WO2020048430A1

WO2020048430A1 - Chroma block prediction method and device

Info

Publication number: WO2020048430A1
Application number: PCT/CN2019/104079
Authority: WO
Inventors: 马祥; 杨海涛; 陈建乐
Original assignee: 华为技术有限公司
Priority date: 2018-09-03
Filing date: 2019-09-03
Publication date: 2020-03-12
Also published as: CN110876061A; CN110876061B

Abstract

Provided are a chroma block prediction method and device. Said method comprises: searching for values of luminance points in a template of a luminance block corresponding to a current chroma block, to obtain a luminance extreme value; obtaining a value of a chroma point corresponding to the luminance extreme value; and determining a third luminance value and determining the value of the chroma point corresponding to the third luminance value. Said method further comprises: according to the luminance extreme value and the value of the chroma point corresponding to the luminance extreme value, and the third luminance value and the value of the chroma point corresponding to the third luminance value, obtaining two sets of linear model coefficients; and then according to the two sets of linear model coefficients and the reconstructed value of the luminance block, obtaining a predicted value of the current chroma block. The method is able to reduce the complexity of a multivariate mixed linear model (MMLM), improving the efficiency of chroma encoding and decoding.

Description

Chroma block prediction method and device

This application claims the priority of a Chinese patent application filed on September 3, 2018 with the State Intellectual Property Office of China, with the application number 201811022643.0, and the application name being "Chroma Block Forecasting Method and Device", the entire contents of which are incorporated herein by reference Applying.

Technical field

The present application relates to the field of video encoding and decoding, and more particularly, to a method and device for predicting chroma blocks.

Background technique

With the rapid development of Internet technology and the increasing enrichment of people's material spiritual culture, the demand for video applications on the Internet, especially for high-definition videos, is increasing, and the amount of data for high-definition videos is very large. To be able to transmit on the Internet with limited bandwidth, the first problem that must be solved is the problem of video encoding and decoding. Video codecs are widely used in digital video applications, such as broadcast digital TV, video distribution on the Internet and mobile networks, real-time conversation applications such as video chat and video conferencing, DVD and Blu-ray discs, video content capture and editing systems, and camcorders Security applications.

Each picture of a video sequence is usually partitioned into a set of non-overlapping blocks, usually encoded at the block level. For example, prediction blocks are generated by spatial (intra-picture) prediction and temporal (inter-picture) prediction. Accordingly, the prediction modes may include an intra prediction mode (spatial prediction) and an inter prediction mode (temporal prediction). The intra prediction mode set may include 35 different intra prediction modes, for example, a non-directional mode such as a DC (or average) mode and a planar mode; or a directional mode as defined in H.265; or Includes 67 different intra-prediction modes, such as non-directional modes such as DC (or average) mode and planar mode; or directional modes as defined in the developing H.266. The set of inter prediction modes depends on the available reference pictures and other inter prediction parameters, such as whether to use the entire reference picture or only a part of the reference picture.

The existing video is generally a color video, which contains a chrominance component in addition to a luminance component. Therefore, in addition to encoding the luminance component, it is also necessary to encode the chrominance component. In the prior art, when intra prediction is performed, the value of the chrominance component can be obtained through a relatively complicated method, and the efficiency of chrominance coding and decoding is low.

Summary of the Invention

The embodiments of the present application (or the present disclosure) provide an apparatus and method for chroma block prediction.

In a first aspect, the present invention relates to a prediction method for a chroma block. The method is performed by a device that decodes a video stream or a device that encodes a video stream. The method includes: searching a value of a brightness point in a template of a brightness block corresponding to a current chroma block to obtain a brightness extreme value, the brightness extreme value including a brightness maximum value and a brightness minimum value; and obtaining a brightness maximum value The value of the chroma point corresponding to the value, and the value of the chroma point corresponding to the minimum brightness value. A template or a template region refers to an adjacent region of the luminance block.

The method further includes determining a third luminance value and determining a value of a chroma point corresponding to the third luminance value. Then, according to the brightness maximum value and the value of the chroma point corresponding to the brightness maximum value, the third brightness value and the value of the chroma point corresponding to the third brightness value, a first set of linear models is obtained. Coefficient; obtaining a second set of linearity according to the minimum brightness value and the value of the chroma point corresponding to the minimum brightness value, the third brightness value and the value of the chroma point corresponding to the third brightness value Model coefficients. The method further includes obtaining a predicted value of the current chrominance block according to the two sets of linear model coefficients and a reconstruction value of the luminance block.

