CN110868590B

CN110868590B - Image dividing method and device

Info

Publication number: CN110868590B
Application number: CN201910191131.5A
Authority: CN
Inventors: 赵寅; 杨海涛; 陈建乐
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2018-08-28
Filing date: 2019-03-13
Publication date: 2024-01-30
Anticipated expiration: 2039-03-13
Also published as: CN110868590A; CN116193146A

Abstract

The embodiment of the invention provides an image dividing method and device. Determining a dividing mode of a current node, wherein the current node comprises a brightness block and a chromaticity block; determining that the chromaticity block of the current node is not divided any more according to the dividing mode of the current node and the size of the current node; and dividing the luminance block of the current node according to the dividing mode of the current node when the chrominance block of the current node is not divided any more. When the chroma block of the current node is not divided any more, the method can divide the luma block of the current node only, thereby improving the coding and decoding efficiency, reducing the maximum throughput rate of the coder and decoder and being beneficial to the realization of the coder and decoder.

Description

Image dividing method and device

Technical Field

The present application relates to the field of video coding and decoding, and more particularly, to an image partitioning (picture partition) method and apparatus.

Background

With the rapid development of internet technology and the increasing abundance of physical and mental culture of people, the application requirements for videos in the internet, especially for high-definition videos, are increasing, the data volume of the high-definition videos is very large, and the problem that the high-definition videos must be firstly solved in order to be transmitted in the internet with limited bandwidth is the problem of video encoding and decoding. Video codecs are widely used in digital video applications such as broadcast digital television, video distribution over the internet and mobile networks, real-time conversational applications such as video chat and video conferencing, DVD and blu-ray discs, video content acquisition and editing systems, and security applications for camcorders.

Each picture of a video sequence is typically partitioned into non-overlapping sets of blocks, typically encoded at the block level. For example, the prediction block is generated by spatial (intra-picture) prediction and temporal (inter-picture) prediction. Accordingly, the prediction modes may include intra prediction modes (spatial prediction) and inter prediction modes (temporal prediction). Wherein the set of intra prediction modes may include 35 different intra prediction modes, for example, a non-directional mode such as a DC (or mean) mode and a planar mode; or a directivity pattern as defined in h.265; or 67 different intra prediction modes, for example, a non-directional mode such as a DC (or mean) mode and a plane mode; or a directivity pattern as defined in h.266 under development. The set of inter prediction modes depends on the available reference pictures and other inter prediction parameters, e.g. on whether the entire reference picture is used or only a part of the reference picture is used.

Existing video is typically color video, which contains a chrominance component in addition to a luminance component. Therefore, in addition to encoding and decoding the luminance component, it is also necessary to encode and decode the chrominance component. However, the encoding and decoding efficiency in the prior art is relatively low.

Disclosure of Invention

Embodiments of the present application (or the present disclosure) provide apparatus and methods for image segmentation.

In a first aspect, embodiments of the present invention relate to a method of image division. The method is performed by a device that decodes a video stream or encodes a video stream. Determining a dividing mode of a current node, wherein the current node comprises a brightness block and a chromaticity block; determining that the chromaticity block of the current node is not divided any more according to the dividing mode of the current node and the size of the current node; and dividing the luminance block of the current node according to the dividing mode of the current node when the chrominance block of the current node is not divided any more.

When the chroma block of the current node is not divided, the method of the first aspect can divide the luma block of the current node only, thereby improving the coding and decoding efficiency, reducing the maximum throughput rate of the coder and decoder and being beneficial to the realization of the coder and decoder.

In a second aspect, embodiments of the present invention relate to a device for decoding a video stream, comprising a processor and a memory. The memory stores instructions that cause the processor to perform the method according to the first aspect.

In a third aspect, embodiments of the present invention relate to an apparatus for encoding a video stream, comprising a processor and a memory. The memory stores instructions that cause the processor to perform the method according to the first aspect.

In a fourth aspect, a computer-readable storage medium having instructions stored thereon that, when executed, cause one or more processors to encode video data is presented. The instructions cause the one or more processors to perform the method according to any possible embodiment of the first aspect.

In a fifth aspect, embodiments of the invention relate to a computer program comprising a program code for performing the method according to any of the possible embodiments of the first aspect when run on a computer.

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

Drawings

In order to more clearly describe the technical solutions in the embodiments or the background of the present application, the following description will describe the drawings that are required to be used in the embodiments or the background of the present application.

FIG. 1A shows a block diagram of an example video coding system for implementing an embodiment of the invention;

Fig. 1B shows a block diagram of an example video encoding system incorporating either or both of encoder 20 of fig. 2 and decoder 30 of fig. 3;

FIG. 2 shows a block diagram of an example architecture of a video encoder for implementing an embodiment of the invention;

FIG. 3 shows a block diagram of an example architecture of a video decoder for implementing an embodiment of the invention;

FIG. 4 shows a block diagram of an example encoding or decoding device;

FIG. 5 shows a block diagram of another example encoding or decoding device;

FIG. 6 shows an example of a YUV format sampling grid;

FIGS. 7A through 7E illustrate five different partition types;

FIG. 8 illustrates a quad-tree and binary tree combination partitioning approach;

FIG. 9 shows a flow chart of a method of a first embodiment of the invention;

FIG. 10 shows a flow chart of step 906 of a first embodiment of the invention;

fig. 11 shows a method flow chart of a third embodiment of the invention.

In the following, like reference numerals refer to like or at least functionally equivalent features, unless specifically noted otherwise.

Detailed Description

Video coding generally refers to processing a sequence of pictures that form a video or video sequence. In the field of video coding, the terms "picture", "frame" or "image" may be used as synonyms. Video encoding as used in this application (or this disclosure) refers to video encoding or video decoding. Video encoding is performed on the source side, typically including processing (e.g., by compression) the original video picture to reduce the amount of data required to represent the video picture, thereby more efficiently storing and/or transmitting. Video decoding is performed on the destination side, typically involving inverse processing with respect to the encoder to reconstruct the video pictures. The embodiment relates to video picture "encoding" is understood to relate to "encoding" or "decoding" of a video sequence. The combination of the encoding portion and the decoding portion is also called codec (encoding and decoding).

Each picture of a video sequence is typically partitioned into non-overlapping sets of blocks, typically encoded at the block level. In other words, the encoder side typically processes, i.e. encodes, video at the block (also referred to as image block, or video block) level, e.g. generates a prediction block by spatial (intra-picture) prediction and temporal (inter-picture) prediction, subtracts the prediction block from the current block (currently processed or to-be-processed block) to obtain a residual block, transforms the residual block in the transform domain and quantizes the residual block to reduce the amount of data to be transmitted (compressed), while the decoder side applies the inverse processing part of the relative encoder to the encoded or compressed block to reconstruct the current block for representation. In addition, the encoder replicates the decoder processing loop so that the encoder and decoder generate the same predictions (e.g., intra-prediction and inter-prediction) and/or reconstructions for processing, i.e., encoding, the subsequent blocks.

The term "block" may be part of a picture or frame. The key terms are defined as follows:

current block: referring to the block currently being processed. For example, in encoding, refers to the block currently being encoded; in decoding, a block currently being decoded is referred to. If the currently processed block is a chroma component block, it is referred to as the current chroma block. The luminance block corresponding to the current chrominance block may be referred to as the current luminance block.

CTU: a coding tree unit (coding tree unit) in which an image is composed of a plurality of CTUs, and a CTU generally corresponds to a square image area, and includes luminance pixels and chrominance pixels (or may include only luminance pixels or may include only chrominance pixels) in the image area; the CTU also contains syntax elements indicating how the CTU is divided into at least one Coding Unit (CU), and a method of decoding each coding unit to obtain a reconstructed image.

CU: the coding unit, which generally corresponds to a rectangular area of a×b, comprises a×b luminance pixels and its corresponding chrominance pixels, a is the width of the rectangle, B is the height of the rectangle, a and B may be the same or different, and the values of a and B are generally integers of power of 2, such as 256, 128, 64, 32, 16, 8, 4. An encoding unit can decode to obtain a reconstructed image of a rectangular area of axb through decoding processing, which generally includes processes of prediction, inverse quantization, inverse transformation, etc., to generate a predicted image and a residual, and the predicted image and the residual are superimposed to obtain the reconstructed image.

Embodiments of encoder 20, decoder 30, and encoding system 10 are described below based on fig. 1A, 1B through 3.

Fig. 1A is a conceptual or schematic block diagram illustrating an exemplary encoding system 10, e.g., a video encoding system 10 that may utilize the techniques of this application (this disclosure). Encoder 20 (e.g., video encoder 20) and decoder 30 (e.g., video decoder 30) of video encoding system 10 represent examples of devices that may be used to perform intra-prediction according to the various examples described herein. As shown in fig. 1A, encoding system 10 includes a source device 12 for providing encoded data 13, e.g., encoded pictures 13, to a destination device 14, e.g., decoding encoded data 13.

Source device 12 includes an encoder 20, and may additionally optionally include a picture source 16, a preprocessing unit 18, such as picture preprocessing unit 18, and a communication interface or communication unit 22.

The picture source 16 may include or may be any type of picture capture device for capturing, for example, real world pictures, and/or any type of picture or comment (for screen content encoding, some text on the screen is also considered part of the picture or image to be encoded), for example, a computer graphics processor for generating computer animated pictures, or any type of device for capturing and/or providing real world pictures, computer animated pictures (e.g., screen content, virtual Reality (VR) pictures), and/or any combination thereof (e.g., real scene (augmented reality, AR) pictures).

A picture may be regarded as a two-dimensional array or matrix of sampling points with luminance values. The sampling points in the array may also be referred to as pixels (pixels) or pixels (pels). The number of sampling points of the array or picture in the horizontal and vertical directions (or axes) defines the size and/or resolution of the picture. To represent color, three color components are typically employed, i.e., a picture may be represented as or contain three sample arrays. In RBG format or color space, a picture includes corresponding red, green, and blue sample arrays. However, in video coding, each pixel is typically represented in a luminance/chrominance format or color space, e.g., YCbCr, including a luminance component indicated by Y (which may sometimes be indicated by L) and two chrominance components indicated by Cb and Cr. The luminance (luma) component Y represents the luminance or grayscale intensity (e.g., the same in a grayscale picture), while the two chrominance (chroma) components Cb and Cr represent the chrominance or color information components. Accordingly, a picture in YCbCr format includes a luma sample array of luma sample values (Y) and two chroma sample arrays of chroma values (Cb and Cr). Pictures in RGB format may be converted or transformed into YCbCr format and vice versa, a process also known as color transformation or conversion. If the picture is black, the picture may include only the luma sample array.

Picture source 16 (e.g., video source 16) may be, for example, a camera for capturing pictures, a memory such as a picture memory, a memory that includes or stores previously captured or generated pictures, and/or any type of (internal or external) interface that captures or receives pictures. The camera may be, for example, an integrated camera, either local or integrated in the source device, and the memory may be, for example, an integrated memory, either local or integrated in the source device. The interface may be, for example, an external interface that receives pictures from an external video source, such as an external picture capture device, like a camera, an external memory or an external picture generation device, such as an external computer graphics processor, a computer or a server. The interface may be any kind of interface according to any proprietary or standardized interface protocol, e.g. a wired or wireless interface, an optical interface. The interface to acquire the picture data 17 may be the same interface as the communication interface 22 or a part of the communication interface 22.

The picture or picture data 17 (e.g., video data 16) may also be referred to as an original picture or original picture data 17, as distinguished from the preprocessing unit 18 and the processing performed by the preprocessing unit 18.

The preprocessing unit 18 is for receiving (original) picture data 17 and performing preprocessing on the picture data 17 to obtain a preprocessed picture 19 or preprocessed picture data 19. For example, preprocessing performed by preprocessing unit 18 may include truing, color format conversion (e.g., from RGB to YCbCr), toning, or denoising. It is understood that the preprocessing unit 18 may be an optional component.

