MOTION VECTOR PREDICTOR BY USING MOTION VECTOR PREDICTOR LOOKAHEAD/LOOKBEHIND

Abstract

A video bitstream is received. The video bitstream includes coded information of a current block in a current picture and of a plurality of reference pictures of the current picture in a reference list. A plurality of intermediate vectors associated with one of the plurality of reference pictures is determined. The plurality of intermediate vectors includes an initial vector and a plurality of intermediate motion vectors (MVs). The initial vector is associated with the current picture. Each of the plurality of intermediate MVs is defined between two respective reference pictures of the plurality of reference pictures. A candidate motion vector predictor (MVP) is determined for the current block based on a sum of the plurality of intermediate vectors. The current block is reconstructed based on an MVP candidate list that includes the candidate MVP.

Description

TECHNICAL FIELD

The present disclosure describes aspects generally related to video coding.

BACKGROUND

The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

Image/video compression can help transmit image/video data across different devices, storage and networks with minimal quality degradation. In some examples, video codec technology can compress video based on spatial and temporal redundancy. In an example, a video codec can use techniques referred to as intra prediction that can compress an image based on spatial redundancy. For example, the intra prediction can use reference data from the current picture under reconstruction for sample prediction. In another example, a video codec can use techniques referred to as inter prediction that can compress an image based on temporal redundancy. For example, the inter prediction can predict samples in a current picture from a previously reconstructed picture with motion compensation. The motion compensation can be indicated by a motion vector (MV).

SUMMARY

Aspects of the disclosure include bitstreams, methods, and apparatuses for video encoding/decoding. In some examples, an apparatus for video encoding/decoding includes processing circuitry.

According to an aspect of the disclosure, a method of video decoding is provided. In the method, a video bitstream is received. The video bitstream includes coded information of a current block in a current picture and of a plurality of reference pictures of the current picture in a reference list. A plurality of intermediate vectors associated with one of the plurality of reference pictures is determined. The plurality of intermediate vectors includes an initial vector and a plurality of intermediate motion vectors (MVs). The initial vector is associated with the current picture. Each of the plurality of intermediate MVs is defined between two respective reference pictures of the plurality of reference pictures. A candidate motion vector predictor (MVP) is determined for the current block based on a sum of the plurality of intermediate vectors. The current block is reconstructed based on an MVP candidate list that includes the candidate MVP.

According to another aspect of the disclosure, a method of video encoding is provided. In the method, a plurality of intermediate vectors of a current block in a current picture is determined. The plurality of intermediate vectors is associated with one of a plurality of reference pictures in a reference list. The plurality of intermediate vectors includes an initial vector and a plurality of intermediate MVs. The initial vector is associated with the current picture. Each of the plurality of intermediate MVs is defined between two respective reference pictures of the plurality of reference pictures. A candidate MVP for the current block is determined based on a sum of the plurality of intermediate vectors. The current block is encoded based on an MVP candidate list that includes the candidate MVP.

According to yet another aspect of the disclosure, a method of processing visual media data is provided. In the method, a bitstream of the visual media data is processed according to a format rule. In an example, the bitstream includes coded information of a current block in a current picture and of a plurality of reference pictures of the current picture in a reference list. The format rule specifies that a plurality of intermediate vectors associated with one of the plurality of reference pictures is determined. The plurality of intermediate vectors includes an initial vector and a plurality of intermediate MVs. The initial vector is associated with the current picture. Each of the plurality of intermediate MVs is defined between two respective reference pictures of the plurality of reference pictures. The format rule specifies that a candidate MVP for the current block is determined based on a sum of the plurality of intermediate vectors. The format rule specifies that the current block is processed based on an MVP candidate list that includes the candidate MVP.

Aspects of the disclosure also provide an apparatus for video decoding. The apparatus for video decoding includes processing circuitry configured to implement any of the described methods for video decoding.

Aspects of the disclosure also provide an apparatus for video encoding. The apparatus for video encoding includes processing circuitry configured to implement any of the described methods for video encoding.

Aspects of the disclosure also provide a non-transitory computer-readable medium storing instructions which, when executed by a computer, cause the computer to perform any of the described methods for video decoding/encoding/processing.

Technical solutions of the disclosure include methods and apparatuses for improving derivation of a motion vector predictor (or a merge candidate) for a current block by using lookahead and/or lookbehind. In an example, a video bitstream is received. The video bitstream includes coded information of a current block in a current picture and of a plurality of reference pictures of the current picture in a reference list. A plurality of intermediate vectors associated with one of the plurality of reference pictures is determined. The plurality of intermediate vectors includes an initial vector and a plurality of intermediate MVs. The initial vector is associated with the current picture. Each of the plurality of intermediate MVs is defined between two respective reference pictures of the plurality of reference pictures. A candidate MVP is determined for the current block based on a sum of the plurality of intermediate vectors. The current block is reconstructed based on an MVP candidate list that includes the candidate MVP. By using lookahead and/or lookbehind, derivation of a motion vector predictor (or a merge candidate) for a current block is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosed subject matter will be more apparent from the following detailed description and the accompanying drawings in which:

FIG. 1 is a schematic illustration of an example of a block diagram of a communication system (100).

FIG. 2 is a schematic illustration of an example of a block diagram of a decoder.

FIG. 3 is a schematic illustration of an example of a block diagram of an encoder.

FIG. 4 is a schematic illustration of a first example of a lookahead motion vector predictor construction for different reference indices in a forward reference list.

FIG. 5 is a schematic illustration of an example of motion field positions in a lookahead motion vector predictor construction.

FIG. 6 is a schematic illustration of an example of a lookahead motion vector predictor construction based on a scaled associated pointed motion vector.

FIG. 7 is a schematic illustration of an example of the lookahead motion vector predictor construction for different reference indices in the forward reference list.

FIG. 8 shows a flow chart outlining a decoding process according to some aspects of the disclosure.

FIG. 9 shows a flow chart outlining an encoding process according to some aspects of the disclosure.

FIG. 10 is a schematic illustration of a computer system in accordance with an aspect.

DETAILED DESCRIPTION

FIG. 1 shows a block diagram of a video processing system (100) in some examples. The video processing system (100) is an example of an application for the disclosed subject matter, a video encoder and a video decoder in a streaming environment. The disclosed subject matter can be equally applicable to other video enabled applications, including, for example, video conferencing, digital TV, streaming services, storing of compressed video on digital media including CD, DVD, memory stick and the like, and so on.

The video processing system (100) includes a capture subsystem (113), that can include a video source (101), for example a digital camera, creating for example a stream of video pictures (102) that are uncompressed. In an example, the stream of video pictures (102) includes samples that are taken by the digital camera. The stream of video pictures (102), depicted as a bold line to emphasize a high data volume when compared to encoded video data (104) (or coded video bitstreams), can be processed by an electronic device (120) that includes a video encoder (103) coupled to the video source (101). The video encoder (103) can include hardware, software, or a combination thereof to enable or implement aspects of the disclosed subject matter as described in more detail below. The encoded video data (104) (or encoded video bitstream), depicted as a thin line to emphasize the lower data volume when compared to the stream of video pictures (102), can be stored on a streaming server (105) for future use. One or more streaming client subsystems, such as client subsystems (106) and (108) in FIG. 1 can access the streaming server (105) to retrieve copies (107) and (109) of the encoded video data (104). A client subsystem (106) can include a video decoder (110), for example, in an electronic device (130). The video decoder (110) decodes the incoming copy (107) of the encoded video data and creates an outgoing stream of video pictures (111) that can be rendered on a display (112) (e.g., display screen) or other rendering device (not depicted). In some streaming systems, the encoded video data (104), (107), and (109) (e.g., video bitstreams) can be encoded according to certain video coding/compression standards. Examples of those standards include ITU-T Recommendation H.265. In an example, a video coding standard under development is informally known as Versatile Video Coding (VVC). The disclosed subject matter may be used in the context of VVC.

It is noted that the electronic devices (120) and (130) can include other components (not shown). For example, the electronic device (120) can include a video decoder (not shown) and the electronic device (130) can include a video encoder (not shown) as well.

FIG. 2 shows an example of a block diagram of a video decoder (210). The video decoder (210) can be included in an electronic device (230). The electronic device (230) can include a receiver (231) (e.g., receiving circuitry). The video decoder (210) can be used in the place of the video decoder (110) in the FIG. 1 example.

