Reference sample memory size restrictions for intra block copy

A method for video decoding at a decoder is provided. In the method, reconstructed samples of a reconstructed block of a picture are stored in a first reference sample memory. The first reference sample memory is configured to store at least one set of a number of luma samples and corresponding chroma samples of the reconstructed block. Further, reconstructed samples of a current block of the picture are stored in a second reference sample memory. The second reference sample memory is configured to store only one set of the number of luma samples and corresponding chroma samples of the current block. A current sub-block in the current block is reconstructed using an intra block copy (IBC) mode based on the stored reconstructed samples of a reference sub-block of the reconstructed block or the stored reconstructed samples of a reference sub-block of the current block.

TECHNICAL FIELD

BACKGROUND

Motion compensation can be a lossy compression technique and can relate to techniques where a block of sample data from a previously reconstructed picture or part thereof (reference picture), after being spatially shifted in a direction indicated by a motion vector (MV henceforth), is used for the prediction of a newly reconstructed picture or picture part. In some cases, the reference picture can be the same as the picture currently under reconstruction. MVs can have two dimensions X and Y, or three dimensions, the third being an indication of the reference picture in use (the latter, indirectly, can be a time dimension).

In some video compression techniques, an MV applicable to a certain area of sample data can be predicted from other MVs, for example from those related to another area of sample data spatially adjacent to the area under reconstruction, and preceding that MV in decoding order. Doing so can substantially reduce the amount of data required for coding the MV, thereby removing redundancy and increasing compression. MV prediction can work effectively, for example, because when coding an input video signal derived from a camera (known as natural video) there is a statistical likelihood that areas larger than the area to which a single MV is applicable move in a similar direction and, therefore, can in some cases be predicted using a similar motion vector derived from MVs of neighboring area. That results in the MV found for a given area to be similar or the same as the MV predicted from the surrounding MVs, and that in turn can be represented, after entropy coding, in a smaller number of bits than what would be used if coding the MV directly. In some cases, MV prediction can be an example of lossless compression of a signal (namely: the MVs) derived from the original signal (namely: the sample stream). In other cases, MV prediction itself can be lossy, for example because of rounding errors when calculating a predictor from several surrounding MVs.

Various MV prediction mechanisms are described in H.265/HEVC (ITU-T Rec. H.265, “High Efficiency Video Coding”, December 2016). Out of the many MV prediction mechanisms that H.265 offers, described here is a technique henceforth referred to as “spatial merge”.

Referring toFIG. 1, a current block (101) comprises samples that have been found by the encoder during the motion search process to be predictable from a previous block of the same size that has been spatially shifted. Instead of coding that MV directly, the MV can be derived from metadata associated with one or more reference pictures, for example from the most recent (in decoding order) reference picture, using the MV associated with either one of five surrounding samples, denoted A0, A1, and B0, B1, B2(102through106, respectively). In H.265, the MV prediction can use predictors from the same reference picture that the neighboring block is using.

SUMMARY

Aspects of the disclosure provide methods and apparatuses for video coding at a decoder. In an embodiment, a method of video coding at a decoder is provided. In the method, reconstructed samples of a reconstructed block of a picture are stored in a first reference sample memory. The first reference sample memory is configured to store at least one set of a number of luma samples and corresponding chroma samples of the reconstructed block. Further, reconstructed samples of a current block of the picture are stored in a second reference sample memory. The second reference sample memory is configured to store only one set of the number of luma samples and corresponding chroma samples of the current block. A current sub-block in the current block is reconstructed using an intra block copy (IBC) mode based on the stored reconstructed samples of a reference sub-block of the reconstructed block or the stored reconstructed samples of a reference sub-block of the current block.

In an embodiment, each of the at least one set of the luma samples of the reconstructed block and the one set of the luma samples of the current block includes 64×64 luma samples.

In an embodiment, a maximum size of the first reference sample memory is limited to a size of two sets of the luma samples and the corresponding chroma samples.

In an embodiment, a coding tree unit (CTU) is partitioned into one or more non-overlapping blocks. The one or more non-overlapping blocks include the current block, and the reconstructed block is determined based on a location of the current block relative to the CTU and a decoding order of the one or more non-overlapping blocks. In some examples, when the current block is a top-left block of the CTU, the reconstructed block is determined to be a top-right block of another CTU. The other CTU is to the left of the CTU. In some examples, when the current block is a top-right block of the CTU or a bottom-left block of the CTU, the reconstructed block is determined to be a top-left block of the CTU. In some examples, when the current block is a bottom-right block of the CTU, the reconstructed block is determined to be a top-right block of the CTU. In some examples, when the current block is a bottom-left block of the CTU, the reconstructed block is determined to be a top-right block of the CTU.

In an embodiment, reconstructed samples of another reconstructed block of the picture are stored in the first reference sample memory. A size of the other reconstructed block does not exceed one set of the number of luma samples and corresponding chroma samples. The current sub-block in the current block is reconstructed using the IBC mode based on the stored reconstructed samples of the reference sub-block of the reconstructed block, the stored reconstructed samples of a reference sub-block of the other reconstructed block, or the stored reconstructed samples of the reference sub-block of the current block. In some examples, when the current block is a top-left block of the CTU, the reconstructed block is determined to be a top-right block and a bottom-right block of another CTU. The other CTU is to the left of the CTU.

In an embodiment, a method of video coding at a decoder is provided. In the method, reconstructed samples of a current block of a picture are stored in a reference sample memory. A size of the current block does not exceed one set of luma samples and corresponding chroma samples. A current sub-block in the current block is reconstructed using an intra block copy (IBC) mode based on the stored reconstructed samples of a reference sub-block of the current block. A maximum size of the reference sample memory is limited to the one set of luma samples and corresponding chroma samples.

Aspects of the disclosure also provide non-transitory computer-readable storage mediums storing instructions which when executed by a computer cause the computer to perform any of the above methods.