Encoder 20, e.g., video encoder 20, is operative to receive preprocessed picture data 19 and provide encoded picture data 21 (details are described further below, e.g., based on fig. 2 or fig. 4). In one example, encoder 20 may be used to perform embodiments one through three described below.

The communication interface 22 of the source device 12 may be used to receive the encoded picture data 21 and transmit it to other devices, such as the destination device 14 or any other device, for storage or direct reconstruction, or for processing the encoded picture data 21 before storing the encoded data 13 and/or transmitting the encoded data 13 to the other devices, such as the destination device 14 or any other device for decoding or storage, respectively.

The destination device 14 includes a decoder 30 (e.g., a video decoder 30), and may additionally, i.e., alternatively, include a communication interface or unit 28, a post-processing unit 32, and a display device 34.

The communication interface 28 of the destination device 14 is for receiving the encoded picture data 21 or the encoded data 13, e.g. directly from the source device 12 or any other source, e.g. a storage device, e.g. an encoded picture data storage device.

Communication interface 22 and communication interface 28 may be used to transmit or receive encoded picture data 21 or encoded data 13 via a direct communication link between source device 12 and destination device 14, such as a direct wired or wireless connection, or via any type of network, such as a wired or wireless network or any combination thereof, or any type of private and public networks, or any combination thereof.

The communication interface 22 may, for example, be used to encapsulate the encoded picture data 21 into a suitable format, such as packets, for transmission over a communication link or communication network.

The communication interface 28 forming a corresponding part of the communication interface 22 may for example be used for unpacking the encoded data 13 to obtain the encoded picture data 21.

Both communication interface 22 and communication interface 28 may be configured as unidirectional communication interfaces, as indicated by the arrow from source device 12 to destination device 14 for encoded picture data 13 in fig. 1A, or as bi-directional communication interfaces, and may be used, for example, to send and receive messages to establish a connection, acknowledge and exchange any other information related to the communication link and/or data transmission, such as encoded picture data transmission.

Decoder 30 is used to receive encoded picture data 21 and provide decoded picture data 31 or decoded picture 31 (details will be described further below, e.g., based on fig. 3 or fig. 5). In one example, decoder 30 may be used to perform embodiments one through three described below.

The post-processor 32 of the destination device 14 is used to post-process the decoded picture data 31 (also referred to as reconstructed slice data), e.g., the decoded picture 131, to obtain post-processed picture data 33, e.g., the post-processed picture 33. Post-processing performed by post-processing unit 32 may include, for example, color format conversion (e.g., conversion from YCbCr to RGB), toning, truing, or resampling, or any other processing for preparing decoded picture data 31 for display by display device 34, for example.

The display device 34 of the destination device 14 is for receiving the post-processed picture data 33 to display the picture to, for example, a user or viewer. The display device 34 may be or include any type of display for presenting reconstructed pictures, for example, an integrated or external display or monitor. For example, the display may include a liquid crystal display (liquid crystal display, LCD), an organic light emitting diode (organic light emitting diode, OLED) display, a plasma display, a projector, a micro LED display, a liquid crystal on silicon (liquid crystal on silicon, LCoS), a digital light processor (digital light processor, DLP), or any other type of display.

Although fig. 1A depicts source device 12 and destination device 14 as separate devices, device embodiments may also include the functionality of both source device 12 and destination device 14, or both, i.e., source device 12 or corresponding functionality and destination device 14 or corresponding functionality. In such embodiments, the source device 12 or corresponding functionality and the destination device 14 or corresponding functionality may be implemented using the same hardware and/or software, or using separate hardware and/or software, or any combination thereof.

It will be apparent to those skilled in the art from this description that the functionality of the different units or the existence and (exact) division of the functionality of the source device 12 and/or destination device 14 shown in fig. 1A may vary depending on the actual device and application.

Encoder 20 (e.g., video encoder 20) and decoder 30 (e.g., video decoder 30) may each be implemented as any of a variety of suitable circuits, such as one or more microprocessors, digital signal processors (digital signal processor, DSPs), application-specific integrated circuits (ASICs), field-programmable gate array, FPGA, discrete logic, hardware, or any combinations thereof. If the techniques are implemented in part in software, an apparatus may store instructions of the software in a suitable non-transitory computer-readable storage medium and may execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Any of the foregoing (including hardware, software, a combination of hardware and software, etc.) may be considered one or more processors. Each of video encoder 20 and video decoder 30 may be contained in one or more encoders or decoders, either of which may be integrated as part of a combined encoder/decoder (codec) in the corresponding device.

Source device 12 may be referred to as a video encoding device or video encoding apparatus. Destination device 14 may be referred to as a video decoding device or video decoding apparatus. The source device 12 and the destination device 14 may be examples of video encoding devices or video encoding apparatus.

Source device 12 and destination device 14 may comprise any of a variety of devices, including any type of handheld or stationary device, such as a notebook or laptop computer, mobile phone, smart phone, tablet or tablet computer, video camera, desktop computer, set-top box, television, display device, digital media player, video game console, video streaming device (e.g., content service server or content distribution server), broadcast receiver device, broadcast transmitter device, etc., and may not use or use any type of operating system.

In some cases, source device 12 and destination device 14 may be equipped for wireless communication. Thus, the source device 12 and the destination device 14 may be wireless communication devices.

In some cases, the video encoding system 10 shown in fig. 1A is merely an example, and the techniques of this disclosure may be applicable to video encoding settings (e.g., video encoding or video decoding) that do not necessarily involve any data communication between encoding and decoding devices. In other examples, the data may be retrieved from local memory, streamed over a network, and the like. The video encoding device may encode and store data to the memory and/or the video decoding device may retrieve and decode data from the memory. In some examples, encoding and decoding are performed by devices that do not communicate with each other, but instead only encode data to memory and/or retrieve data from memory and decode data.

It should be appreciated that for each of the examples described above with reference to video encoder 20, video decoder 30 may be used to perform the reverse process. Regarding signaling syntax elements, video decoder 30 may be configured to receive and parse such syntax elements and decode the associated video data accordingly. In some examples, video encoder 20 may entropy encode the syntax elements into an encoded video bitstream. In such examples, video decoder 30 may parse such syntax elements and decode the relevant video data accordingly.

Fig. 1B is an illustration of an example of a video encoding system 40 including encoder 20 of fig. 2 and/or decoder 30 of fig. 3, according to an example embodiment. The system 40 may implement a combination of the various techniques of the present application. In the illustrated embodiment, video encoding system 40 may include an imaging device 41, a video encoder 20, a video decoder 30 (and/or a video encoder implemented by logic circuitry 47 of a processing unit 46), an antenna 42, one or more processors 43, one or more memories 44, and/or a display device 45.

As shown, imaging device 41, antenna 42, processing unit 46, logic 47, video encoder 20, video decoder 30, processor 43, memory 44, and/or display device 45 are capable of communicating with each other. As discussed, although video encoding system 40 is depicted with video encoder 20 and video decoder 30, in different examples, video encoding system 40 may include only video encoder 20 or only video decoder 30.

In some examples, as shown, video encoding system 40 may include an antenna 42. For example, the antenna 42 may be used to transmit or receive an encoded bitstream of video data. Additionally, in some examples, video encoding system 40 may include a display device 45. The display device 45 may be used to present video data. In some examples, as shown, logic circuitry 47 may be implemented by processing unit 46. The processing unit 46 may comprise application-specific integrated circuit (ASIC) logic, a graphics processor, a general-purpose processor, or the like. The video encoding system 40 may also include an optional processor 43, which optional processor 43 may similarly include application-specific integrated circuit (ASIC) logic, a graphics processor, a general purpose processor, or the like. In some examples, logic 47 may be implemented in hardware, such as video encoding dedicated hardware, processor 43 may be implemented in general purpose software, an operating system, or the like. In addition, the memory 44 may be any type of memory, such as volatile memory (e.g., static random access memory (Static Random Access Memory, SRAM), dynamic random access memory (Dynamic Random Access Memory, DRAM), etc.) or non-volatile memory (e.g., flash memory, etc.), and the like. In a non-limiting example, the memory 44 may be implemented by an overspeed cache. In some examples, logic circuitry 47 may access memory 44 (e.g., for implementing an image buffer). In other examples, logic 47 and/or processing unit 46 may include memory (e.g., a cache, etc.) for implementing an image buffer, etc.

In some examples, video encoder 20 implemented by logic circuitry may include an image buffer (e.g., implemented by processing unit 46 or memory 44) and a graphics processing unit (e.g., implemented by processing unit 46). The graphics processing unit may be communicatively coupled to the image buffer. The graphics processing unit may include video encoder 20 implemented by logic circuitry 47 to implement the various modules discussed with reference to fig. 2 and/or any other encoder system or subsystem described herein. Logic circuitry may be used to perform various operations discussed herein.

Video decoder 30 may be implemented in a similar manner by logic circuit 47 to implement the various modules discussed with reference to decoder 30 of fig. 3 and/or any other decoder system or subsystem described herein. In some examples, video decoder 30 implemented by logic circuitry may include an image buffer (implemented by processing unit 2820 or memory 44) and a graphics processing unit (e.g., implemented by processing unit 46). The graphics processing unit may be communicatively coupled to the image buffer. The graphics processing unit may include video decoder 30 implemented by logic circuit 47 to implement the various modules discussed with reference to fig. 3 and/or any other decoder system or subsystem described herein.

In some examples, antenna 42 of video encoding system 40 may be used to receive an encoded bitstream of video data. As discussed, the encoded bitstream may include data related to the encoded video frame, indicators, index values, mode selection data, etc., discussed herein, such as data related to the encoded partitions (e.g., transform coefficients or quantized transform coefficients, optional indicators (as discussed), and/or data defining the encoded partitions). Video encoding system 40 may also include a video decoder 30 coupled to antenna 42 and used to decode the encoded bitstream. The display device 45 is used to present video frames.

Encoder & encoding method

Fig. 2 shows a schematic/conceptual block diagram of an example of a video encoder 20 for implementing the techniques of this application (disclosure). In the example of fig. 2, video encoder 20 includes residual calculation unit 204, transform processing unit 206, quantization unit 208, inverse quantization unit 210, inverse transform processing unit 212, reconstruction unit 214, buffer 216, loop filter unit 220, decoded picture buffer (decoded picture buffer, DPB) 230, prediction processing unit 260, and entropy encoding unit 270. The prediction processing unit 260 may include an inter prediction unit 244, an intra prediction unit 254, and a mode selection unit 262. The inter prediction unit 244 may include a motion estimation unit and a motion compensation unit (not shown). The video encoder 20 shown in fig. 2 may also be referred to as a hybrid video encoder or a video encoder according to a hybrid video codec.

For example, the residual calculation unit 204, the transform processing unit 206, the quantization unit 208, the prediction processing unit 260 and the entropy encoding unit 270 form a forward signal path of the encoder 20, whereas for example the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the buffer 216, the loop filter 220, the decoded picture buffer (decoded picture buffer, DPB) 230, the prediction processing unit 260 form a backward signal path of the encoder, wherein the backward signal path of the encoder corresponds to the signal path of the decoder (see decoder 30 in fig. 3).

Encoder 20 receives picture 201 or a block 203 of picture 201, e.g., a picture in a sequence of pictures forming a video or video sequence, through, e.g., input 202. The picture block 203 may also be referred to as a current picture block or a picture block to be encoded, and the picture 201 may be referred to as a current picture or a picture to be encoded (especially when distinguishing the current picture from other pictures in video encoding, such as previously encoded and/or decoded pictures in the same video sequence, i.e. a video sequence also comprising the current picture).

Segmentation

An embodiment of encoder 20 may comprise a partitioning unit (not shown in fig. 2) for partitioning picture 201 into a plurality of blocks, e.g. blocks 203, typically into a plurality of non-overlapping blocks. The segmentation unit may be used to use the same block size for all pictures in the video sequence and a corresponding grid defining the block size, or to alter the block size between pictures or subsets or groups of pictures and to segment each picture into corresponding blocks.