According to the method of the first aspect of the present invention, according to the brightness extreme value and the value of the chromaticity point corresponding to the brightness extreme value, the third brightness value and the value of the chromaticity point corresponding to the third brightness value are obtained by Extreme value method to obtain two sets of linear model coefficients. Compared with the prior art, which obtains two sets of linear model coefficients by the least square method, the embodiment of the present invention can reduce the complexity of the multi-linear model MMLM and improve the efficiency of chroma encoding and decoding.

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

In a third aspect, the invention relates to a device 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 proposed, which stores instructions thereon, which, 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 possible embodiment of the first aspect.

In a fifth aspect, the invention relates to a computer program comprising program code which, when run on a computer, performs the method according to any possible embodiment of the first aspect.

The embodiments of the present invention can effectively reduce the complexity of the linear mode MMLM and improve the efficiency of chroma encoding and decoding.

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, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly explain the technical solutions in the embodiments of the present application or the background art, the drawings that are needed in the embodiments of the present application or the background art will be described below.

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

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

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

3 is a block diagram showing an example structure of a video decoder for implementing an embodiment of the present invention;

4 is a block diagram illustrating an example of an encoding device or a decoding device;

FIG. 5 is a block diagram illustrating an example of another encoding device or decoding device;

Figure 6 shows an example of a YUV format sampling grid;

FIG. 7 illustrates an embodiment of a linear mode (LM);

8 (a) shows a schematic diagram of an upper template and a left template;

8 (b) shows another schematic diagram of an upper template and a left template;

FIG. 9 shows a method according to the first embodiment of the present invention;

FIG. 10 shows a flowchart of a method according to a second embodiment of the present invention;

11 shows a schematic diagram of a linear model according to a second embodiment of the present invention;

FIG. 12 shows a flowchart of a method according to a third embodiment of the present invention;

13 shows a schematic diagram of a linear model according to a third embodiment of the present invention;

14 shows a method flowchart of a fourth embodiment of the present invention;

15 shows a schematic diagram of a linear model according to a fourth embodiment of the present invention;

16 shows a method flowchart of Embodiment 5 of the present invention;

FIG. 17 is a schematic diagram of a linear model according to a fifth embodiment of the present invention.

If there is no specific note about the same reference symbols below, the same reference symbols refer to the same or at least functionally equivalent features.

detailed description

Video coding generally refers to processing a sequence of pictures that form a video or a video sequence. In the field of video coding, the terms "picture", "frame" or "image" can be used as synonyms. Video encoding used in this application (or this disclosure) means video encoding or video decoding. Video encoding is performed on the source side and typically involves processing (e.g., by compressing) the original video picture to reduce the amount of data required to represent the video picture, thereby storing and / or transmitting more efficiently. Video decoding is performed on the destination side and usually involves inverse processing relative to the encoder to reconstruct the video picture. The video picture “encoding” involved in the embodiment should be understood as the “encoding” or “decoding” of the video sequence. The combination of the encoding part and the decoding part is also called codec (encoding and decoding, or simply encoding).

In the existing multiple linear models (MMLM, Multiple Models, Linear Models), more complex operations are required to derive linear model coefficients, and the efficiency of chroma encoding and decoding is low. Multilinear models are also called multilinear models. The embodiments of the present invention provide a linear model coefficient derivation method and device for reducing the complexity of MMLM.

Each picture of a video sequence is usually partitioned into a set of non-overlapping blocks, usually encoded at the block level. In other words, the encoder side usually processes at the block (also called image block, or video block) level, that is, encodes the video. For example, the prediction block is generated by spatial (intra-picture) prediction and temporal (inter-picture) prediction. The current block (currently processed or block to be processed) is subtracted from the prediction block to obtain the residual block, the residual block is transformed in the transform domain and the residual block is quantized to reduce the amount of data to be transmitted (compressed), and the decoder side will The inverse processing part relative to the encoder is applied to the encoded or compressed block to reconstruct the current block for representation. In addition, the encoder duplicates the decoder processing loop so that the encoder and decoder generate the same predictions (such as intra prediction and inter prediction) and / or reconstruction for processing, that is, encoding subsequent blocks.

The term "block" may be part of a picture or frame. This application defines the following key terms:

Current block: Refers to the block currently being processed. For example, in encoding, it means the block that is currently being encoded; in decoding, it means the block that is currently being decoded. If the currently processed block is a chroma component block, it is called the current chroma block. The luma block corresponding to the current chroma block may be referred to as the current luma block.

