block copy (IBC), and/or palette modes.

The CPB memory 320 may store video data, such as an encoded video bitstream, to be decoded by components of the video decoder 300. For example, video data stored in the CPB memory 320 may be obtained from the computer-readable medium 110 (fig. 1). The CPB memory 320 may include CPBs that store encoded video data (e.g., syntax elements) from the encoded video bitstream. Further, the CPB memory 320 may store video data other than syntax elements of the coded pictures, such as temporary data representing outputs from various units of the video decoder 300. DPB 314 typically stores decoded pictures that video decoder 300 may output and/or use as reference video data when decoding subsequent data or pictures of a decoded video bitstream. CPB memory 320 and DPB 314 may be formed from 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. CPB memory 320 and DPB 314 may be provided by the same memory device or separate memory devices. In various examples, CPB memory 320 may be on-chip with other components of video decoder 300, or off-chip with respect to those components.

Additionally or alternatively, in some examples, video decoder 300 may retrieve decoded video data from memory 120 (fig. 1). That is, memory 120 may utilize CPB memory 320 to store data as discussed above. Also, when some or all of the functions of video decoder 300 are implemented in software to be executed by the processing circuitry of video decoder 300, memory 120 may store instructions to be executed by video decoder 300.

Various units shown in fig. 10 are illustrated to aid in understanding the operations performed by video decoder 300. The units may be implemented as fixed function circuits, programmable circuits or a combination thereof. Similar to fig. 9, the fixed function circuit refers to a circuit that provides a specific function and presets an executable operation. Programmable circuitry refers to circuitry that can be programmed to perform various tasks and provide flexible functionality in the operations that can be performed. For example, the programmable circuit may execute software or firmware that causes the programmable circuit to operate in a manner defined by instructions of the software or firmware. Fixed function circuitry may execute software instructions (e.g., to receive parameters or output parameters) but the type of operation that fixed function circuitry performs is typically not variable. In some examples, one or more of the units may be different circuit blocks (fixed function or programmable), and in some examples, one or more of the units may be an integrated circuit.

The video decoder 300 may include an ALU, an EFU, a digital circuit, an analog circuit, and/or a programmable core formed of programmable circuits. In examples where the operations of video decoder 300 are performed by software executing on programmable circuits, on-chip or off-chip memory may store instructions (e.g., object code) of the software received and executed by video decoder 300.

The entropy decoding unit 302 may receive encoded video data from the CPB and entropy decode the video data to reproduce the syntax element. The prediction processing unit 304, the inverse quantization unit 306, the inverse transform processing unit 308, the reconstruction unit 310, and the filter unit 312 may generate decoded video data based on syntax elements extracted from the bitstream.

Typically, the video decoder 300 reconstructs the pictures block by block. The video decoder 300 may perform a reconstruction operation on each block separately (where the block currently being reconstructed (i.e., decoded) may be referred to as a "current block").

The entropy decoding unit 302 may entropy decode syntax elements defining quantized transform coefficients of the quantized transform coefficient block, as well as transform information, such as Quantization Parameters (QP) and/or transform mode indications. The inverse quantization unit 306 may determine a quantization degree using a QP associated with the quantized transform coefficient block and, as such, determine an inverse quantization degree to be applied by the inverse quantization unit 306. The inverse quantization unit 306 may, for example, perform a bit-wise left-shift operation to inversely quantize the quantized transform coefficients. The inverse quantization unit 306 may thereby form a transform coefficient block including the transform coefficients.

After the inverse quantization unit 306 forms the transform coefficient block, the inverse transform processing unit 308 may apply one or more inverse transforms to the transform coefficient block to generate a residual block associated with the current block. For example, the inverse transform processing unit 308 may apply an inverse DCT, an inverse integer transform, an inverse Karhunen-Loeve transform (KLT), an inverse rotation transform, an inverse direction transform, or another inverse transform to the transform coefficient block.

Further, the prediction processing unit 304 generates a prediction block from the prediction information syntax element entropy-decoded by the entropy decoding unit 302. For example, if the prediction information syntax element indicates that the current block is inter-predicted, the motion compensation unit 316 may generate the prediction block. In this case, the prediction information syntax element may indicate a reference picture in DPB 314 from which the reference block is to be retrieved, and a motion vector identifying a position of the reference block in the reference picture relative to a position of the current block in the current picture. Motion compensation unit 316 may generally perform the inter-prediction process in a substantially similar manner as described with respect to motion compensation unit 224 (fig. 9).

As another example, if the prediction information syntax element indicates that the current block is intra-predicted, the intra-prediction unit 318 may generate the prediction block according to the intra-prediction mode indicated by the prediction information syntax element. Likewise, intra-prediction unit 318 may generally perform an intra-prediction process in a substantially similar manner as described with respect to intra-prediction unit 226 (fig. 9). Intra-prediction unit 318 may retrieve data for neighboring samples of the current block from DPB 314.

The reconstruction unit 310 may reconstruct the current block using the prediction block and the residual block. For example, the reconstruction unit 310 may add samples of the residual block to corresponding samples of the prediction block to reconstruct the current block.

The filter unit 312 may perform one or more filtering operations on the reconstructed block. For example, the filter unit 312 may perform a deblocking operation to reduce blocking artifacts along edges of reconstructed blocks. The operation of the filter unit 312 is not necessarily performed in all examples.

Video decoder 300 may store the reconstructed block in DPB 314. For example, in an example in which the operation of filter unit 312 is not performed, reconstruction unit 310 may store the reconstructed block into DPB 314. In an example in which the operations of filter unit 312 are performed, filter unit 312 may store the filtered reconstructed block into DPB 314. As discussed above, DPB 314 may provide reference information (such as samples of the current picture for intra prediction and previously decoded pictures for subsequent motion compensation) to prediction processing unit 304. Further, video decoder 300 may output decoded pictures (e.g., decoded video) from DPB 314 for subsequent presentation on a display device, such as display device 118 of fig. 1.

Fig. 11 is a flowchart illustrating an example method of requesting new resolution for a picture in accordance with the techniques of this disclosure. The method of fig. 11 is explained with respect to video encoder 200 and video decoder 300, but may also be performed by other devices or components (e.g., of source device 102 and destination device 116).

Initially, the video encoder 200 encodes the full resolution picture (350). Video encoder 200 may send the encoded pictures to destination device 116 and, thus, to video decoder 300 (352). Video decoder 300 may receive the encoded picture (354). Video decoder 300 may then decode the encoded picture (356). In accordance with the techniques of this disclosure, video decoder 300 may request a reduced resolution picture (358) relative to the full resolution picture. Before requesting a reduced resolution picture, the video decoder 300 (or the destination device 116 of fig. 1) may determine that the destination device 116 is to enter a power save mode. As part of the power saving mode, the video decoder 300 may request reduced resolution video data, which may reduce the power consumed by the video decoder 300. Video decoder 300 may form a VSRR message (such as VSRR resolution change message 140 of fig. 3) specifying a reduced size (such as reduced width and/or height) of one or more subsequent pictures. The VSRR message may further specify layers, such as spatial layers, scalable layers, view and/or temporal layers, that include pictures of the size for which a reduction is being requested.