In one example, prediction processing unit 260 of video encoder 20 may be configured to perform any combination of the above-described partitioning techniques.

Like picture 201, block 203 is also or may be regarded as a two-dimensional array or matrix of sampling points with luminance values (sampling values), albeit of smaller size than picture 201. In other words, block 203 may include, for example, one sampling array (e.g., a luminance array in the case of black-and-white picture 201) or three sampling arrays (e.g., one luminance array and two chrominance arrays in the case of color pictures) or any other number and/or class of arrays depending on the color format applied. The number of sampling points in the horizontal and vertical directions (or axes) of the block 203 defines the size of the block 203.

The encoder 20 as shown in fig. 2 is used to encode a picture 201 block by block, e.g. perform encoding and prediction on each block 203.

Residual calculation

The residual calculation unit 204 is configured to calculate a residual block 205 based on the picture block 203 and the prediction block 265 (further details of the prediction block 265 are provided below), for example, by subtracting sample values of the prediction block 265 from sample values of the picture block 203 on a sample-by-sample (pixel-by-pixel) basis to obtain the residual block 205 in a sample domain.

Transformation

The transform processing unit 206 is configured to apply a transform, such as a discrete cosine transform (discrete cosine transform, DCT) or a discrete sine transform (discrete sine transform, DST), on the sample values of the residual block 205 to obtain transform coefficients 207 in the transform domain. The transform coefficients 207 may also be referred to as transform residual coefficients and represent the residual block 205 in the transform domain.

The transform processing unit 206 may be used to apply integer approximations of DCT/DST, such as the transforms specified for HEVC/H.265. Such integer approximations are typically scaled by some factor compared to the orthogonal DCT transform. To maintain the norms of the forward and inverse transformed processed residual blocks, an additional scaling factor is applied as part of the transformation process. The scaling factor is typically selected based on certain constraints, e.g., the scaling factor is a tradeoff between power of 2, bit depth of transform coefficients, accuracy, and implementation cost for shift operations, etc. For example, a specific scaling factor is specified for inverse transformation by, for example, the inverse transformation processing unit 212 on the decoder 30 side (and for corresponding inverse transformation by, for example, the inverse transformation processing unit 212 on the encoder 20 side), and accordingly, a corresponding scaling factor may be specified for positive transformation by the transformation processing unit 206 on the encoder 20 side.

Quantization

The quantization unit 208 is for quantizing the transform coefficients 207, for example by applying scalar quantization or vector quantization, to obtain quantized transform coefficients 209. The quantized transform coefficients 209 may also be referred to as quantized residual coefficients 209. The quantization process may reduce the bit depth associated with some or all of the transform coefficients 207. For example, n-bit transform coefficients may be rounded down to m-bit transform coefficients during quantization, where n is greater than m. The quantization level may be modified by adjusting quantization parameters (quantization parameter, QP). For example, for scalar quantization, different scales may be applied to achieve finer or coarser quantization. Smaller quantization step sizes correspond to finer quantization, while larger quantization step sizes correspond to coarser quantization. The appropriate quantization step size may be indicated by a quantization parameter (quantization parameter, QP). For example, the quantization parameter may be an index of a predefined set of suitable quantization steps. For example, smaller quantization parameters may correspond to fine quantization (smaller quantization step size) and larger quantization parameters may correspond to coarse quantization (larger quantization step size) and vice versa. Quantization may involve division by a quantization step size and corresponding quantization or inverse quantization, e.g., performed by inverse quantization 210, or may involve multiplication by a quantization step size. Embodiments according to some standards, such as HEVC, may use quantization parameters to determine quantization step sizes. In general, the quantization step size may be calculated based on quantization parameters using a fixed-point approximation of an equation that includes division. Additional scaling factors may be introduced for quantization and inverse quantization to recover norms of residual blocks that may be modified due to the scale used in the fixed point approximation of the equation for quantization step size and quantization parameters. In one example embodiment, the inverse transformed and inverse quantized scales may be combined. Alternatively, a custom quantization table may be used and signaled from the encoder to the decoder, e.g., in a bitstream. Quantization is a lossy operation, where the larger the quantization step size, the larger the loss.

The inverse quantization unit 210 is configured to apply inverse quantization of the quantization unit 208 on the quantized coefficients to obtain inverse quantized coefficients 211, e.g., apply an inverse quantization scheme of the quantization scheme applied by the quantization unit 208 based on or using the same quantization step size as the quantization unit 208. The dequantized coefficients 211 may also be referred to as dequantized residual coefficients 211, correspond to the transform coefficients 207, although the losses due to quantization are typically different from the transform coefficients.

The inverse transform processing unit 212 is configured to apply an inverse transform of the transform applied by the transform processing unit 206, for example, an inverse discrete cosine transform (discretecosine transform, DCT) or an inverse discrete sine transform (discrete sine transform, DST), to obtain an inverse transform block 213 in the sample domain. The inverse transform block 213 may also be referred to as an inverse transformed inverse quantized block 213 or an inverse transformed residual block 213.

A reconstruction unit 214 (e.g., a summer 214) is used to add the inverse transform block 213 (i.e., the reconstructed residual block 213) to the prediction block 265 to obtain the reconstructed block 215 in the sample domain, e.g., to add sample values of the reconstructed residual block 213 to sample values of the prediction block 265.

Optionally, a buffer unit 216, e.g. a line buffer 216 (or simply "buffer" 216), is used to buffer or store the reconstructed block 215 and the corresponding sample values for e.g. intra prediction. In other embodiments, the encoder may be configured to use the unfiltered reconstructed block and/or the corresponding sample values stored in the buffer unit 216 for any kind of estimation and/or prediction, such as intra prediction.

For example, embodiments of encoder 20 may be configured such that buffer unit 216 is used not only to store reconstructed blocks 215 for intra prediction 254, but also for loop filter unit 220 (not shown in fig. 2), and/or such that buffer unit 216 and decoded picture buffer unit 230 form one buffer, for example. Other embodiments may be used to use the filtered block 221 and/or blocks or samples (neither shown in fig. 2) from the decoded picture buffer 230 as an input or basis for the intra prediction 254.

The loop filter unit 220 (or simply "loop filter" 220) is used to filter the reconstructed block 215 to obtain a filtered block 221, which facilitates pixel transitions or improves video quality. Loop filter unit 220 is intended to represent one or more loop filters, such as deblocking filters, sample-adaptive offset (SAO) filters, or other filters, such as bilateral filters, adaptive loop filters (adaptive loop filter, ALF), or sharpening or smoothing filters, or collaborative filters. Although loop filter unit 220 is shown in fig. 2 as an in-loop filter, in other configurations loop filter unit 220 may be implemented as a post-loop filter. The filtered block 221 may also be referred to as a filtered reconstructed block 221. Decoded picture buffer 230 may store the reconstructed encoded block after loop filter unit 220 performs a filtering operation on the reconstructed encoded block.

Embodiments of encoder 20 (and correspondingly loop filter unit 220) may be configured to output loop filter parameters (e.g., sample adaptive offset information), e.g., directly or after entropy encoding by entropy encoding unit 270 or any other entropy encoding unit, e.g., such that decoder 30 may receive and apply the same loop filter parameters for decoding.

Decoded picture buffer (decoded picture buffer, DPB) 230 may be a reference picture memory that stores reference picture data for use by video encoder 20 in encoding video data. DPB 230 may be formed of any of a variety of memory devices, such as dynamic random access memory (dynamic random access memory, DRAM) (including Synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM)), or other types of memory devices. DPB 230 and buffer 216 may be provided by the same memory device or separate memory devices. In a certain example, a decoded picture buffer (decoded picture buffer, DPB) 230 is used to store the filtered block 221. The decoded picture buffer 230 may further be used to store the same current picture or other previously filtered blocks, e.g., previously reconstructed and filtered blocks 221, of different pictures, e.g., previously reconstructed pictures, and may provide complete previously reconstructed, i.e., decoded pictures (and corresponding reference blocks and samples) and/or partially reconstructed current pictures (and corresponding reference blocks and samples), e.g., for inter prediction. In a certain example, if the reconstructed block 215 is reconstructed without in-loop filtering, the decoded picture buffer (decoded picture buffer, DPB) 230 is used to store the reconstructed block 215.

The prediction processing unit 260, also referred to as block prediction processing unit 260, is adapted to receive or obtain block 203 (current block 203 of current picture 201) and reconstructed slice data, e.g. reference samples of the same (current) picture from buffer 216 and/or reference picture data 231 of one or more previously decoded pictures from decoded picture buffer 230, and to process such data for prediction, i.e. to provide a prediction block 265 which may be an inter prediction block 245 or an intra prediction block 255.

The mode selection unit 262 may be used to select a prediction mode (e.g., intra or inter prediction mode) and/or a corresponding prediction block 245 or 255 used as the prediction block 265 to calculate the residual block 205 and reconstruct the reconstructed block 215.

Embodiments of mode selection unit 262 may be used to select the prediction mode (e.g., from those supported by prediction processing unit 260) that provides the best match or minimum residual (minimum residual meaning better compression in transmission or storage), or that provides the minimum signaling overhead (minimum signaling overhead meaning better compression in transmission or storage), or both. The mode selection unit 262 may be adapted to determine a prediction mode based on a rate-distortion optimization (rate distortion optimization, RDO), i.e. to select the prediction mode that provides the least rate-distortion optimization, or to select a prediction mode for which the associated rate-distortion at least meets a prediction mode selection criterion.

The prediction processing performed by an instance of encoder 20 (e.g., by prediction processing unit 260) and the mode selection performed (e.g., by mode selection unit 262) will be explained in detail below.

As described above, the encoder 20 is configured to determine or select the best or optimal prediction mode from a (predetermined) set of prediction modes. The set of prediction modes may include, for example, intra prediction modes and/or inter prediction modes.

The set of intra prediction modes may include 35 different intra prediction modes, or may include 67 different intra prediction modes, or may include the intra prediction mode defined in h.266 in progress.

The set of inter prediction modes depends on the available reference pictures (i.e. at least part of the decoded pictures stored in the DBP 230 as described before) and other inter prediction parameters, e.g. on whether the entire reference picture is used or only a part of the reference picture is used, e.g. a search window area surrounding the area of the current block, to search for the best matching reference block, and/or on whether pixel interpolation like half-pixel and/or quarter-pixel interpolation is applied, for example.

In addition to the above prediction modes, a skip mode and/or a direct mode may also be applied.

The prediction processing unit 260 may be further operative to partition the block 203 into smaller block partitions or sub-blocks, for example, by iteratively using a quad-tree (QT) partition, a binary-tree (BT) partition, or a ternary-tree (TT) partition, or any combination thereof, and to perform prediction for each of the block partitions or sub-blocks, for example, wherein the mode selection includes selecting a tree structure of the partitioned block 203 and selecting a prediction mode applied to each of the block partitions or sub-blocks.

The inter prediction unit 244 may include a motion estimation (motion estimation, ME) unit (not shown in fig. 2) and a motion compensation (motion compensation, MC) unit (not shown in fig. 2). The motion estimation unit is used to receive or obtain a picture block 203 (current picture block 203 of the current picture 201) and a decoded picture 231, or at least one or more previously reconstructed blocks, e.g. reconstructed blocks of one or more other/different previously decoded pictures 231, for motion estimation. For example, the video sequence may include a current picture and a previously decoded picture 31, or in other words, the current picture and the previously decoded picture 31 may be part of, or form, a sequence of pictures that form the video sequence.

For example, encoder 20 may be configured to select a reference block from a plurality of reference blocks of the same or different pictures of a plurality of other pictures, and provide the reference picture and/or an offset (spatial offset) between a position (X, Y coordinates) of the reference block and a position of a current block to a motion estimation unit (not shown in fig. 2) as an inter prediction parameter. This offset is also called Motion Vector (MV).

