CN110868590A

CN110868590A - Image dividing method and device

Info

Publication number: CN110868590A
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: 2020-03-06
Anticipated expiration: 2039-03-13
Also published as: CN110868590B; CN116193146A

Abstract

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

Description

Image dividing method and device

Technical Field

The present invention relates to the field of video encoding and decoding, and more particularly, to a method and apparatus for image partitioning (pictepristration).

Background

With the rapid development of internet science and technology and the increasing abundance of human physical and mental culture, the application requirements for videos in the internet, particularly high-definition videos, are more and more, the data volume of the high-definition videos is very large, and the problem that the video coding and decoding must be firstly solved for the high-definition videos to be transmitted in the internet with limited bandwidth is the video coding and decoding problem. Video codecs are widely used in digital video applications such as broadcast digital television, video dissemination 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 mode may include an intra prediction mode (spatial prediction) and an inter prediction mode (temporal prediction). Wherein, the intra prediction mode set may include 35 different intra prediction modes, for example, non-directional modes such as DC (or mean) mode and planar mode; or a directivity pattern as defined in h.265; or may include 67 different intra prediction modes, e.g., non-directional modes such as DC (or mean) mode and planar 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 portion of the reference picture is used.

Conventional video is generally color video, and includes a chrominance component in addition to a luminance component. Therefore, in addition to the encoding and decoding of the luminance component, the encoding and decoding of the chrominance component are required. However, the coding and decoding efficiency in the prior art is low.

Disclosure of Invention

The embodiment of the application (or the disclosure) provides an image dividing device and method.

In a first aspect, embodiments of the present invention relate to a method for image partitioning. The method is performed by an apparatus for decoding a video stream or encoding a video stream. The method comprises the steps of determining a dividing mode of a current node, wherein the current node comprises a brightness block and a chrominance block; determining that the chroma 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 chroma block of the current node is not divided, dividing the brightness block of the current node according to the dividing mode of the current node.

In the method of the first aspect, when the chroma block of the current node is not divided, the method may only divide the luma block of the current node, thereby improving the codec efficiency, reducing the maximum throughput of the codec, and facilitating implementation of the codec.

In a second aspect, an embodiment of the invention is directed to an apparatus 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 invention are directed 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 is presented having instructions stored thereon that, when executed, cause one or more processors to encode video data. The instructions cause the one or more processors to perform a method according to any of the possible embodiments of the first aspect.

In a fifth aspect, embodiments of the invention relate to a computer program comprising program code for performing a method according to any of the possible embodiments of the first aspect when the program code runs 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 illustrate the technical solutions in the embodiments or the background art of the present application, the drawings required to be used in the embodiments or the background art of the present application will be described below.

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

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

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

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

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

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

fig. 6 shows an example YUV format sampling grid;

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

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

FIG. 9 is a flow chart of a method according to a first embodiment of the present invention;

FIG. 10 is a flowchart of step 906 of a first embodiment of the present invention;

fig. 11 shows a flowchart of a method of a third embodiment of the invention.

In the following, identical reference signs refer to identical or at least functionally equivalent features, if no specific remarks are made with respect to the identical reference signs.

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 compressing) the original video picture to reduce the amount of data required to represent the video picture for more efficient storage and/or transmission. Video decoding is performed at the destination side, typically involving inverse processing with respect to the encoder, to reconstruct the video pictures. Embodiments are directed to video picture "encoding" to be understood as referring to "encoding" or "decoding" of a video sequence. The combination of the encoding part and the decoding part 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 (the currently processed or to be processed block) to obtain a residual block, transforms the residual block and quantizes the residual block in the transform domain to reduce the amount of data to be transmitted (compressed), while the decoder side applies the inverse processing portion relative to the encoder to the encoded or compressed block to reconstruct the current block for representation. In addition, the encoder replicates the decoder processing loop such that the encoder and decoder generate the same prediction (e.g., intra-prediction and inter-prediction) and/or reconstruction for processing, i.e., encoding, subsequent blocks.

The term "block" may be a portion of a picture or frame. The present application defines key terms as follows:

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

And (3) CTU: a coding tree unit (coding tree unit), one image is composed of a plurality of CTUs, one CTU generally corresponds to a square image region, and includes luminance pixels and chrominance pixels (or may include only luminance pixels, or may include only chrominance pixels) in the image region; syntax elements are also included in the CTU that indicate how the CTU is divided into at least one Coding Unit (CU), and the method of decoding each coding unit resulting in a reconstructed picture.

CU: the coding unit, which generally corresponds to an a × B rectangular region, includes 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 a and B generally take values to the power of 2, i.e. 256, 128, 64, 32, 16, 8, 4. An encoding unit can decode to obtain a reconstructed image of an A × B rectangular region through decoding processing, wherein the decoding processing generally comprises prediction, inverse quantization, inverse transformation and the like, predicted images and residual errors are generated, and the predicted images and the residual errors are superposed to obtain the reconstructed image.

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

Fig. 1A is a conceptual or schematic block diagram depicting an exemplary encoding system 10, such as a video encoding system 10 that may utilize the techniques of the present application (the present disclosure). Encoder 20 (e.g., video encoder 20) and decoder 30 (e.g., video decoder 30) of video encoding system 10 represent examples of equipment that may be used to perform intra prediction according to various examples described in this application. 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 that decodes encoded data 13, for example.

Source device 12 includes an encoder 20 and, in a further alternative, may include a picture source 16, a pre-processing unit 18, such as picture pre-processing unit 18, and a communication interface or unit 22.

The picture source 16 may include or may be any type of picture capture device for capturing real-world pictures, for example, and/or any type of picture or comment generation device (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 obtaining and/or providing real-world pictures, computer animated pictures (e.g., screen content, Virtual Reality (VR) pictures), and/or any combination thereof (e.g., Augmented Reality (AR) pictures).

A picture can be seen as a two-dimensional array or matrix of sample points having intensity values. The sample points in the array may also be referred to as pixels (short for pixels) or pels (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 the RBG format or color space, a picture includes corresponding red, green, and blue sampling arrays. However, in video coding, each pixel is typically represented in a luminance/chrominance format or color space, e.g., YCbCr, comprising a luminance component (sometimes also indicated by L) indicated by Y and two chrominance components indicated by Cb and Cr. The luminance (luma) component Y represents the luminance or gray level intensity (e.g. both are the same in a gray scale 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 luminance sample array of luminance sample values (Y), and two chrominance sample arrays of chrominance 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 luminance 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 store, any type of (internal or external) interface that includes or stores previously captured or generated pictures, and/or obtains or receives pictures. The camera may be, for example, an integrated camera local or integrated in the source device, and the memory may be an integrated memory local or integrated in the source device, for example. The interface may be, for example, an external interface that receives pictures from an external video source, for example, an external picture capturing device such as a camera, an external memory, or an external picture generating device, for example, an external computer graphics processor, computer, or 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 for obtaining picture data 17 may be the same interface as communication interface 22 or part of communication interface 22.

Unlike pre-processing unit 18 and the processing performed by pre-processing unit 18, picture or picture data 17 (e.g., video data 16) may also be referred to as raw picture or raw picture data 17.

Pre-processing unit 18 is configured to receive (raw) picture data 17 and perform pre-processing on picture data 17 to obtain a pre-processed picture 19 or pre-processed picture data 19. For example, the pre-processing performed by pre-processing unit 18 may include trimming, color format conversion (e.g., from RGB to YCbCr), toning, or denoising. It is to be understood that the pre-processing unit 18 may be an optional component.

Encoder 20, e.g., video encoder 20, is used to receive pre-processed picture data 19 and provide encoded picture data 21 (details will be 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.