The receiver (231) may receive one or more coded video sequences, included in a bitstream for example, to be decoded by the video decoder (210). In an aspect, one coded video sequence is received at a time, where the decoding of each coded video sequence is independent from the decoding of other coded video sequences. The coded video sequence may be received from a channel (201), which may be a hardware/software link to a storage device which stores the encoded video data. The receiver (231) may receive the encoded video data with other data, for example, coded audio data and/or ancillary data streams, that may be forwarded to their respective using entities (not depicted). The receiver (231) may separate the coded video sequence from the other data. To combat network jitter, a buffer memory (215) may be coupled in between the receiver (231) and an entropy decoder/parser (220) (“parser (220)” henceforth). In certain applications, the buffer memory (215) is part of the video decoder (210). In others, it can be outside of the video decoder (210) (not depicted). In still others, there can be a buffer memory (not depicted) outside of the video decoder (210), for example to combat network jitter, and in addition another buffer memory (215) inside the video decoder (210), for example to handle playout timing. When the receiver (231) is receiving data from a store/forward device of sufficient bandwidth and controllability, or from an isosynchronous network, the buffer memory (215) may not be needed, or can be small. For use on best effort packet networks such as the Internet, the buffer memory (215) may be required, can be comparatively large and can be advantageously of adaptive size, and may at least partially be implemented in an operating system or similar elements (not depicted) outside of the video decoder (210).

The video decoder (210) may include the parser (220) to reconstruct symbols (221) from the coded video sequence. Categories of those symbols include information used to manage operation of the video decoder (210), and potentially information to control a rendering device such as a render device (212) (e.g., a display screen) that is not an integral part of the electronic device (230) but can be coupled to the electronic device (230), as shown in FIG. 2. The control information for the rendering device(s) may be in the form of Supplemental Enhancement Information (SEI) messages or Video Usability Information (VUI) parameter set fragments (not depicted). The parser (220) may parse/entropy-decode the coded video sequence that is received. The coding of the coded video sequence can be in accordance with a video coding technology or standard, and can follow various principles, including variable length coding, Huffman coding, arithmetic coding with or without context sensitivity, and so forth. The parser (220) may extract from the coded video sequence, a set of subgroup parameters for at least one of the subgroups of pixels in the video decoder, based upon at least one parameter corresponding to the group. Subgroups can include Groups of Pictures (GOPs), pictures, tiles, slices, macroblocks, Coding Units (CUs), blocks, Transform Units (TUs), Prediction Units (PUs) and so forth. The parser (220) may also extract from the coded video sequence information such as transform coefficients, quantizer parameter values, motion vectors, and so forth.

The parser (220) may perform an entropy decoding/parsing operation on the video sequence received from the buffer memory (215), so as to create symbols (221).

Reconstruction of the symbols (221) can involve multiple different units depending on the type of the coded video picture or parts thereof (such as: inter and intra picture, inter and intra block), and other factors. Which units are involved, and how, can be controlled by subgroup control information parsed from the coded video sequence by the parser (220). The flow of such subgroup control information between the parser (220) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, the video decoder (210) can be conceptually subdivided into a number of functional units as described below. In a practical implementation operating under commercial constraints, many of these units interact closely with each other and can, at least partly, be integrated into each other. However, for the purpose of describing the disclosed subject matter, the conceptual subdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (251). The scaler/inverse transform unit (251) receives a quantized transform coefficient as well as control information, including which transform to use, block size, quantization factor, quantization scaling matrices, etc. as symbol(s) (221) from the parser (220). The scaler/inverse transform unit (251) can output blocks comprising sample values, that can be input into aggregator (255).

In some cases, the output samples of the scaler/inverse transform unit (251) can pertain to an intra coded block. The intra coded block is a block that is not using predictive information from previously reconstructed pictures, but can use predictive information from previously reconstructed parts of the current picture. Such predictive information can be provided by an intra picture prediction unit (252). In some cases, the intra picture prediction unit (252) generates a block of the same size and shape of the block under reconstruction, using surrounding already reconstructed information fetched from the current picture buffer (258). The current picture buffer (258) buffers, for example, partly reconstructed current picture and/or fully reconstructed current picture. The aggregator (255), in some cases, adds, on a per sample basis, the prediction information the intra prediction unit (252) has generated to the output sample information as provided by the scaler/inverse transform unit (251).

In other cases, the output samples of the scaler/inverse transform unit (251) can pertain to an inter coded, and potentially motion compensated, block. In such a case, a motion compensation prediction unit (253) can access reference picture memory (257) to fetch samples used for prediction. After motion compensating the fetched samples in accordance with the symbols (221) pertaining to the block, these samples can be added by the aggregator (255) to the output of the scaler/inverse transform unit (251) (in this case called the residual samples or residual signal) so as to generate output sample information. The addresses within the reference picture memory (257) from where the motion compensation prediction unit (253) fetches prediction samples can be controlled by motion vectors, available to the motion compensation prediction unit (253) in the form of symbols (221) that can have, for example X, Y, and reference picture components. Motion compensation also can include interpolation of sample values as fetched from the reference picture memory (257) when sub-sample exact motion vectors are in use, motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (255) can be subject to various loop filtering techniques in the loop filter unit (256). Video compression technologies can include in-loop filter technologies that are controlled by parameters included in the coded video sequence (also referred to as coded video bitstream) and made available to the loop filter unit (256) as symbols (221) from the parser (220). Video compression can also be responsive to meta-information obtained during the decoding of previous (in decoding order) parts of the coded picture or coded video sequence, as well as responsive to previously reconstructed and loop-filtered sample values.

The output of the loop filter unit (256) can be a sample stream that can be output to the render device (212) as well as stored in the reference picture memory (257) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used as reference pictures for future prediction. For example, once a coded picture corresponding to a current picture is fully reconstructed and the coded picture has been identified as a reference picture (by, for example, the parser (220)), the current picture buffer (258) can become a part of the reference picture memory (257), and a fresh current picture buffer can be reallocated before commencing the reconstruction of the following coded picture.

The video decoder (210) may perform decoding operations according to a predetermined video compression technology or a standard, such as ITU-T Rec. H.265. The coded video sequence may conform to a syntax specified by the video compression technology or standard being used, in the sense that the coded video sequence adheres to both the syntax of the video compression technology or standard and the profiles as documented in the video compression technology or standard. Specifically, a profile can select certain tools as the only tools available for use under that profile from all the tools available in the video compression technology or standard. Also necessary for compliance can be that the complexity of the coded video sequence is within bounds as defined by the level of the video compression technology or standard. In some cases, levels restrict the maximum picture size, maximum frame rate, maximum reconstruction sample rate (measured in, for example megasamples per second), maximum reference picture size, and so on. Limits set by levels can, in some cases, be further restricted through Hypothetical Reference Decoder (HRD) specifications and metadata for HRD buffer management signaled in the coded video sequence.

In an aspect, the receiver (231) may receive additional (redundant) data with the encoded video. The additional data may be included as part of the coded video sequence(s). The additional data may be used by the video decoder (210) to properly decode the data and/or to more accurately reconstruct the original video data. Additional data can be in the form of, for example, temporal, spatial, or signal noise ratio (SNR) enhancement layers, redundant slices, redundant pictures, forward error correction codes, and so on.

FIG. 3 shows an example of a block diagram of a video encoder (303). The video encoder (303) is included in an electronic device (320). The electronic device (320) includes a transmitter (340) (e.g., transmitting circuitry). The video encoder (303) can be used in the place of the video encoder (103) in the FIG. 1 example.

The video encoder (303) may receive video samples from a video source (301) (that is not part of the electronic device (320) in the FIG. 3 example) that may capture video image(s) to be coded by the video encoder (303). In another example, the video source (301) is a part of the electronic device (320).

The video source (301) may provide the source video sequence to be coded by the video encoder (303) in the form of a digital video sample stream that can be of any suitable bit depth (for example: 8 bit, 10 bit, 12 bit, . . . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . ), and any suitable sampling structure (for example Y CrCb 4:2:0, Y CrCb 4:4:4). In a media serving system, the video source (301) may be a storage device storing previously prepared video. In a videoconferencing system, the video source (301) may be a camera that captures local image information as a video sequence. Video data may be provided as a plurality of individual pictures that impart motion when viewed in sequence. The pictures themselves may be organized as a spatial array of pixels. Each pixel can comprise one or more samples depending on the sampling structure, color space, etc. in use. The description below focuses on samples.

According to an aspect, the video encoder (303) may code and compress the pictures of the source video sequence into a coded video sequence (343) in real time or under any other time constraints as required. Enforcing appropriate coding speed is one function of a controller (350). In some aspects, the controller (350) controls other functional units as described below and is functionally coupled to the other functional units. The coupling is not depicted for clarity. Parameters set by the controller (350) can include rate control related parameters (picture skip, quantizer, lambda value of rate-distortion optimization techniques, . . . ), picture size, group of pictures (GOP) layout, maximum motion vector search range, and so forth. The controller (350) can be configured to have other suitable functions that pertain to the video encoder (303) optimized for a certain system design.