The motion compensation unit is used to obtain, for example, receive inter prediction parameters and perform inter prediction based on or using the inter prediction parameters to obtain the inter prediction block 245. The motion compensation performed by the motion compensation unit (not shown in fig. 2) may involve fetching or generating a prediction block based on motion/block vectors determined by motion estimation (possibly performing interpolation of sub-pixel accuracy). Interpolation filtering may generate additional pixel samples from known pixel samples, potentially increasing the number of candidate prediction blocks available for encoding a picture block. Upon receiving the motion vector for the PU of the current picture block, motion compensation unit 246 may locate the prediction block to which the motion vector points in a reference picture list. Motion compensation unit 246 may also generate syntax elements associated with the blocks and video slices for use by video decoder 30 in decoding the picture blocks of the video slices.

The intra prediction unit 254 is used to obtain, for example, a picture block 203 (current picture block) that receives the same picture and one or more previously reconstructed blocks, for example, reconstructed neighboring blocks, for intra estimation. For example, encoder 20 may be configured to select an intra-prediction mode from a plurality of intra-prediction modes.

Embodiments of encoder 20 may be used to select an intra-prediction mode based on optimization criteria, such as based on a minimum residual (e.g., the intra-prediction mode that provides a prediction block 255 most similar to current picture block 203) or minimum rate distortion.

The intra prediction unit 254 is further adapted to determine an intra prediction block 255 based on intra prediction parameters like the selected intra prediction mode. In any case, after the intra-prediction mode for the block is selected, the intra-prediction unit 254 is also configured to provide the intra-prediction parameters, i.e., information indicating the selected intra-prediction mode for the block, to the entropy encoding unit 270. In one example, intra-prediction unit 254 may be used to perform any combination of the intra-prediction techniques described below.

The entropy encoding unit 270 is configured to apply an entropy encoding algorithm or scheme (e.g., a variable length coding (variable length coding, VLC) scheme, a Context Adaptive VLC (CAVLC) scheme, an arithmetic coding scheme, a context adaptive binary arithmetic coding (context adaptive binary arithmetic coding, CABAC), a syntax-based context-based binary arithmetic coding (SBAC), a probability interval partitioning entropy (probabilityinterval partitioning entropy, PIPE) coding, or other entropy encoding methods or techniques) to one or all of the quantized residual coefficients 209, inter-prediction parameters, intra-prediction parameters, and/or loop filter parameters (or not) to obtain encoded picture data 21 that may be output by the output 272 in the form of, for example, an encoded bitstream 21. The encoded bitstream may be transmitted to video decoder 30 or archived for later transmission or retrieval by video decoder 30. Entropy encoding unit 270 may also be used to entropy encode other syntax elements of the current video slice being encoded.

Other structural variations of video encoder 20 may be used to encode the video stream. For example, the non-transform based encoder 20 may directly quantize the residual signal without a transform processing unit 206 for certain blocks or frames. In another embodiment, encoder 20 may have quantization unit 208 and inverse quantization unit 210 combined into a single unit.

Fig. 3 illustrates an exemplary video decoder 30 for implementing the techniques of this application. Video decoder 30 is operative to receive encoded picture data (e.g., encoded bitstream) 21, e.g., encoded by encoder 20, to obtain decoded picture 231. During the decoding process, video decoder 30 receives video data, such as an encoded video bitstream representing picture blocks of an encoded video slice and associated syntax elements, from video encoder 20.

In the example of fig. 3, decoder 30 includes entropy decoding unit 304, inverse quantization unit 310, inverse transform processing unit 312, reconstruction unit 314 (e.g., summer 314), buffer 316, loop filter 320, decoded picture buffer 330, and prediction processing unit 360. The prediction processing unit 360 may include an inter prediction unit 344, an intra prediction unit 354, and a mode selection unit 362. In some examples, video decoder 30 may perform a decoding pass that is substantially reciprocal to the encoding pass described with reference to video encoder 20 of fig. 2.

Entropy decoding unit 304 is used to perform entropy decoding on encoded picture data 21 to obtain, for example, quantized coefficients 309 and/or decoded encoding parameters (not shown in fig. 3), e.g., any or all of inter-prediction, intra-prediction parameters, loop filter parameters, and/or other syntax elements (decoded). Entropy decoding unit 304 is further configured to forward inter-prediction parameters, intra-prediction parameters, and/or other syntax elements to prediction processing unit 360. Video decoder 30 may receive syntax elements at the video stripe level and/or the video block level.

Inverse quantization unit 310 may be functionally identical to inverse quantization unit 110, inverse transform processing unit 312 may be functionally identical to inverse transform processing unit 212, reconstruction unit 314 may be functionally identical to reconstruction unit 214, buffer 316 may be functionally identical to buffer 216, loop filter 320 may be functionally identical to loop filter 220, and decoded picture buffer 330 may be functionally identical to decoded picture buffer 230.

The prediction processing unit 360 may include an inter prediction unit 344 and an intra prediction unit 354, where the inter prediction unit 344 may be similar in function to the inter prediction unit 244 and the intra prediction unit 354 may be similar in function to the intra prediction unit 254. The prediction processing unit 360 is typically used to perform block prediction and/or to obtain a prediction block 365 from the encoded data 21, as well as to receive or obtain prediction related parameters and/or information about the selected prediction mode (explicitly or implicitly) from, for example, the entropy decoding unit 304.

When a video slice is encoded as an intra-coded (I) slice, the intra-prediction unit 354 of the prediction processing unit 360 is used to generate a prediction block 365 for a picture block of the current video slice based on the signaled intra-prediction mode and data from a previously decoded block of the current frame or picture. When a video frame is encoded as an inter-coded (i.e., B or P) slice, an inter-prediction unit 344 (e.g., a motion compensation unit) of prediction processing unit 360 is used to generate a prediction block 365 for a video block of the current video slice based on the motion vector and other syntax elements received from entropy decoding unit 304. For inter prediction, a prediction block may be generated from one reference picture within one reference picture list. Video decoder 30 may construct a reference frame list based on the reference pictures stored in DPB 330 using default construction techniques: list 0 and list 1.

The prediction processing unit 360 is configured to determine prediction information for a video block of a current video slice by parsing the motion vector and other syntax elements, and generate a prediction block for the current video block being decoded using the prediction information. For example, prediction processing unit 360 uses some syntax elements received to determine a prediction mode (e.g., intra or inter prediction) for encoding video blocks of a video slice, an inter prediction slice type (e.g., B slice, P slice, or GPB slice), construction information for one or more of the reference picture lists of the slice, motion vectors for each inter-encoded video block of the slice, inter prediction state for each inter-encoded video block of the slice, and other information to decode video blocks of the current video slice.

Inverse quantization unit 310 may be used to inverse quantize (i.e., inverse quantize) the quantized transform coefficients provided in the bitstream and decoded by entropy decoding unit 304. The inverse quantization process may include using quantization parameters calculated by video encoder 20 for each video block in a video stripe to determine the degree of quantization that should be applied and likewise the degree of inverse quantization that should be applied.

The inverse transform processing unit 312 is configured to apply an inverse transform (e.g., an inverse DCT, an inverse integer transform, or a conceptually similar inverse transform process) to the transform coefficients in order to generate a residual block in the pixel domain.

A reconstruction unit 314 (e.g., a summer 314) is used to add the inverse transform block 313 (i.e., the reconstructed residual block 313) to the prediction block 365 to obtain a reconstructed block 315 in the sample domain, e.g., by adding sample values of the reconstructed residual block 313 to sample values of the prediction block 365.

Loop filter unit 320 is used (during or after the encoding cycle) to filter reconstructed block 315 to obtain filtered block 321, to smooth pixel transitions or improve video quality. In one example, loop filter unit 320 may be used to perform any combination of the filtering techniques described below. Loop filter unit 320 is intended to represent one or more loop filters, such as a deblocking filter, a sample-adaptive offset (SAO) filter, or other filters, such as a bilateral filter, an adaptive loop filter (adaptive loop filter, ALF), or a sharpening or smoothing filter, or a collaborative filter. Although loop filter unit 320 is shown in fig. 3 as an in-loop filter, in other configurations loop filter unit 320 may be implemented as a post-loop filter.

The decoded video blocks 321 in a given frame or picture are then stored in a decoded picture buffer 330 that stores reference pictures for subsequent motion compensation.

Decoder 30 is for outputting decoded picture 31, e.g., via output 332, for presentation to a user or for viewing by a user.

Other variations of video decoder 30 may be used to decode the compressed bitstream. For example, decoder 30 may generate the output video stream without loop filter unit 320. For example, the non-transform based decoder 30 may directly inverse quantize the residual signal without an inverse transform processing unit 312 for certain blocks or frames. In another embodiment, the video decoder 30 may have an inverse quantization unit 310 and an inverse transform processing unit 312 combined into a single unit.

Fig. 4 is a schematic diagram of the structure of a video decoding apparatus 400 (e.g., a video encoding apparatus 400 or a video decoding apparatus 400) according to an embodiment of the present invention. The video coding apparatus 400 is adapted to implement the embodiments described herein. In one embodiment, video coding device 400 may be a video decoder (e.g., video decoder 30 of fig. 1A) or a video encoder (e.g., video encoder 20 of fig. 1A). In another embodiment, video coding device 400 may be one or more components of video decoder 30 of fig. 1A or video encoder 20 of fig. 1A described above.

The video coding apparatus 400 includes: an ingress port 410 and a receiving unit (Rx) 420 for receiving data, a processor, logic unit or Central Processing Unit (CPU) 430 for processing data, a transmitter unit (Tx) 440 and an egress port 450 for transmitting data, and a memory 460 for storing data. The video decoding apparatus 400 may further include a photoelectric conversion component and an electro-optical (E0) component coupled with the inlet port 410, the receiver unit 420, the transmitter unit 440, and the outlet port 450 for an outlet or inlet of an optical or electrical signal.

The processor 430 is implemented in hardware and software. Processor 430 may be implemented as one or more CPU chips, cores (e.g., multi-core processors), FPGAs, ASICs, and DSPs. Processor 430 is in communication with inlet port 410, receiver unit 420, transmitter unit 440, outlet port 450, and memory 460. The processor 430 includes a coding module 470 (e.g., an encoding module 470 or a decoding module 470). The encoding/decoding module 470 implements the embodiments disclosed above. For example, the encoding/decoding module 470 implements, processes, or provides various encoding operations. Thus, substantial improvements are provided to the functionality of the video coding device 400 by the encoding/decoding module 470 and affect the transition of the video coding device 400 to different states. Alternatively, the encoding/decoding module 470 is implemented in instructions stored in the memory 460 and executed by the processor 430.

Memory 460 includes one or more disks, tape drives, and solid state drives, and may be used as an overflow data storage device for storing programs when selectively executing such programs, as well as storing instructions and data read during program execution. Memory 460 may be volatile and/or nonvolatile and may be Read Only Memory (ROM), random Access Memory (RAM), random access memory (TCAM) and/or Static Random Access Memory (SRAM).

Fig. 5 is a simplified block diagram of an apparatus 500 that may be used as either or both of the source device 12 and the destination device 14 in fig. 1A, according to an example embodiment. Apparatus 500 may implement the techniques of this application and apparatus 500 for implementing image partitioning may take the form of a computing system comprising multiple computing devices, or a single computing device such as a mobile phone, tablet, laptop, notebook, desktop, or the like.

The processor 502 in the apparatus 500 may be a central processor. Processor 502 may be any other type of device or devices capable of manipulating or processing information, either as is known or later developed. As shown, while the disclosed embodiments may be practiced with a single processor, such as processor 502, advantages in speed and efficiency may be realized with more than one processor.