Communication interface 22 of source device 12 may be used to receive encoded picture data 21 and transmit to other devices, e.g., destination device 14 or any other device for storage or direct reconstruction, or to process encoded picture data 21 prior to correspondingly storing encoded data 13 and/or transmitting encoded data 13 to other devices, e.g., destination device 14 or any other device for decoding or storage.

Destination device 14 includes a decoder 30 (e.g., a video decoder 30), and may additionally, that is, optionally, include a communication interface or unit 28, a post-processing unit 32, and a display device 34.

Communication interface 28 of destination device 14 is used, for example, to receive encoded picture data 21 or encoded data 13 directly from source device 12 or any other source, such as a storage device, such as 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 by way of a direct communication link between source device 12 and destination device 14, such as a direct wired or wireless connection, or by way of 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.

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

Communication interface 28, which forms a corresponding part of communication interface 22, may for example be used to decapsulate encoded data 13 to obtain encoded picture data 21.

Both communication interface 22 and communication interface 28 may be configured as a unidirectional communication interface, as indicated by the arrow from source device 12 to destination device 14 for encoded picture data 13 in fig. 1A, or as a bidirectional communication interface, and may be used, for example, to send and receive messages to establish a connection, acknowledge and exchange any other information related to a communication link and/or a data transmission, e.g., an 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, the decoder 30 may be used to perform the following embodiments one through three.

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

Display device 34 of destination device 14 is used to receive post-processed picture data 33 to display a picture to, for example, a user or viewer. Display device 34 may be or may include any type of display for presenting the reconstructed picture, such as an integrated or external display or monitor. For example, the display may include a Liquid Crystal Display (LCD), an Organic Light Emitting Diode (OLED) display, a plasma display, a projector, a micro LED display, a liquid crystal on silicon (LCoS), a Digital Light Processor (DLP), or any other display of any kind.

Although fig. 1A depicts source apparatus 12 and destination apparatus 14 as separate apparatuses, an apparatus embodiment may also include the functionality of both source apparatus 12 and destination apparatus 14 or both, i.e., source apparatus 12 or corresponding functionality and destination apparatus 14 or corresponding functionality. In such embodiments, source device 12 or corresponding functionality and 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 existence and (exact) division of the functionality of the different elements, or source device 12 and/or destination device 14 as 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 (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), 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 included in one or more encoders or decoders, either of which may be integrated as part of a combined encoder/decoder (codec) in a corresponding device.

Source device 12 may be referred to as a video encoding device or a video encoding apparatus. Destination device 14 may be referred to as a video decoding device or a video decoding apparatus. Source device 12 and 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, a mobile phone, a smart phone, a tablet or tablet computer, a camcorder, a desktop computer, a set-top box, a television, a display device, a digital media player, a video game console, a video streaming device (e.g., a content service server or a content distribution server), a broadcast receiver device, a 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, source device 12 and 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 application may be applicable to video encoding settings (e.g., video encoding or video decoding) that do not necessarily involve any data communication between the encoding and decoding devices. In other examples, the data may be retrieved from local storage, streamed over a network, and so on. A video encoding device may encode and store data to a memory, and/or a video decoding device may retrieve and decode data from a memory. In some examples, the encoding and decoding are performed by devices that do not communicate with each other, but merely encode data to and/or retrieve data from memory and decode data.

It should be understood 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. With respect to 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 instances, 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. 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, video encoder 20, video decoder 30 (and/or a video encoder implemented by logic 47 of processing unit 46), an antenna 42, one or more processors 43, one or more memories 44, and/or a display device 45.

As shown, the imaging device 41, the antenna 42, the processing unit 46, the logic circuit 47, the video encoder 20, the video decoder 30, the processor 43, the memory 44, and/or the 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. Display device 45 may be used to present video data. In some examples, logic 47 may be implemented by processing unit 46, as shown. The processing unit 46 may comprise application-specific integrated circuit (ASIC) logic, a graphics processor, a general-purpose processor, or the like. Video coding system 40 may also include an optional processor 43, which optional processor 43 similarly may include application-specific integrated circuit (ASIC) logic, a graphics processor, a general-purpose processor, or the like. In some examples, the logic 47 may be implemented in hardware, such as video encoding specific hardware, and the processor 43 may be implemented in general purpose software, an operating system, and so on. In addition, the Memory 44 may be any type of Memory, such as a volatile Memory (e.g., Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), etc.), a nonvolatile Memory (e.g., flash Memory, etc.), and the like. In a non-limiting example, storage 44 may be implemented by a speed cache memory. In some instances, logic circuitry 47 may access memory 44 (e.g., to implement an image buffer). In other examples, logic 47 and/or processing unit 46 may include memory (e.g., cache, etc.) for implementing image buffers, 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 circuitry 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, logic circuit implemented video decoder 30 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 circuitry 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 encoding partition (e.g., transform coefficients or quantized transform coefficients, (as discussed) optional indicators, and/or data defining the encoding partition). Video encoding system 40 may also include a video decoder 30 coupled to antenna 42 and configured to decode the encoded bitstream. The display device 45 is used to present video frames.

Encoder and 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. In the example of fig. 2, video encoder 20 includes a residual calculation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210, an inverse transform processing unit 212, a reconstruction unit 214, a buffer 216, a loop filter unit 220, a Decoded Picture Buffer (DPB) 230, a prediction processing unit 260, and an entropy encoding unit 270. Prediction processing unit 260 may include inter prediction unit 244, intra prediction unit 254, and mode selection unit 262. 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, and, 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 (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 a signal path of a decoder (see the decoder 30 in fig. 3).

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

Segmentation

An embodiment of encoder 20 may include a partitioning unit (not shown in fig. 2) for partitioning picture 201 into a plurality of blocks, such as block 203, typically into a plurality of non-overlapping blocks. The partitioning unit may be used to use the same block size for all pictures in a 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 partition each picture into corresponding blocks.

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

Like picture 201, block 203 is also or can be viewed as a two-dimensional array or matrix of sample points having intensity values (sample values), although smaller in size than picture 201. In other words, the block 203 may comprise, for example, one sample array (e.g., a luma array in the case of a black and white picture 201) or three sample arrays (e.g., a luma array and two chroma arrays in the case of a color picture) 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., performing encoding and prediction for 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), e.g. by subtracting sample values of the picture block 203 from sample values of the prediction block 265 on a sample-by-sample (pixel-by-pixel) basis to obtain the residual block 205 in the sample domain.

Transformation of

The transform processing unit 206 is configured to apply a transform, such as a Discrete Cosine Transform (DCT) or a Discrete Sine Transform (DST), on the sample values of the residual block 205 to obtain transform coefficients 207 in a 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 transform specified for HEVC/h.265. Such integer approximations are typically scaled by some factor compared to the orthogonal DCT transform. To maintain the norm of the residual block processed by the forward transform and the inverse transform, an additional scaling factor is applied as part of the transform process. The scaling factor is typically selected based on certain constraints, e.g., the scaling factor is a power of 2 for a shift operation, a trade-off between bit depth of transform coefficients, accuracy and implementation cost, etc. For example, a specific scaling factor may be specified on the decoder 30 side for the inverse transform by, for example, inverse transform processing unit 212 (and on the encoder 20 side for the corresponding inverse transform by, for example, inverse transform processing unit 212), and correspondingly, a corresponding scaling factor may be specified on the encoder 20 side for the forward transform by transform processing unit 206.