Reference block: refers to the block that provides a reference signal for the current block. During the search process, multiple reference blocks can be traversed to find the best reference block.

Predicted block: The block that provides prediction for the current block is called the predicted block. For example, after traversing multiple reference blocks, the best reference block is found. This best reference block will provide prediction for the current block. This block is called a prediction block.

Image block signal: pixel value or sample value or sample signal in the image block.

Prediction signal: A pixel value or a sample value or a sampled signal within a prediction block is called a prediction signal.

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

FIG. 1A is a conceptual or schematic block diagram illustrating an exemplary encoding system 10. For example, a video encoding system 10 that can use the technology of the present application (the present disclosure). The encoder 20 (eg, video encoder 20) and decoder 30 (eg, video decoder 30) of the video encoding system 10 represent device instances that can be used to perform intra prediction according to various examples described in this application. As shown in FIG. 1A, the encoding system 10 includes a source device 12 for providing the encoded data 13, such as the encoded picture 13, to a destination device 14 that decodes the encoded data 13, for example.

The source device 12 includes an encoder 20, and may optionally include a picture source 16, such as a pre-processing unit 18 of a picture pre-processing unit 18, and a communication interface or communication unit 22.

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

Pictures can be viewed as a two-dimensional array or matrix of sample points with luminance values. The sampling points in the array may also be called pixels (short for picture element) or pixels. 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. In order to represent color, three color components are usually used, that is, a picture can be represented as or contain three sampling arrays. In RBG format or color space, pictures include corresponding red, green, and blue sampling arrays. However, in video coding, each pixel is usually represented in a luma / chroma format or color space, for example, YCbCr, including the luma component indicated by Y (sometimes also indicated by L) and the two chroma indicated by Cb and Cr Weight. Luma (abbreviated as luma) component Y represents luminance or gray level intensity (for example, both are the same in a grayscale picture), while two chroma (abbreviated as chroma) components Cb and Cr represent chroma or color information components . Correspondingly, a picture in the YCbCr format includes a luminance sampling array of luminance sampling values (Y), and two chrominance sampling arrays of chrominance values (Cb and Cr). Pictures in RGB format can be converted or converted to YCbCr format, and vice versa. This process is also called color conversion or conversion. If the picture is black, the picture can only include an array of luminance samples.

The picture source 16 (e.g., the video source 16) may be, for example, a camera for capturing pictures, such as a memory of a picture memory, including or storing a previously captured or generated picture, and / or any category (internal) of obtaining or receiving a picture Or external) interface. The camera may be, for example, an integrated camera that is local or integrated in the source device, and the memory may be local or, for example, an integrated memory that is integrated in the source device. The interface may be, for example, an external interface for receiving pictures from an external video source. The external video source is, for example, an external picture capture device, such as a camera, external storage, or an external picture generation device. The external picture generation device is, for example, an external computer graphics processor, Or server. The interface may be any type of interface according to any proprietary or standardized interface protocol, such as a wired or wireless interface, an optical interface. The interface for acquiring the picture data 17 may be the same interface as the communication interface 22 or a part of the communication interface 22.

Different from the processing performed by the pre-processing unit 18 and the pre-processing unit 18, a picture or picture data 17 (for example, video data 16) may also be referred to as an original picture or original picture data 17.

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

An encoder 20 (eg, video encoder 20) is used to receive the pre-processed picture data 19 and provide the encoded picture data 21 (details will be further described below, for example, based on FIG. 2 or FIG. 4). In one example, the encoder 20 may be used to perform embodiments one to seven described below.

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

The destination device 14 includes a decoder 30 (for example, a video decoder 30), and in addition, optionally, it may include a communication interface or communication unit 28, a post-processing unit 32, and a display device 34.

The communication interface 28 of the destination device 14 is used, for example, to receive the encoded picture data 21 or the encoded data 13 directly from the source device 12 or any other source. Any other source is, for example, a storage device, and the storage device is, for example, encoded picture data storage. device.

The communication interface 22 and the communication interface 28 can be used for direct communication through a direct communication link between the source device 12 and the destination device 14 or transmission or reception of encoded picture data 21 or encoded data 13 through any type of network The link is, for example, a direct wired or wireless connection, and any type of network is, for example, a wired or wireless network or any combination thereof, or any type of private and public network, or any combination thereof.