The video encoder 200 may receive a request for reduced resolution (360). In response, video encoder 200 may send an indication of reduced resolution for one or more subsequent pictures (362). The reduced resolution may be a requested reduced resolution or a different resolution. In this example, assume that the reduced resolution is the requested reduced resolution. The video encoder 200 may send, for example, a VSRN message indicating a reduced resolution, such as VSRN message 150 of fig. 4. The VSRN message may further indicate a layer including a picture to which the reduced resolution is applied. The video decoder 300 may receive an indication of reduced resolution (e.g., VSRN message) (364).

Further, video encoder 200 may shrink the subsequent picture (366) to a reduced resolution. Video encoder 200 may also encode the reduced resolution picture (368). The video encoder 200 may then send the encoded pictures to the destination device 116, and thus to the video decoder 300 (370). Video decoder 300 may, in turn, receive the encoded picture (372) and decode the encoded picture (374). Although not shown in fig. 11, the video decoder 300 or a post-processing unit of the destination device 116 may upsample the decoded picture to full resolution prior to display of the decoded picture.

In this way, the method of fig. 11 represents an example of a method for requesting reduced resolution video data, the method comprising: decoding, by a video decoder of a client device, a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution; in response to determining that the client device is to enter a power saving mode, sending, by the client device, a message requesting reduced resolution relative to the first resolution for a second sequence of pictures that follows the first sequence of pictures in decoding order; and decoding, by the video decoder of the client device, the second picture sequence of the video data of the bitstream, the second picture sequence having the reduced resolution.

Fig. 12 is a flowchart illustrating an example method of requesting region decoding in accordance with the techniques of this disclosure. The method of fig. 12 is explained with respect to video encoder 200 and video decoder 300, but may also be performed by other devices or components (e.g., of source device 102 and destination device 116).

Initially, video encoder 200 encodes the full resolution picture (380). The video encoder 200 may send the encoded pictures to the destination device 116, and thus to the video decoder 300 (382). Video decoder 300 may receive the encoded picture (384). Video decoder 300 may then decode the encoded picture (386). In accordance with the techniques of this disclosure, video decoder 300 may request a region for a future picture relative to a full resolution picture (388). Before requesting a reduced resolution picture, the video decoder 300 (or the destination device 116 of fig. 1) may determine that the destination device 116 is to enter a power save mode. As part of the power saving mode, the video decoder 300 may request reduced resolution video data, which may reduce the power consumed by the video decoder 300. The video decoder 300 may form a VSRR message, such as the VSRR region encoded message 160 of fig. 5, that specifies the region of the subsequent picture relative to the first picture, for example, using an up-offset, a bottom-offset, a left-offset, and a right-offset. The VSRR message may further specify layers, such as spatial layers, scalable layers, view and/or temporal layers, that include the picture from which the region is being requested.

Video encoder 200 may receive a request for a region of a future picture (390). In response, video encoder 200 may send an indication of the region for one or more subsequent pictures (392). The actual area may be the requested area or a different area. In this example, assume that the actual region is the requested region. The video encoder 200 may send, for example, a VSRN message indicating the region, such as VSRN message 170 of fig. 6. The VSRN message may further indicate the layer that includes the picture of the application region extraction. Video decoder 300 may receive an indication of a region of a picture (e.g., VSRN message) (394).

Further, video encoder 200 may extract regions from subsequent pictures (396). The video encoder 200 may also encode the extracted region (398). The video encoder 200 may then send the encoded region to the destination device 116 and, thus, to the video decoder 300 (400). The video decoder 300, in turn, may receive the encoded region (402) and decode the encoded region (404). Further, the video decoder 300 or a post-processing unit of the destination device 116 may combine the decoded region with an outer region, e.g., a full resolution picture, to form a full resolution picture (406).

In this way, the method of fig. 12 represents an example of a method for requesting reduced resolution video data, the method comprising: decoding, by a video decoder of a client device, a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution; in response to determining that the client device is to enter a power saving mode, sending, by the client device, a message requesting reduced resolution relative to the first resolution for a second sequence of pictures that follows the first sequence of pictures in decoding order; and decoding, by the video decoder of the client device, the second picture sequence of the video data of the bitstream, the second picture sequence having the reduced resolution.

Fig. 13 is a flowchart illustrating an example method of requesting reduced resolution for video data in accordance with the techniques of this disclosure. The method of fig. 13 is explained with respect to video encoder 200 and video decoder 300, but may also be performed by other devices or components (e.g., of destination device 116).

Initially, video decoder 300 may decode a first sequence of pictures having a first resolution (420). The first resolution may be a spatial resolution (e.g., 8K, 4K, 1080P, etc.), a temporal resolution (e.g., 240fps, 120fps, 60fps, etc.), or both.

The video decoder 300 may then determine to enter a power saving mode (422). For example, the user may request to enter the power saving mode via a user interface of the destination device 116. Additionally or alternatively, the power sensor 126 of the destination device 116 may determine that the battery power of the battery 124 is below a threshold and automatically cause the destination device 116 to enter a power saving mode.

As a result of entering the power saving mode, the video decoder 300 (or another component of the destination device 116, e.g., the communication interface 122) may request reduced resolution video data from the source device 102 (424). For example, video decoder 300 may construct a Video Spatial Resolution Request (VSRR) message (e.g., according to fig. 3) and/or a VSRR region encoding message to request a picture of reduced spatial resolution. The reduced spatial resolution may be lower than the first resolution, e.g., 720p, 480p, etc. As another example, the video decoder 300 may construct a message requesting a reduced temporal resolution that may be less than the first resolution, e.g., 30fps, 24fps, 15fps, etc. In some examples, the video decoder 300 may request both reduced spatial resolution and reduced temporal resolution. The request for both reduced spatial resolution and reduced temporal resolution may be included in the same message or in two separate messages.

In response, the video decoder 300 may receive the reduced resolution video data, and the video decoder 300 may decode the second sequence of pictures having the reduced resolution (426).

In this way, the method of fig. 13 represents an example of a method for requesting reduced resolution video data, the method comprising: decoding, by a video decoder of a client device, a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution; in response to determining that the client device is to enter a power saving mode, sending, by the client device, a message requesting reduced resolution relative to the first resolution for a second sequence of pictures that follows the first sequence of pictures in decoding order; and decoding, by the video decoder of the client device, the second picture sequence of the video data of the bitstream, the second picture sequence having the reduced resolution.