Quantization

Quantization unit 208 is used to quantize transform coefficients 207, e.g., by applying scalar quantization or vector quantization, to obtain quantized transform coefficients 209. 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 transform coefficients 207. For example, an n-bit transform coefficient may be rounded down to an m-bit transform coefficient during quantization, where n is greater than m. The quantization level may be modified by adjusting a Quantization Parameter (QP). For example, for scalar quantization, different scales may be applied to achieve finer or coarser quantization. Smaller quantization steps correspond to finer quantization and larger quantization steps correspond to coarser quantization. An appropriate quantization step size may be indicated by a Quantization Parameter (QP). For example, the quantization parameter may be an index of a predefined set of suitable quantization step sizes. For example, a smaller quantization parameter may correspond to a fine quantization (smaller quantization step size) and a larger quantization parameter may correspond to a coarse quantization (larger quantization step size), or vice versa. The quantization may comprise a division by a quantization step size and a corresponding quantization or inverse quantization, e.g. performed by inverse quantization 210, or may comprise a multiplication by a quantization step size. Embodiments according to some standards, such as HEVC, may use a quantization parameter to determine the quantization step size. In general, the quantization step size may be calculated based on the quantization parameter using a fixed point approximation of an equation that includes division. Additional scaling factors may be introduced for quantization and dequantization to recover the norm of the residual block that may be modified due to the scale used in the fixed point approximation of the equation for the quantization step size and quantization parameter. In one example implementation, the inverse transform and inverse quantization 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 greater 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., to apply an inverse quantization scheme of the quantization scheme applied by the quantization unit 208 based on or using the same quantization step as the quantization unit 208. The dequantized coefficients 211 may also be referred to as dequantized residual coefficients 211, corresponding to transform coefficients 207, although the loss due to quantization is typically not the same as 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 (DCT) or an inverse 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 transform dequantized block 213 or an inverse transform residual block 213.

The reconstruction unit 214 (e.g., 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 (or simply "buffer" 216), such as a line buffer 216, is used to buffer or store the reconstructed block 215 and corresponding sample values, for example, for intra prediction. In other embodiments, the encoder may be used to use the unfiltered reconstructed block and/or corresponding sample values stored in buffer unit 216 for any class of estimation and/or prediction, such as intra prediction.

For example, an embodiment 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 filtered block 221 and/or blocks or samples from decoded picture buffer 230 (neither shown in fig. 2) as input or basis for 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, so as to facilitate pixel transition or improve video quality. Loop filter unit 220 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 (ALF), or a sharpening or smoothing filter, or a collaborative filter. 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. The decoded picture buffer 230 may store the reconstructed encoded block after the loop filter unit 220 performs a filtering operation on the reconstructed encoded block.

Embodiments of encoder 20 (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 (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 from any of a variety of memory devices, such as Dynamic Random Access Memory (DRAM) including Synchronous DRAM (SDRAM), Magnetoresistive RAM (MRAM), Resistive RAM (RRAM), or other types of memory devices. The DPB 230 and the buffer 216 may be provided by the same memory device or separate memory devices. In a certain example, a Decoded Picture Buffer (DPB) 230 is used to store filtered blocks 221. Decoded picture buffer 230 may further be used to store other previous filtered blocks, such as previous reconstructed and filtered blocks 221, of the same current picture or of a different picture, such as a previous reconstructed picture, and may provide the complete previous reconstructed, i.e., decoded picture (and corresponding reference blocks and samples) and/or the partially reconstructed current picture (and corresponding reference blocks and samples), e.g., for inter prediction. In a certain example, if reconstructed block 215 is reconstructed without in-loop filtering, Decoded Picture Buffer (DPB) 230 is used to store reconstructed block 215.

Prediction processing unit 260, also referred to as block prediction processing unit 260, is used to receive or obtain block 203 (current block 203 of current picture 201) and reconstructed picture 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 prediction block 265, which may be inter-predicted block 245 or intra-predicted 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 prediction modes (e.g., from those supported by prediction processing unit 260) that provide the best match or the smallest residual (smallest residual means better compression in transmission or storage), or that provide the smallest signaling overhead (smallest signaling overhead means better compression in transmission or storage), or both. The mode selection unit 262 may be configured to determine a prediction mode based on Rate Distortion Optimization (RDO), i.e., select a prediction mode that provides the minimum rate distortion optimization, or select a prediction mode in which the associated rate distortion at least meets the prediction mode selection criteria.

The prediction processing performed by the example of the encoder 20 (e.g., by the prediction processing unit 260) and the mode selection performed (e.g., by the 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 set of (predetermined) prediction modes. The prediction mode set may include, for example, intra prediction modes and/or inter prediction modes.

The intra prediction mode set may include 35 different intra prediction modes, or may include 67 different intra prediction modes, or may include an intra prediction mode defined in h.266 under development.

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

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

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

The inter prediction unit 244 may include a Motion Estimation (ME) unit (not shown in fig. 2) and a Motion Compensation (MC) unit (not shown in fig. 2). The motion estimation unit is used to receive or obtain picture block 203 (current picture block 203 of current picture 201) and 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 comprise 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 forming the video sequence.

For example, the encoder 20 may be configured to select a reference block from a plurality of reference blocks of the same or different one 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 the current block to a motion estimation unit (not shown in fig. 2) as an inter prediction parameter. This offset is also called a Motion Vector (MV).

The motion compensation unit is used to obtain, e.g., 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 taking or generating a prediction block based on a motion/block vector determined by motion estimation (possibly performing interpolation to sub-pixel precision). Interpolation filtering may generate additional pixel samples from known pixel samples, potentially increasing the number of candidate prediction blocks that may be used to encode 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 in one reference picture list to which the motion vector points. Motion compensation unit 246 may also generate syntax elements associated with the blocks and video slices for use by video decoder 30 in decoding picture blocks of the video slices.

The intra prediction unit 254 is used to obtain, e.g., receive, the picture block 203 (current picture block) of the same picture and one or more previously reconstructed blocks, e.g., reconstructed neighboring blocks, for intra estimation. For example, encoder 20 may be used 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., an intra prediction mode that provides a prediction block 255 that is most similar to current picture block 203) or a minimum code rate distortion.

The intra-prediction unit 254 is further configured to determine the intra-prediction block 255 based on the intra-prediction parameters as the selected intra-prediction mode. In any case, after selecting the intra-prediction mode for the block, intra-prediction unit 254 is also used to provide intra-prediction parameters, i.e., information indicating the selected intra-prediction mode for the block, to 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.

Entropy encoding unit 270 is configured to apply an entropy encoding algorithm or scheme (e.g., a Variable Length Coding (VLC) scheme, a Context Adaptive VLC (CAVLC) scheme, an arithmetic coding scheme, a Context Adaptive Binary Arithmetic Coding (CABAC), syntax-based context-adaptive binary arithmetic coding (SBAC), Probability Interval Partition Entropy (PIPE) coding, or other entropy encoding methods or techniques) to individual or all of 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 output 272 in the form of, for example, 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 quantize the residual signal directly without the 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 the present application. Video decoder 30 is operative to receive encoded picture data (e.g., an encoded bitstream) 21, e.g., encoded by encoder 20, to obtain a 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 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), such as any or all of inter-prediction, intra-prediction parameters, loop filter parameters, and/or other syntax elements (decoded). The entropy decoding unit 304 is further for forwarding the inter-prediction parameters, the intra-prediction parameters, and/or other syntax elements to the prediction processing unit 360. Video decoder 30 may receive syntax elements at the video slice 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.

Prediction processing unit 360 may include inter prediction unit 344 and intra prediction unit 354, where inter prediction unit 344 may be functionally similar to inter prediction unit 244 and intra prediction unit 354 may be functionally similar to 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 (explicitly or implicitly) prediction related parameters and/or information about the selected prediction mode from, for example, the entropy decoding unit 304.