DETAILED DESCRIPTION OF EMBODIMENTS

I. Video Coding Encoder and Decoder

FIG. 2illustrates a simplified block diagram of a communication system (200) according to an embodiment of the present disclosure. The communication system (200) includes a plurality of terminal devices that can communicate with each other, via, for example, a network (250). For example, the communication system (200) includes a first pair of terminal devices (210) and (220) interconnected via the network (250). In theFIG. 2example, the first pair of terminal devices (210) and (220) performs unidirectional transmission of data. For example, the terminal device (210) may code video data (e.g., a stream of video pictures that are captured by the terminal device (210)) for transmission to the other terminal device (220) via the network (250). The encoded video data can be transmitted in the form of one or more coded video bitstreams. The terminal device (220) may receive the coded video data from the network (250), decode the coded video data to recover the video pictures and display video pictures according to the recovered video data. Unidirectional data transmission may be common in media serving applications and the like.

In another example, the communication system (200) includes a second pair of terminal devices (230) and (240) that performs bidirectional transmission of coded video data that may occur, for example, during videoconferencing. For bidirectional transmission of data, in an example, each terminal device of the terminal devices (230) and (240) may code video data (e.g., a stream of video pictures that are captured by the terminal device) for transmission to the other terminal device of the terminal devices (230) and (240) via the network (250). Each terminal device of the terminal devices (230) and (240) also may receive the coded video data transmitted by the other terminal device of the terminal devices (230) and (240), and may decode the coded video data to recover the video pictures and may display video pictures at an accessible display device according to the recovered video data.

In theFIG. 2example, the terminal devices (210), (220), (230) and (240) may be illustrated as servers, personal computers, and smart phones, but the principles of the present disclosure may be not so limited. Embodiments of the present disclosure find application with laptop computers, tablet computers, media players, and/or dedicated video conferencing equipment. The network (250) represents any number of networks that convey coded video data among the terminal devices (210), (220), (230), and (240), including for example wireline (wired) and/or wireless communication networks. The communication network (250) may exchange data in circuit-switched and/or packet-switched channels. Representative networks include telecommunications networks, local area networks, wide area networks, and/or the Internet. For the purposes of the present discussion, the architecture and topology of the network (250) may be immaterial to the operation of the present disclosure unless explained herein below.

A streaming system may include a capture subsystem (313), that can include a video source (301), for example a digital camera, creating for example a stream of video pictures (302) that are uncompressed. In an example, the stream of video pictures (302) includes samples that are taken by the digital camera. The stream of video pictures (302), depicted as a bold line to emphasize a high data volume when compared to encoded video data (304) (or coded video bitstreams), can be processed by an electronic device (320) that includes a video encoder (303) coupled to the video source (301). The video encoder (303) 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 (304) (or encoded video bitstream (304)), depicted as a thin line to emphasize the lower data volume when compared to the stream of video pictures (302), can be stored on a streaming server (305) for future use. One or more streaming client subsystems, such as client subsystems (306) and (308) inFIG. 3can access the streaming server (305) to retrieve copies (307) and (309) of the encoded video data (304). A client subsystem (306) can include a video decoder (310), for example, in an electronic device (330). The video decoder (310) decodes the incoming copy (307) of the encoded video data and creates an outgoing stream of video pictures (311) that can be rendered on a display (312) (e.g., display screen) or other rendering device (not depicted). In some streaming systems, the encoded video data (304), (307), and (309) (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 (320) and (330) can include other components (not shown). For example, the electronic device (320) can include a video decoder (not shown) and the electronic device (330) can include a video encoder (not shown) as well.

FIG. 4shows a block diagram of a video decoder (410) according to an embodiment of the present disclosure. The video decoder (410) can be included in an electronic device (430). The electronic device (430) can include a receiver (431) (e.g., receiving circuitry). The video decoder (410) can be used in the place of the video decoder (310) in theFIG. 3example.

The video decoder (410) may include the parser (420) to reconstruct symbols (421) from the coded video sequence. Categories of those symbols include information used to manage operation of the video decoder (410), and potentially information to control a rendering device such as a render device (412) (e.g., a display screen) that is not an integral part of the electronic device (430) but can be coupled to the electronic device (430), as was shown inFIG. 4. 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 (420) 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 (420) 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 (420) may also extract from the coded video sequence information such as transform coefficients, quantizer parameter values, motion vectors, and so forth.

The parser (420) may perform an entropy decoding/parsing operation on the video sequence received from the buffer memory (415), so as to create symbols (421).

A first unit is the scaler/inverse transform unit (451). The scaler/inverse transform unit (451) 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) (421) from the parser (420). The scaler/inverse transform unit (451) can output blocks comprising sample values, that can be input into aggregator (455).

In some cases, the output samples of the scaler/inverse transform (451) can pertain to an intra coded block; that 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 (452). In some cases, the intra picture prediction unit (452) 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 (458). The current picture buffer (458) buffers, for example, partly reconstructed current picture and/or fully reconstructed current picture. The aggregator (455), in some cases, adds, on a per sample basis, the prediction information the intra prediction unit (452) has generated to the output sample information as provided by the scaler/inverse transform unit (451).

In other cases, the output samples of the scaler/inverse transform unit (451) can pertain to an inter coded, and potentially motion compensated block. In such a case, a motion compensation prediction unit (453) can access reference picture memory (457) to fetch samples used for prediction. After motion compensating the fetched samples in accordance with the symbols (421) pertaining to the block, these samples can be added by the aggregator (455) to the output of the scaler/inverse transform unit (451) (in this case called the residual samples or residual signal) so as to generate output sample information. The addresses within the reference picture memory (457) from where the motion compensation prediction unit (453) fetches prediction samples can be controlled by motion vectors, available to the motion compensation prediction unit (453) in the form of symbols (421) 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 (457) when sub-sample exact motion vectors are in use, motion vector prediction mechanisms, and so forth.