In some aspects, the video encoder (303) is configured to operate in a coding loop. As an oversimplified description, in an example, the coding loop can include a source coder (330) (e.g., responsible for creating symbols, such as a symbol stream, based on an input picture to be coded, and a reference picture(s)), and a (local) decoder (333) embedded in the video encoder (303). The decoder (333) reconstructs the symbols to create the sample data in a similar manner as a (remote) decoder also would create. The reconstructed sample stream (sample data) is input to the reference picture memory (334). As the decoding of a symbol stream leads to bit-exact results independent of decoder location (local or remote), the content in the reference picture memory (334) is also bit exact between the local encoder and remote encoder. In other words, the prediction part of an encoder “sees” as reference picture samples exactly the same sample values as a decoder would “see” when using prediction during decoding. This fundamental principle of reference picture synchronicity (and resulting drift, if synchronicity cannot be maintained, for example because of channel errors) is used in some related arts as well.

The operation of the “local” decoder (333) can be the same as a “remote” decoder, such as the video decoder (210), which has already been described in detail above in conjunction with FIG. 2. Briefly referring also to FIG. 2, however, as symbols are available and encoding/decoding of symbols to a coded video sequence by an entropy coder (345) and the parser (220) can be lossless, the entropy decoding parts of the video decoder (210), including the buffer memory (215), and parser (220) may not be fully implemented in the local decoder (333).

In an aspect, a decoder technology except the parsing/entropy decoding that is present in a decoder is present, in an identical or a substantially identical functional form, in a corresponding encoder. Accordingly, the disclosed subject matter focuses on decoder operation. The description of encoder technologies can be abbreviated as they are the inverse of the comprehensively described decoder technologies. In certain areas a more detail description is provided below.

During operation, in some examples, the source coder (330) may perform motion compensated predictive coding, which codes an input picture predictively with reference to one or more previously coded picture from the video sequence that were designated as “reference pictures.” In this manner, the coding engine (332) codes differences between pixel blocks of an input picture and pixel blocks of reference picture(s) that may be selected as prediction reference(s) to the input picture.

The local video decoder (333) may decode coded video data of pictures that may be designated as reference pictures, based on symbols created by the source coder (330). Operations of the coding engine (332) may advantageously be lossy processes. When the coded video data may be decoded at a video decoder (not shown in FIG. 3), the reconstructed video sequence typically may be a replica of the source video sequence with some errors. The local video decoder (333) replicates decoding processes that may be performed by the video decoder on reference pictures and may cause reconstructed reference pictures to be stored in the reference picture memory (334). In this manner, the video encoder (303) may store copies of reconstructed reference pictures locally that have common content as the reconstructed reference pictures that will be obtained by a far-end video decoder (absent transmission errors).

The predictor (335) may perform prediction searches for the coding engine (332). That is, for a new picture to be coded, the predictor (335) may search the reference picture memory (334) for sample data (as candidate reference pixel blocks) or certain metadata such as reference picture motion vectors, block shapes, and so on, that may serve as an appropriate prediction reference for the new pictures. The predictor (335) may operate on a sample block-by-pixel block basis to find appropriate prediction references. In some cases, as determined by search results obtained by the predictor (335), an input picture may have prediction references drawn from multiple reference pictures stored in the reference picture memory (334).

The controller (350) may manage coding operations of the source coder (330), including, for example, setting of parameters and subgroup parameters used for encoding the video data.

Output of all aforementioned functional units may be subjected to entropy coding in the entropy coder (345). The entropy coder (345) translates the symbols as generated by the various functional units into a coded video sequence, by applying lossless compression to the symbols according to technologies such as Huffman coding, variable length coding, arithmetic coding, and so forth.

The transmitter (340) may buffer the coded video sequence(s) as created by the entropy coder (345) to prepare for transmission via a communication channel (360), which may be a hardware/software link to a storage device which would store the encoded video data. The transmitter (340) may merge coded video data from the video encoder (303) with other data to be transmitted, for example, coded audio data and/or ancillary data streams (sources not shown).

The controller (350) may manage operation of the video encoder (303). During coding, the controller (350) may assign to each coded picture a certain coded picture type, which may affect the coding techniques that may be applied to the respective picture. For example, pictures often may be assigned as one of the following picture types:

An Intra Picture (I picture) may be coded and decoded without using any other picture in the sequence as a source of prediction. Some video codecs allow for different types of intra pictures, including, for example Independent Decoder Refresh (“IDR”) Pictures.

A predictive picture (P picture) may be coded and decoded using intra prediction or inter prediction using a motion vector and reference index to predict the sample values of each block.

A bi-directionally predictive picture (B Picture) may be coded and decoded using intra prediction or inter prediction using two motion vectors and reference indices to predict the sample values of each block. Similarly, multiple-predictive pictures can use more than two reference pictures and associated metadata for the reconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality of sample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 samples each) and coded on a block-by-block basis. Blocks may be coded predictively with reference to other (already coded) blocks as determined by the coding assignment applied to the blocks' respective pictures. For example, blocks of I pictures may be coded non-predictively or they may be coded predictively with reference to already coded blocks of the same picture (spatial prediction or intra prediction). Pixel blocks of P pictures may be coded predictively, via spatial prediction or via temporal prediction with reference to one previously coded reference picture. Blocks of B pictures may be coded predictively, via spatial prediction or via temporal prediction with reference to one or two previously coded reference pictures.

The video encoder (303) may perform coding operations according to a predetermined video coding technology or standard, such as ITU-T Rec. H.265. In its operation, the video encoder (303) may perform various compression operations, including predictive coding operations that exploit temporal and spatial redundancies in the input video sequence. The coded video data, therefore, may conform to a syntax specified by the video coding technology or standard being used.

In an aspect, the transmitter (340) may transmit additional data with the encoded video. The source coder (330) may include such data as part of the coded video sequence. Additional data may comprise temporal/spatial/SNR enhancement layers, other forms of redundant data such as redundant pictures and slices, SEI messages, VUI parameter set fragments, and so on.

A video may be captured as a plurality of source pictures (video pictures) in a temporal sequence. Intra-picture prediction (often abbreviated to intra prediction) makes use of spatial correlation in a given picture, and inter-picture prediction makes uses of the (temporal or other) correlation between the pictures. In an example, a specific picture under encoding/decoding, which is referred to as a current picture, is partitioned into blocks. When a block in the current picture is similar to a reference block in a previously coded and still buffered reference picture in the video, the block in the current picture can be coded by a vector that is referred to as a motion vector. The motion vector points to the reference block in the reference picture, and can have a third dimension identifying the reference picture, in case multiple reference pictures are in use.

In some aspects, a bi-prediction technique can be used in the inter-picture prediction. According to the bi-prediction technique, two reference pictures, such as a first reference picture and a second reference picture that are both prior in decoding order to the current picture in the video (but may be in the past and future, respectively, in display order) are used. A block in the current picture can be coded by a first motion vector that points to a first reference block in the first reference picture, and a second motion vector that points to a second reference block in the second reference picture. The block can be predicted by a combination of the first reference block and the second reference block.

Further, a merge mode technique can be used in the inter-picture prediction to improve coding efficiency.

According to some aspects of the disclosure, predictions, such as inter-picture predictions and intra-picture predictions, are performed in the unit of blocks. For example, according to the HEVC standard, a picture in a sequence of video pictures is partitioned into coding tree units (CTU) for compression, the CTUs in a picture have the same size, such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTU includes three coding tree blocks (CTBs), which are one luma CTB and two chroma CTBs. Each CTU can be recursively quadtree split into one or multiple coding units (CUs). For example, a CTU of 64×64 pixels can be split into one CU of 64×64 pixels, or 4 CUs of 32×32 pixels, or 16 CUs of 16×16 pixels. In an example, each CU is analyzed to determine a prediction type for the CU, such as an inter prediction type or an intra prediction type. The CU is split into one or more prediction units (PUs) depending on the temporal and/or spatial predictability. Generally, each PU includes a luma prediction block (PB), and two chroma PBs. In an aspect, a prediction operation in coding (encoding/decoding) is performed in the unit of a prediction block. Using a luma prediction block as an example of a prediction block, the prediction block includes a matrix of values (e.g., luma values) for pixels, such as 8×8 pixels, 16×16 pixels, 8×16 pixels, 16×8 pixels, and the like.

It is noted that the video encoders (103) and (303), and the video decoders (110) and (210) can be implemented using any suitable technique. In an aspect, the video encoders (103) and (303) and the video decoders (110) and (210) can be implemented using one or more integrated circuits. In another aspect, the video encoders (103) and (303), and the video decoders (110) and (210) can be implemented using one or more processors that execute software instructions.

Aspects of the disclosure includes methods and systems directed to derivation of a motion vector predictor by using motion vector predictor lookahead and/or lookbehind technique.