When the video slice is encoded as an intra-coded (I) slice, intra-prediction unit 354 of prediction processing unit 360 is used to generate a prediction block 365 for the picture block of the current video slice based on the signaled intra-prediction mode and data from previously decoded blocks of the current frame or picture. When a video frame is encoded as an inter-coded (i.e., B or P) slice, inter prediction unit 344 (e.g., a motion compensation unit) of prediction processing unit 360 is used to generate a prediction block 365 for the video block of the current video slice based on the motion vectors 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 the reference frame list using default construction techniques based on the reference pictures stored in DPB 330: list 0 and list 1.

Prediction processing unit 360 is used to determine prediction information for the video blocks of the current video slice by parsing the motion vectors and other syntax elements, and to generate a prediction block for the current video block being decoded using the prediction information. For example, prediction processing unit 360 uses some of the 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 a reference picture list of the slice, a motion vector for each inter-coded video block of the slice, an inter prediction state for each inter-coded 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 the video slice to determine the degree of quantization that should be applied and likewise the degree of inverse quantization that should be applied.

Inverse transform processing unit 312 is used 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 produce a block of residuals in the pixel domain.

The reconstruction unit 314 (e.g., summer 314) is used to add the inverse transform block 313 (i.e., reconstructed residual block 313) to the prediction block 365 to obtain the 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 (either during or after the encoding cycle) is used to filter reconstructed block 315 to obtain filtered block 321 to facilitate 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 (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.

Decoded video block 321 in a given frame or picture is then stored in decoded picture buffer 330, which stores reference pictures for subsequent motion compensation.

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

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

Fig. 4 is a schematic structural diagram of a video coding apparatus 400 (e.g., a video encoding apparatus 400 or a video decoding apparatus 400) according to an embodiment of the present invention. Video coding apparatus 400 is suitable for implementing 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.

Video coding apparatus 400 includes: an ingress port 410 and a reception 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. Video coding device 400 may also include optical-to-electrical conversion components and electrical-to-optical (E0) components coupled with ingress port 410, receiver unit 420, transmitter unit 440, and egress port 450 for egress or ingress of optical or electrical signals.

The processor 430 is implemented by 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. Processor 430 includes a coding module 470 (e.g., encoding module 470 or 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. Accordingly, substantial improvements are provided to the functionality of the video coding apparatus 400 by the encoding/decoding module 470 and affect the transition of the video coding apparatus 400 to different states. Alternatively, the encode/decode module 470 is implemented as instructions stored in the memory 460 and executed by the processor 430.

The memory 460, which may include one or more disks, tape drives, and solid state drives, may be used as an over-flow data storage device for storing programs when such programs are selectively executed, and for storing instructions and data that are read during program execution. The 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 source device 12 and 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 containing multiple computing devices, or a single computing device such as a mobile phone, tablet computer, laptop computer, notebook computer, desktop computer, or the like.

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

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

Device 500 may also include one or more output apparatuses, such as a display 518. In one example, display 518 may be a touch-sensitive display that combines a display and a touch-sensitive element operable to sense touch inputs. A display 518 may be coupled to the processor 502 via the bus 512. Other output devices that permit a user to program apparatus 500 or otherwise use apparatus 500 may be provided in addition to display 518, or other output devices may be provided as an alternative to display 518. When the output device is or includes a display, the display may be implemented in different ways, including by a Liquid Crystal Display (LCD), a Cathode Ray Tube (CRT) display, a plasma display, or a 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 or later developed that can sense an image, such as an image of a user running 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 image sensing device 520 may be configured such that its field of view includes an area proximate display 518 and 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 known or later developed that can sense sound in the vicinity of the apparatus 500. The sound sensing device 522 may be positioned to face directly the user operating the apparatus 500 and may be used to receive sounds, such as speech or other utterances, emitted by the user while operating the apparatus 500.

Although the processor 502 and 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 multiple directly couplable machines (each machine having one or more processors), or distributed in a local area or other network. Memory 504 may be distributed among multiple machines, such as a network-based memory or a memory among multiple machines running apparatus 500. Although only a single bus is depicted here, the bus 512 of the device 500 may be formed from multiple buses. Further, the secondary memory 514 may be directly coupled to other components of the apparatus 500 or may be accessible over a network and may comprise a single integrated unit, such as one memory card, or multiple units, such as multiple memory cards. Accordingly, 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 a luminance (Y) component. Therefore, in addition to encoding the luminance component, the chrominance component needs to be encoded. There are generally YUV4:4:4, YUV4:2:2, and YUV4:2:0, according to the sampling method of the luminance component and the chrominance component in color video. As shown in fig. 6, where the crosses represent luminance component sampling points and the circles represent chrominance component sampling points.

4:4:4 format: indicating that the chrominance components have not been downsampled;

-4:2:2 format: indicating that the chrominance components are down-sampled 2:1 horizontally relative to the luminance components and not vertically. For every two U sampling points or V sampling points, each row comprises four Y sampling points;

-4:2:0 format: representing a 2:1 horizontal down-sampling of the chrominance components relative to the luminance components, and a 2:1 vertical down-sampling.

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

The definition of the five partition types is as follows. It should be noted that a square is considered a special case of a rectangle.

Quad-tree (QT) partitioning: the block is further divided into four rectangular blocks of equal size. FIG. 7A illustrates an example of quad-tree partitioning. The CTU partitioning method based on the quadtree QT is characterized in that the CTU is used as a root node (root) of the quadtree, and the CTU is recursively partitioned into a plurality of leaf nodes (leaf nodes) according to a partitioning mode of the quadtree. One node corresponds to one image area, if the node is not divided, the node is called a leaf node, and the image area corresponding to the node forms a CU; if the nodes are divided, the image area corresponding to the nodes is divided into four areas (the length and the width of each area are half of the divided area) with the same size, each area corresponds to one node, and whether the nodes are divided is required to be determined respectively. Whether one 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 the sake of brevity, the size and shape of the node in this application refers to the size and shape of the image region corresponding to the node, i.e. the node is a rectangular region in the image. Nodes obtained after the nodes (nodes) in the Coding tree are divided may be referred to as child nodes (child nodes) of the nodes, and are referred to as child nodes for short.

More specifically, for a 64 × 64 CTU node (0 in the quadtree level), according to its corresponding split _ CU _ flag, it is selected to be divided into 1 64 × 64 CU without division, or to be divided into 4 32 × 32 nodes (1 in the quadtree level). Each of the four 32 × 32 nodes may select continuous partitioning or non-partitioning according to its corresponding split _ cu _ flag; if one 32 × 32 node continues to divide, four 16 × 16 nodes (quad tree level 2) result. And so on until all nodes are no longer partitioned, such that a CTU is partitioned into a set of CUs. The minimum size (size) of a CU is identified in SPS, e.g., 8 × 8 is the minimum CU. In the above recursive partitioning process, if the size of a node is equal to the minimum CU size (minimum CU size), the node defaults to no longer being partitioned, and does not need to include its partition flag bit in the bitstream.

When a node is analyzed as a leaf node, the leaf node is a CU, the coding information (including information such as prediction mode and transform coefficient of the CU, for example, coding _ unit () syntax structure in h.266) corresponding to the CU is further analyzed, and then decoding processing such as prediction, inverse quantization, inverse transform, loop filter, and the like is performed on the CU according to the coding information, thereby generating a reconstructed image corresponding to the CU. A Quadtree (QT) structure enables a CTU to be partitioned into a set of CUs of suitable size according to image local features, e.g., smooth regions partitioned into larger CUs and texture rich regions partitioned into smaller CUs.