In an embodiment, the Memory 504 in the apparatus 500 may be a Read Only Memory (ROM) device or a random access Memory (random access Memory, RAM) device. Any other suitable type of storage device may be used as memory 504. Memory 504 may include code and data 506 that is accessed by processor 502 using bus 512. Memory 504 may further include an operating system 508 and an application 510, application 510 containing at least one program that permits processor 502 to perform the methods described herein. For example, application 510 may include applications 1 through N, applications 1 through N further including video encoding applications that perform the methods described herein. The apparatus 500 may also contain additional memory in the form of a secondary memory 514, which secondary memory 514 may be, for example, a memory card for use with a mobile computing device. Because video communication sessions may contain a large amount of information, such information may be stored in whole or in part in slave memory 514 and loaded into memory 504 for processing as needed.

The apparatus 500 may also include one or more output devices, such as a display 518. In one example, display 518 may be a touch-sensitive display that combines the display and touch-sensitive elements operable to sense touch inputs. A display 518 may be coupled to the processor 502 by a bus 512. Other output devices may be provided in addition to the display 518 that permit a user to program or otherwise use the apparatus 500, or other output devices may be provided as alternatives to the display 518. When the output device is a display or comprises a display, the display may be implemented in different ways, including by a liquid crystal display (liquid crystal display, LCD), cathode-ray tube (CRT) display, plasma display or light emitting diode (light emitting diode, LED) display, such as an Organic LED (OLED) display.

The apparatus 500 may also include or be in communication with an image sensing device 520, the image sensing device 520 being, for example, a camera or any other image sensing device 520 now available or hereafter developed that can sense images, such as images of a user operating the apparatus 500. The image sensing device 520 may be placed directly facing the user running the apparatus 500. In an example, the position and optical axis of the image sensing device 520 may be configured such that its field of view includes an area proximate to the display 518 and the display 518 is visible from that area.

The apparatus 500 may also include or be in communication with a sound sensing device 522, such as a microphone or any other sound sensing device now available or later developed that may sense sound in the vicinity of the apparatus 500. The sound sensing device 522 may be placed directly facing the user operating the apparatus 500 and may be used to receive sounds, such as speech or other sounds, emitted by the user while operating the apparatus 500.

Although the processor 502 and the memory 504 of the apparatus 500 are depicted in fig. 5 as being integrated in a single unit, other configurations may also be used. The operations of processor 502 may be distributed among a plurality of directly couplable machines, each having one or more processors, or distributed in a local area or other network. The memory 504 may be distributed across multiple machines, such as network-based memory or memory in multiple machines running the apparatus 500. Although depicted here as a single bus, the bus 512 of the apparatus 500 may be formed from multiple buses. Further, slave memory 514 may be coupled directly to other components of apparatus 500 or may be accessible over a network, and may comprise a single integrated unit, such as a memory card, or multiple units, such as multiple memory cards. Thus, the apparatus 500 may be implemented in a variety of configurations.

As described earlier in this application, color video contains chrominance components (U, V) in addition to the luminance (Y) component. Therefore, in addition to encoding the luminance component, it is also necessary to encode the chrominance component. Depending on the sampling method of the luminance component and the chrominance component in color video, there are typically YUV4:4:4, YUV4:2:2, and YUV4:2:0. As shown in fig. 6, where the crosses represent luminance component sample points and the circles represent chrominance component sample points.

-4:4:4 format: indicating that the chrominance components are not downsampled;

-4:2:2 format: indicating that the chrominance components are downsampled 2:1 horizontally relative to the luminance components, without vertical downsampling. For every two U sampling points or V sampling points, each row contains four Y sampling points;

-4:2:0 format: representing the chroma component being downsampled horizontally by 2:1 with respect to the luma component, and downsampled vertically by 2:1.

The video decoder may be used to divide video blocks with five different division types allowed at each depth according to three different division structures (QT, BT, and TT). The division types include a quadtree division (QT division structure), a horizontal binary tree division (BT division structure), a vertical binary tree division (BT division structure), a horizontal center-side trigeminal tree division (TT division structure), and a vertical center-side trigeminal tree division (TT division structure), as shown in fig. 7A to 7E.

The five partition types are defined as follows. Note that a square is considered to be a special case of a rectangle.

Quadtree (QT) split: the block is further divided into four rectangular blocks of the same size. Fig. 7A shows an example of quadtree partitioning. According to the method for dividing the CTU based on the quadtree QT, the CTU is used as a root node (root) of the quadtree, and the CTU is recursively divided into a plurality of leaf nodes according to the dividing mode of the quadtree. A node corresponds to an image region, and if the node is not divided, the node is called a leaf node, and the image region corresponding to the node forms a CU; if the nodes are divided, the image area corresponding to the nodes is divided into four areas with the same size (the length and the width of the image area are half of the divided areas respectively), each area corresponds to one node, and whether the nodes are divided or not needs to be determined respectively. Whether a node is divided is indicated by a division flag bit split_cu_flag corresponding to the node in the code stream. The quadtree level (qtDepth) of the root node is 0 and the quadtree level of the child node is the quadtree level +1 of the parent node. For simplicity, the size and shape of a node in the present application refers to the size and shape of an image area corresponding to the node, i.e., the node is a rectangular area in the image. The node obtained after the node (node) in the Coding tree is divided may be called a child node (child node) of the node, which is simply called a child node.

More specifically, for a 64×64 CTU node (quadtree level 0), according to its corresponding split_cu_flag, it is selected to be not divided into 1 64×64 CUs, or to be divided into 4 nodes of 32×32 (quadtree level 1). Each of the four 32×32 nodes may further select to continue dividing or not dividing according to the split_cu_flag corresponding to the node; if a 32×32 node continues to divide, four 16×16 nodes are generated (quadtree level 2). And so on until all nodes are no longer partitioned, such that a CTU is partitioned into a set of CUs. The smallest size (size) of a CU is identified in the SPS, e.g., 8 x 8 as the smallest CU. In the recursive partitioning described above, if a node is equal to the minimum CU size (minimum CU size), the node defaults to no longer partitioning and does not need to include its partition flag in the code stream.

After parsing that a node is a leaf node, the leaf node is a CU, further parses coding information (including information such as a prediction mode and a transform coefficient of the CU, for example, a coding_unit () syntax structure in h.266) corresponding to the CU, and then performs decoding processes such as prediction, dequantization, inverse transform, loop filtering and the like on the CU according to the coding information to generate a reconstructed image corresponding to the CU. A Quadtree (QT) structure enables CTUs to be divided into a set of CUs of suitable size according to image local characteristics, e.g. smooth regions into larger CUs and texture rich regions into smaller CUs.

A division manner in which a CTU is divided into a set of CUs corresponds to one coding tree. What coding tree should be used by the CTU is typically determined by the rate distortion optimization (rate distortion optimization, RDO) technique of the encoder. The encoder attempts multiple CTU partitioning schemes, each partitioning scheme corresponding to a rate distortion cost (RD cost); the encoder compares the RD costs of the various attempted partitioning schemes, finds the partitioning scheme with the minimum RD cost, and uses the minimum RD cost as the optimal partitioning scheme for the CTU for the actual encoding of the CTU. The various CTU partitioning schemes tried by the encoder all need to meet the partitioning rules specified by the decoder, and these can be correctly identified by the decoder.

Vertical Binary Tree (BT) partitions: the block is vertically divided into two rectangular blocks of the same size. Fig. 7B is an example of a vertical binary tree partition.

Horizontal binary tree partitioning: the block is divided horizontally into two rectangular blocks of the same size. Fig. 7C is an example of a horizontal binary tree partition.

Vertical center-side tree (TT) partitioning: the block is vertically divided into three rectangular blocks such that the two side blocks are the same size, while the size of the center block is the sum of the two side blocks. Fig. 7D is an example of a vertical center-side trigeminal tree division.

Horizontal center-side trigeminal tree partitioning: the block is divided horizontally into three rectangular blocks such that the two side blocks are the same size, while the size of the center block is the sum of the two side blocks. Fig. 7E is an example of a horizontal center-side trigeminal tree division.

The specific partitioning method of fig. 7B-7E is similar to that of fig. 7A, and is not repeated here. In addition, a QT cascading BT/TT dividing mode can be used, namely the QT-BTT mode is called simply, namely, nodes on the first-stage coding tree can only be divided into child nodes by using QT, and leaf nodes of the first-stage coding tree are root nodes of the second-stage coding tree; nodes on the second-level coding tree can be divided into child nodes by using one of four dividing modes of horizontal bisection, vertical bisection, horizontal trisection and vertical trisection; leaf nodes of the second-level coding tree are coding units. Specifically, a cascading manner is adopted for binary tree division and quadtree division, which may be simply referred to as QTBT division manner, for example, CTU first divides according to QT, and leaf nodes of QT allow BT division to be continuously used, as shown in fig. 8. Each endpoint in the right graph of fig. 8 represents a node, 4 continuous lines are connected from one node to represent a quadtree partition, 2 broken lines are connected from one node to represent a binary tree partition, and the node obtained after the partition may be called a child node of the node, which is simply called a child node. In the child nodes, a to m are 13 leaf nodes, each leaf node representing 1 CU; 1 on a binary tree node represents a vertical partition, and 0 represents a horizontal partition; one CTU is divided into 13 CUs a to m according to the right diagram, as shown in the left diagram of fig. 8. In the QTBT partitioning manner, each CU has a QT level (QT-tree depth) and a BT level (Binary tree depth, BT depth), where the QT level represents the QT level of the QT leaf node CU to which the CU belongs, and the BT level represents the BT level of the BT leaf node to which the CU belongs, for example, QT levels a and b are 1 and BT level is 2 in fig. 8; c. d, e has QT level of 1 and BT level of 1; f. the QT level of k and l is 2, and the BT level is 1; i. QT level of j is 2 and bt level is 0; g. the QT level of h is 2, and the BT level is 2; the QT level for m is 1 and bt level is 0. If a CTU is divided into only one CU, then the QT level of this CU is 0 and the bt level is 0.

For blocks associated with a particular depth, encoder 20 determines which partition type to use (including no further partitions) and signals the determined partition type to decoder 30 either explicitly or implicitly (e.g., the partition type may be derived from a predetermined rule). Encoder 20 may determine the partition type to use based on the rate-distortion cost of the inspection block using the different partition types.

If the node is divided to generate a 2xM chroma block, especially a 2x2, 2x4 or 2x8 chroma block, the chroma coding and decoding efficiency is lower, and the processing cost of the hardware decoder is higher, which is not beneficial to the realization of the hardware decoder. When the chroma block of the current node is not divided any more, the embodiment of the application can divide the luma block of the current node only, thereby improving the coding and decoding efficiency, reducing the maximum throughput rate of the decoder and being beneficial to the realization of the decoder. Specifically, in the embodiment of the present application, when a node is divided by using a dividing manner and includes a sub-node having a side length of a first threshold value (or includes a side length of a chrominance block smaller than a second threshold value), a luminance block included in the node is divided by using the dividing manner, and the chrominance block included in the node is not divided any more. In this way, it is possible to avoid the generation of chroma blocks having a side length of the first threshold (or a side length smaller than the second threshold). In a specific implementation, the first threshold may be 2 and the second threshold may be 4. The following describes in detail embodiments one to three. Embodiments of the present application are described in terms of video data format YUV4:2:0, and similar approaches may be used for YUV4:2:2 data.

An encoding tool of Intra Block Copy (IBC) is adopted in an extension standard SCC of HEVC, and is mainly used for improving the encoding efficiency of screen content video. The IBC mode is a block-level coding mode, and at the coding end, a Block Matching (BM) method is used to find the best block vector (block vector) or motion vector (motion vector) for each CU. The motion vector is here mainly used to represent the displacement of the current block to a reference block, also called displacement vector (displacement vector), which is a reconstructed block within the current image. IBC mode may be considered a third prediction mode other than intra prediction or inter prediction modes. To save memory space and reduce the complexity of the decoder, IBC modes in VTM4 only allow prediction using reconstructed parts of predefined areas of the current CTU.

In the VTM, at the CU level, an identification bit is used to indicate whether the current CU uses the IBC mode, which is classified as IBC AMVP mode, IBC skip mode, or IBC merge mode.