Video coding has been widely used in many applications, such as broadcasting, video recording, video streaming, etc. Various emerging video coding standards, such as H.264, H.265/HEVC, H.266/VVC, and AV1, have been published and widely adopted in these video applications. In an example, a hybrid video codec includes a plurality of coding modules, such as an intra prediction, an inter prediction, a transform coding, a quantization, an entropy coding, and a post in-loop filter. In inter prediction coding, a final motion vector may either be derived based on spatial/temporal information or be a sum of a signalled motion vector difference and a derived or a selected motion vector predictor. A motion vector predictor candidate may be generated based on a motion vector from a spatial, a temporal, a non-adjacent, or a history-based coded block. In the disclosure, a motion vector predictor construction in inter prediction coding is provided to improve coding efficiency of the inter prediction coding.

In the disclosure, a first motion vector predictor (MVP) for a current block may be derived from a motion vector from one of a plurality of spatial neighbouring blocks of the current block. During derivation of a MVP candidate for a reference index, RefIdx_i, a scaled motion vector may be used as the MVP if a picture order count (POC), also called a display order count, of the MVP candidate is not equal to a POC of the reference picture with the reference index RefIdx_j for the current block. Another approach is that the MVP candidate may not be available if the POC of the MVP candidate is not equal to the POC of the reference picture with RefIdx_i for the current block. For example, if a reference block indicated by the MVP candidate is not positioned in the reference picture with the reference index, RefIdx_i, the MVP candidate may not be selected.

In an aspect of the disclosure, an MVP candidate is constructed by using the first MVP candidate construction with lookahead/lookbehind. FIG. 4 shows an example of the MVP candidate construction by using the first MVP candidate construction with lookahead in a forward reference list (e.g., reference list 0). It is noted that FIG. 4 is merely an example. The MVP candidate construction may be conducted by using the first MVP candidate construction with lookbehind in a backward reference list (e.g., reference list 1).

A shown in FIG. 4, a current block (402) is included in a current picture (404). The current picture (404) has a plurality of reference pictures, such as reference pictures identified by reference indices 0-2, in a reference list (e.g., a forward reference list 0). The reference indices 0-2 may indicate different reference pictures in the reference list or different directions in the reference list. The reference pictures identified by the reference indices 0-2 may be adjacent or non-adjacent. For example, the reference indices 0 and 1 may indicate two adjacent reference pictures or two non-adjacent reference pictures in the reference list.

A motion vector predictor mv_L0(0) of the current block (402) may be derived based on an MVP construction from spatial or temporal information for a non-merge mode. The derived MVP, mv_L0(0), may be considered as an initial vector (or initial MVP). The derived MVP, mv_L0(0), may point from the current picture (404) to the reference index 0, such as point to a reference block (406) in the reference picture identified by the reference index 0. A lookahead MVP for the reference index 1 may be derived by using a sum of the mv_L0(0) and an associated pointed motion vector (or intermediate motion vector), mv_L0(1). The associated pointed motion vector mv_L0(1) may be defined from the reference block (406) in the reference index 0 to a reference block (408) in the reference index 1.

Still referring to FIG. 4, in some aspects, a block vector (BV) may be used to derive the lookahead MVP for reference index 1. The BV may be defined from the reference block (408) to a reference block (410) in the reference index 1. Thus, the derived lookahead MVP for reference index 1 may be equal to mv_L0(0)+mv_L0(1)+bv₍₁₎. Similarly, a lookahead MVP for the reference index 2 may be derived by using a sum of the derived MVP, mv_L0(0), associated recursive pointed motion vectors, mv_L0(1) and mv_L0(2), and the block vector bv₍₁₎. In an example of FIG. 4, the associated pointed motion vector mv_L0(2) may be defined from the reference block (410) in the reference index 1 to a reference block (412) in the reference index 2.

In an aspect of the disclosure, a plurality of MVPs may be derived for the current block in various reference pictures. For example, in addition to the direct MVP mv_L0(0) in the reference picture indicated by reference index 0, a new propagated lookahead MVP, such as MV(refIdx1), for the reference index 1 may be derived as mv_L0(0)+mv_L0(1)+bv₍₁₎. Similarly, a new propagated lookahead MVP, such as MV(refIdx2), for the reference picture indicated may be derived as mv_L0(0)+mv_L0(1)+mv_L0(2)+bv₍₁₎.

In an aspect, the associated pointed motion vector from a reference index i to a reference j may be derived by checking availability of a motion vector in a corresponding motion field.

In an aspect, the availability of the motion vector within the motion field is checked by scanning the availability of the motion vector in one or more positions. A scanning order may be a predefined order if multiple positions are checked. FIG. 5 shows an example of candidate motion field positions. As shown in FIG. 5, an associated pointed motion vector mv_L0(1) from the reference index 0 to the reference index 1 is derived based on availability of a motion vector from 5 motion field positions. For example, the 5 motion fields position are defined in a reference block (506) that is indicated by the MVP, mv_L0(0). The MVP, mv_L0(0), may point from a current block (502) in current picture (504) to a reference block (506) in a reference index 0. In an example of FIG. 5, a scanning order starts from a center and check four corners one by one in the reference block (506). A first available motion vector, such as a first available un-scaled motion vector, such as mv_L0(1), from the reference index 0 to reference index 1 is selected. According to the derived MV, mv_L0(1), a reference block (508) in the reference index 1 is identified.

In an aspect, a lookahead/lookbehind MVP for each reference index is inserted right after an available un-scaled motion vector from a spatial neighboring coded block in an MVP candidate list.

In an aspect, a lookahead/lookbehind MVP in a selected reference picture is inserted before a scaled MVP when a POC, also called a display order count, of the MVP candidate (e.g., the scaled MVP or the lookahead/lookbehind MVP) is not equal to a POC of the selected reference picture with RefIdx_j for the current block.

In an aspect, availability of a motion vector is checked firstly in FIG. 5. If no motion vector is available after scanning all positions, availability of a block vector is checked.

In an aspect, a flag is signaled. The may be signaled in a high-level syntax, such as a sequence parameter set (SPS), a picture parameter set (PPS), an adaptation parameter set (APS), a picture header, a slice header, to indicate whether a block vector (e.g., bv₍₁₎ in FIG. 4) is used for lookahead motion vector predictor construction.

In an example of FIG. 4, the motion vector predictor for the reference index 1 is equal to mv_L0(0)+mv_L0(1)+bv₍₁₎ when the block vector is determined to be used for lookahead MVP construction.

In an example of FIG. 4, the motion vector predictor for the reference index 1 is equal to mv_L0(0)+mv_L0(1) when the block vector is determined not to be used for lookahead MVP construction.

In an aspect, template-matching reordering is used to reorder the MVP candidate list for a non-merge mode by using template-matching costs of the MVP candidates in the MVP candidate list in a predefined order, such as an ascending order, when the MVP candidate list for the non-merge mode has at least one lookahead MVP candidate. In an example, a lookahead motion vector of a lookahead MVP candidate is used as a motion vector for the template-matching process.

In an aspect, a depth of the MVP propagation shown in FIG. 4 is limited.

In an example of FIG. 4, when BV is added, the BV is not considered to increase the depth of the propagation. In an example, when the depth of the propagation is set to a predefined value, such as 1, MV (refIdx1) (e.g., mv_L0(0)+mv_L0(1)+bv₍₁₎) is available but MV (refIdx2) (e.g., mv_L0(0)+mv_L0(1)+mv_L0(2)+bv₍₁₎) is not available.

In an example, when BV is added, the BV is considered to increase the depth of the propagation. In an example, when the depth of the propagation is set to 1, MV (refIdx1) (e.g., mv_L0(0)+mv_L0(1)+bv₍₁₎ is not available but only mv_L0(0)+mv_L0(1) is available.

In an aspect, a scaled associated pointed motion vector from a reference index i to a reference index p is derived by using an associated pointed motion vector from the reference index i to a reference index j with an appropriate temporal scaling factor when the reference index p is between the reference index i and the reference index j in a temporal direction. An example of the scaled associated pointed motion vector is shown in FIG. 6. As shown in FIG. 6, a scaled associated pointed motion vector mv_L0(0→1) from a reference index 0 to a reference index 1 may be derived by using a derived motion vector mv_L0(0→2) from the reference 0 to a reference index 2 with an appropriate temporal scaling.

In an aspect of the disclosure, a block vector BV and an associated pointed motion vector of the BV is used to construct an MVP candidate when a spatial/temporal coded block is coded in a coded mode with (or as) the block vector. FIG. 7 shows an example of a proposed lookahead/lookbehind MVP candidate construction by using a derived block vector predictor from a conventional MVP candidate construction process with an associated pointed motion vector for a reference list 0 and/or a reference list 1.