One way of partitioning a CTU into a set of CUs corresponds to a coding tree (coding tree). What coding tree the CTU should adopt is usually determined by Rate Distortion Optimization (RDO) technique of the encoder. The encoder tries a plurality of CTU partitioning modes, wherein each partitioning mode corresponds to a rate distortion cost (RDcost); and the encoder compares the RD cost of various tried partition modes, finds the partition mode with the minimum RD cost, and uses the partition mode as the optimal partition mode of the CTU for the actual coding of the CTU. The various CTU partitioning schemes attempted by the encoder need to comply with the partitioning rules specified by the decoder, so that they can be correctly identified by the decoder.

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

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

Vertical center-side Ternary 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 vertical center-side ternary tree partitioning.

Horizontal center-side treelet partitioning: the block is horizontally 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. 7E is an example of horizontal center-side ternary tree partitioning.

The specific partitioning method in fig. 7B-7E is similar to the description in fig. 7A, and is not repeated here. In addition, a QT cascade BT/TT division mode can be used, the QT cascade BT/TT division mode is called QT-BTT for short, namely, the nodes on the first-level coding tree can only be divided into child nodes by using the QT, and the leaf nodes of the first-level coding tree are root nodes of the second-level coding tree; the nodes on the second-level coding tree can be divided into sub-nodes by using one of four dividing modes of horizontal dichotomy, vertical dichotomy, horizontal trisection and vertical trisection; leaf nodes of the second level coding tree are coding units. Specifically, a cascading manner is adopted for the binary tree partition and the quadtree partition, which may be referred to as a QTBT partition manner for short, for example, a CTU is first partitioned according to QT, and the leaf nodes of QT allow BT partition to be continuously used, as shown in fig. 8. Each end point in the right diagram of fig. 8 represents a node, a node connects with 4 solid lines to represent quad tree division, a node connects with 2 dotted lines to represent binary tree division, and the node obtained after division may be referred to as a child node of the node, which is referred to as a child node for short. In the child nodes, a to m are 13 leaf nodes, each leaf node representing 1 CU; 1 on a node of the binary tree represents a vertical partition, and 0 represents a horizontal partition; one CTU is divided into 13 CUs from a to m according to the right drawing, as shown in the left drawing of fig. 8. In the QTBT partition mode, each CU has a QT level (Quad-tree depth, QT depth) and a BT level (Binary tree depth, BT depth), the QT level represents a QT level of a QT leaf node CU to which the CU belongs, the BT level represents a BT level of a BT leaf node CU to which the CU belongs, for example, the QT level of a and b in fig. 8 is 1, and the BT level is 2; c. d, e have 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, BT level is 0; g. QT level of h is 2, BT level is 2; m has a QT level of 1 and a BT level of 0. If the CTU is divided into only one CU, the QT level of the 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). The encoder 20 may determine the partition type to use based on the check block using the rate-distortion cost of the different partition types.

If the node is divided to generate 2xM chroma blocks, especially 2x2, 2x4, or 2x8 chroma blocks, the chroma coding and decoding efficiency is low, the processing cost of the hardware decoder is high, and the implementation of the hardware decoder is not facilitated. When the chroma block of the current node is not divided, the embodiment of the application can only divide the brightness block of the current node, thereby improving the coding and decoding efficiency, reducing the maximum throughput rate of a 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 method and a child node generated by the node includes a chroma block with a side length being a first threshold (or includes a chroma block with a side length being smaller than a second threshold), a luminance block included in the node is divided by using the dividing method, and a chroma block included in the node is not divided. In this way, the generation of chroma blocks with a side length of the first threshold (or a side length of less than the second threshold) can be avoided. In a specific implementation, the first threshold may be 2 and the second threshold may be 4. The following is a detailed description with reference to examples one to three. Embodiments of the application are illustrated with the video data format YUV4:2:0, in a similar manner for YUV4:2:2 data.

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

In VTM, at the CU level, a flag is used to indicate whether the current CU uses the IBC mode, which is classified as IBCAMVP mode, IBC skip mode, or IBC merge mode.

Example one

Fig. 9 shows a flow chart 900 of a method according to a first embodiment of the invention.

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

The first embodiment of the present invention can be implemented by a video decoding apparatus, and specifically, can be the apparatus described in any of fig. 3 to 5.

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

When implemented by a video decoding device, step 902: and the video decoding device analyzes the code stream and determines the division mode of the current node. The current node may be divided into at least one of a Quarter (QT), a horizontal bi (horizontal BT), a horizontal tri (horizontal TT), a Vertical bi (Vertical BT), and a Vertical tri (Vertical TT), or may be divided into other division modes, which is not limited in the embodiment of the present invention. The information of the partition mode of the current node is usually transmitted in the 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 a video encoding apparatus, step 902 determines a partitioning method of a current node.

Step 904: and judging whether the chrominance 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 not divided, executing step 906; when the chroma block of the current node needs to be partitioned, step 908 is performed.

Specifically, in an implementation manner, it may be determined whether the current node is divided according to the dividing manner of the current node to generate a chroma block having a side length of a first threshold (or whether a chroma block having a side length of less than a second threshold is generated). And if the child node generated by the current node division comprises the chroma block with the side length being the first threshold (or comprises the chroma block with the side length being smaller than the second threshold), the chroma block of the current node is not divided. For example, the first threshold may be 2 and the second threshold may be 4.

In the embodiment of the present invention, the chroma block with the side length being the first threshold refers to the chroma block with the width being the first threshold or the chroma block with the height being the first threshold.

In another implementation, for example: when any one of the following conditions 1 to 5 is satisfied, determining that the chroma block of the current node is not divided; otherwise, determining that the chroma 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 division mode of the current node is vertical halving.

Condition 2: the current node is higher than 2 times of the second threshold value and the division mode of the current node is horizontal halving.

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

Condition 4: the current node is higher than 4 times of the second threshold value and the division mode of the current node is horizontal trisection.

Condition 5: the width of the current node is equal to 2 times of the second threshold value, and the division mode of the current node is four.

In general, 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 particular implementations, for example, the second threshold may be 4.

In a third implementation manner, it may be determined whether the current node is divided according to the dividing manner of the current node to generate a chroma block whose width is equal to the first threshold (or whether a chroma block whose width is smaller than the second threshold is generated). And if the child node generated by the current node division contains the chroma block with the width being the first threshold value (or contains the chroma block with the width being less than the second threshold value), the chroma block of the current node is not divided. For example, the first threshold may be 2 and the second threshold may be 4.

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

Specifically, if any one of the following conditions 1 to 2 is satisfied, it may be determined that the current node is divided according to the dividing manner of the current node to generate a chroma block whose chroma pixel number is less than a third threshold; otherwise, it may be determined that the current node is divided according to the dividing manner of the current node and the chrominance blocks having the chrominance pixel number less than the third threshold value are not generated:

condition 1: the product of the width and the height of the current node is less than 128, and the division mode of the current node is vertical halving or horizontal halving.

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 vertical divisions or three horizontal divisions or four divisions.

Specifically, as another embodiment, if any one of the following conditions 3 to 4 is satisfied, it may be determined that the current node is divided according to the dividing manner of the current node to generate a chroma block whose chroma pixel number is less than a third threshold; otherwise, it may be determined that the current node is divided according to the dividing manner of the current node and the chrominance blocks having the chrominance pixel number less than the third threshold value are not generated:

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

In a fifth implementation manner, it may be determined whether the current node is divided according to the dividing manner of the current node to generate a chroma block higher than the first threshold (or whether a chroma block higher than the second threshold is generated). And if the child node generated by the current node division contains the chroma block with the height being the first threshold value (or contains the chroma block with the height being less than the second threshold value), the chroma block of the current node is not divided. For example, the first threshold may be 2 and the second threshold may be 4.