The output of the loop filter unit (456) can be a sample stream that can be output to the render device (412) as well as stored in the reference picture memory (457) 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 (420)), the current picture buffer (458) can become a part of the reference picture memory (457), and a fresh current picture buffer can be reallocated before commencing the reconstruction of the following coded picture.

FIG. 5shows a block diagram of a video encoder (503) according to an embodiment of the present disclosure. The video encoder (503) is included in an electronic device (520). The electronic device (520) includes a transmitter (540) (e.g., transmitting circuitry). The video encoder (503) can be used in the place of the video encoder (303) in theFIG. 3example.

The video encoder (503) may receive video samples from a video source (501) (that is not part of the electronic device (520) in theFIG. 5example) that may capture video image(s) to be coded by the video encoder (503). In another example, the video source (501) is a part of the electronic device (520).

According to an embodiment, the video encoder (503) may code and compress the pictures of the source video sequence into a coded video sequence (543) in real time or under any other time constraints as required by the application. Enforcing appropriate coding speed is one function of a controller (550). In some embodiments, the controller (550) 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 (550) 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 (550) can be configured to have other suitable functions that pertain to the video encoder (503) optimized for a certain system design.

The operation of the “local” decoder (533) can be the same as of a “remote” decoder, such as the video decoder (410), which has already been described in detail above in conjunction withFIG. 4. Briefly referring also toFIG. 4, however, as symbols are available and encoding/decoding of symbols to a coded video sequence by an entropy coder (545) and the parser (420) can be lossless, the entropy decoding parts of the video decoder (410), including the buffer memory (415), and parser (420) may not be fully implemented in the local decoder (533).

The local video decoder (533) may decode coded video data of pictures that may be designated as reference pictures, based on symbols created by the source coder (530). Operations of the coding engine (532) may advantageously be lossy processes. When the coded video data may be decoded at a video decoder (not shown inFIG. 5), the reconstructed video sequence typically may be a replica of the source video sequence with some errors. The local video decoder (533) 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 cache (534). In this manner, the video encoder (503) 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 (535) may perform prediction searches for the coding engine (532). That is, for a new picture to be coded, the predictor (535) may search the reference picture memory (534) 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 (535) 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 (535), an input picture may have prediction references drawn from multiple reference pictures stored in the reference picture memory (534).

The controller (550) may manage coding operations of the source coder (530), including, for example, setting of parameters and subgroup parameters used for encoding the video data.

The transmitter (540) may buffer the coded video sequence(s) as created by the entropy coder (545) to prepare for transmission via a communication channel (560), which may be a hardware/software link to a storage device which would store the encoded video data. The transmitter (540) may merge coded video data from the video coder (503) with other data to be transmitted, for example, coded audio data and/or ancillary data streams (sources not shown).

The controller (550) may manage operation of the video encoder (503). During coding, the controller (550) 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:

FIG. 6shows a diagram of a video encoder (603) according to another embodiment of the disclosure. The video encoder (603) is configured to receive a processing block (e.g., a prediction block) of sample values within a current video picture in a sequence of video pictures, and encode the processing block into a coded picture that is part of a coded video sequence. In an example, the video encoder (603) is used in the place of the video encoder (303) in theFIG. 3example.

In an HEVC example, the video encoder (603) receives a matrix of sample values for a processing block, such as a prediction block of 8×8 samples, and the like. The video encoder (603) determines whether the processing block is best coded using intra mode, inter mode, or bi-prediction mode using, for example, rate-distortion optimization. When the processing block is to be coded in intra mode, the video encoder (603) may use an intra prediction technique to encode the processing block into the coded picture; and when the processing block is to be coded in inter mode or bi-prediction mode, the video encoder (603) may use an inter prediction or bi-prediction technique, respectively, to encode the processing block into the coded picture. In certain video coding technologies, merge mode can be an inter picture prediction submode where the motion vector is derived from one or more motion vector predictors without the benefit of a coded motion vector component outside the predictors. In certain other video coding technologies, a motion vector component applicable to the subject block may be present. In an example, the video encoder (603) includes other components, such as a mode decision module (not shown) to determine the mode of the processing blocks.

In theFIG. 6example, the video encoder (603) includes the inter encoder (630), an intra encoder (622), a residue calculator (623), a switch (626), a residue encoder (624), a general controller (621), and an entropy encoder (625) coupled together as shown inFIG. 6.

The intra encoder (622) is configured to receive the samples of the current block (e.g., a processing block), in some cases compare the block to blocks already coded in the same picture, generate quantized coefficients after transform, and in some cases also intra prediction information (e.g., an intra prediction direction information according to one or more intra encoding techniques). In an example, the intra encoder (622) also calculates intra prediction results (e.g., predicted block) based on the intra prediction information and reference blocks in the same picture.

The general controller (621) is configured to determine general control data and control other components of the video encoder (603) based on the general control data. In an example, the general controller (621) determines the mode of the block, and provides a control signal to the switch (626) based on the mode. For example, when the mode is the intra mode, the general controller (621) controls the switch (626) to select the intra mode result for use by the residue calculator (623), and controls the entropy encoder (625) to select the intra prediction information and include the intra prediction information in the bitstream; and when the mode is the inter mode, the general controller (621) controls the switch (626) to select the inter prediction result for use by the residue calculator (623), and controls the entropy encoder (625) to select the inter prediction information and include the inter prediction information in the bitstream.

The residue calculator (623) is configured to calculate a difference (residue data) between the received block and prediction results selected from the intra encoder (622) or the inter encoder (630). The residue encoder (624) is configured to operate based on the residue data to encode the residue data to generate the transform coefficients. In an example, the residue encoder (624) is configured to convert the residue data from a spatial domain to a frequency domain, and generate the transform coefficients. The transform coefficients are then subject to quantization processing to obtain quantized transform coefficients. In various embodiments, the video encoder (603) also includes a residue decoder (628). The residue decoder (628) is configured to perform inverse-transform, and generate the decoded residue data. The decoded residue data can be suitably used by the intra encoder (622) and the inter encoder (630). For example, the inter encoder (630) can generate decoded blocks based on the decoded residue data and inter prediction information, and the intra encoder (622) can generate decoded blocks based on the decoded residue data and the intra prediction information. The decoded blocks are suitably processed to generate decoded pictures and the decoded pictures can be buffered in a memory circuit (not shown) and used as reference pictures in some examples.