Some examples of the technology of the present disclosure are summarized in the following clauses:

Clause 1: a method of processing a picture size request for video data, the method comprising: coding a first picture of video data having a first size; processing a message specifying a reduced size relative to the first size for a second picture, the second picture following the first picture in coding order; and coding the second picture of the video data having the reduced size.

Clause 2: the method of clause 1, wherein processing the message comprises processing a Video Spatial Resolution Request (VSRR) message specifying the reduced size.

Clause 3: the method of clause 2, wherein processing the VSRR message comprises processing a VSRR resolution change message comprising a picture width field specifying a request width for the reduced size of the second picture, and a picture height field specifying a request height for the reduced size of the second picture.

Clause 4: the method of clause 2, wherein processing the VSRR message comprises processing a VSRR region encoded message comprising a top offset field specifying a requested offset for a top of the second picture relative to a top of the first picture, a bottom offset field specifying a requested offset for a bottom of the second picture relative to a bottom of the first picture, a left offset field specifying a requested offset for a left side of the second picture relative to a left side of the first picture, and a right offset field specifying a requested offset for a right side of the second picture relative to a right side of the first picture.

Clause 5: the method of any of clauses 2-4, further comprising processing a Video Spatial Resolution Notification (VSRN) message specifying the reduced size in response to the VSRR message.

Clause 6: the method of clause 5, wherein processing the VSRN message comprises processing the VSRN message in response to a Video Spatial Resolution Request (VSRR) resolution change message, wherein processing the VSRN message comprises processing a picture width field that specifies a width of the reduced size for the second picture, and a picture height field that specifies a height of the reduced size for the second picture.

Clause 7: the method of clause 5, wherein processing the VSRN message comprises processing the VSRN message in response to a Video Spatial Resolution Request (VSRR) region encoded message, wherein processing the VSRN message comprises processing a top offset field that specifies an offset for a top of the second picture relative to a top of the first picture, a bottom offset field that specifies an offset for a bottom of the second picture relative to a bottom of the first picture, a left offset field that specifies an offset for a left side of the second picture relative to a left side of the first picture, and a right offset field that specifies an offset for a right side of the second picture relative to a right side of the first picture.

Clause 8: the method of clause 1, wherein processing the message comprises processing a Video Spatial Resolution Notification (VSRN) message specifying the reduced size.

Clause 9: the method of clause 8, wherein processing the VSRN message comprises processing the VSRN message in response to a Video Spatial Resolution Request (VSRR) resolution change message, wherein processing the VSRN message comprises processing a picture width field that specifies a width of the reduced size for the second picture, and a picture height field that specifies a height of the reduced size for the second picture.

Clause 10: the method of clause 8, wherein processing the VSRN message comprises processing the VSRN message in response to a Video Spatial Resolution Request (VSRR) region encoded message, wherein processing the VSRN message comprises processing a top offset field that specifies an offset for a top of the second picture relative to a top of the first picture, a bottom offset field that specifies an offset for a bottom of the second picture relative to a bottom of the first picture, a left offset field that specifies an offset for a left side of the second picture relative to a left side of the first picture, and a right offset field that specifies an offset for a right side of the second picture relative to a right side of the first picture.

Clause 11: the method of any of clauses 1 to 10, wherein processing the message comprises forming the message.

Clause 12: the method of any of clauses 1 to 10, wherein processing the message comprises receiving the message.

Clause 13: the method of any of clauses 1-12, wherein coding the first picture comprises decoding the first picture, and wherein coding the second picture comprises decoding the second picture.

Clause 14: the method of clause 13, wherein processing the message comprises forming a Video Spatial Resolution Request (VSRR) message.

Clause 15: the method of clause 14, further comprising receiving a Video Spatial Resolution Notification (VSRN) message in response to the VSRR message, the VSRN message specifying the reduced size for the second picture.

Clause 16: the method of clause 14, further comprising receiving a Video Spatial Resolution Notification (VSRN) message in response to the VSRR message, the VSRN message specifying a third size for the second picture, the third size being smaller than the first size and different than the reduced size.

Clause 17: the method of any of clauses 1-16, wherein coding the first picture comprises encoding the first picture, and wherein coding the second picture comprises encoding the second picture.

Clause 18: the method of clause 17, further comprising receiving a Video Spatial Resolution Request (VSRR) message requesting the reduced size for the second picture, wherein processing the message includes forming a Video Spatial Resolution Notification (VSRN) message in response to the VSRR message, the VSRN message specifying the reduced size for the second picture.

Clause 19: the method of clause 17, further comprising receiving a Video Spatial Resolution Request (VSRR) message requesting the reduced size for the second picture, wherein processing the message includes forming a Video Spatial Resolution Notification (VSRN) message in response to the VSRR message, the VSRN message specifying a third size for the second picture, the third size being smaller than the first size and different than the reduced size.

Clause 20: the method of any of clauses 1-19, wherein the message specifies a layer of the video data comprising the second picture.

Clause 21: the method of clause 20, wherein the layer comprises a spatial layer, a scalable layer, or a view.

Clause 22: the method of clause 21, wherein processing the message comprises processing a layer identifier field that specifies the layer.

Clause 23: the method of any of clauses 20 to 22, wherein the layer comprises a temporal layer.

Clause 24: the method of clause 23, wherein processing the message comprises processing a temporal layer identifier field that specifies the temporal layer.

Clause 25: a method of processing a picture size request for video data, the method comprising: coding a first picture of video data having a first size; processing a message specifying a reduced size relative to the first size for a second picture, the second picture following the first picture in coding order; and coding the second picture of the video data having the reduced size.

Clause 26: the method of clause 25, wherein processing the message comprises processing a Video Spatial Resolution Request (VSRR) message specifying the reduced size.

Clause 27: the method of clause 26, wherein processing the VSRR message comprises processing a VSRR resolution change message comprising a picture width field specifying a request width for the reduced size of the second picture, and a picture height field specifying a request height for the reduced size of the second picture.

Clause 28: the method of clause 26, wherein processing the VSRR message comprises processing a VSRR region encoded message comprising a top offset field specifying a requested offset for the top of the second picture relative to the top of the first picture, a bottom offset field specifying a requested offset for the bottom of the second picture relative to the bottom of the first picture, a left offset field specifying a requested offset for the left side of the second picture relative to the left side of the first picture, and a right offset field specifying a requested offset for the right side of the second picture relative to the right side of the first picture.

Clause 29: the method of clause 26, further comprising processing a Video Spatial Resolution Notification (VSRN) message specifying the reduced size in response to the VSRR message.