As shown in FIG. 7, a current block (702) is included in a current picture (704). A BV_MVP is derived based on an MVP/BVP construction from spatial or temporal information for a non-merge mode. The BV_MVP may point from the current block (702) to a reference block (706) in the current picture (704). A lookahead MVP in a reference list, such as a forward reference list, may be derived by using BV_MVP and mv_L0(0) in a reference index 0. For example, the lookahead MVP at the reference index 0 is defined as mv_L0(0)+BV_MVP. The motion vector mv_L0(0) may point from the reference block (706) to a reference block (708) in a reference picture identified by the reference index 0. A lookahead MVP for a reference index 1 may be derived by using a sum of the BV_MVP and associated pointed motion vectors mv_L0(0) and mv_L0(1). Thus, the lookahead MVP for the reference index 1 is defined as mv_L0(0)+BV_MVP+mv_L0(1). A block vector BV may also be used to derive a lookahead MVP for the reference index 1 and the derived lookahead MVP for the reference index 1 may be equal to BV_MVP+mv_L0(0)+mv_L0(1)+bv₍₁₎. The BV bv₍₁₎ may point from a reference block (710) to a reference block (712) in the reference index 1. The associated pointed motion vector mv_L0(1) may point from the reference block (708) to the reference block (710). Similarly, a lookahead MVP for a reference index 2 may be derived by using a sum of the derived MVP/BVP (e.g., B_VMVP), associated recursive pointed motion vectors (e.g., mv_L0(0), mV_L0(1), and mv_L0(2)), and the block vector b_v(1). Thus, the lookahead MVP for the reference index 2 is defined as BV_MVP+mv_L0(0)+mv_L0(1)+mv_L0(2)+bv₍₁₎. The associated pointed motion vector (or intermediate motion vector) mv_L0(2) may point from the reference block (712) in the reference index 1 to a reference block (714) in the reference index 2.

In an aspect, an MVP candidate based on the lookahead and/or lookbehind is inserted right after an available un-scale motion vector from a spatial neighboring coded block.

In an aspect, a motion vector predictor is not available when a lookahead motion vector does not point to a target reference picture during the motion vector predictor construction.

In an aspect, the lookahead/lookbehind MVP for each reference index, such as the lookahead/lookbehind MVP shown in FIG. 7, is inserted right after an available un-scaled motion vector from a spatial neighboring coded block in an MVP candidate list.

In an aspect, the lookahead/lookbehind MVP in a selected reference picture, such as the lookahead/lookbehind MVP shown in FIG. 7, is inserted before a scaled MVP when a POC, also called a display order count, of the MVP candidate (e.g., the scaled MVP or the lookahead/lookbehind MVP) is not equal to a POC of the selected reference picture with RefIdx_j for the current block.

In an aspect of the disclosure, a block vector and an associated pointed motion vector of the block vector are applied to construct a merged candidate when a spatial/temporal coded block is coded in a coded mode with (or as) the block vector. An example of the construction is shown in FIG. 7. As shown in FIG. 7, a lookahead/lookbehind merged candidate construction may be conducted by using a derived block vector predictor (e.g., BV_MVP) from a MVP candidate construction process with an associated pointed motion vector for a reference list 0 and/or a reference list 1. BV_MVP may be derived based on a MVP/BVP construction from spatial or temporal information for a non-merge mode. A lookahead merged motion vector may be derived by using a sum of the derived MVP/BVP (e.g., BV_MVP), associated recursive pointed motion vectors (e.g., mv_L0(0), mV_L0(1), and mV_L0(2)), and a block vectors (e.g., b_v(1)).

In an aspect, a maximum lookahead/lookbehind depth is applied to constrain a tracing depth of the lookahead/lookbehind. For example, a lookahead merge motion vector is equal to BV_MVP+mv_L0(0) when the maximum depth is lookahead depth is equal to a predefined value, such as 1.

In an aspect, the merged candidate is not available when a final lookahead merged motion vector does not point to a reference picture in the reference list 0 and/or the reference list 1.

FIG. 8 shows a flow chart outlining a process (800) according to an aspect of the disclosure. The process (800) can be used in a video decoder. In various aspects, the process (800) is executed by processing circuitry, such as the processing circuitry that performs functions of the video decoder (110), the processing circuitry that performs functions of the video decoder (210), and the like. In some aspects, the process (800) is implemented in software instructions, thus when the processing circuitry executes the software instructions, the processing circuitry performs the process (800). The process starts at (S801) and proceeds to (S810).

At (S810), a video bitstream is received. The bitstream includes coded information of a current block in a current picture and of a plurality of reference pictures of the current picture in a reference list.

At (S820), a plurality of intermediate vectors associated with one of the plurality of reference pictures is determined. The plurality of intermediate vectors includes an initial vector and a plurality of intermediate MVs. The initial vector is associated with the current picture. Each of the plurality of intermediate MVs is defined between two respective reference pictures of the plurality of reference pictures.

At (S830), a candidate MVP for the current block is determined based on a sum of the plurality of intermediate vectors.

At (S840), the current block is reconstructed based on an MVP candidate list that includes the candidate MVP.

In an aspect, the two respective reference pictures are two respective adjacent reference pictures in the reference list. In an aspect, the two respective reference pictures are two respective non-adjacent reference pictures in the reference list.

In an aspect, the initial vector is determined as a first MV from the current block to a first reference block in a first one of the plurality of reference pictures. A first intermediate MV of the plurality of intermediate MVs is determined as a second MV from the first reference block in the first one of the plurality of reference pictures to a second reference block in a second one of the plurality of reference pictures.

In an aspect, the plurality of intermediate vectors is determined to include a BV. The BV is defined from the second reference block in the second one of the plurality of reference pictures to a third reference block in the second one of the plurality of reference pictures.

In an aspect, the plurality of intermediate vectors is determined to include a BV. The BV is defined from the current block to a first reference block in the current picture. A first intermediate MV of the plurality of intermediate MVs is determined as a MV from the first reference block in the current picture to a second reference block in a first one of the plurality of reference pictures.

In an aspect, a first one of the plurality of intermediate MVs is defined from a first reference block in a first reference picture of the plurality of reference pictures to a second reference block in a second reference picture of the plurality of reference pictures. The second reference block is a prediction block of the first reference block.

In an aspect, a plurality of candidate motion field positions in a first one of the plurality of reference pictures is determined. The plurality of candidate motion field positions is scanned to determine a plurality of candidate MVs from the plurality of candidate motion field positions to a second one of the plurality of reference pictures. A first intermediate MV of the plurality of intermediate MVs is determined as a first one of the plurality of candidate MVs that is an un-scaled MV.

In an aspect, the plurality of candidate motion field positions includes: a center position of a reference block indicated by the initial vector in the first one of the plurality of reference pictures, and four corners of the reference block in the first one of the plurality of reference pictures.

In an aspect, the MVP candidate list is constructed based on a plurality of MVP candidates. The plurality of MVP candidates includes (i) an un-scaled MVP from a spatial neighboring coded block of the current block, (ii) the candidate MVP arranged subsequent to the un-scaled MVP, and (iii) a scaled MVP arranged subsequent to the candidate MVP. A POC associated with the scaled MVP is not equal to a POC of the one of the plurality of reference pictures associated with the candidate MVP. The plurality of MVP candidates is reordered based on template costs of the plurality of MVP candidates.

In an aspect, a MV is determined from a first reference picture of the plurality of reference pictures to a third reference picture of the plurality of reference pictures. A scaled MV is determined by scaling the MV with a temporal scaling factor. A MV from the first reference picture of the plurality of reference pictures to a second reference picture of the plurality of reference pictures is derived based on the scaled MV.

In an aspect, the reference list is one of a forward reference list and a backward reference list with respect to the current picture.

In an aspect, a total number of the plurality of intermediate vectors that is defined between the current picture and the one of the plurality of reference pictures associated with the plurality of intermediate vectors is determined according to a maximum trace depth.

Then, the process proceeds to (S899) and terminates.

The process (800) can be suitably adapted. Step(s) in the process (800) can be modified and/or omitted. Additional step(s) can be added. Any suitable order of implementation can be used.

FIG. 9 shows a flow chart outlining a process (900) according to an aspect of the disclosure. The process (900) can be used in a video encoder. In various aspects, the process (900) is executed by processing circuitry, such as the processing circuitry that performs functions of the video encoder (103), the processing circuitry that performs functions of the video encoder (303), and the like. In some aspects, the process (900) is implemented in software instructions, thus when the processing circuitry executes the software instructions, the processing circuitry performs the process (900). The process starts at (S901) and proceeds to (S910).

At (S910), a plurality of intermediate vectors of a current block in a current picture is determined. The plurality of intermediate vectors is associated with one of a plurality of reference pictures in a reference list. The plurality of intermediate vectors includes an initial vector and a plurality of intermediate MVs. The initial vector is associated with the current picture. Each of the plurality of intermediate MVs is defined between two respective reference pictures of the plurality of reference pictures.