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

Optionally, as shown in fig. 10, step 906 may further include step 9062: and analyzing the brightness block of the current node, and acquiring the 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: and the child nodes of each brightness block are not divided by default (namely, each brightness node is a coding unit, the child node of one brightness block corresponds to one coding unit only containing the brightness block), and the data of the coding units are sequentially analyzed for the child nodes of each brightness block to obtain the prediction information and the residual error information of each brightness block. The brightness block of a brightness node is a sub-region in the brightness block of the current node, and the brightness blocks of all the brightness nodes form the brightness block of the current node. Or;

the second method comprises the following steps: and sequentially judging whether the sub-nodes of each brightness block need to be continuously divided, and analyzing the division modes and the corresponding coding unit data when the sub-nodes need to be continuously divided. More specifically, if a luminance node is not divided, analyzing the coding unit data corresponding to the luminance node to obtain the prediction information and residual information corresponding to the luminance block of the luminance node; if one brightness node is continuously divided, whether the sub-node of the brightness node (it needs to be noted that the sub-node only contains the brightness block) needs to be divided is continuously judged until the prediction information and the residual error information of each sub-region in the brightness block of the current node are determined.

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

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

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

Specifically, step 9064 may include step 90642 and step 90644. Step 90642 may be step 90642A or step 90642B.

Step 90642a specifically includes:

and acquiring a prediction mode of a preset position in the brightness block of the current node as a prediction mode of the chroma block of the current node. The position of the top left corner of the luminance block of the current node may be represented as (x0, y0) and the size is WxH, and the preset positions may include, but are not limited to, the top left corner, the bottom 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 so on of the luminance block. The prediction mode indicates whether intra prediction or inter prediction is used to predict pixels in a preset position, such as 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 the prediction mode of the chroma by using one of the following methods:

the method comprises the following steps: the chrominance block acquires motion information of a preset position as motion information of the chrominance block using inter-frame prediction.

The second method comprises the following steps: the chroma block divides the chroma block into chroma predictor blocks (chroma predictor block size is, for example, 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 brightness block of the brightness image position corresponding to the chroma prediction sub-block adopts inter-frame prediction, the motion information of the brightness image position corresponding to the chroma prediction sub-block is used as the motion information of the chroma prediction sub-block; otherwise, acquiring the motion information of the preset position as the motion information of the chroma prediction subblock.

For a YUV4:2:0 image, the coordinates of the chroma predictor block in the chroma image are (xC, yC), and the coordinates of the position of the luminance image corresponding to the chroma predictor block are (xC < 1, yC < 1).

The third method comprises the following steps: resolving a flag bit of pred _ mode _ flag to determine whether the chroma block uses intra prediction or inter prediction; if the chroma block uses intra-frame prediction, an intra-frame prediction mode is analyzed from the code stream and used as the intra-frame prediction mode of the chroma block; if the chrominance block uses inter prediction, motion information of a preset position is acquired as motion information of the chrominance block.

The method four comprises the following steps: resolving a flag bit of pred _ mode _ flag to determine whether the chroma block uses intra prediction or inter prediction; if the chroma block uses intra-frame prediction, an intra-frame prediction mode is analyzed from the code stream and is used as the intra-frame prediction mode of the chroma block, wherein the intra-frame prediction mode can be one of a linear model mode and a DM mode, and a brightness intra-frame prediction mode corresponding to the DM mode is set to be a plane mode; if the chroma block uses inter prediction, the chroma block is divided into chroma prediction sub-blocks, and the motion information of the chroma prediction sub-blocks is obtained by the following method:

The context model adopted when the pred _ mode _ flag bit is analyzed is a preset model, and the model number is 2, for example.

And if the prediction mode of the preset position is intra-frame prediction, the chroma block uses the intra-frame prediction to analyze an intra-frame prediction mode from the code stream as the intra-frame prediction mode of the chroma block. Or directly determining the intra prediction mode of the chrominance block as one of a direct current mode, a planar mode, an angular mode, a linear model mode, or a DM mode.

If the prediction mode of the preset position is the IBC mode, the chroma block uses the IBC mode for prediction, and displacement vector (displacement vector) information of the preset position is acquired as displacement vector information of the chroma block. Alternatively, the first and second electrodes may be,

if the prediction mode at the preset position is the IBC mode, determining the prediction mode of the chroma block according to a flag bit pred _ mode _ IBC _ flag:

1) if pred _ mode _ IBC _ flag is 1, the chroma block uses the IBC mode; more specifically, the IBC prediction method for the chroma block may use the method in VTM4.0, that is, the chroma block is divided into sub-blocks of 2 × 2, and the displacement vector of each sub-block is equal to the displacement vector of the luminance region corresponding to the sub-block.

2) If pred _ mode _ ibc _ flag is 0, the chroma block uses either an intra prediction mode or an inter prediction mode.

When the intra prediction mode is used, the syntax element is parsed from the code stream to determine the intra prediction mode of the chroma. Or, directly determining the intra prediction mode of the chroma block as one of a chroma intra prediction mode set, where the chroma intra prediction mode set is: dc mode, planar mode, angular mode, linear mode, DM mode.

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

It should be noted that, when there is no pred _ mode _ IBC _ flag in the code stream, if the image type of the current node is an I frame/I slice and the IBC mode is allowed to be used, the default pred _ mode _ IBC _ flag is 1, that is, the chroma block uses the IBC mode by default; if the picture type is P/B frame/slice, the default pred _ mode _ ibc _ flag is 0.

Wherein, whether the prediction mode of the preset position is the IBC mode can be determined in the VTM according to the 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 appear in the bitstream, if the value of pred _ mode _ ibc _ flag is equal to the value of sps _ ibc _ enabled _ flag in I frame/I slice, if pred _ mode _ ibc _ flag is 0 in P frame/slice, or B frame/slice. Wherein an sps _ ibc _ enabled _ flag of 1 indicates that the current picture is allowed to be a reference picture in the decoding process of the current picture, and an sps _ ibc _ enabled _ flag of 0 indicates that the current picture is not allowed to be a reference picture in the decoding process of the current picture.

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

Step 90642B specifically includes:

the prediction modes in a plurality of luminance blocks of the current node are obtained, and the prediction mode of the chrominance block corresponding to the current node is determined by using the following method.

If a plurality of luminance blocks are intra-predicted, the chrominance block uses the intra-prediction to resolve one intra-prediction mode from the code stream as the intra-prediction mode of the chrominance block.

If the plurality of luminance blocks are all inter predicted, a prediction mode of the chrominance is determined using one of the following methods:

the method comprises the following steps: the chrominance block acquires motion information of a preset position as motion information of the chrominance block using inter-frame prediction. The preset position is the same as in the first embodiment.

The second method comprises the following steps: resolving a flag bit of pred _ mode _ flag to determine whether the chroma block uses intra prediction or inter prediction; if the chroma block uses intra-frame prediction, an intra-frame prediction mode is analyzed from the code stream and used as the intra-frame prediction mode of the chroma block; if the chrominance block uses inter prediction, motion information of a preset position is acquired as motion information of the chrominance block.

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

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

2) And if the prediction mode of the preset position is intra-frame prediction, the chroma block uses the intra-frame prediction to analyze an intra-frame prediction mode from the code stream as the intra-frame prediction mode of the chroma block. Or directly determining the intra prediction mode of the chrominance block as one of a direct current mode, a planar mode, an angular mode, a linear model mode, or a DM mode.

3) And if the prediction mode of the preset position is the IBC mode, predicting the chroma block by using the IBC mode, and acquiring the displacement vector information of the preset position as the displacement vector information of the chroma block.