Clause 30: the method of clause 29, wherein processing the VSRN message comprises processing the VSRN message in response to a Video Spatial Resolution Request (VSRR) resolution change message, wherein processing the VSRN message comprises processing a picture width field that specifies a width of the reduced size for the second picture, and a picture height field that specifies a height of the reduced size for the second picture.

Clause 31: the method of clause 29, wherein processing the VSRN message comprises processing the VSRN message in response to a Video Spatial Resolution Request (VSRR) region encoded message, wherein processing the VSRN message comprises processing a top offset field that specifies an offset for a top of the second picture relative to a top of the first picture, a bottom offset field that specifies an offset for a bottom of the second picture relative to a bottom of the first picture, a left offset field that specifies an offset for a left side of the second picture relative to a left side of the first picture, and a right offset field that specifies an offset for a right side of the second picture relative to a right side of the first picture.

Clause 32: the method of clause 25, wherein processing the message comprises processing a Video Spatial Resolution Notification (VSRN) message specifying the reduced size.

Clause 33: the method of clause 32, wherein processing the VSRN message comprises processing the VSRN message in response to a Video Spatial Resolution Request (VSRR) resolution change message, wherein processing the VSRN message comprises processing a picture width field that specifies a width of the reduced size for the second picture, and a picture height field that specifies a height of the reduced size for the second picture.

Clause 34: the method of clause 32, wherein processing the VSRN message comprises processing the VSRN message in response to a Video Spatial Resolution Request (VSRR) region encoded message, wherein processing the VSRN message comprises processing a top offset field that specifies an offset for a top of the second picture relative to a top of the first picture, a bottom offset field that specifies an offset for a bottom of the second picture relative to a bottom of the first picture, a left offset field that specifies an offset for a left side of the second picture relative to a left side of the first picture, and a right offset field that specifies an offset for a right side of the second picture relative to a right side of the first picture.

Clause 35: the method of clause 25, wherein processing the message comprises forming the message.

Clause 36: the method of clause 25, wherein processing the message comprises receiving the message.

Clause 37: the method of clause 25, wherein coding the first picture comprises decoding the first picture, and wherein coding the second picture comprises decoding the second picture.

Clause 38: the method of clause 37, wherein processing the message comprises forming a Video Spatial Resolution Request (VSRR) message.

Clause 39: the method of clause 38, further comprising receiving a Video Spatial Resolution Notification (VSRN) message in response to the VSRR message, the VSRN message specifying the reduced size for the second picture.

Clause 40: the method of clause 38, further comprising receiving a Video Spatial Resolution Notification (VSRN) message in response to the VSRR message, the VSRN message specifying a third size for the second picture, the third size being smaller than the first size and different than the reduced size.

Clause 41: the method of clause 25, wherein coding the first picture comprises encoding the first picture, and wherein coding the second picture comprises encoding the second picture.

Clause 42: the method of clause 41, further comprising receiving a Video Spatial Resolution Request (VSRR) message requesting the reduced size for the second picture, wherein processing the message includes forming a Video Spatial Resolution Notification (VSRN) message in response to the VSRR message, the VSRN message specifying the reduced size for the second picture.

Clause 43: the method of clause 41, further comprising receiving a Video Spatial Resolution Request (VSRR) message requesting the reduced size for the second picture, wherein processing the message includes forming a Video Spatial Resolution Notification (VSRN) message in response to the VSRR message, the VSRN message specifying a third size for the second picture, the third size being smaller than the first size and different than the reduced size.

Clause 44: the method of clause 25, wherein the message specifies a layer of the video data that includes the second picture.

Clause 45: the method of clause 44, wherein the layer comprises a spatial layer, a scalable layer, or a view.

Clause 46: the method of clause 45, wherein processing the message comprises processing a layer identifier field that specifies the layer.

Clause 47: the method of clause 44, wherein the layer comprises a temporal layer.

Clause 48: the method of clause 47, wherein processing the message comprises processing a time layer identifier field that specifies the time layer.

Clause 49: a method of processing a frame rate request for video data, the method comprising: coding a first plurality of pictures of video data having a first frame rate; processing a message specifying a reduced frame rate relative to the first frame rate for a second plurality of pictures, the second plurality of pictures following the first plurality of pictures in coding order; and coding the second plurality of pictures of the video data having the reduced frame rate.

Clause 50: the method of clause 49, wherein the message comprises a Video Temporal Resolution Request (VTRR) message requesting the reduced frame rate.

Clause 51: the method of clause 49, wherein the message comprises a video temporal resolution notification (VTRR) message specifying the reduced frame rate.

Clause 52: the method of any one of clauses 49 to 51, wherein processing the message comprises receiving the message.

Clause 53: the method of any of clauses 49 to 51, wherein processing the message comprises forming and sending the message.

Clause 54: the method of any of clauses 49-53, wherein coding the first plurality of pictures comprises decoding the first plurality of pictures, and wherein coding the second plurality of pictures comprises decoding the second plurality of pictures.

Clause 55: the method of any of clauses 49-53, wherein coding the first plurality of pictures comprises encoding the first plurality of pictures, and wherein coding the second plurality of pictures comprises encoding the second plurality of pictures.

Clause 56: a method of processing a frame rate request for video data, the method comprising: coding a first plurality of pictures of video data having a first frame rate; processing a message specifying a reduced frame rate relative to the first frame rate for a second plurality of pictures, the second plurality of pictures following the first plurality of pictures in coding order; and coding the second plurality of pictures of the video data having the reduced frame rate.

Clause 57: the method of clause 56, wherein the message comprises a Video Temporal Resolution Request (VTRR) message requesting the reduced frame rate.

Clause 58: the method of clause 56, wherein the message comprises a video temporal resolution notification (VTRR) message specifying the reduced frame rate.

Clause 59: the method of clause 56, wherein processing the message comprises receiving the message.

Clause 60: the method of clause 56, wherein processing the message comprises forming and sending the message.

Clause 61: the method of clause 56, wherein coding the first plurality of pictures comprises decoding the first plurality of pictures, and wherein coding the second plurality of pictures comprises decoding the second plurality of pictures.

Clause 62: the method of clause 56, wherein coding the first plurality of pictures comprises encoding the first plurality of pictures, and wherein coding the second plurality of pictures comprises encoding the second plurality of pictures.

Clause 63: an apparatus for processing a picture size request for video data, the apparatus comprising one or more means for performing the method of any of clauses 1-62.

Clause 64: the apparatus of clause 63, further comprising a display configured to display the decoded video data.

Clause 65: the device of any one of clauses 63 and 64, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set top box.

Clause 66: the apparatus of clauses 63-65, further comprising a memory configured to store the video data.

Clause 67: a computer readable storage medium having stored thereon instructions that, when executed, cause a processor to perform the method according to any of clauses 1-62.