At (S920), a candidate MVP for the current block is determined based on a sum of the plurality of intermediate vectors.

At (S930), the current block is encoded based on an MVP candidate list that includes the candidate MVP.

In an aspect, the initial vector is determined as a first MV from the current block to a first reference block in a first one of the plurality of reference pictures. A first intermediate MV of the plurality of intermediate MVs is determined as a second MV from the first reference block in the first one of the plurality of reference pictures to a second reference block in a second one of the plurality of reference pictures.

The plurality of intermediate vectors is determined to include a BV from the second reference block in the second one of the plurality of reference pictures to a third reference block in the second one of the plurality of reference pictures.

The plurality of intermediate vectors is determined to include a BV from the current block to a first reference block in the current picture. A first intermediate MV of the plurality of intermediate MVs is determined as a MV from the first reference block in the current picture to a second reference block in a first one of the plurality of reference pictures.

In an aspect, a first one of the plurality of intermediate MVs is defined from a first reference block in a first reference picture of the plurality of reference pictures to a second reference block in a second reference picture of the plurality of reference pictures. The second reference block is a prediction block of the first reference block.

In an aspect, a plurality of candidate motion field positions is determined in a first one of the plurality of reference pictures. The plurality of candidate motion field positions is scanned to determine a plurality of candidate MVs from the plurality of candidate motion field positions to a second one of the plurality of reference pictures. A first intermediate MV of the plurality of intermediate MVs is determined as a first one of the plurality of candidate MVs that is an un-scaled MV.

In an aspect, the plurality of candidate motion field positions includes a center position of a reference block indicated by the initial vector in the first one of the plurality of reference pictures, and four corners of the reference block in the first one of the plurality of reference pictures.

In an aspect, the MVP candidate list is constructed based on a plurality of MVP candidates. The plurality of MVP candidates includes (i) an un-scaled MVP from a spatial neighboring coded block of the current block, (ii) the candidate MVP arranged subsequent to the un-scaled MVP, and (iii) a scaled MVP arranged subsequent to the candidate MVP. A POC associated with the scaled MVP is not equal to a POC of the one of the plurality of reference pictures associated with the candidate MVP. The plurality of MVP candidates is reordered based on template costs of the plurality of MVP candidates.

Then, the process proceeds to (S999) and terminates.

The process (900) can be suitably adapted. Step(s) in the process (900) can be modified and/or omitted. Additional step(s) can be added. Any suitable order of implementation can be used.

In an aspect, a method of processing visual media data (or video data) includes processing a bitstream of the visual media data according to a format rule. For example, the bitstream may be a bitstream that is decoded/encoded in any of the decoding and/or encoding methods described herein. The format rule may specify one or more constraints of the bitstream and/or one or more processes to be performed by the decoder and/or encoder.

In an example, the bitstream includes coded information of a current block in a current picture and of a plurality of reference pictures of the current picture in a reference list. The format rule specifies that a plurality of intermediate vectors associated with one of the plurality of reference pictures is determined. The plurality of intermediate vectors includes an initial vector and a plurality of intermediate MVs. The initial vector is associated with the current picture. Each of the plurality of intermediate MVs is defined between two respective reference pictures of the plurality of reference pictures. The format rule specifies that a candidate MVP for the current block is determined based on a sum of the plurality of intermediate vectors. The format rule specifies that the current block is processed based on an MVP candidate list that includes the candidate MVP.

The techniques described above, can be implemented as computer software using computer-readable instructions and physically stored in one or more computer-readable media. For example, FIG. 10 shows a computer system (1000) suitable for implementing certain aspects of the disclosed subject matter.

The computer software can be coded using any suitable machine code or computer language, that may be subject to assembly, compilation, linking, or like mechanisms to create code comprising instructions that can be executed directly, or through interpretation, micro-code execution, and the like, by one or more computer central processing units (CPUs), Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers or components thereof, including, for example, personal computers, tablet computers, servers, smartphones, gaming devices, internet of things devices, and the like.

The components shown in FIG. 10 for computer system (1000) are examples and are not intended to suggest any limitation as to the scope of use or functionality of the computer software implementing aspects of the present disclosure. Neither should the configuration of components be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the example aspect of computer system (1000).

Computer system (1000) may include certain human interface input devices. Such a human interface input device may be responsive to input by one or more human users through, for example, tactile input (such as: keystrokes, swipes, data glove movements), audio input (such as: voice, clapping), visual input (such as: gestures), olfactory input (not depicted). The human interface devices can also be used to capture certain media not necessarily directly related to conscious input by a human, such as audio (such as: speech, music, ambient sound), images (such as: scanned images, photographic images obtain from a still image camera), video (such as two-dimensional video, three-dimensional video including stereoscopic video).

Input human interface devices may include one or more of (only one of each depicted): keyboard (1001), mouse (1002), trackpad (1003), touch screen (1010), data-glove (not shown), joystick (1005), microphone (1006), scanner (1007), camera (1008).

Computer system (1000) may also include certain human interface output devices. Such human interface output devices may be stimulating the senses of one or more human users through, for example, tactile output, sound, light, and smell/taste. Such human interface output devices may include tactile output devices (for example tactile feedback by the touch-screen (1010), data-glove (not shown), or joystick (1005), but there can also be tactile feedback devices that do not serve as input devices), audio output devices (such as: speakers (1009), headphones (not depicted)), visual output devices (such as screens (1010) to include CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch-screen input capability, each with or without tactile feedback capability—some of which may be capable to output two dimensional visual output or more than three dimensional output through means such as stereographic output; virtual-reality glasses (not depicted), holographic displays and smoke tanks (not depicted)), and printers (not depicted).

Computer system (1000) can also include human accessible storage devices and their associated media such as optical media including CD/DVD ROM/RW (1020) with CD/DVD or the like media (1021), thumb-drive (1022), removable hard drive or solid state drive (1023), legacy magnetic media such as tape and floppy disc (not depicted), specialized ROM/ASIC/PLD based devices such as security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computer readable media” as used in connection with the presently disclosed subject matter does not encompass transmission media, carrier waves, or other transitory signals.

Computer system (1000) can also include an interface (1054) to one or more communication networks (1055). Networks can for example be wireless, wireline, optical. Networks can further be local, wide-area, metropolitan, vehicular and industrial, real-time, delay-tolerant, and so on. Examples of networks include local area networks such as Ethernet, wireless LANs, cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TV wireline or wireless wide area digital networks to include cable TV, satellite TV, and terrestrial broadcast TV, vehicular and industrial to include CANBus, and so forth. Certain networks commonly require external network interface adapters that attached to certain general purpose data ports or peripheral buses (1049) (such as, for example USB ports of the computer system (1000)); others are commonly integrated into the core of the computer system (1000) by attachment to a system bus as described below (for example Ethernet interface into a PC computer system or cellular network interface into a smartphone computer system). Using any of these networks, computer system (1000) can communicate with other entities. Such communication can be uni-directional, receive only (for example, broadcast TV), uni-directional send-only (for example CANbus to certain CANbus devices), or bi-directional, for example to other computer systems using local or wide area digital networks. Certain protocols and protocol stacks can be used on each of those networks and network interfaces as described above.

Aforementioned human interface devices, human-accessible storage devices, and network interfaces can be attached to a core (1040) of the computer system (1000).

The core (1040) can include one or more Central Processing Units (CPU) (1041), Graphics Processing Units (GPU) (1042), specialized programmable processing units in the form of Field Programmable Gate Areas (FPGA) (1043), hardware accelerators for certain tasks (1044), graphics adapters (1050), and so forth. These devices, along with Read-only memory (ROM) (1045), Random-access memory (1046), internal mass storage such as internal non-user accessible hard drives, SSDs, and the like (1047), may be connected through a system bus (1048). In some computer systems, the system bus (1048) can be accessible in the form of one or more physical plugs to enable extensions by additional CPUs, GPU, and the like. The peripheral devices can be attached either directly to the core's system bus (1048), or through a peripheral bus (1049). In an example, the screen (1010) can be connected to the graphics adapter (1050). Architectures for a peripheral bus include PCI, USB, and the like.

CPUs (1041), GPUs (1042), FPGAs (1043), and accelerators (1044) can execute certain instructions that, in combination, can make up the aforementioned computer code. That computer code can be stored in ROM (1045) or RAM (1046). Transitional data can also be stored in RAM (1046), whereas permanent data can be stored for example, in the internal mass storage (1047). Fast storage and retrieve to any of the memory devices can be enabled through the use of cache memory, that can be closely associated with one or more CPU (1041), GPU (1042), mass storage (1047), ROM (1045), RAM (1046), and the like.