4) The prediction mode directly specifying the chroma is one of a set of modes, which is an AMVP mode, an IBC mode, a skip mode, a dc mode, a planar mode, an angular mode, a linear mode, and a DM mode.

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

Step 908: the current node is divided into sub-nodes, each of which contains a luma block and a chroma block. Step 901 is executed for each child node, and the partitioning manner of the child node is continuously analyzed to determine whether each child node (also referred to as node) needs to be partitioned.

After the partition mode of the sub-region of the brightness block and the prediction information and residual information of each sub-region are obtained, inter-frame prediction processing or intra-frame prediction processing can be executed on each sub-region according to the corresponding prediction mode of each sub-region, and inter-frame prediction images or intra-frame prediction images of each sub-region are obtained. And according to the residual information of each sub-region, carrying out inverse quantization and inverse transformation processing on the transformation coefficient to obtain a residual image, and overlapping the residual image on the prediction image of the corresponding sub-region to generate a reconstructed image of the brightness block.

After the prediction information and the residual information of the chroma block are obtained, inter-frame prediction processing or intra-frame prediction processing can be performed on the chroma block according to the prediction mode of the chroma block, and an inter-frame prediction image or an intra-frame prediction image of the chroma block is obtained. And according to the residual information of the chroma block, carrying out inverse quantization and inverse transformation processing on the transformation coefficient to obtain a residual image, and overlapping the residual image on a predicted image of the chroma block to generate a reconstructed image of the chroma block.

In the first embodiment of the present invention, when the chroma block of the current node is not divided, the method may only divide the luma block of the current node, so that the coding and decoding efficiency may be improved, the maximum throughput rate of the decoder may be reduced, and the implementation of the decoder may be facilitated.

Example two

Step 9062 adds the following constraints compared to example one: each luma node (i.e., the children of each luma block) uses the same prediction mode, i.e., each luma node uses either intra prediction or inter prediction. Other steps are similar to those of the embodiment and are not described again.

Using the same prediction mode for each luma node, either of the following methods may be used:

the method comprises the following steps: if the current frame is an I frame, each sub-node of the current node defaults to use intra-frame prediction; if the current frame is a P frame or a B frame, the first node (which may be referred to as a first sub-node) performing the parsing process is parsed to obtain the prediction mode thereof, and the prediction modes of the remaining sub-nodes (which may be referred to as brightness nodes) default to the prediction mode of the first node performing the parsing process. Or

The second method comprises the following steps: if the current frame is an I frame, each sub-node of the current node defaults to use intra-frame prediction; if the current frame is a P frame or a B frame, each child node of the current node uses inter prediction by default.

EXAMPLE III

Fig. 11 shows a method flowchart 1100 of a third embodiment of the invention. Embodiment three is similar to the embodiment except for step 1104. Step 1104: and judging whether the chroma 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 a first analysis processing node (which may be referred to as a first sub-node) of the current node, wherein the first sub-node only comprises a luma block. The plurality of sub-nodes of the current node use the same prediction mode, wherein each sub-node contains only luminance blocks.

The embodiment of the present invention is not limited to determining the partition mode of the current node and the size of the current node first, or determining the prediction mode of the first child node first.

And the third embodiment determines the division mode of the chroma block of the current node and the corresponding prediction information and residual information analysis mode by combining the prediction mode of the first child node of the current node on the basis of the first embodiment or the second embodiment.

In an embodiment, according to the dividing mode of the current node and the size of the current node, it is determined that the child nodes generated by dividing the current node include chroma blocks with side lengths equal to a first threshold or smaller than a second threshold, and if the prediction mode of the first child node is intra-frame prediction, the chroma blocks of the current node are not divided. Similarly 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 equal to 2 times of the second threshold value, and the division mode of the current node is vertical bisection; or

Condition 2: the current node is higher than 2 times of a second threshold value, and the division mode of the current node is horizontal halving; or

Condition 3: the width of the current node is equal to 4 times of a second threshold value, and the division mode of the current node is vertical trisection; or

Condition 4: the current node is higher than 4 times of a second threshold value, and the division mode of the current node is horizontal trisection; or

Condition 5: and if the width of the current node is equal to 2 times of the second threshold value and the division mode of the current node is four, the chroma block of the current node is not divided.

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 dividing manner of the current node to generate a chroma block with a width of the first threshold (or whether a chroma block with a width smaller than the second threshold is generated). If the child node generated by the current node division comprises the chroma block with the width being the first threshold value (or comprises the chroma block with the width being smaller than the second threshold value) and the prediction mode of the first child node is intra-frame prediction, the chroma block of the current node is not divided any more. 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 manner, it may be determined whether the current node is divided according to the dividing manner of the current node to generate a chroma block with a chroma pixel number less than a third threshold. And if the sub-node generated by the current node division comprises the chroma blocks of which the chroma pixel number is less than a 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 divided. For example, the third threshold may be 16. The chrominance blocks having the number of chrominance pixels less than 16 include, but are not limited to, 2x2 chrominance blocks, 2x4 chrominance blocks, 4x2 chrominance blocks. The third threshold may be 8. Then the chrominance blocks having a chrominance pixel number less than 8 include, but are not limited to, 2x2 chrominance blocks.

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 is divided according to the dividing manner of the current node to generate a chroma block with a height higher than the first threshold (or whether a chroma block with a height lower than the second threshold is generated). If the child node generated by the current node division comprises the chroma block with the height being the first threshold value (or comprises the chroma block with the height being less than the second threshold value), and the prediction mode of the first child node is intra-frame prediction, the chroma block of the current node is not divided. 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 only containing the chroma block. The method 1100 may further include obtaining prediction information and/or residual information of the chroma block.

In another embodiment, it is determined that the child nodes generated by dividing the current node include chroma blocks with side lengths smaller than a threshold according to the dividing mode of the current node and the size of the current node, and if the prediction mode of the first child node is inter-frame prediction, the chroma blocks of the current node are divided according to the dividing mode of the current node. Optionally, the motion information of the corresponding child node of the chroma block is determined according to the motion information of the child node of the current node. For example, the motion information of the child node of the chroma block of the current node may be set as the motion information of the corresponding luma node (i.e., the motion information of the child nodes of the chroma block does not need to be parsed from the code stream). And respectively analyzing the residual error information of the child nodes of the chroma block to obtain the residual error information of each child 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: and if the width of the current node is equal to 2 times of the second threshold value and the division mode of the current node is four, the chrominance block of the current node still needs to be divided.

The third embodiment can also determine the dividing mode of the chroma block and the corresponding prediction information and residual information analysis mode according to the prediction mode of the brightness node, and 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 equally apply to the corresponding apparatus or system for performing the methods, and vice versa. For example, if one or more particular method steps are described, the corresponding apparatus may comprise one or more units, such as functional units, to perform the described one or more method steps (e.g., a unit performs one or more steps, or multiple units, each of which performs 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, for example, if a particular apparatus is described based on one or more units, such as functional units, the corresponding method may comprise one step to perform the functionality of the one or more units (e.g., one step performs the functionality of the one or more units, or multiple steps, each of which performs the functionality of one or more of the plurality of 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. Computer readable media may comprise computer readable storage media corresponding to tangible media, such as data storage media or communication media, including any medium that facilitates transfer of a computer program from one place to another, such as according to a communication protocol. In this manner, the computer-readable medium may generally correspond to (1) a non-transitory tangible computer-readable storage medium, or (2) a communication medium, e.g., a signal or carrier wave. A data storage medium may be any available medium 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 instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. 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 instead directed to non-transitory tangible storage media. Disk and disc, as used herein, includes Compact Disc (CD), laser disc, optical disc, Digital Versatile Disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

The instructions may be executed by one or more processors, such as one or more Digital Signal Processors (DSPs), general purpose microprocessors, Application Specific Integrated Circuits (ASICs), field programmable 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. In addition, 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 composite 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 (IC), or a collection of ICs (e.g., a chipset). This disclosure describes various components, modules, or units to emphasize functional aspects of the apparatus for performing the disclosed techniques, but does not necessarily require realization by different hardware units. Specifically, as described above, the various units may be combined in a codec hardware unit, or provided by a collection of interoperative hardware units, including one or more processors as described above, in conjunction with suitable software and/or firmware.