Clause 68: an apparatus for processing a picture size request for video data, the apparatus comprising: means for coding a first picture of a first size of video data; means for processing a message specifying a reduced size relative to the first size for a second picture, the second picture following the first picture in coding order; and means for coding the second picture of the video data having the reduced size.

Clause 69: an apparatus for processing a frame rate request for video data, the apparatus comprising: means for coding a first plurality of pictures of video data having a first frame rate; means for processing a message specifying a reduced frame rate relative to the first frame rate for a second plurality of pictures, the second plurality of pictures following the first plurality of pictures in coding order; and means for coding the second plurality of pictures of the video data having the reduced frame rate.

Clause 70: a method of requesting reduced resolution for video data, the method comprising: decoding, by a video decoder of a client device, a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution; in response to determining that the client device is to enter a power saving mode, sending, by the client device, a message requesting reduced resolution relative to the first resolution for a second sequence of pictures, the second sequence of pictures following the first sequence of pictures in coding order; and decoding, by the video decoder of the client device, the second sequence of pictures of the video data of the bitstream, the second sequence of pictures having the reduced resolution.

Clause 71: the method of clause 70, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures and the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures.

Clause 72: the method of clause 71, further comprising forming the message as a Video Spatial Resolution Request (VSRR) message specifying the reduced spatial resolution.

Clause 73: the method of clause 72, wherein forming the VSRR message comprises forming a VSRR resolution change message to include a picture width field specifying a request width for the reduced spatial resolution of the pictures in the second sequence of pictures, and a picture height field specifying a request height of the pictures in the second sequence of pictures.

Clause 74: the method of clause 72, wherein forming the VSRR message comprises forming the VSRR message as a region coded message comprising: a top offset field specifying a requested offset for a top of the pictures in the second sequence of pictures relative to a top of the pictures in the first sequence of pictures, a bottom offset field specifying a requested offset for a bottom of the pictures in the second sequence of pictures relative to a bottom of the pictures in the first sequence of pictures, a left offset field specifying a requested offset for a left of the pictures in the second sequence of pictures relative to a left of the pictures in the first sequence of pictures, and a right offset field specifying a requested offset for a right of the pictures in the second sequence of pictures relative to a right of the pictures in the first sequence of pictures.

Clause 75: the method of clause 71, further comprising receiving a Video Spatial Resolution Notification (VSRN) message specifying the reduced spatial resolution.

Clause 76: the method of clause 75, further comprising processing a picture width field specifying a width of the picture in the second sequence of pictures and a picture height field specifying a height of the picture in the second sequence of pictures according to the VSRN message.

Clause 77: the method of clause 75, further comprising processing a top offset field specifying an offset for a top of the pictures in the second sequence of pictures relative to a top of the pictures in the first sequence of pictures, a bottom offset field specifying an offset for a bottom of the pictures in the second sequence of pictures relative to a bottom of the pictures in the first sequence of pictures, a left offset field specifying an offset for a left of the pictures in the second sequence of pictures relative to a left of the pictures in the first sequence of pictures, and a right offset field specifying an offset for a right of the pictures in the second sequence of pictures relative to a right of the pictures in the first sequence of pictures according to the VSRN message.

Clause 78: the method of clause 70, wherein the first resolution comprises a first frame rate for the first sequence of pictures, and wherein the reduced resolution comprises a reduced second frame rate for the second sequence of pictures.

Clause 79: the method of clause 78, further comprising forming the message as a Video Temporal Resolution Request (VTRR) message requesting the reduced frame rate.

Clause 80: the method of clause 70, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures, the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures, and the first sequence of pictures has a first frame rate, the method further comprising forming the message requesting both the reduced spatial resolution and reduced frame rate for the second sequence of pictures.

Clause 81: the method of clause 70, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures, the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures, the first sequence of pictures has a first frame rate, and the message comprises a first message requesting the reduced second spatial resolution for the pictures in the second sequence of pictures, the method further comprising sending a second message requesting a reduced second frame rate for the second sequence of pictures.

Clause 82: the method of clause 70, wherein the message comprises a first message, the method further comprising sending a second message requesting zero value resolution for a third sequence of pictures to indicate that only audio data is needed within a playback time corresponding to the third sequence of pictures.

Clause 83: the method of clause 70, wherein the message comprises a first message, the method further comprising: in response to determining that the client device is coupled to an external power source, a second message requesting enhanced resolution for a third sequence of pictures is sent, the third sequence of pictures following the second sequence of pictures in coding order.

Clause 84: an apparatus for requesting reduced resolution for video data, the apparatus comprising: a memory configured to store video data; and one or more processors implemented in the circuit and configured to: decoding a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution; in response to determining that the device is to enter a power saving mode, sending a message requesting reduced resolution relative to the first resolution for a second sequence of pictures, the second sequence of pictures following the first sequence of pictures in coding order; and decoding the second sequence of pictures of the video data of the bitstream, the second sequence of pictures having the reduced resolution.

Clause 85: the apparatus of clause 84, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures and the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures.

Clause 86: the apparatus of clause 85, wherein the one or more processors are further configured to form the message as a Video Spatial Resolution Request (VSRR) message specifying the reduced spatial resolution.

Clause 87: the apparatus of clause 86, wherein the one or more processors are configured to form a VSRR resolution change message to include a picture width field specifying a request width for the reduced spatial resolution of the pictures in the second sequence of pictures, and a picture height field specifying a request height of the pictures in the second sequence of pictures.

Clause 88: the apparatus of clause 86, wherein the one or more processors are configured to form the VSRR message as a region coded message comprising: a top offset field specifying a requested offset for a top of the pictures in the second sequence of pictures relative to a top of the pictures in the first sequence of pictures, a bottom offset field specifying a requested offset for a bottom of the pictures in the second sequence of pictures relative to a bottom of the pictures in the first sequence of pictures, a left offset field specifying a requested offset for a left of the pictures in the second sequence of pictures relative to a left of the pictures in the first sequence of pictures, and a right offset field specifying a requested offset for a right of the pictures in the second sequence of pictures relative to a right of the pictures in the first sequence of pictures.

Clause 89: the apparatus of clause 85, wherein the one or more processors are further configured to receive a Video Spatial Resolution Notification (VSRN) message specifying the reduced spatial resolution.

Clause 90: the device of clause 89, wherein the one or more processors are further configured to process a picture width field specifying the width of the pictures in the second sequence of pictures and a picture height field specifying the height of the pictures in the second sequence of pictures according to the VSRN messages.

Clause 91: the device of clause 89, wherein the one or more processors are further configured to process a top offset field specifying an offset for a top of the pictures in the second sequence of pictures relative to a top of the pictures in the first sequence of pictures, a bottom offset field specifying an offset for a bottom of the pictures in the second sequence of pictures relative to a bottom of the pictures in the first sequence of pictures, a left offset field specifying an offset for a left of the pictures in the second sequence of pictures relative to a left of the pictures in the first sequence of pictures, and a right offset field specifying an offset for a right of the pictures in the second sequence of pictures relative to a right of the pictures in the first sequence of pictures according to the VSRN message.