The computer readable media can have computer code thereon for performing various computer-implemented operations. The media and computer code can be those specially designed and constructed for the purposes of the present disclosure, or they can be of the kind well known and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system having architecture (1000), and specifically the core (1040) can provide functionality as a result of processor(s) (including CPUs, GPUs, FPGA, accelerators, and the like) executing software embodied in one or more tangible, computer-readable media. Such computer-readable media can be media associated with user-accessible mass storage as introduced above, as well as certain storage of the core (1040) that are of non-transitory nature, such as core-internal mass storage (1047) or ROM (1045). The software implementing various aspects of the present disclosure can be stored in such devices and executed by core (1040). A computer-readable medium can include one or more memory devices or chips, according to particular needs. The software can cause the core (1040) and specifically the processors therein (including CPU, GPU, FPGA, and the like) to execute particular processes or particular parts of particular processes described herein, including defining data structures stored in RAM (1046) and modifying such data structures according to the processes defined by the software. In addition or as an alternative, the computer system can provide functionality as a result of logic hardwired or otherwise embodied in a circuit (for example: accelerator (1044)), which can operate in place of or together with software to execute particular processes or particular parts of particular processes described herein. Reference to software can encompass logic, and vice versa, where appropriate. Reference to a computer-readable media can encompass a circuit (such as an integrated circuit (IC)) storing software for execution, a circuit embodying logic for execution, or both, where appropriate. The present disclosure encompasses any suitable combination of hardware and software.

The use of “at least one of” or “one of” in the disclosure is intended to include any one or a combination of the recited elements. For example, references to at least one of A, B, or C; at least one of A, B, and C; at least one of A, B, and/or C; and at least one of A to C are intended to include only A, only B, only C or any combination thereof. References to one of A or B and one of A and B are intended to include A or B or (A and B). The use of “one of” does not preclude any combination of the recited elements when applicable, such as when the elements are not mutually exclusive.

While this disclosure has described several examples of aspects, there are alterations, permutations, and various substitute equivalents, which fall within the scope of the disclosure. It will thus be appreciated that those skilled in the art will be able to devise numerous systems and methods which, although not explicitly shown or described herein, embody the principles of the disclosure and are thus within the spirit and scope thereof.

The above disclosure also encompasses the features noted below. The features may be combined in various manners and are not limited to the combinations noted below.

(1) A method of video decoding, the method including: receiving a video bitstream including coded information of a current block in a current picture and of a plurality of reference pictures of the current picture in a reference list; determining a plurality of intermediate vectors associated with one of the plurality of reference pictures, the plurality of intermediate vectors including an initial vector and a plurality of intermediate motion vectors (MVs), the initial vector being associated with the current picture, each of the plurality of intermediate MVs being defined between two respective reference pictures of the plurality of reference pictures; determining a candidate motion vector predictor (MVP) for the current block based on a sum of the plurality of intermediate vectors; and reconstructing the current block based on a MVP candidate list that includes the candidate MVP.

(2) The method of feature (1), in which the determining the plurality of intermediate vectors includes: determining the initial vector as a first MV from the current block to a first reference block in a first one of the plurality of reference pictures, and determining a first intermediate MV of the plurality of intermediate MVs as a second MV from the first reference block in the first one of the plurality of reference pictures to a second reference block in a second one of the plurality of reference pictures.

(3) The method of feature (2), in which the determining the plurality of intermediate vectors includes: determining that the plurality of intermediate vectors includes a block vector (BV) from the second reference block in the second one of the plurality of reference pictures to a third reference block in the second one of the plurality of reference pictures.

(4) The method of any of features (1) to (3), in which the determining the plurality of intermediate vectors includes: determining the plurality of intermediate vectors includes a block vector (BV) from the current block to a first reference block in the current picture; and determining a first intermediate MV of the plurality of intermediate MVs as a MV from the first reference block in the current picture to a second reference block in a first one of the plurality of reference pictures.

(5) The method of any of features (1) to (4), in which: a first one of the plurality of intermediate MVs is defined from a first reference block in a first reference picture of the plurality of reference pictures to a second reference block in a second reference picture of the plurality of reference pictures, and the second reference block is a prediction block of the first reference block.

(6) The method of any of features (1) to (5), in which the determining the plurality of intermediate vectors further includes: determining a plurality of candidate motion field positions in a first one of the plurality of reference pictures; scanning the plurality of candidate motion field positions to determine a plurality of candidate MVs from the plurality of candidate motion field positions to a second one of the plurality of reference pictures; and determining a first intermediate MV of the plurality of intermediate MVs as a first one of the plurality of candidate MVs that is an un-scaled MV.

(7) The method of feature (6), in which the plurality of candidate motion field positions includes: a center position of a reference block indicated by the initial vector in the first one of the plurality of reference pictures, and four corners of the reference block in the first one of the plurality of reference pictures.

(8) The method of any of features (1) to (7), further including: constructing the MVP candidate list based on a plurality of MVP candidates, the plurality of MVP candidates including an un-scaled MVP from a spatial neighboring coded block of the current block, the candidate MVP arranged subsequent to the un-scaled MVP, and a scaled MVP arranged subsequent to the candidate MVP, a POC associated with the scaled MVP being not equal to a POC of the one of the plurality of reference pictures associated with the candidate MVP; and reordering the plurality of MVP candidates based on template costs of the plurality of MVP candidates.

(9) The method of any of features (1) to (8), in which the determining the plurality of intermediate vectors further includes: determining a MV from a first reference picture of the plurality of reference pictures to a third reference picture of the plurality of reference pictures; determining a scaled MV by scaling the MV with a temporal scaling factor; and deriving a MV from the first reference picture of the plurality of reference pictures to a second reference picture of the plurality of reference pictures based on the scaled MV.

(10) The method of any of features (1) to (9), in which the reference list is one of a forward reference list and a backward reference list with respect to the current picture.

(11) The method of any of features (1) to (10), in which a total number of the plurality of intermediate vectors that is defined between the current picture and the one of the plurality of reference pictures associated with the plurality of intermediate vectors is determined according to a maximum trace depth.

(12) A method of video encoding, the method including: determining a plurality of intermediate vectors of a current block in a current picture, the plurality of intermediate vectors being associated with one of a plurality of reference pictures in a reference list, the plurality of intermediate vectors including an initial vector and a plurality of intermediate motion vectors (MVs), the initial vector being associated with the current picture, each of the plurality of intermediate MVs being defined between two respective reference pictures of the plurality of reference pictures; determining a candidate motion vector predictor (MVP) for the current block based on a sum of the plurality of intermediate vectors; and encoding the current block based on a MVP candidate list that includes the candidate MVP.

(13) The method of feature (12), in which the determining the plurality of intermediate vectors includes: determining the initial vector as a first MV from the current block to a first reference block in a first one of the plurality of reference pictures, and determining a first intermediate MV of the plurality of intermediate MVs as a second MV from the first reference block in the first one of the plurality of reference pictures to a second reference block in a second one of the plurality of reference pictures.

(14) The method of feature (13), in which the determining the plurality of intermediate vectors includes: determining that the plurality of intermediate vectors includes a block vector (BV) from the second reference block in the second one of the plurality of reference pictures to a third reference block in the second one of the plurality of reference pictures.

(15) The method of any of features (12) to (14), in which the determining the plurality of intermediate vectors includes: determining the plurality of intermediate vectors includes a block vector (BV) from the current block to a first reference block in the current picture; and determining a first intermediate MV of the plurality of intermediate MVs as a MV from the first reference block in the current picture to a second reference block in a first one of the plurality of reference pictures.

(16) The method of any of features (12) to (15), in which: a first one of the plurality of intermediate MVs is defined from a first reference block in a first reference picture of the plurality of reference pictures to a second reference block in a second reference picture of the plurality of reference pictures, and the second reference block is a prediction block of the first reference block.

(17) The method of any of features (12) to (16), in which the determining the plurality of intermediate vectors further includes: determining a plurality of candidate motion field positions in a first one of the plurality of reference pictures; scanning the plurality of candidate motion field positions to determine a plurality of candidate MVs from the plurality of candidate motion field positions to a second one of the plurality of reference pictures; and determining a first intermediate MV of the plurality of intermediate MVs as a first one of the plurality of candidate MVs that is an un-scaled MV.

(18) The method of feature (17), in which the plurality of candidate motion field positions includes: a center position of a reference block indicated by the initial vector in the first one of the plurality of reference pictures, and four corners of the reference block in the first one of the plurality of reference pictures.