FIG. 7shows a diagram of a video decoder (710) according to another embodiment of the disclosure. The video decoder (710) is configured to receive coded pictures that are part of a coded video sequence, and decode the coded pictures to generate reconstructed pictures. In an example, the video decoder (710) is used in the place of the video decoder (310) in theFIG. 3example.

In theFIG. 7example, the video decoder (710) includes an entropy decoder (771), an inter decoder (780), a residue decoder (773), a reconstruction module (774), and an intra decoder (772) coupled together as shown inFIG. 7.

The entropy decoder (771) can be configured to reconstruct, from the coded picture, certain symbols that represent the syntax elements of which the coded picture is made up. Such symbols can include, for example, the mode in which a block is coded (such as, for example, intra mode, inter mode, bi-predicted mode, the latter two in merge submode or another submode), prediction information (such as, for example, intra prediction information or inter prediction information) that can identify certain sample or metadata that is used for prediction by the intra decoder (772) or the inter decoder (780), respectively, residual information in the form of, for example, quantized transform coefficients, and the like. In an example, when the prediction mode is inter or bi-predicted mode, the inter prediction information is provided to the inter decoder (780); and when the prediction type is the intra prediction type, the intra prediction information is provided to the intra decoder (772). The residual information can be subject to inverse quantization and is provided to the residue decoder (773).

The inter decoder (780) is configured to receive the inter prediction information, and generate inter prediction results based on the inter prediction information.

The intra decoder (772) is configured to receive the intra prediction information, and generate prediction results based on the intra prediction information.

The residue decoder (773) is configured to perform inverse quantization to extract de-quantized transform coefficients, and process the de-quantized transform coefficients to convert the residual from the frequency domain to the spatial domain. The residue decoder (773) may also require certain control information (to include the Quantizer Parameter (QP)), and that information may be provided by the entropy decoder (771) (data path not depicted as this may be low volume control information only).

The reconstruction module (774) is configured to combine, in the spatial domain, the residual as output by the residue decoder (773) and the prediction results (as output by the inter or intra prediction modules as the case may be) to form a reconstructed block, that may be part of the reconstructed picture, which in turn may be part of the reconstructed video. It is noted that other suitable operations, such as a deblocking operation and the like, can be performed to improve the visual quality.

It is noted that the video encoders (303), (503), and (603), and the video decoders (310), (410), and (710) can be implemented using any suitable technique. In an embodiment, the video encoders (303), (503), and (603), and the video decoders (310), (410), and (710) can be implemented using one or more integrated circuits. In another embodiment, the video encoders (303), (503), and (503), and the video decoders (310), (410), and (710) can be implemented using one or more processors that execute software instructions.

II. Reference Search Range Optimization of Intra Block Copy

A. Intra Block Copy

A block can be coded using a reference block from a different or same picture. A block based compensation using a reference block from a different picture can be referred to as motion compensation. Block based compensation using a reference block from a previously reconstructed area within the same picture can be referred to as intra picture block compensation, current picture referencing (CPR), or intra block copy (IBC). A displacement vector that indicates the offset between the current block and the reference block can be referred to as a block vector (BV). Different from a motion vector in motion compensation, which can be any value (positive or negative, at either x or y direction), a BV is subject to constraints to ensure that the reference block has already been reconstructed and the reconstructed samples thereof are available. In some embodiments, in view of parallel processing constraints, a reference area that is beyond a tile boundary or wavefront ladder shape boundary is excluded.

The coding of a BV can be either explicit or implicit. In the explicit mode, the difference between a BV and its predictor can be signaled in a manner similar to an Advanced Motion Vector Prediction (AMVP) mode in inter coding. In the implicit mode, the BV can be recovered from a predictor, for example in a similar way as a motion vector in merge mode. The resolution of a BV, in some implementations, is set to integer positions or, in some examples, fractional positions.

The use of IBC at the block level can be signaled using a block level flag (or IBC flag). In some examples, this flag can be signaled when the current block is not coded in merge mode. In some examples, this flag can be signaled by a reference index approach, for example, by treating the current decoded picture as a reference picture. In HEVC Screen Content Coding (HEVC SCC), such a reference picture is placed in the last position of the list. This special reference picture is also managed together with other temporal reference pictures in the Decoded Picture Buffer (DPB).

While an embodiment of intra block copy is used as an example in the present disclosure, the embodiments of the present disclosure can be applied to variations for intra block copy. The variations for intra block copy include, for example, flipped intra block copy where the reference block is flipped horizontally or vertically before being used to predict current block, or line based intra block copy where each compensation unit inside an M×N coding block is an M×1 or 1×N line.

FIG. 8is a schematic illustration of a current block (810) in a current picture (800) to be coded using intra block copy (IBC) in accordance with an embodiment. InFIG. 8, an example of using IBC is shown where the current picture (800) includes 15 blocks arranged into 3 rows and 5 columns. In some examples, each block corresponds to a coding tree unit (CTU). The current block (810) includes a sub-block (812) (e.g., a coding block in the CTU) that has a block vector (822) pointing to a reference sub-block (832) in the current picture (800).

The reconstructed samples of the current picture can be stored in a memory or memory block (e.g., a dedicated or designated memory or portion of memory). In consideration of implementation cost, the reference area where the reconstructed samples for reference blocks remain available may not be as large as an entire frame, depending on a memory size of the dedicated memory. Therefore, for a current sub-block using IBC, in some examples, an IBC reference sub-block may be limited to only certain neighboring areas, but not the entire picture.