Example 1

Fig. 9 shows a method flow diagram 900 of a first embodiment of the invention.

Step 901: judging whether a current node needs to be divided or not, wherein the current node comprises a brightness block and a chromaticity block. If the current node is not divided into sub-nodes, the current node is a Coding Unit (CU), step 910 is executed, and coding unit information is parsed; if the current node needs partitioning, step 902 is performed.

An embodiment of the present invention may be implemented by a video decoding apparatus, and in particular may be an apparatus as described in any of fig. 3-5.

The first embodiment of the present invention may also be implemented by a video encoding apparatus, and may specifically be any of the apparatuses described in fig. 2, 4-5.

When implemented by a video decoding device, step 902: the video decoding device analyzes the code stream and determines the dividing mode of the current node. The current node may be divided into at least one of a Quarter (QT), a horizontal BT, a horizontal TT, a Vertical BT, and a Vertical TT, and may be divided into other manners, which are not limited in the embodiment of the present invention. The partition mode information of the current node is usually transmitted in a code stream, and the partition mode of the current node can be obtained by analyzing the corresponding syntax element in the code stream.

When implemented by the video encoding apparatus, a partitioning method of the current node is determined, step 902.

Step 904: and judging whether the chromaticity block of the current node needs to be divided or not according to the dividing mode of the current node and the size of the current node. When the chroma block of the current node is no longer partitioned, performing step 906; when the chroma block of the current node needs to be divided, step 908 is performed.

Specifically, in one implementation, it may be determined whether the current node divides according to the division manner of the current node, whether a chroma block with a side length of a first threshold value will be generated (or whether a chroma block with a side length smaller than a second threshold value will be generated). If the child node generated by the current node partition is judged to contain the chroma blocks with the side length being the first threshold value (or contains the chroma blocks with the side length being smaller than the second threshold value), the chroma blocks of the current node are not partitioned. For example, the first threshold may be 2 and the second threshold may be 4.

In the embodiment of the invention, the chroma blocks with the side length of the first threshold value refer to the chroma blocks with the width of the first threshold value or the height of the first threshold value.

In another implementation, for example: it may be determined that the chroma block of the current node is not divided any more when any one of the following conditions 1 to 5 is satisfied; otherwise, determining that the chromaticity block of the current node needs to be divided.

Condition 1: the width of the current node is equal to 2 times of the second threshold value and the dividing mode of the current node is vertical bisection.

Condition 2: the height of the current node is equal to 2 times of the second threshold value, and the dividing mode of the current node is horizontal bisection.

Condition 3: the width of the current node is equal to 4 times of the second threshold value, and the dividing mode of the current node is vertical three minutes.

Condition 4: the height of the current node is equal to 4 times of the second threshold value, and the dividing mode of the current node is horizontal three minutes.

Condition 5: the width of the current node is equal to 2 times of the second threshold value and the dividing mode of the current node is quarter.

Typically, the width of the current node is the width of the luminance block corresponding to the current node, and the height of the current node is the height of the luminance block corresponding to the current node. In a specific implementation, for example, the second threshold may be 4.

In a third implementation, it may be determined whether the current node divides according to the division of the current node, to generate a chroma block having a width of the first threshold (or to generate a chroma block having a width less than the second threshold). If it is determined that the child node generated by the current node partition contains a chroma block having a width of a first threshold (or contains a chroma block having a width smaller than a second threshold), the chroma block of the current node is not partitioned. For example, the first threshold may be 2 and the second threshold may be 4.

In a fourth implementation, it may be determined whether the current node divides according to the division manner of the current node to generate a chroma block having a number of chroma pixels less than the third threshold. And if the child node generated by the current node division is judged to contain the chroma blocks with the number of the chroma pixels less than the third threshold value, the chroma blocks of the current node are not divided. For example, the third threshold may be 16. Chroma blocks with a number of chroma pixels less than 16 include, but are not limited to, 2x2 chroma blocks, 2x4 chroma blocks, 4x2 chroma blocks. The third threshold may be 8. Then a chroma block with a chroma pixel number less than 8 includes, but is not limited to, a 2x2 chroma block.

Specifically, if any one of the following conditions 1 to 2 is satisfied, it may be determined that the current node divides a chromaticity block that may generate a chromaticity pixel number less than the third threshold value in accordance with the division manner of the current node; otherwise, it may be determined that the current node divides the chroma blocks that do not generate chroma pixels less than the third threshold according to the division manner of the current node:

condition 1: the product of the width and the height of the current node is less than 128 and the current node is divided into vertical bisection or horizontal bisection.

Condition 2: the product of the width and the height of the current node is less than 256 and the current node is divided into three parts vertically or three parts horizontally or four parts horizontally.

Specifically, as another embodiment, if any one of the following conditions 3 to 4 is satisfied, it may be determined that the current node divides a chromaticity block that would generate a chromaticity pixel number less than the third threshold value in accordance with the division manner of the current node; otherwise, it may be determined that the current node divides the chroma blocks that do not generate chroma pixels less than the third threshold according to the division manner of the current node:

condition 3: the product of the width and the height of the current node is equal to 64 and the current node is divided into vertical halves or horizontal halves or quarters or horizontal thirds or vertical thirds.

Condition 4: the product of the width and the height of the current node is equal to 128 and the current node is divided into three parts vertically or three parts horizontally.

In a fifth implementation, it may be determined whether the current node divides according to the division of the current node, and may generate a chroma block higher than the first threshold (or may generate a chroma block higher than the second threshold). If it is determined that the child node generated by the current node partition contains a chroma block that is higher than a first threshold (or contains a chroma block that is higher than a second threshold), the chroma block of the current node is no longer partitioned. For example, the first threshold may be 2 and the second threshold may be 4.

Step 906: and dividing a luminance block (luma block) of the current node according to the dividing mode of the current node to obtain a child node (also called as a child node of the luminance block, called as a luminance node for short) of the current node. Each child node contains only luminance blocks. The chroma block (chroma block) of the current node is not subdivided into a coding unit containing only chroma blocks.

Optionally, as shown in fig. 10, step 906 may further include step 9062: analyzing the brightness block of the current node, and acquiring prediction information and residual information of each sub-region in the brightness block of the current node, wherein each sub-region corresponds to one sub-node.

Specifically, step 9062 may be implemented by any one of the following methods:

the method comprises the following steps: the sub-nodes of each luminance block are not divided by default (i.e. each luminance node is a coding unit, and the sub-node of one luminance block corresponds to a coding unit only containing a luminance block), and the sub-nodes of each luminance block are sequentially analyzed for coding unit data to obtain prediction information and residual information of each luminance block. The luminance block of one luminance node is a sub-region in the luminance block of the current node, and the luminance blocks of the respective luminance nodes constitute the luminance block of the current node. Or alternatively;

the second method is as follows: and sequentially judging whether the sub-nodes of each brightness block need to be divided continuously, and analyzing the dividing modes and corresponding coding unit data when the sub-nodes need to be divided continuously. More specifically, if a luminance node is not divided any more, analyzing the corresponding coding unit data to obtain prediction information and residual information corresponding to the luminance block of the luminance node; if a luminance node continues to be divided, then a determination is continued on a sub-node (it should be noted that the sub-node still only includes a luminance block) of the luminance node as to whether the division is required or not until prediction information and residual information of each sub-region in the luminance block of the current node are determined.

The prediction information includes, but is not limited to: prediction mode (indicating intra-prediction or inter-prediction mode), intra-prediction mode, and/or motion information, etc. The intra prediction Mode of the luminance block may be one of a Planar Mode (Planar Mode), a direct current Mode (DC Mode), an angular Mode (angular Mode), and a chrominance derived Mode (chroma derived Mode, DM); the motion information may include information of a prediction direction (forward, backward, or bi-directional), a reference frame index (reference index), and/or a motion vector (motion vector), etc.

The residual information includes: coded block flag (cbf), transform coefficients, and/or transform types (e.g., DCT-2, DST-7, DCT-8), etc.

Optionally, as shown in fig. 10, step 906 may further include step 9064: and obtaining the prediction information and/or residual information of the chroma block.

In particular, step 9064 may include step 90642 and step 90644. Step 90642 can be step 90642a or step 90642B.

Step 90642a specifically includes:

and obtaining a prediction mode of a preset position in the luminance block of the current node, and taking the prediction mode as the prediction mode of the chrominance block of the current node. The upper left corner position of the luminance block of the current node may be represented as (x 0, y 0) and the size of WxH, and the preset position may include, but is not limited to, the upper left corner, the lower right corner (x0+w-1, y0+h-1), the center (x0+w/2, y0+h/2), (x0+w/2, 0), (0, y0+h/2) and the like of the luminance block. The prediction mode indicates whether a pixel at a preset position is predicted using intra prediction or inter prediction, for example, information indicated by a pred_mode_flag syntax element in HEVC. For example, in the VTM, it may be determined whether the prediction mode of the preset position is the IBC mode according to information indicated by the syntax element pred_mode_ IBC _flag.

If the prediction mode of the preset position is inter prediction, determining a prediction mode of chroma using one of the following methods:

the method comprises the following steps: and the chroma block uses inter prediction to acquire motion information of a preset position as the motion information of the chroma block.

The second method is as follows: the chroma block is divided into chroma predictor blocks (chroma predictor block sizes, e.g., 2 chroma pixels wide and 2 chroma pixels high) using inter prediction, and the motion information of the chroma predictor blocks is obtained as follows:

if the luminance block of the luminance image position corresponding to the chrominance prediction sub-block adopts inter prediction, the motion information of the luminance image position corresponding to the chrominance prediction sub-block is used as the motion information of the chrominance prediction sub-block; otherwise, the motion information of the preset position is obtained and used as the motion information of the chroma prediction sub-block.

For a YUV4:2:0 image, the coordinate of the luminance image position corresponding to the chroma predictor block is (xC < 1, yC < 1) if the sitting of the chroma predictor block in the chroma image is marked (xC, yC).

And a third method: analyzing the pred_mode_flag bit to determine whether the chroma block uses intra prediction or inter prediction; if the chroma block uses intra prediction, resolving an intra prediction mode from the code stream as the intra prediction mode of the chroma block; if the chroma block uses inter prediction, motion information of a preset position is acquired as the motion information of the chroma block.

The method four: analyzing the pred_mode_flag bit to determine whether the chroma block uses intra prediction or inter prediction; if the chroma block uses intra prediction, analyzing an intra prediction mode from the code stream as the intra prediction mode of the chroma block, wherein the intra prediction mode can be one of a linear model mode and a DM mode, and the luminance intra prediction mode corresponding to the DM mode is set as a plane mode; if the chroma block uses inter prediction, the chroma block is divided into chroma predictor blocks, and the motion information of the chroma predictor blocks is obtained as follows:

The context model adopted when the pred_mode_flag bit is analyzed is a preset model, for example, the model number is 2.

If the prediction mode of the preset position is intra prediction, the chroma block uses intra prediction to analyze an intra prediction mode from the code stream as the intra prediction mode of the chroma block. Or directly determining that the intra prediction mode of the chroma block is one of a direct current mode, a planar mode, an angle mode, a linear model mode, or a DM mode.

If the prediction mode of the preset position is the IBC mode, the chromaticity block predicts by using the IBC mode, and the displacement vector (displacement vector) information of the preset position is obtained as the displacement vector information of the chromaticity block. Or,

if the prediction mode of the preset position is the IBC mode, determining the prediction mode of the chroma block according to the flag bit pred_mode_ IBC _flag:

1) If pred_mode_ IBC _flag is 1, the chroma block uses IBC mode; more specifically, the IBC prediction method of the chroma block may use a method in VTM4.0, i.e., dividing the chroma block into 2x2 sub-blocks, each of which has a displacement vector equal to that of a luminance region corresponding to the sub-block.

2) If pred_mode_ ibc _flag is 0, the chroma block uses an intra prediction mode or an inter prediction mode.