(19) The method of any of features (12) to (18), further including: constructing the MVP candidate list based on a plurality of MVP candidates, the plurality of MVP candidates including an un-scaled MVP from a spatial neighboring coded block of the current block, the candidate MVP arranged subsequent to the un-scaled MVP, and a scaled MVP arranged subsequent to the candidate MVP, a POC associated with the scaled MVP being not equal to a POC of the one of the plurality of reference pictures associated with the candidate MVP; and reordering the plurality of MVP candidates based on template costs of the plurality of MVP candidates.

(20) A method of processing visual media data, the method including: processing a bitstream of the visual media data according to a format rule, in which: the bitstream includes coded information of a current block in a current picture and of a plurality of reference pictures of the current picture in a reference list; and the format rule specifies that: a plurality of intermediate vectors associated with one of the plurality of reference pictures is determined, the plurality of intermediate vectors including an initial vector and a plurality of intermediate motion vectors (MVs), the initial vector being associated with the current picture, each of the plurality of intermediate MVs being defined between two respective reference pictures of the plurality of reference pictures; a candidate motion vector predictor (MVP) for the current block is constructed based on a sum of the plurality of intermediate vectors; and the current block is processed based on a MVP candidate list that includes the candidate MVP.

(21) An apparatus for video decoding, including processing circuitry that is configured to perform the method of any of features (1) to (11).

(22) An apparatus for video encoding, including processing circuitry that is configured to perform the method of any of features (12) to (19).

(23) A non-transitory computer-readable storage medium storing instructions which when executed by at least one processor cause the at least one processor to perform the method of any of features (1) to (20).

Claims

1. A method of video decoding, the method comprising: receiving a video bitstream including coded information of a current block in a current picture and of a plurality of reference pictures of the current picture in a reference list;determining a plurality of intermediate vectors associated with one of the plurality of reference pictures, the plurality of intermediate vectors including an initial vector and a plurality of intermediate motion vectors (MVs), the initial vector being associated with the current picture, each of the plurality of intermediate MVs being defined between two respective reference pictures of the plurality of reference pictures;determining a candidate motion vector predictor (MVP) for the current block based on a sum of the plurality of intermediate vectors; andreconstructing the current block based on an MVP candidate list that includes the candidate MVP.

2. The method of claim 1, wherein the determining the plurality of intermediate vectors comprises: determining the initial vector as a first MV from the current block to a first reference block in a first one of the plurality of reference pictures, anddetermining a first intermediate MV of the plurality of intermediate MVs as a second MV from the first reference block in the first one of the plurality of reference pictures to a second reference block in a second one of the plurality of reference pictures.

3. The method of claim 2, wherein the determining the plurality of intermediate vectors comprises: determining that the plurality of intermediate vectors includes a block vector (BV) from the second reference block in the second one of the plurality of reference pictures to a third reference block in the second one of the plurality of reference pictures.

4. The method of claim 1, wherein the determining the plurality of intermediate vectors comprises: determining the plurality of intermediate vectors includes a block vector (BV) from the current block to a first reference block in the current picture; anddetermining a first intermediate MV of the plurality of intermediate MVs as a MV from the first reference block in the current picture to a second reference block in a first one of the plurality of reference pictures.

5. The method of claim 1, wherein: a first one of the plurality of intermediate MVs is defined from a first reference block in a first reference picture of the plurality of reference pictures to a second reference block in a second reference picture of the plurality of reference pictures, andthe second reference block is a prediction block of the first reference block.

6. The method of claim 1, wherein the determining the plurality of intermediate vectors further comprises: determining a plurality of candidate motion field positions in a first one of the plurality of reference pictures;scanning the plurality of candidate motion field positions to determine a plurality of candidate MVs from the plurality of candidate motion field positions to a second one of the plurality of reference pictures; anddetermining a first intermediate MV of the plurality of intermediate MVs as a first one of the plurality of candidate MVs that is an un-scaled MV.

7. The method of claim 6, wherein the plurality of candidate motion field positions includes: a center position of a reference block indicated by the initial vector in the first one of the plurality of reference pictures, andfour corners of the reference block in the first one of the plurality of reference pictures.

8. The method of claim 1, further comprising: constructing the MVP candidate list based on a plurality of MVP candidates, the plurality of MVP candidates including an un-scaled MVP from a spatial neighboring coded block of the current block, the candidate MVP arranged subsequent to the un-scaled MVP, and a scaled MVP arranged subsequent to the candidate MVP, a picture order count (POC) associated with the scaled MVP being not equal to a POC of the one of the plurality of reference pictures associated with the candidate MVP; andreordering the plurality of MVP candidates based on template costs of the plurality of MVP candidates.

9. The method of claim 1, wherein the determining the plurality of intermediate vectors further comprises: determining a MV from a first reference picture of the plurality of reference pictures to a third reference picture of the plurality of reference pictures;determining a scaled MV by scaling the MV with a temporal scaling factor; andderiving a MV from the first reference picture of the plurality of reference pictures to a second reference picture of the plurality of reference pictures based on the scaled MV.

10. The method of claim 1, wherein the reference list is one of a forward reference list and a backward reference list with respect to the current picture.

11. The method of claim 1, wherein a total number of the plurality of intermediate vectors that is defined between the current picture and the one of the plurality of reference pictures associated with the plurality of intermediate vectors is determined according to a maximum trace depth.

12. A method of video encoding, the method comprising: determining a plurality of intermediate vectors of a current block in a current picture, the plurality of intermediate vectors being associated with one of a plurality of reference pictures in a reference list, the plurality of intermediate vectors including an initial vector and a plurality of intermediate motion vectors (MVs), the initial vector being associated with the current picture, each of the plurality of intermediate MVs being defined between two respective reference pictures of the plurality of reference pictures;determining a candidate motion vector predictor (MVP) for the current block based on a sum of the plurality of intermediate vectors; andencoding the current block based on an MVP candidate list that includes the candidate MVP.

13. The method of claim 12, wherein the determining the plurality of intermediate vectors comprises: determining the initial vector as a first MV from the current block to a first reference block in a first one of the plurality of reference pictures, anddetermining a first intermediate MV of the plurality of intermediate MVs as a second MV from the first reference block in the first one of the plurality of reference pictures to a second reference block in a second one of the plurality of reference pictures.

14. The method of claim 13, wherein the determining the plurality of intermediate vectors comprises: determining that the plurality of intermediate vectors includes a block vector (BV) from the second reference block in the second one of the plurality of reference pictures to a third reference block in the second one of the plurality of reference pictures.

15. The method of claim 12, wherein the determining the plurality of intermediate vectors comprises: determining the plurality of intermediate vectors includes a block vector (BV) from the current block to a first reference block in the current picture; anddetermining a first intermediate MV of the plurality of intermediate MVs as a MV from the first reference block in the current picture to a second reference block in a first one of the plurality of reference pictures.

16. The method of claim 12, wherein: a first one of the plurality of intermediate MVs is defined from a first reference block in a first reference picture of the plurality of reference pictures to a second reference block in a second reference picture of the plurality of reference pictures, andthe second reference block is a prediction block of the first reference block.

17. The method of claim 12, wherein the determining the plurality of intermediate vectors further comprises: determining a plurality of candidate motion field positions in a first one of the plurality of reference pictures;scanning the plurality of candidate motion field positions to determine a plurality of candidate MVs from the plurality of candidate motion field positions to a second one of the plurality of reference pictures; anddetermining a first intermediate MV of the plurality of intermediate MVs as a first one of the plurality of candidate MVs that is an un-scaled MV.

18. The method of claim 17, wherein the plurality of candidate motion field positions includes: a center position of a reference block indicated by the initial vector in the first one of the plurality of reference pictures, and four corners of the reference block in the first one of the plurality of reference pictures.

19. The method of claim 12, further comprising: constructing the MVP candidate list based on a plurality of MVP candidates, the plurality of MVP candidates including an un-scaled MVP from a spatial neighboring coded block of the current block, the candidate MVP arranged subsequent to the un-scaled MVP, and a scaled MVP arranged subsequent to the candidate MVP, a picture order count (POC) associated with the scaled MVP being not equal to a POC of the one of the plurality of reference pictures associated with the candidate MVP; andreordering the plurality of MVP candidates based on template costs of the plurality of MVP candidates.

20. A method of processing visual media data, the method comprising: processing a bitstream of the visual media data according to a format rule, wherein:the bitstream includes coded information of a current block in a current picture and of a plurality of reference pictures of the current picture in a reference list; andthe format rule specifies that: a plurality of intermediate vectors associated with one of the plurality of reference pictures is determined, the plurality of intermediate vectors including an initial vector and a plurality of intermediate motion vectors (MVs), the initial vector being associated with the current picture, each of the plurality of intermediate MVs being defined between two respective reference pictures of the plurality of reference pictures;a candidate motion vector predictor (MVP) for the current block is determined based on a sum of the plurality of intermediate vectors; andthe current block is processed based on an MVP candidate list that includes the candidate MVP.