In one example, the memory size is limited to a size of one CTU, which means the IBC mode can only be used when the reference block is within the same CTU as the current block. In another example, the memory size is limited to a size of two CTUs, which means the IBC mode can only be used when the reference block is either within the current CTU, or the CTU to the left of current CTU. When the reference block is outside the constrained reference area (i.e., designated local area), even if it has been reconstructed, the reference samples cannot be used for intra picture block compensation.

With the constrained reference area, the efficiency of IBC is limited. There is a need to further improve the efficiency of IBC with the constrained reference area.

B. Block Partitioning in VVC

In the current VVC standard, a picture may be divided into an array of non-overlapped CTUs. The size of a CTU may be set to be 128×128 luma samples and the corresponding chroma samples depending on the color format. A CTU can be split into CUs using one or a combination of the following tree splitting methods.

For example, a CTU can be split into CUs using Quaternary-Tree (QT) split as in HEVC. This splitting method is the same as in HEVC. That is, each parent block is split in half in both horizontal and vertical directions. The resulting four smaller partitions are in the same aspect ratio as its parent block. In VVC, a CTU is firstly split by QT recursively. Each QT leaf node (in square shape) can be further split recursively using the multi-type (Binary-Tree and Ternary-Tree) tree as described below. The Binary-Tree (BT) split refers to dividing the parent block in half in either horizontal or vertical direction. The resulting two smaller partitions are half in size as compared to the parent block. The Ternary-Tree (TT) split refers to dividing the parent block in three parts in either horizontal or vertical direction. The middle part of the three is twice as large as the other two parts. The resulting three smaller partitions are ¼, ½ and ¼ in size respectively as compared to the parent block.

The partition of a parent block may be constrained such that at a 128×128 level, the following partitioning results for partitioning the parent block are allowed: 128×128, two 128×64, two 64×128, and four 64×64. The partition of the parent block may be further constrained such that at a 128×64 or 64×128 level, the TT splits at either a horizontal or vertical direction are not allowed. In addition, if there is any further split, the child blocks may be constrained to two 64×64 blocks.

C. Reference Sample Memory

A memory that stores reference samples of previously coded CUs for future intra block copy reference may be referred to as a reference sample memory. The reference sample memory can be a dedicated or designated memory, as described above.

According to some embodiments of the present disclosure, methods are proposed to improve IBC performance under certain reference area constraints. More specifically, the size of a reference sample memory may be constrained. In the following discussion, the size of the reference sample memory may be fixed to be one set of 64×64 luma samples (together with corresponding chroma samples), two sets of 64×64 luma samples (together with corresponding chroma samples), three sets of 64×64 luma samples (together with corresponding chroma samples), or another suitable memory size. In one example, the size of the reference sample memory is a size of one CTU, such as one previously coded CTU or one left CTU. In another example, the size of the reference sample memory is the size of two CTUs, such as two previously coded CTUs or two left CTUs, or one current CTU together with one left CTU. In some embodiments, each CTU requires a memory size for storing 128×128 luma samples, together with corresponding chroma samples. When a reference block is outside the stored, reconstructed areas, the reference block cannot be used for IBC.

Embodiments of the present disclosure include methods for utilizing the one or more 64×64 sized reference sample memory blocks to optimize the search range of IBC.

The size of an IBC coded block can be as large as any regular inter coded block in general. In some embodiments of the present disclosure, in order to utilize the reference sample memory more efficiently, the size of an IBC coded block is limited to, for example, 64 luma samples at either width or height edge and chroma samples with corresponding size constraints, depending on the color format. The color can be, for example, in 4:2:0 format and the size of a chroma block in IBC mode may not be larger than 32 samples on each side. In another example, lower limits, such as 32 luma samples on each side can be used as the size of the IBC coded block. In the following discussion of the present disclosure, it is assumed that the maximum IBC coded block size is 64×64 luma samples and corresponding chroma samples. The size of the corresponding chroma samples may depend on the color format, as described above.

I. Reference Sample Memory with Two Sets of 64×64 Luma Samples

When the maximum size of the reference sample memory that can be used to store intra block copy reference samples is two sets of 64×64 luma samples, the following descriptions provide a few methods to efficiently utilize this memory size to perform IBC.

For example, one 64×64 reference sample memory block is used to store samples of a current 64×64 coding region, while another 64×64 reference sample memory block is used to store a previously coded 64×64 coding region.

FIG. 9describes an example of a coding order and reference sample memory usage.

The hatched region is the 64×64 region, which includes the current coding block. The shaded region(s) are already coded 64×64 regions in the current or left CTU. The hatched 64×64 regions have not yet been coded. When the current coding block falls into one of the four 64×64 regions in the current CTU, the reference sample memory can store another 64×64 coded region for the reference of the IBC mode. The current 64×64 region, together with the other 64×64 reference region, are indicated by a dotted rectangular inFIG. 9.

The top row ofFIG. 9shows an exemplary coding order of each 64×64 region under horizontal binary split or quad-tree split at a 128×128 level. When the current block (911) is a top-left block of the current CTU, the reconstructed block (912) can be determined to be a block of another CTU, such as a top-right block of another CTU, which is to the left of the CTU. Therefore, if a current sub-block (current coding block) falls into the top-left 64×64 block (911) of the current CTU, then in addition to the already reconstructed samples in the current top-left 64×64 region (911), the reconstruction of the current sub-block can also refer to the reference samples in the left 64×64 block (912), which is in the CTU to the left of the current CTU, using the IBC mode.

When the current block (921) is a top-right block of the current CTU, the reconstructed block (922) can be determined to be another block of the same CTU, such as a top-left block of the same CTU. Therefore, if a current sub-block falls into the top-right 64×64 block (921) of the current CTU, then in addition to the already reconstructed samples in the current top-right 64×64 region (921), the reconstruction of the current sub-block can also refer to the reference samples in the top-left 64×64 block (922) of the current CTU, using the IBC mode.