Clause 92: the apparatus of clause 84, wherein the first resolution comprises a first frame rate for the first sequence of pictures, and wherein the reduced resolution comprises a reduced second frame rate for the second sequence of pictures.

Clause 93: the apparatus of clause 92, wherein the one or more processors are configured to form the message as a Video Temporal Resolution Request (VTRR) message requesting the reduced frame rate.

Clause 94: the device of clause 84, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures, the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures, and the first sequence of pictures has a first frame rate, and wherein the one or more processors are further configured to form the message requesting both the reduced spatial resolution and reduced frame rate for the second sequence of pictures.

Clause 95: the device of clause 84, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures, the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures, the first sequence of pictures has a first frame rate, and the message comprises a first message requesting the reduced second spatial resolution for the pictures in the second sequence of pictures, wherein the one or more processors are further configured to send a second message requesting the reduced second frame rate for the second sequence of pictures.

Clause 96: the apparatus of clause 84, further comprising a display configured to display the decoded video data.

Clause 97: a computer-readable storage medium having stored thereon instructions that, when executed, cause a processor of a client device to: decoding a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution; in response to determining that the device is to enter a power saving mode, sending a message requesting reduced resolution relative to the first resolution for a second sequence of pictures, the second sequence of pictures following the first sequence of pictures in coding order; and decoding the second sequence of pictures of the video data of the bitstream, the second sequence of pictures having the reduced resolution.

Clause 98: an apparatus for requesting reduced resolution for video data, the apparatus comprising: means for decoding a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution; means for sending a message requesting reduced resolution relative to the first resolution for a second sequence of pictures that follows the first sequence of pictures in coding order in response to determining that the client device is to enter a power save mode; and means for decoding the second sequence of pictures of the video data of the bitstream, the second sequence of pictures having the reduced resolution.

Clause 99: the apparatus of clause 98, wherein the reduced resolution comprises at least one of a reduced spatial resolution or a reduced temporal resolution.

Clause 100: a method of requesting reduced resolution for video data, the method comprising: decoding, by a video decoder of a client device, a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution; in response to determining that the client device is to enter a power saving mode, sending, by the client device, a message requesting reduced resolution relative to the first resolution for a second sequence of pictures, the second sequence of pictures following the first sequence of pictures in coding order; and decoding, by the video decoder of the client device, the second sequence of pictures of the video data of the bitstream, the second sequence of pictures having the reduced resolution.

Clause 101: the method of clause 100, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures and the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures.

Clause 102: the method of clause 101, further comprising forming the message as a Video Spatial Resolution Request (VSRR) message specifying the reduced spatial resolution.

Clause 103: the method of clause 102, wherein forming the VSRR message comprises forming a VSRR resolution change message to include a picture width field specifying a request width for the reduced spatial resolution of the pictures in the second sequence of pictures, and a picture height field specifying a request height of the pictures in the second sequence of pictures.

Clause 104: the method of clause 102, wherein forming the VSRR message comprises forming the VSRR message as a region coded message comprising: a top offset field specifying a requested offset for a top of the pictures in the second sequence of pictures relative to a top of the pictures in the first sequence of pictures, a bottom offset field specifying a requested offset for a bottom of the pictures in the second sequence of pictures relative to a bottom of the pictures in the first sequence of pictures, a left offset field specifying a requested offset for a left of the pictures in the second sequence of pictures relative to a left of the pictures in the first sequence of pictures, and a right offset field specifying a requested offset for a right of the pictures in the second sequence of pictures relative to a right of the pictures in the first sequence of pictures.

Clause 105: the method of any of clauses 100 to 104, further comprising receiving a Video Spatial Resolution Notification (VSRN) message specifying the reduced resolution.

Clause 106: the method of clause 105, further comprising processing a picture width field specifying a width of the picture in the second sequence of pictures and a picture height field specifying a height of the picture in the second sequence of pictures according to the VSRN message.

Clause 107: the method of clause 105, further comprising processing a top offset field specifying an offset for a top of the pictures in the second sequence of pictures relative to a top of the pictures in the first sequence of pictures, a bottom offset field specifying an offset for a bottom of the pictures in the second sequence of pictures relative to a bottom of the pictures in the first sequence of pictures, a left offset field specifying an offset for a left of the pictures in the second sequence of pictures relative to a left of the pictures in the first sequence of pictures, and a right offset field specifying an offset for a right of the pictures in the second sequence of pictures relative to a right of the pictures in the first sequence of pictures according to the VSRN message.

Clause 108: the method of any one of clauses 100-107, wherein the first resolution comprises a first frame rate for the first sequence of pictures, and wherein the reduced resolution comprises a reduced second frame rate for the second sequence of pictures.

Clause 109: the method of clause 108, further comprising forming the message as a Video Temporal Resolution Request (VTRR) message requesting the reduced frame rate.

Clause 110: the method of any of clauses 100-109, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures, the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures, and the first sequence of pictures has a first frame rate, the method further comprising forming the message requesting both the reduced spatial resolution and reduced frame rate for the second sequence of pictures.

Clause 111: the method of any of clauses 100-109, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures, the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures, the first sequence of pictures has a first frame rate, and the message comprises a first message requesting the reduced second spatial resolution for the pictures in the second sequence of pictures, the method further comprising sending a second message requesting a reduced second frame rate for the second sequence of pictures.

Clause 112: the method of any of clauses 100-111, wherein the message comprises a first message, the method further comprising sending a second message requesting zero value resolution for a third sequence of pictures to indicate that only audio data is needed during a playback time corresponding to the third sequence of pictures.

Clause 113: the method of any one of clauses 100 to 112, wherein the message comprises a first message, the method further comprising: in response to determining that the client device is coupled to an external power source, a second message requesting enhanced resolution for a third sequence of pictures is sent, the third sequence of pictures following the second sequence of pictures in coding order.

Clause 114: an apparatus for requesting reduced resolution for video data, the apparatus comprising: a memory configured to store video data; and one or more processors implemented in the circuit and configured to: decoding a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution; in response to determining that the device is to enter a power saving mode, sending a message requesting reduced resolution relative to the first resolution for a second sequence of pictures, the second sequence of pictures following the first sequence of pictures in coding order; and decoding the second sequence of pictures of the video data of the bitstream, the second sequence of pictures having the reduced resolution.

Clause 115: the apparatus of clause 114, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures and the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures.

Clause 116: the apparatus of clause 115, wherein the one or more processors are further configured to form the message as a Video Spatial Resolution Request (VSRR) message specifying the reduced spatial resolution.