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

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

Both the communication interface 22 and the communication interface 28 may be configured as unidirectional communication interfaces, as indicated by the arrows for the encoded picture data 13 from the source device 12 to the destination device 14 in FIG. 1A, or configured as bidirectional communication interfaces, and It can 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 data transmission such as encoded picture data transmission.

The decoder 30 is configured to receive the encoded picture data 21 and provide the decoded picture data 31 or the decoded picture 31 (details will be further described below, for example, based on FIG. 3 or FIG. 5). In one example, the decoder 30 may be used to perform the following embodiments one to seven.

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

The display device 34 of the destination device 14 is used to receive the post-processed picture data 33 to display a picture to, for example, a user or a viewer. The display device 34 may be or may include any kind of display for presenting a 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), Digital light processor (DLP) or any other display of any kind.

Although FIG. 1A illustrates the source device 12 and the destination device 14 as separate devices, the device embodiment may also include the source device 12 and the destination device 14 or both of the functionality, that is, the source device 12 or corresponding And the functionality of the destination device 14 or equivalent. In such embodiments, the same hardware and / or software, or separate hardware and / or software, or any combination thereof may be used to implement the source device 12 or corresponding functionality and the destination device 14 or corresponding functionality .

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

Both the encoder 20 (e.g., video encoder 20) and decoder 30 (e.g., video decoder 30) may be implemented as any of a variety of suitable circuits, such as one or more microprocessors, digital signal processors (digital signal processor, DSP), application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), discrete logic, hardware, or any combination thereof. If the technology is implemented partially in software, the device may store the software's instructions in a suitable non-transitory computer-readable storage medium, and may use one or more processors to execute the instructions in hardware to perform the techniques of the present disclosure. . Any one of the foregoing (including hardware, software, a combination of hardware and software, etc.) can be considered as one or more processors. Each of the video encoder 20 and the video decoder 30 may be included in one or more encoders or decoders, and any of the encoders or decoders may be integrated as a combined encoder / decoder in a corresponding device (Codec).

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

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

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

In some cases, the video encoding system 10 shown in FIG. 1A is merely an example, and the techniques of this application may be applicable to video encoding settings (eg, video encoding or video decoding) that do not necessarily include any data communication between encoding and decoding devices. . In other examples, data may be retrieved from local storage, streamed over a network, and the like. The video encoding device may encode the data and store the data to a memory, and / or the video decoding device may retrieve the data from the memory and decode the data. In some examples, encoding and decoding are performed by devices that do not communicate with each other, but only 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. Regarding signaling syntax elements, video decoder 30 may be used to receive and parse such syntax elements, and decode related video data accordingly. In some examples, video encoder 20 may entropy encode syntax elements into an encoded video bitstream. In such examples, video decoder 30 may parse such syntax elements and decode related video data accordingly.

FIG. 1B is an explanatory diagram of an example of a video encoding system 40 including the encoder 20 of FIG. 2 and / or the decoder 30 of FIG. 3 according to an exemplary embodiment. The system 40 may implement a combination of various techniques of the present application. In the illustrated embodiment, the video encoding system 40 may include an imaging device 41, a video encoder 20, a video decoder 30 (and / or a video encoder implemented by the logic circuit 47 of the 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, antenna 42, processing unit 46, logic circuit 47, video encoder 20, video decoder 30, processor 43, memory 44, and / or display device 45 can communicate with each other. As discussed, although video encoding system 40 is shown 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, the video encoding system 40 may include an antenna 42. For example, the antenna 42 may be used to transmit or receive an encoded bit stream of video data. In addition, in some examples, the video encoding system 40 may include a display device 45. The display device 45 may be used to present video data. In some examples, as shown, the logic circuit 47 may be implemented by the processing unit 46. The processing unit 46 may include application-specific integrated circuit (ASIC) logic, a graphics processor, a general-purpose processor, and the like. The video encoding system 40 may also include an optional processor 43, which may similarly include application-specific integrated circuit (ASIC) logic, a graphics processor, a general-purpose processor, and the like. In some examples, the logic circuit 47 may be implemented by hardware, such as dedicated hardware for video encoding, and the processor 43 may be implemented by general software, operating system, and the like. In addition, the memory 44 may be any type of memory, such as volatile memory (e.g., Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), etc.) or non-volatile memory Memory (for example, flash memory, etc.). In a non-limiting example, the memory 44 may be implemented by a cache memory. In some examples, the logic circuit 47 may access the memory 44 (eg, for implementing an image buffer). In other examples, the logic circuit 47 and / or the processing unit 46 may include a memory (eg, a cache, etc.) for implementing an image buffer or the like.