When the current block (931) is a bottom-left block of the current CTU, the reconstructed block (932) can be determined to be another block of the same CTU, such as a top-right block of the same CTU. Therefore, if a current sub-block falls into the bottom-left 64×64 block (931) of the current CTU, then in addition to the already reconstructed samples in the current bottom-left 64×64 region (931) of the current CTU, the reconstruction of the current sub-block can also refer to the reference samples in the top-right 64×64 block (932) of the current CTU, using the IBC mode.

When the current block (941) is a bottom-right block of the current CTU, the reconstructed block (942) can be determined to be another block of the same CTU, such as a top-right block of the same CTU. Therefore, if a current sub-block falls into the bottom-right 64×64 block (941) of the current CTU, then in addition to the already reconstructed samples in the current bottom-right 64×64 region (941) of the current CTU, the reconstruction of the current sub-block can also refer to the reference samples in the top-right 64×64 block (942) of the current CTU, using the IBC mode.

FIG. 9just provides exemplary reference area assignments, other possible reference area assignments, such as using the top-right 64×64 region as the reference area for the bottom-right 64×64 region (labeled “3”), are also within the scope of this disclosure.

The bottom row ofFIG. 9shows an exemplary coding order of each 64×64 region under vertical binary split or quad-tree split at 128×128 level. When the current block (951) is a top-left block of the current CTU, the reconstructed block (952) can be determined to be a block of another CTU, such as a top-right block of another CTU, which is to the left of the CTU. Therefore, if a current sub-block falls into the top-left 64×64 block (951) of the current CTU, then in addition to the already reconstructed samples in the current top-left 64×64 region (951), the reconstruction of the current sub-block can also refer to the reference samples in the left 64×64 block (952), which is in the CTU to the left of the current CTU, using the IBC mode.

When the current block (961) is a bottom-left block of the current CTU, the reconstructed block (962) can be determined to be another block of the same CTU, such as a top-left block of the same CTU. Therefore, if a current sub-block falls into the bottom-left 64×64 block (961) of the current CTU, then in addition to the already reconstructed samples in the current bottom-left 64×64 region (961) of the current CTU, the reconstruction of the current sub-block can also refer to the reference samples in the top-left 64×64 block (962) of the current CTU, using the IBC mode.

When the current block (971) is a top-right block of the current CTU, the reconstructed block (972) can be determined to be another block of the same CTU, such as a top-left block of the same CTU. Therefore, if a current sub-block falls into the top-right 64×64 block (971) of the current CTU, then in addition to the already reconstructed samples in the current top-right 64×64 region (971), the reconstruction of the current sub-block can also refer to the reference samples in the top-left 64×64 block (972) of the current CTU, using the IBC mode.

When the current block (981) is a bottom-right block of the current CTU, the reconstructed block (982) can be determined to be another block of the same CTU, such as a top-right block of the same CTU. Therefore, if a current sub-block falls into the bottom-right 64×64 block (981) of the current CTU, then in addition to the already reconstructed samples in the current bottom-right 64×64 region (981) of the current CTU, the reconstruction of the current sub-block can also refer to the reference samples in the top-right 64×64 block (982) of the current CTU, using the IBC mode.

Other assignments can be made in a similar fashion. For example, the 64×64 reference area may be another already coded area.

Table 1 below summarizes availabilities of reference samples from the 64×64 region other than the current 64×64 region in view ofFIG. 9. TL, TR, BL and BR refer to top-left, top-right, bottom-left and bottom-right, respectively. The mark “X” means not available, and the mark “Y” means available.

In the above example, whether a reference block for the current block in IBC mode is in the left CTU can be determined based on (i) whether all the samples in the reference block are from the left CTU or (ii) whether one or more reference samples in the reference block is from the left CTU.

II. Reference Sample Memory with Three Sets of 64×64 Luma Samples

In some embodiments of the present disclosure, the maximum size of a memory that can be used to store IBC reference samples is three sets of 64×64 luma samples and corresponding chroma samples. The following discussion provides method for utilizing this memory size to perform the IBC mode.

In one example, one 64×64 reference sample memory block is used to store samples of a current 64×64 coding region, while another two 64×64 sized reference sample memory blocks is used to store previously coded two 64×64 coding regions as additional reference areas for the IBC.

As shown inFIG. 10, the hatched region in each of the CTU is the 64×64 region, which includes the current coding block. The shaded regions are already coded 64×64 regions in the current or left CTU, while the hatched 64×64 region has not yet been coded. When the current coding block falls into one of the four shaded 64×64 regions in the current CTU, the reference sample memory can store another two 64×64 coded regions for the reference of IBC. The current 64×64 region, together with the other two 64×64 reference regions, are indicated by a dotted rectangular inFIG. 10.

The top row ofFIG. 10shows a coding order of each 64×64 region under a horizontal binary split or quad-tree split, for example at a 128×128 level. When the current block (1011) is a top-left block of the current CTU, the reconstructed blocks (1012a,1012b) can be blocks of another CTU, such as a top-right block of another CTU and a bottom-right block of the other CTU, which is to the left of the CTU. Therefore, if a current sub-block falls into the top-left 64×64 block (1011) of the current CTU, then in addition to the already reconstructed samples in the current top-left 64×64 region (1011), the reconstruction of the current sub-block can also refer to the reference samples in the top-right 64×64 block and the bottom-right 64×64 block of the left CTU, using the IBC mode.

When the current block (1021) is a top-right block of the current CTU, the reconstructed blocks (e.g.,1022a,1022b) can be blocks of another CTU and the same CTU, such as the top-left block of the current CTU and a top-right block of the other CTU, which is to the left of the CTU. Therefore, if a current sub-block falls into the top-right 64×64 block (1021) of the current CTU, then in addition to the already reconstructed samples in the current top-right 64×64 region (1021), the reconstruction of the current sub-block can also refer to the reference samples in the top-left 64×64 block of the current CTU and the top-right 64×64 block of the left CTU, using the IBC mode.