Clause 117: the apparatus of clause 116, wherein the one or more processors are configured to form a VSRR resolution change message to include a picture width field specifying a request width for the reduced spatial resolution of the pictures in the second sequence of pictures, and a picture height field specifying a request height of the pictures in the second sequence of pictures.

Clause 118: the apparatus of clause 116, wherein the one or more processors are configured to form the VSRR message as a region coded message comprising: a top offset field specifying a requested offset for a top of the pictures in the second sequence of pictures relative to a top of the pictures in the first sequence of pictures, a bottom offset field specifying a requested offset for a bottom of the pictures in the second sequence of pictures relative to a bottom of the pictures in the first sequence of pictures, a left offset field specifying a requested offset for a left of the pictures in the second sequence of pictures relative to a left of the pictures in the first sequence of pictures, and a right offset field specifying a requested offset for a right of the pictures in the second sequence of pictures relative to a right of the pictures in the first sequence of pictures.

Clause 119: the apparatus of any one of clauses 115 to 118, wherein the one or more processors are further configured to receive a Video Spatial Resolution Notification (VSRN) message specifying the reduced resolution.

Clause 120: the device of clause 119, wherein the one or more processors are further configured to process a picture width field specifying a width of the pictures in the second sequence of pictures and a picture height field specifying a height of the pictures in the second sequence of pictures according to the VSRN messages.

Clause 121: the device of clause 119, wherein the one or more processors are further configured to process a top offset field specifying an offset for a top of the pictures in the second sequence of pictures relative to a top of the pictures in the first sequence of pictures, a bottom offset field specifying an offset for a bottom of the pictures in the second sequence of pictures relative to a bottom of the pictures in the first sequence of pictures, a left offset field specifying an offset for a left of the pictures in the second sequence of pictures relative to a left of the pictures in the first sequence of pictures, and a right offset field specifying an offset for a right of the pictures in the second sequence of pictures relative to a right of the pictures in the first sequence of pictures according to the VSRN message.

Clause 122: the device of any of clauses 114-121, wherein the first resolution comprises a first frame rate for the first sequence of pictures, and wherein the reduced resolution comprises a reduced second frame rate for the second sequence of pictures.

Clause 123: the apparatus of clause 122, wherein the one or more processors are configured to form the message as a Video Temporal Resolution Request (VTRR) message requesting the reduced frame rate.

Clause 124: the device of any of clauses 114-123, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures, the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures, and the first sequence of pictures has a first frame rate, and wherein the one or more processors are further configured to form the message requesting both the reduced spatial resolution and reduced frame rate for the second sequence of pictures.

Clause 125: the device of any of clauses 114-123, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures, the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures, the first sequence of pictures has a first frame rate, and the message comprises a first message requesting the reduced second spatial resolution for the pictures in the second sequence of pictures, wherein the one or more processors are further configured to send a second message requesting the reduced second frame rate for the second sequence of pictures.

Clause 126: the device of any of clauses 114 to 125, further comprising a display configured to display the decoded video data.

Clause 127: a computer-readable storage medium having stored thereon instructions that, when executed, cause a processor of a client device to: decoding a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution; in response to determining that the device is to enter a power saving mode, sending a message requesting reduced resolution relative to the first resolution for a second sequence of pictures, the second sequence of pictures following the first sequence of pictures in coding order; and decoding the second sequence of pictures of the video data of the bitstream, the second sequence of pictures having the reduced resolution.

Clause 128: an apparatus for requesting reduced resolution for video data, the apparatus comprising: means for decoding a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution; means for sending a message requesting reduced resolution relative to the first resolution for a second sequence of pictures that follows the first sequence of pictures in coding order in response to determining that the client device is to enter a power save mode; and means for decoding the second sequence of pictures of the video data of the bitstream, the second sequence of pictures having the reduced resolution.

Clause 129: the apparatus of clause 128, wherein the reduced resolution comprises at least one of a reduced spatial resolution or a reduced temporal resolution.

It is to be appreciated that certain acts or events of any of the techniques described herein can be performed in a different order, may be added, combined, or omitted entirely, depending on the example (e.g., not all of the described acts or events are necessary to implement the techniques). Further, in some examples, an action or event may be performed concurrently (e.g., by multi-threaded processing, interrupt processing, or multiple processors) rather than sequentially.

In one or more examples, the described functionality may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium, and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media (which corresponds to tangible media, 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. In this manner, the computer-readable medium may generally correspond to (1) a non-transitory tangible computer-readable storage medium, 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 implementing the techniques described in this disclosure. The computer program product may include a computer-readable medium.

By way of example, and not limitation, 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. For example, if the instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but instead are directed to non-transitory tangible storage media. Disk and disc, as used herein, 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.

The instructions may be executed by one or more processors, such as one or more Digital Signal Processors (DSPs), general purpose microprocessors, application Specific Integrated Circuits (ASICs), field Programmable Gate Arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Thus, the terms "processor" and "processing circuitry" as used herein may refer to any one of the foregoing structures or any other structure suitable for implementation of the techniques described herein. Additionally, in some aspects, the functionality described herein may be provided within dedicated hardware and/or software modules configured for encoding and decoding, or incorporated into a combined codec. Also, the techniques may 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 chipset). 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, the various units may be combined in a codec hardware unit, or the various units may be provided by a collection of interoperable hardware units (including one or more processors as described above) in combination with appropriate software and/or firmware.

Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method of requesting reduced resolution for video data, the method comprising:

Decoding, by a video decoder of a client device, a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution;

In response to determining that the client device is to enter a power saving mode, sending, by the client device, a message requesting reduced resolution relative to the first resolution for a second sequence of pictures, the second sequence of pictures following the first sequence of pictures in coding order; and

Decoding, by the video decoder of the client device, the second sequence of pictures of the video data of the bitstream, the second sequence of pictures having the reduced resolution.

2. The method of claim 1, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures and the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures.

3. The method of claim 2, further comprising forming the message as a Video Spatial Resolution Request (VSRR) message specifying the reduced spatial resolution.

4. The method of claim 3, wherein forming the VSRR message comprises forming the VSRR message to include a picture width field specifying a request width for the reduced spatial resolution of the pictures in the second sequence of pictures, and a picture height field specifying a request height of the pictures in the second sequence of pictures.

5. The method of claim 3, wherein forming the VSRR message comprises forming the VSRR message as a region coded message comprising: a top offset field specifying a requested offset for a top of the pictures in the second sequence of pictures relative to a top of the pictures in the first sequence of pictures, a bottom offset field specifying a requested offset for a bottom of the pictures in the second sequence of pictures relative to a bottom of the pictures in the first sequence of pictures, a left offset field specifying a requested offset for a left of the pictures in the second sequence of pictures relative to a left of the pictures in the first sequence of pictures, and a right offset field specifying a requested offset for a right of the pictures in the second sequence of pictures relative to a right of the pictures in the first sequence of pictures.