When intra prediction modes are used, syntax elements are parsed from the bitstream to determine intra prediction modes for chroma. Alternatively, the intra-prediction mode of the chroma block is directly determined to be one of a set of intra-prediction modes of chroma, the set of intra-prediction modes of chroma being: direct current mode, planar mode, angular mode, linear model, DM mode.

When the inter prediction mode is used, motion information of a preset position may be acquired as motion information of a chroma block.

It should be noted that, when the pred_mode_ IBC _flag does not exist in the code stream, if the image type where the current node is located is an I frame/I slice and the IBC mode is allowed to be used, the pred_mode_ IBC _flag is defaulted to 1, that is, the chroma block defaults to use the IBC mode; if the picture type is P/B frame/slice, default pred_mode_ ibc _flag is 0.

Wherein, the VTM may determine whether the prediction mode of the preset position is the IBC mode according to information indicated by the syntax element pred_mode_ IBC _flag. For example, pred_mode_ IBC _flag of 1 indicates that IBC prediction mode is used, and 0 indicates that IBC mode is not used. When the pred_mode_ ibc _flag does not occur in the bitstream, the value of pred_mode_ ibc _flag is equal to the value of sps_ ibc _enabled_flag if in the I frame/I slice, and pred_mode_ ibc _flag is 0 if in the P frame/slice, or B frame/slice. Wherein, the sps_ ibc _enabled_flag being 1 indicates that the current picture is allowed to be used as a reference picture in the decoding process of the current picture, and the sps_ ibc _enabled_flag being 0 indicates that the current picture is not allowed to be used as a reference picture in the decoding process of the current picture.

The intra prediction mode of the chroma block may be one of a direct current mode, a planar mode, an angular mode, a linear model (cross-component linear model, CCLM) mode, and a chroma deriving mode (chroma derived mode, DM). Such as direct current mode, planar mode, angular mode, linear model mode, chrominance derived mode in VTM.

Step 90642B specifically includes:

and obtaining the prediction modes in the plurality of brightness blocks of the current node, and determining the prediction modes of the chroma blocks corresponding to the current node by using the following method.

If the plurality of luminance blocks are intra-predicted, the chrominance block uses intra-prediction to parse an intra-prediction mode from the code stream as the intra-prediction mode for the chrominance block.

If the plurality of luma blocks are inter predicted, a prediction mode of chroma is determined using one of the following methods:

the method comprises the following steps: and the chroma block uses inter prediction to acquire motion information of a preset position as the motion information of the chroma block. The preset position has the same meaning as in the first embodiment.

The second method is as follows: analyzing the pred_mode_flag bit to determine whether the chroma block uses intra prediction or inter prediction; if the chroma block uses intra prediction, resolving an intra prediction mode from the code stream as the intra prediction mode of the chroma block; if the chroma block uses inter prediction, motion information of a preset position is acquired as the motion information of the chroma block.

If inter prediction and intra prediction are included in the plurality of luminance blocks, mode information of the chrominance blocks may be determined using one of the following ways:

1) If the prediction mode of the preset position is inter prediction, the chroma block uses inter prediction to acquire the motion information of the preset position as the motion information of the chroma block.

2) If the prediction mode of the preset position is intra prediction, the chroma block uses intra prediction to analyze an intra prediction mode from the code stream as the intra prediction mode of the chroma block. Or directly determining that the intra prediction mode of the chroma block is one of a direct current mode, a planar mode, an angle mode, a linear model mode, or a DM mode.

3) If the prediction mode of the preset position is the IBC mode, the chromaticity block predicts by using the IBC mode, and the displacement vector information of the preset position is obtained as the displacement vector information of the chromaticity block.

4) The prediction mode of the direct specified chromaticity is one of a mode set, which is an AMVP mode, an IBC mode, a skip mode, a direct current mode, a plane mode, an angle mode, a linear model mode, and a DM mode.

Step 90644: residual information of the chroma block is parsed. The residual of the chroma block is contained in one transform unit. The transform type may default to a DCT-2 transform.

Step 908: the current node is divided into sub-nodes, each sub-node containing a luma block and a chroma block. Step 901 is executed for each child node, and the division mode of the child node is continuously analyzed to determine whether each child node (also called node) still needs division.

After obtaining the sub-region division mode of the brightness block and the prediction information and residual information of each sub-region, the inter-prediction processing or the intra-prediction processing can be performed on each sub-region according to the corresponding prediction mode of each sub-region, so as to obtain the inter-prediction image or the intra-prediction image of each sub-region. And then, according to the residual information of each subarea, carrying out inverse quantization and inverse transformation on the transformation coefficient to obtain a residual image, and superposing the residual image on the predicted image of the corresponding subarea to generate a reconstructed image of the brightness block.

After obtaining the prediction information and residual information of the chroma block, the inter prediction process or the intra prediction process can be performed on the chroma block according to the prediction mode of the chroma block, so as to obtain an inter prediction image or an intra prediction image of the chroma block. And then, according to the residual information of the chroma block, carrying out inverse quantization and inverse transformation on the transformation coefficient to obtain a residual image, and superposing the residual image on a predicted image of the chroma block to generate a reconstructed image of the chroma block.

According to the embodiment of the invention, when the chroma block of the current node is not partitioned any more, the method can only partition the luma block of the current node, so that the coding and decoding efficiency can be improved, the maximum throughput rate of a decoder is reduced, and the realization of the decoder is facilitated.

Example two

In contrast to example one, step 9062 adds the following constraints: each luma node (i.e., a sub-node of each luma block) uses the same prediction mode, i.e., each luma node uses intra prediction or each uses inter prediction. Other steps are similar to those of the embodiment and will not be described again.

The same prediction mode is used by each luminance node, and any one of the following methods can be adopted:

the method comprises the following steps: if the current frame is an I frame, each sub-node of the current node defaults to intra-frame prediction; if the current frame is a P frame or a B frame, analyzing the first node (which can be simply called a first sub-node) to obtain the prediction mode of the first node, and defaulting the prediction modes of the other sub-nodes (which are simply called brightness nodes) to the prediction mode of the first node. Or alternatively

The second method is as follows: if the current frame is an I frame, each sub-node of the current node defaults to intra-frame prediction; if the current frame is a P-frame or a B-frame, each child node of the current node defaults to using inter-frame prediction.

Example III

Fig. 11 shows a method flow diagram 1100 of a third embodiment of the invention. Embodiment three is similar to embodiment except for step 1104. Step 1104: judging whether the chromaticity block of the current node is divided or not according to the dividing mode of the current node, the size of the current node and the prediction mode of the first node (which can be simply called a first sub-node) for analyzing the current node, wherein the first sub-node only comprises the brightness block. The plurality of sub-nodes of the current node use the same prediction mode, wherein each sub-node contains only luma blocks.

As to whether the dividing manner of the current node and the size of the current node are determined first or whether the prediction mode of the first child node is determined first, the embodiment of the present invention is not limited.

An embodiment III is based on the embodiment I or the embodiment II, and determines a dividing mode of a current node chroma block and a corresponding prediction information and residual information analysis mode by combining a prediction mode of a first child node of the current node.

In one embodiment, according to the dividing manner of the current node and the size of the current node, it is determined that the sub-nodes generated by dividing the current node include chroma blocks with a side length equal to a first threshold or a side length smaller than a second threshold, and the prediction mode of the first sub-node is intra-frame prediction, then the chroma blocks of the current node are not divided any more. Similar to the embodiment, for example, the first threshold may be 2 and the second threshold may be 4.

In another embodiment, when the prediction mode of the first child node is intra prediction, and when any one of the following conditions 1 to 5 holds:

Condition 1: the width of the current node is 2 times of the second threshold value, and the dividing mode of the current node is vertical bisection; or (b)

Condition 2: the height of the current node is 2 times of the second threshold value, and the dividing mode of the current node is horizontal bisection; or (b)

Condition 3: the width of the current node is equal to 4 times of the second threshold value, and the dividing mode of the current node is vertical three minutes; or (b)

Condition 4: the height of the current node is equal to 4 times of the second threshold value, and the dividing mode of the current node is horizontal three minutes; or (b)

Condition 5: and if the width of the current node is equal to 2 times of the second threshold value and the dividing mode of the current node is quarter, the chromaticity block of the current node is not divided any more.

When the prediction mode of the first sub-node is intra prediction, similar to the first embodiment, in a third implementation manner, it may be determined whether the current node is divided according to the division manner of the current node, and whether a chroma block with a width of a first threshold value is generated (or whether a chroma block with a width smaller than a second threshold value is generated). If it is determined that the sub-node generated by the current node partition includes a chroma block having a width of a first threshold (or includes a chroma block having a width smaller than a second threshold), and the prediction mode of the first sub-node is intra-prediction, the chroma block of the current node is not partitioned. For example, the first threshold may be 2 and the second threshold may be 4.

When the prediction mode of the first sub-node is intra prediction, similar to the first embodiment, in a fourth implementation, it may be determined whether the current node is divided according to the dividing manner of the current node, and a number of chroma pixels of the chroma block is less than a third threshold. If the sub-node generated by the current node partition is judged to contain the chroma blocks with the number of chroma pixels less than the third threshold value, and the prediction mode of the first sub-node is intra-frame prediction, the chroma blocks of the current node are not partitioned. For example, the third threshold may be 16. Chroma blocks with a number of chroma pixels less than 16 include, but are not limited to, 2x2 chroma blocks, 2x4 chroma blocks, 4x2 chroma blocks. The third threshold may be 8. Then a chroma block with a chroma pixel number less than 8 includes, but is not limited to, a 2x2 chroma block.

When the prediction mode of the first sub-node is intra prediction, similar to the first embodiment, in a fifth implementation manner, it may be determined whether the current node generates a chroma block with a height of the first threshold (or generates a chroma block with a height of less than the second threshold) according to the partition manner of the current node. If it is determined that the sub-node generated by the current node partition includes a chroma block that is higher than a first threshold (or includes a chroma block that is higher than a second threshold), and the prediction mode of the first sub-node is intra-prediction, the chroma block of the current node is not partitioned. For example, the first threshold may be 2 and the second threshold may be 4.

If the chroma block of the current node is not divided, the chroma block of the current node becomes a coding unit including only the chroma block. The method 1100 may further include obtaining prediction information and/or residual information for the chroma block.

In another embodiment, according to the dividing manner of the current node and the size of the current node, determining that the sub-node generated by dividing the current node includes a chroma block with a side length smaller than a threshold, and if the prediction mode of the first sub-node is inter-frame prediction, dividing the chroma block of the current node according to the dividing manner of the current node. Optionally, the motion information of the corresponding sub-node of the chroma block is determined according to the motion information of the sub-node of the current node. For example, the motion information of the sub-nodes of the chroma block of the current node may be set to the motion information of the corresponding luma node (i.e., the motion information of each sub-node of the chroma block does not need to be parsed from the code stream). And respectively analyzing residual information of the sub-nodes of the chroma block to obtain the residual information of each sub-node of the chroma block.

When the prediction mode of the first child node is inter prediction, and any one of the following conditions is satisfied:

Condition 5: the width of the current node is equal to 2 times of the second threshold value, and the dividing mode of the current node is four, the chromaticity block of the current node still needs to be divided.

In the third embodiment, the dividing mode of the chroma block, the corresponding prediction information and residual information analysis mode can be determined according to the prediction mode of the luma node, so that the method has stronger flexibility. And when the prediction mode of the brightness node is intra-frame prediction, the chroma block of the current node is not divided, so that the chroma coding and decoding efficiency can be improved, the maximum throughput rate of a decoder is reduced, and the realization of the decoder is facilitated.