When the current block (1031) is a bottom-left block of the current CTU, the reconstructed blocks (e.g.,1032a,1032b) can be blocks of the same CTU, such as the top-left block and the top-right block of the current CTU. Therefore, if a current sub-block falls into the bottom-left 64×64 block (1031) of the current CTU, then in addition to the already reconstructed samples in the current bottom-left 64×64 region (1031), the reconstruction of the current sub-block can also refer to the reference samples in the top-left 64×64 block and the top-right 64×64 block of the current CTU, using the IBC mode.

When the current block is a bottom-right block (1041) of the current CTU, the reconstructed blocks (e.g.,1042a,1042b) can be blocks of the same CTU, such as a top-right block and the bottom-left block of the same CTU. Therefore, if a current sub-block falls into the bottom-right 64×64 block (1041) of the current CTU, then in addition to the already reconstructed samples in the current bottom-right 64×64 region (1041) of the current CTU, the reconstruction of the current sub-block can also refer to the reference samples in the top-right 64×64 block and the bottom-left 64×64 block of the current CTU, using the IBC mode.

WhileFIG. 10provides exemplary assignments, other possible reference area assignments, such as using the top-right 64×64 region in the left CTU as the reference area for the bottom-left 64×64 region of current CTU (labeled “1”, in the bottom row), are also within the scope of this disclosure.

The bottom row ofFIG. 10shows an exemplary coding order of each 64×64 region under a vertical binary split or quad-tree split, for example at a 128×128 level. When the current block (1051) is a top-left block of the current CTU, the reconstructed blocks (e.g.,1052a,1052b) can be blocks of another CTU, such as a top-right block and a bottom-right block of the other CTU, which is to the left of the CTU. Therefore, if a current sub-block falls into the top-left 64×64 block (1051) of the current CTU, then in addition to the already reconstructed samples in the current top-left 64×64 region (1051), the reconstruction of the current sub-block can also refer to the reference samples in the top-right 64×64 block and the bottom-right 64×64 block of the left CTU, using the IBC mode.

When the current block is a bottom-left block (1061) of the current CTU, the reconstructed blocks (e.g.,1062a,1062b) can be blocks of the same CTU and another CTU, such as a top-left block of the same CTU and a bottom-right block of the other CTU, which is to the left of the current CTU. Therefore, if a current sub-block falls into the bottom-left 64×64 block (1061) of the current CTU, then in addition to the already reconstructed samples in the current bottom-left 64×64 region (1061) of the current CTU, the reconstruction of the current sub-block can also refer to the reference samples in the top-left 64×64 block of the current CTU and the bottom-right 64×64 block of the left CTU, using the IBC mode.

When the current block (1071) is a top-right block of the current CTU, the reconstructed blocks (e.g.,1072a,1072b) can be blocks of the same CTU, such as a top-left block and a bottom-left block of the same CTU. Therefore, if a current sub-block falls into the top-right 64×64 block (1071) of the current CTU, then in addition to the already reconstructed samples in the current top-right 64×64 region (1071), the reconstruction of the current sub-block can also refer to the reference samples in the top-left 64×64 block and the bottom-left 64×64 block of the current CTU, using the IBC mode.

When the current block is a bottom-right block (1081) of the current CTU, the reconstructed blocks (e.g.,1082a,1082b) can be blocks of the same CTU, such as a top-right block and a bottom-left block of the same CTU. Therefore, if a current sub-block falls into the bottom-right 64×64 block (1081) of the current CTU, then in addition to the already reconstructed samples in the current bottom-right 64×64 region (1081) of the current CTU, the reconstruction of the current sub-block can also refer to the reference samples in the top-right 64×64 block and the bottom-left 64×64 block of the current CTU, using the IBC mode.

In the above example, whether a reference block for the current block in IBC mode is in the left CTU can be determined based on (i) whether all the samples in the reference block are from the left CTU or (ii) whether one or more reference samples in the reference block is from the left CTU.

Other assignments can be made in a similar fashion. For example, the other 64×64 reference area may be another already coded area.

III. Reference Sample Memory with One Set of 64×64 Luma Samples

As shown inFIG. 11, when the maximum size of a memory that can be used to store intra block copy reference samples is one set of 64×64 luma samples, this one 64×64 reference sample memory block can be used to store samples of a current 64×64 coding region (1110), a reference block (1120) for the IBC mode is also from the same 64×64 region as the current block. In one example, when the top-left corner and bottom-right corner of the reference block have been reconstructed, the whole reference block has been reconstructed, and the reconstruction of a current sub-block (current coding block) can refer to the reference samples in the reference block. Both of the reference block and the current sub-block are in the same current 64×64 region.

D. Decoding Process Using the Reference Sample Memory

FIG. 12shows a flow chart outlining a decoding process (1200) according to an embodiment of the disclosure. The process (1200) can be used to decode a block (i.e., a current block) of a picture using IBC mode. In some embodiments, one or more operations are performed before or after process (1200), and some of the operations illustrated inFIG. 12may be reordered or omitted. In various embodiments, the process (1200) is executed by processing circuitry, such as the processing circuitry in the terminal devices (210), (220), (230), and (240), the processing circuitry that performs functions of the video decoder (310), (410), or (710), and the like. In some embodiments, the process (1200) is implemented by software instructions, thus when the processing circuitry executes the software instructions, the processing circuitry performs the process (1200). The process starts at (S1201) and proceeds to (S1210).

At (S1210), reconstructed samples of a reconstructed block of a picture are stored in a first reference sample memory. The first reference sample memory is configured to store at least one set of a number of luma samples and corresponding chroma samples of the reconstructed block. The number of luma samples may be 64×64. In some examples, the reconstructed blocks correspond to the reconstructed blocks described inFIGS. 9-10. In some examples, the reconstructed samples of the reconstructed block can be generated using the system or decoders illustrated inFIGS. 3, 4, and 7.