Claims

1. An image partitioning method, comprising:

determining a division mode of a current node, wherein the current node comprises a brightness block and a chrominance block;

determining that the chroma 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

and when the chrominance block of the current node is not divided, dividing the luminance block of the current node according to the dividing mode of the current node.

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 the chroma blocks with the side length smaller than the 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 any more.

3. The method of claim 1,

when the width of the current node is equal to 2 times of a threshold value and the division mode of the current node is vertical bisection; or

When the height of the current node is higher than 2 times of a threshold value and the division mode of the current node is horizontal halving; or

When the width of the current node is equal to 4 times of a threshold value and the division mode of the current node is vertical trisection; or

When the height of the current node is higher than 4 times of a threshold value and the division mode of the current node is horizontal trisection; or

When the width of the current node is equal to 2 times of the threshold value and the division of the current node is four-fold,

determining that the chroma block of the current node is not to be partitioned.

4. The method according to any one of claims 1 to 3, wherein the luminance block of the current node is divided according to the division manner of the current node, thereby obtaining child nodes of the current node, each child node containing only a luminance block.

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

and analyzing the brightness block of the current node to obtain the prediction information and residual information of each sub-region in the brightness block, wherein the sub-regions correspond to the sub-nodes one to one.

6. The method according to claim 4 or 5, wherein the sub-nodes are not subdivided by default, and each sub-node corresponds to a coding unit containing only luminance blocks.

7. The method of any of claims 1-6, further comprising:

and when the chroma block of the current node is not divided, acquiring the 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 a prediction mode of a luma block in a preset position of the current node.

9. The method as claimed in 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

And analyzing the first flag bit, and determining the prediction mode of the chroma block according to the first flag 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

And dividing the chroma block into chroma prediction sub-blocks, and acquiring 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, parsing an intra prediction mode from the code stream as the intra prediction mode of the chroma block; or

When the chroma block is determined to use an inter-frame prediction mode according to the first zone bit, acquiring the motion information of the brightness block at the preset position as the motion information of the chroma block; or

And when the chroma block is determined to use the inter-frame prediction mode according to the first zone bit, dividing the chroma block into chroma prediction sub-blocks and acquiring 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 brightness block of the brightness image position corresponding to the chroma prediction sub-block adopts inter-frame prediction, the motion information of the brightness image position corresponding to the chroma prediction sub-block is used as the motion information of the chroma prediction sub-block;

otherwise, acquiring the motion information of a preset position as the motion information of the chroma prediction subblock.

13. The method of claim 8, wherein when the prediction mode used for the luma block in the preset position is an intra prediction mode, the chroma 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 code stream as an intra prediction mode of the chroma block of the current node; or

The intra prediction mode of the chroma block of the current node is one of a direct current mode, a planar mode, an angular mode, a linear model mode, or a chroma derivation DM mode.

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

the chroma block of the current node uses an IBC prediction mode; alternatively, the first and second electrodes may be,

and analyzing the 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 an IBC prediction mode, the method further comprises: and obtaining displacement vector (displacement vector) information of the brightness block at the preset position as displacement vector information of the chroma block of the current node.

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

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

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

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

acquiring the prediction modes of a plurality of 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 luminance 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 luma blocks is an inter prediction mode, and the chroma block of the current node uses the inter prediction mode, the motion information of the luma block of a preset position is used as the motion information of the chroma block of the current node; or

When the prediction modes used by the plurality of luminance blocks are inter prediction modes, analyzing a first flag bit, and determining the prediction mode of the chrominance block according to the first flag bit.

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

And when the chrominance block is determined to use the inter-frame prediction mode according to the first zone bit, acquiring the motion information of the luminance block at the preset position as the motion information of the chrominance block.

22. The method of claim 18, wherein when the prediction modes used by the plurality of luma blocks include an inter prediction mode and an intra prediction mode, the prediction mode of the luma block in the preset position of the current node is acquired as the prediction mode of the chroma block of the current node.

23. The method according to any of claims 1-22, wherein if the current node is an I-frame, then each child node of the current node uses an intra prediction mode; or if the current node is a P frame or a B frame, analyzing a first child node to obtain a prediction mode of the first child node, wherein the prediction modes of the rest child nodes are the same as the prediction mode of the first child node, and the first child node is the first node to be analyzed.

24. The method according to any of claims 1-22, wherein if the current node is an I-frame, then each child node of the current node uses an intra prediction mode; or if the current node is a P frame or a B frame, each child node of the current node uses an inter-frame prediction mode.

25. The method of any one of claims 1-24,

and determining that the chrominance block of the current node is not divided any more according to the dividing mode of the current node, the size of the current node and the prediction mode of a first child node of the current node, wherein the first child node only comprises a luminance block, and is the first node for analysis.

26. The method as claimed in claim 25, wherein it is determined that the sub-node generated by partitioning the current node includes the chroma block having the side length smaller than the threshold according to the partitioning manner of the current node and the size of the current node, and the prediction mode of the first sub-node is the intra prediction mode, then the chroma block of the current node is not partitioned.

27. The method of claim 26, wherein when the prediction mode of the first sub-node is intra-prediction and any of the following conditions is true:

and the chroma blocks of the current node are not divided.

28. The method as claimed in any one of claims 1 to 24, wherein it is determined that the sub-nodes generated by dividing the current node include chroma blocks having side lengths smaller than a threshold value according to the division of the current node and the size of the current node, and if the prediction mode of a first sub-node is inter-prediction, the chroma blocks of the current node are divided according to the division of the current node, wherein the first sub-node is a first node for parsing.

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

and determining the motion information of the corresponding child node of the chrominance block according to the motion information of the child node of the current node.

30. The method according to any one of claims 1-24, wherein, if it is determined that the child nodes generated by partitioning the current node include chroma blocks with widths smaller than a threshold value according to the partitioning manner of the current node and the size of the current node, it is determined that the chroma blocks of the current node are not partitioned.

31. The method according to any one of claims 1-24, wherein, when it is determined that the sub-nodes generated by dividing the current node include chroma blocks with a chroma pixel number less than 16 according to the division manner of the current node and the size of the current node, it is determined that the chroma blocks of the current node are not divided.

32. The method of claim 31,

when the product of the width and the height of the current node is less than 128 and the division mode of the current node is vertical halving or horizontal halving; or

When the product of the width and the height of the current node is less than 256 and the division mode of the current node is vertical thirds or horizontal thirds or quarters; or

When the product of the width and the height of the current node is equal to 64 and the division mode of the current node is vertical halving or horizontal trisection or vertical trisection; or

When the product of the width and height of the current node is equal to 128 and the current node is divided into vertical thirds or horizontal thirds,

determining that the chroma block of the current node is not to be partitioned.

33. The method of claim 2, 3, 26, 27, 28 or 30, wherein the threshold is 4.

34. 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 the 1-33.

35. 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 the 1-33.

36. A decoding device, 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 1-33.

37. An encoding device 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 1-33.