It should be understood that the disclosure in connection with the described methods may be equally applicable to a corresponding apparatus or system for performing the methods, and vice versa. For example, if one or more specific method steps are described, the corresponding apparatus may comprise one or more units, such as functional units, to perform the one or more described method steps (e.g., one unit performing one or more steps, or multiple units each performing one or more of the multiple steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, if a specific apparatus is described based on one or more units such as a functional unit, for example, the corresponding method may include one step to perform the functionality of the one or more units (e.g., one step to perform the functionality of the one or more units, or multiple steps each to perform the functionality of one or more units, even if such one or more steps are not explicitly described or illustrated in the figures). Further, it is to be understood that features of the various exemplary embodiments and/or aspects described herein may be combined with each other, unless explicitly stated otherwise.

In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium, and executed by a hardware-based processing unit. A computer-readable medium may comprise a computer-readable storage medium corresponding to a tangible medium, such as a data storage medium or a communication medium, such as any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, a computer-readable medium may generally correspond to (1) a non-transitory tangible computer-readable storage medium, or (2) a communication medium, such as a signal or carrier wave. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and/or data structures for implementing the techniques described in this disclosure. The computer program product may include a computer-readable medium.

By way of example, and not limitation, such computer-readable storage media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (digital subscriber line, DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It should be understood, however, that the computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but are actually directed to non-transitory tangible storage media. Disk and disc, as used herein, includes Compact Disc (CD), laser disc, optical disc, digital versatile disc (digital versatile disc, DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

The instructions may be executed by one or more processors, such as one or more digital signal processors (digital signal processor, DSPs), general purpose microprocessors, application specific integrated circuits (application specific integrated circuit, ASICs), field programmable logic arrays (field programmable logic arrays, FPGAs), or other equivalent integrated or discrete logic circuitry. Thus, the term "processor" as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. Additionally, in some aspects, the functionality described herein may be provided within dedicated hardware and/or software modules for encoding and decoding, or incorporated in a synthetic codec. Also, the techniques may be fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a variety of devices or apparatuses including a wireless handset, an integrated circuit (integrated circuit, IC), or a collection of ICs (e.g., a chipset). The disclosure describes various components, modules, or units in order to emphasize functional aspects of the apparatus for performing the disclosed techniques, but does not necessarily require realization by different hardware units. In particular, as described above, the various units may be combined in a codec hardware unit in combination with suitable software and/or firmware, or provided by a collection of interoperable hardware units, including one or more processors as described above.

Claims

1. An image dividing method, comprising:

determining a dividing mode of a current node, wherein the current node comprises a brightness block and a chromaticity block;

determining that the chromaticity block of the current node is not divided any more according to the dividing mode of the current node and the size of the current node; and

when the chromaticity block of the current node is not divided any more, dividing the brightness block of the current node according to the dividing mode of the current node;

when the product of the width and the height of the current node is less than 128 and the current node is divided into vertical bisection or horizontal bisection, or

When the product of the width and the height of the current node is less than 256 and the dividing mode of the current node is vertical three-way or horizontal three-way, or

When the product of the width and the height of the current node is equal to 64 and the current node is divided into vertical bisection or horizontal trisection or vertical trisection, or

When the product of the width and the height of the current node is equal to 128 and the current node is divided in a vertical trisection or a horizontal trisection,

it is determined that the chroma block of the current node is not subdivided.

2. The method of claim 1, wherein the determining that the chroma block of the current node is no longer partitioned specifically comprises:

And determining that the child nodes generated by dividing the current node contain chroma blocks with side lengths smaller than a threshold value according to the dividing mode of the current node and the size of the current node, and determining that the chroma blocks of the current node are not divided.

3. The method of claim 1, wherein,

when the width of the current node is equal to 2 times of the threshold value and the dividing mode of the current node is vertical bisection, or

When the height of the current node is equal to 2 times of the threshold value and the dividing mode of the current node is horizontal bisection, or

When the width of the current node is equal to 4 times of the threshold value and the dividing mode of the current node is vertical three minutes, or

When the height of the current node is equal to 4 times of the threshold value and the dividing mode of the current node is horizontal three minutes, or

When the width of the current node is equal to 2 times the threshold and the current node is divided in four ways,

it is determined that the chroma block of the current node is not subdivided.

4. A method according to any one of claims 1 to 3, wherein the luminance blocks of the current node are divided in accordance with the division of the current node, so as to obtain sub-nodes of the current node, each sub-node comprising only luminance blocks.

5. The method of claim 4, wherein the method further comprises:

analyzing the brightness block of the current node, and acquiring prediction information and residual information of each subarea in the brightness block, wherein the subareas are in one-to-one correspondence with the child nodes.

6. The method of claim 4, wherein the child nodes are not subdivided by default, each child node corresponding to a coding unit containing only luma blocks.

7. A method according to any one of claims 1-3, wherein the method further comprises:

and when the chroma block of the current node is not divided any more, acquiring a prediction mode of the chroma block.

8. The method of claim 7, wherein the prediction mode of the chroma block of the current node is determined according to the prediction mode of the luma block in the preset position of the current node.

9. The method of claim 8, wherein when the prediction mode used by the luminance block in the preset position is an inter prediction mode, then:

the chroma block of the current node uses an inter prediction mode; or alternatively

And analyzing a first zone bit, and determining the prediction mode of the chroma block according to the first zone bit.

10. The method of claim 9, wherein when the chroma block of the current node uses inter prediction mode, then:

acquiring motion information of a luminance block at a preset position as motion information of the chrominance block; or alternatively

Dividing the chroma block into chroma prediction sub-blocks, and obtaining the motion information of the chroma prediction sub-blocks.

11. The method of claim 9, wherein when it is determined that the chroma block uses an intra prediction mode according to the first flag bit, parsing an intra prediction mode from a bitstream as the intra prediction mode of the chroma block; or alternatively

When the chroma block is determined to use an inter prediction mode according to the first flag bit, acquiring the motion information of the luma block at the preset position as the motion information of the chroma block; or alternatively

And when the chroma block is determined to use the inter prediction mode according to the first flag bit, dividing the chroma block into chroma prediction sub-blocks, and obtaining the motion information of the chroma prediction sub-blocks.

12. The method of claim 10 or 11, wherein the obtaining motion information of the chroma predictor block comprises:

If the luminance block of the luminance image position corresponding to the chrominance prediction sub-block adopts inter prediction, the motion information of the luminance image position corresponding to the chrominance prediction sub-block is used as the motion information of the chrominance prediction sub-block;

otherwise, acquiring motion information of a preset position as the motion information of the chroma prediction sub-block.

13. The method of claim 8, wherein when the prediction mode used by the luminance block in the preset position is an intra prediction mode, then the chrominance block of the current node uses the intra prediction mode.

14. The method of claim 13, wherein an intra prediction mode is parsed from the bitstream as an intra prediction mode of a chroma block of the current node; or alternatively

The intra-frame prediction mode of the chroma block of the current node is one of a direct current mode, a planar mode, an angle mode, a linear model mode or a chroma derived DM mode.

15. The method of claim 8, wherein when the prediction mode used by the luminance block in the preset position is an intra block copy IBC mode, then:

the chromaticity block of the current node uses an IBC prediction mode; or,

And analyzing a second zone bit, and determining the prediction mode of the chroma block according to the second zone bit.

16. The method of claim 15, wherein when the chroma block of the current node uses IBC prediction mode, the method further comprises: and acquiring displacement vector (displacement vector) information of the luminance block at the preset position as displacement vector information of the chrominance block of the current node.

17. The method of claim 15, wherein the chroma block uses IBC mode if the value of the second flag bit is a first value; or alternatively

If the value of the second flag bit is a second value, the chroma block uses an intra prediction mode; or alternatively

And if the value of the second flag bit is a second value, the chroma block uses an inter prediction mode.

18. The method of claim 7, wherein the method comprises:

obtaining prediction modes of the divided brightness blocks;

and determining the prediction mode of the chroma block of the current node according to the prediction modes of the divided multiple brightness blocks.

19. The method of claim 18, wherein when the prediction mode used by the plurality of luma blocks is an intra prediction mode, then the chroma block of the current node uses the intra prediction mode.

20. The method of claim 18, wherein when the prediction mode used by the plurality of luminance blocks is an inter prediction mode, and when the chroma block of the current node uses the inter prediction mode, motion information of a luminance block at a preset position is used as the motion information of the chroma block of the current node; or alternatively

And when the prediction modes used by the plurality of luminance blocks are inter prediction modes, analyzing a first zone bit, and determining the prediction modes of the chrominance blocks according to the first zone bit.

21. The method of claim 20, wherein when it is determined that the chroma block uses the intra prediction mode according to the first flag bit, parsing an intra prediction mode from a bitstream as the intra prediction mode of the chroma block; or alternatively

And when the chroma block is determined to use the inter prediction mode according to the first flag bit, acquiring the motion information of the brightness block at a preset position as the motion information of the chroma block.

22. The method of claim 18, wherein when the prediction modes used by the plurality of luminance blocks include an inter prediction mode and an intra prediction mode, then obtaining a prediction mode of a luminance block in a preset position of the current node as a prediction mode of a chrominance block of the current node.

23. A method according to any one of claims 1-3, wherein if the current node is a P-frame or a B-frame, a first sub-node is parsed to obtain a prediction mode of the first sub-node, and the prediction modes of the remaining sub-nodes are the same as the prediction mode of the first sub-node, wherein the first sub-node is the first node to parse.

24. A method according to any of claims 1-3, wherein each child node of the current node uses intra-prediction mode if the current node is an I-frame; or if the current node is a P frame or a B frame, each sub-node of the current node uses an inter-prediction mode.

25. A method according to any one of claim 1 to 3,

according to the dividing mode of the current node, the size of the current node and the prediction mode of a first sub-node of the current node, determining that the chromaticity block of the current node is not divided any more, wherein the first sub-node only comprises a brightness block, and the first sub-node is a first node for analyzing.

26. The method of claim 25, wherein the sub-nodes generated by dividing the current node are determined to include chroma blocks with side lengths smaller than a threshold according to the dividing manner of the current node and the size of the current node, and the prediction mode of the first sub-node is an intra prediction mode, the chroma blocks of the current node are not divided any more.

27. The method of claim 26, wherein when the prediction mode of the first child node is intra prediction, and any of the following conditions are met:

the chroma block of the current node is no longer partitioned.

28. A method according to any one of claims 1-3, wherein the sub-nodes generated by dividing the current node are determined to include chroma blocks with side lengths smaller than a threshold according to the dividing manner of the current node and the size of the current node, and if the prediction mode of the first sub-node is inter-frame prediction, the chroma blocks of the current node are divided according to the dividing manner of the current node, wherein the first sub-node is the first node for parsing.

29. The method of claim 28, wherein the method further comprises:

and determining the motion information of the corresponding sub-node of the chroma block according to the motion information of the sub-node of the current node.

30. A method according to any one of claims 1-3, wherein the determination that the sub-nodes generated by dividing the current node contain chroma blocks having a width smaller than a threshold value is based on the dividing method of the current node and the size of the current node, and the determination that the chroma blocks of the current node are not divided.

31. A method according to any one of claims 1-3, wherein the determination that the sub-node generated by dividing the current node contains a chroma block having a chroma pixel number less than 16 is based on the dividing method of the current node and the size of the current node, and the determination that the chroma block of the current node is not divided.

32. A method as claimed in claim 2,3, 26, 27, 28 or 30, wherein the threshold is 4.

33. An apparatus for decoding a video stream, comprising a processor and a memory, the memory storing instructions that cause the processor to perform the method of any of claims 1-32.

34. An apparatus for encoding a video stream, comprising a processor and a memory, the memory storing instructions that cause the processor to perform the method of any of claims 1-10, 12-13, 15-20, 22-32.

35. A decoding apparatus comprising: a non-volatile memory and a processor coupled to each other, the memory for storing program instructions that cause the processor to perform the method of any of claims 1-32.

36. An encoding apparatus, comprising: a non-volatile memory and a processor coupled to each other, the memory for storing program instructions that cause the processor to perform the method of any one of claims 1-10, 12-13, 15-20, 22-32.