At (S1220), reconstructed samples of a current block of the picture are stored in a second reference sample memory. The second reference sample memory is configured to store only one set of the number of luma samples and corresponding chroma samples of the current block. Additional sets of the number of luma samples and corresponding chroma samples of the current block may be stored for a larger second reference sample memory. In some examples, the second reference sample memory only stores reconstructed samples of a 64×64 region. A reference sample memory may include both, for example partitioned into, the first reference sample memory and the second reference sample memory.

At (S1230), a current sub-block in the current block is reconstructed using an intra block copy (IBC) mode. The IBC mode is based on, for example, the stored reconstructed samples of a reference sub-block of the reconstructed block or the stored reconstructed samples of a reference sub-block of the current block in the first reference sample memory.

After (S1230), the process proceeds to (S1299) and terminates.

FIG. 13shows a flow chart outlining a decoding process (1300) according to an embodiment of the disclosure. The process (1300) can be used to decode a block (i.e., a current block) of a picture using IBC mode. In some embodiments, one or more operations are performed before or after process (1300), and some of the operations illustrated inFIG. 13may be reordered or omitted.

In various embodiments, the process (1300) is executed by processing circuitry, such as the processing circuitry in the terminal devices (210), (220), (230), and (240), the processing circuitry that performs functions of the video encoder (303), (503), or (603), and the like. In some embodiments, the process (1300) is implemented by software instructions, thus when the processing circuitry executes the software instructions, the processing circuitry performs the process (1300). The process starts at (1301) and proceeds to (S1310).

At (S1310), reconstructed samples of a current block of a picture are stored in a reference sample memory. A size of the current block does not exceed one set of a number of luma samples and corresponding chroma samples according to one embodiment. In some examples, the number of luma samples may be 64×64.

At (S1320), a current sub-block in the current block is reconstructed using an intra block copy (IBC) mode. The IBC mode is based on, for example, the stored reconstructed samples of a reference sub-block of the current block. In this case, a maximum size of the reference sample memory can be limited to the one set of a number of luma samples and corresponding chroma samples. The number of luma samples may be 64×64 and the one 64×64 reference sample memory block can be used to store samples of a current 64×64 coding region. A reference block for the IBC mode may be also in the same 64×64 region. In some examples, the current region corresponds to the block (1310) and the reference block corresponds to the block (1320) inFIG. 11. In some examples, the reconstructed samples of the current block can be generated using the system or encoders illustrated inFIGS. 3, 5, and 6.

After (S1320), the process proceeds to (S1399) and terminates.

III. Computer System

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. 14shows a computer system (1400) suitable for implementing certain embodiments of the disclosed subject matter.

Input human interface devices may include one or more of (only one of each depicted): keyboard (1401), mouse (1402), trackpad (1403), touch screen (1410), data-glove (not shown), joystick (1405), microphone (1406), scanner (1407), camera (1408).

Computer system (1400) 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 (1410), data-glove (not shown), or joystick (1405), but there can also be tactile feedback devices that do not serve as input devices), audio output devices (such as: speakers (1409), headphones (not depicted)), visual output devices (such as screens (1410) 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 (1400) can also include human accessible storage devices and their associated media such as optical media including CD/DVD ROM/RW (1420) with CD/DVD or the like media (1421), thumb-drive (1422), removable hard drive or solid state drive (1423), 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.

Aforementioned human interface devices, human-accessible storage devices, and network interfaces can be attached to a core (1440) of the computer system (1400).

The core (1440) can include one or more Central Processing Units (CPU) (1441), Graphics Processing Units (GPU) (1442), specialized programmable processing units in the form of Field Programmable Gate Areas (FPGA) (1443), hardware accelerators for certain tasks (1444), and so forth. These devices, along with Read-only memory (ROM) (1445), Random-access memory (1446), internal mass storage such as internal non-user accessible hard drives, SSDs, and the like (1447), may be connected through a system bus (1448). In some computer systems, the system bus (1448) 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 (1448), or through a peripheral bus (1449). Architectures for a peripheral bus include PCI, USB, and the like.

CPUs (1441), GPUs (1442), FPGAs (1443), and accelerators (1444) can execute certain instructions that, in combination, can make up the aforementioned computer code. That computer code can be stored in ROM (1445) or RAM (1446). Transitional data can be also be stored in RAM (1446), whereas permanent data can be stored for example, in the internal mass storage (1447). 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 (1441), GPU (1442), mass storage (1447), ROM (1445), RAM (1446), and the like.

As an example and not by way of limitation, the computer system having architecture (1400), and specifically the core (1440) 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 (1440) that are of non-transitory nature, such as core-internal mass storage (1447) or ROM (1445). The software implementing various embodiments of the present disclosure can be stored in such devices and executed by core (1440). A computer-readable medium can include one or more memory devices or chips, according to particular needs. The software can cause the core (1440) 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 (1446) 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 (1444)), 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.

JEM: joint exploration model

VVC: versatile video coding

BMS: benchmark set

MV: Motion Vector

HEVC: High Efficiency Video Coding

SEI: Supplementary Enhancement Information

VUI: Video Usability Information

GOPs: Groups of Pictures

PUs: Prediction Units

CTUs: Coding Tree Units

CTBs: Coding Tree Blocks

HRD: Hypothetical Reference Decoder

SNR: Signal Noise Ratio

CPUs: Central Processing Units

GPUs: Graphics Processing Units

CRT: Cathode Ray Tube

CD: Compact Disc

DVD: Digital Video Disc

RAM: Random Access Memory

PLD: Programmable Logic Device

LAN: Local Area Network

GSM: Global System for Mobile communications

CANBus: Controller Area Network Bus

USB: Universal Serial Bus

PCI: Peripheral Component Interconnect

FPGA: Field Programmable Gate Areas

IC: Integrated Circuit

CU: Coding Unit

IBC: Intra Block Copy

CPR: Current Picture Referencing

BV: Block Vector

AMVP: Advanced Motion Vector Prediction

DPB: Decoded Picture Buffer