6. The method of claim 2, further comprising receiving a Video Spatial Resolution Notification (VSRN) message specifying the reduced spatial resolution.

7. The method of claim 6, further comprising processing a picture width field specifying a width of the picture in the second sequence of pictures and a picture height field specifying a height of the picture in the second sequence of pictures according to the VSRN message.

8. The method of claim 6, further comprising processing a top offset field specifying an offset for a top of the pictures in the second sequence of pictures relative to a top of the pictures in the first sequence of pictures, a bottom offset field specifying an offset for a bottom of the pictures in the second sequence of pictures relative to a bottom of the pictures in the first sequence of pictures, a left offset field specifying an offset for a left of the pictures in the second sequence of pictures relative to a left of the pictures in the first sequence of pictures, and a right offset field specifying an offset for a right of the pictures in the second sequence of pictures relative to a right of the pictures in the first sequence of pictures according to the VSRN message.

9. The method of claim 1, wherein the first resolution comprises a first frame rate for the first sequence of pictures, and wherein the reduced resolution comprises a reduced second frame rate for the second sequence of pictures.

10. The method of claim 9, further comprising forming the message as a Video Temporal Resolution Request (VTRR) message requesting the reduced frame rate.

11. The method of claim 1, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures, the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures, and the first sequence of pictures has a first frame rate, the method further comprising forming the message requesting both the reduced spatial resolution and reduced frame rate for the second sequence of pictures.

12. The method of claim 1, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures, the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures, the first sequence of pictures has a first frame rate, and the message comprises a first message requesting the reduced second spatial resolution for the pictures in the second sequence of pictures, the method further comprising sending a second message requesting a reduced second frame rate for the second sequence of pictures.

13. The method of claim 1, wherein the message comprises a first message, the method further comprising sending a second message requesting zero value resolution for a third sequence of pictures to indicate that only audio data is required during a playback time corresponding to the third sequence of pictures.

14. The method of claim 1, wherein the message comprises a first message, the method further comprising: in response to determining that the client device is coupled to an external power source, a second message requesting enhanced resolution for a third sequence of pictures is sent, the third sequence of pictures following the second sequence of pictures in coding order.

15. An apparatus for requesting reduced resolution for video data, the apparatus comprising:

A memory configured to store video data; and

One or more processors implemented in circuitry and configured to:

decoding a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution;

In response to determining that the device is to enter a power saving mode, sending a message requesting reduced resolution relative to the first resolution for a second sequence of pictures, the second sequence of pictures following the first sequence of pictures in coding order; and

Decoding the second sequence of pictures of the video data of the bitstream, the second sequence of pictures having the reduced resolution.

16. The apparatus of claim 15, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures and the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures.

17. The apparatus of claim 16, wherein the one or more processors are further configured to form the message as a Video Spatial Resolution Request (VSRR) message specifying the reduced spatial resolution.

18. The apparatus of claim 17, wherein the one or more processors are configured to form the VSRR message to include a picture width field specifying a request width for the reduced spatial resolution of the pictures in the second sequence of pictures, and a picture height field specifying a request height of the pictures in the second sequence of pictures.

19. The apparatus of claim 17, wherein the one or more processors are configured to form the VSRR message as a region coded message comprising: a top offset field specifying a requested offset for a top of the pictures in the second sequence of pictures relative to a top of the pictures in the first sequence of pictures, a bottom offset field specifying a requested offset for a bottom of the pictures in the second sequence of pictures relative to a bottom of the pictures in the first sequence of pictures, a left offset field specifying a requested offset for a left of the pictures in the second sequence of pictures relative to a left of the pictures in the first sequence of pictures, and a right offset field specifying a requested offset for a right of the pictures in the second sequence of pictures relative to a right of the pictures in the first sequence of pictures.

20. The device of claim 16, wherein the one or more processors are further configured to receive a Video Spatial Resolution Notification (VSRN) message specifying the reduced spatial resolution.

21. The device of claim 20, wherein the one or more processors are further configured to process a picture width field specifying a width of the pictures in the second sequence of pictures and a picture height field specifying a height of the pictures in the second sequence of pictures according to the VSRN messages.

22. The device of claim 20, wherein the one or more processors are further configured to process, in accordance with the VSRN message, a top offset field that specifies an offset for a top of the pictures in the second sequence of pictures relative to a top of the pictures in the first sequence of pictures, a bottom offset field that specifies an offset for a bottom of the pictures in the second sequence of pictures relative to a bottom of the pictures in the first sequence of pictures, a left offset field that specifies an offset for a left side of the pictures in the second sequence of pictures relative to a left side of the pictures in the first sequence of pictures, and a right offset field that specifies an offset for a right side of the pictures in the second sequence of pictures relative to a right side of the pictures in the first sequence of pictures.

23. The apparatus of claim 15, wherein the first resolution comprises a first frame rate for the first sequence of pictures, and wherein the reduced resolution comprises a reduced second frame rate for the second sequence of pictures.

24. The device of claim 23, wherein the one or more processors are configured to form the message as a Video Temporal Resolution Request (VTRR) message requesting the reduced frame rate.

25. The device of claim 15, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures, the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures, and the first sequence of pictures has a first frame rate, and wherein the one or more processors are further configured to form the message requesting both the reduced spatial resolution and reduced frame rate for the second sequence of pictures.

26. The device of claim 15, wherein the first resolution comprises a first spatial resolution for pictures in the first sequence of pictures, the reduced resolution comprises a reduced second spatial resolution for pictures in the second sequence of pictures, the first sequence of pictures has a first frame rate, and the message comprises a first message requesting the reduced second spatial resolution for the pictures in the second sequence of pictures, wherein the one or more processors are further configured to send a second message requesting the reduced second frame rate for the second sequence of pictures.

27. The device of claim 15, further comprising a display configured to display the decoded video data.

28. A computer-readable storage medium having stored thereon instructions that, when executed, cause a processor of a client device to:

29. An apparatus for requesting reduced resolution for video data, the apparatus comprising:

Means for decoding a first sequence of pictures of a bitstream, the first sequence of pictures having a first resolution;

Means for sending a message requesting reduced resolution relative to the first resolution for a second sequence of pictures that follows the first sequence of pictures in coding order in response to determining that the client device is to enter a power save mode; and

Means for decoding the second sequence of pictures of the video data of the bitstream, the second sequence of pictures having the reduced resolution.

30. The apparatus of claim 29, wherein the reduced resolution comprises at least one of a reduced spatial resolution or a reduced temporal resolution.