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

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

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

Encoder & encoding method

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

For example, the residual calculation unit 204, the transformation processing unit 206, the quantization unit 208, the prediction processing unit 260, and the entropy encoding unit 270 form the forward signal path of the encoder 20, while the inverse quantization unit 210, the inverse transformation processing unit 212, The constructing unit 214, the buffer 216, the loop filter 220, the decoded picture buffer (DPB) 230, and the prediction processing unit 260 form a backward signal path of the encoder, wherein the backward signal path of the encoder corresponds to To the decoder's signal path (see decoder 30 in Figure 3).

The encoder 20 receives a picture 201 or a block 203 of the picture 201 through, for example, an input 202, for example, a picture in a picture sequence forming a video or a video sequence. The picture block 203 can also be called the current picture block or the picture block to be encoded, and the picture 201 can be called the current picture or the picture to be encoded (especially when the current picture is distinguished from other pictures in video encoding, other pictures such as the same video sequence (Ie previously encoded and / or decoded pictures in the video sequence of the current picture).

segmentation

An embodiment of the encoder 20 may include a segmentation unit (not shown in FIG. 2) for segmenting the picture 201 into multiple blocks, such as the block 203, and generally into multiple non-overlapping blocks. The segmentation unit can be used to use the same block size and corresponding raster to define the block size for all pictures in the video sequence, or to change the block size between pictures or subsets or groups of pictures, and split each picture into Corresponding block.

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

Like picture 201, block 203 is also or can be regarded as a two-dimensional array or matrix of sampling points with brightness values (sampling values), although its size is smaller than picture 201. In other words, the block 203 may include, for example, one sampling array (e.g., a luminance array in the case of a black and white picture 201) or three sampling arrays (e.g., one luminance array and two chroma arrays in the case of a color picture) or a basis An array of any other number and / or category of color formats 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 shown in FIG. 2 is used to encode a picture 201 block by block, for example, performing encoding and prediction on each block 203.

Residual calculation

The residual calculation unit 204 is configured to calculate the residual block 205 based on the picture block 203 and the prediction block 265 (the other details of the prediction block 265 are provided below). For example, the sample value of the picture block 203 is subtracted from the prediction by sample-by-sample (pixel-by-pixel). Sample values of block 265 to obtain residual block 205 in the sample domain.

Transform

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

The transform processing unit 206 may be used to apply an integer approximation of DCT / DST, such as the transform specified for HEVC / H.265. Compared to an orthogonal DCT transform, this integer approximation is usually scaled by a factor. To maintain the norm of the residual blocks processed by the forward and inverse transforms, an additional scaling factor is applied as part of the transform process. The scaling factor is usually selected based on certain constraints, for example, the scaling factor is a power of two used for shift operations, the bit depth of the transform coefficients, the trade-off between accuracy, and implementation cost. For example, a specific scaling factor is specified on the decoder 30 side by, for example, the inverse transform processing unit 212 (and on the encoder 20 side by, for example, the inverse transform processing unit 212 as the corresponding inverse transform), and accordingly, the The 20 side specifies a corresponding scaling factor for the positive transformation through the transformation processing unit 206.

Quantify

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

The inverse quantization unit 210 is configured to apply the inverse quantization of the quantization unit 208 on the quantized coefficients to obtain the inverse quantized coefficients 211. For example, based on or using the same quantization step size as the quantization unit 208, apply the quantization scheme applied by the quantization unit 208 Inverse quantization scheme. The dequantized coefficient 211 may also be referred to as a dequantized residual coefficient 211, which corresponds to the transform coefficient 207, although the loss due to quantization is usually different from the transform coefficient.

The inverse transform processing unit 212 is used 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), so that Obtain an inverse transform block 213. The inverse transform block 213 may also be referred to as an inverse transform inverse quantized block 213 or an inverse transform residual block 213.

The reconstruction unit 214 (for example, the summer 214) is used to add the inverse transform block 213 (that is, the reconstructed residual block 213) to the prediction block 265 to obtain the reconstructed block 215 in the sample domain. For example, The sample values of the reconstructed residual block 213 are added to the 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 any unfiltered reconstructed block and / or corresponding sample values stored in the buffer unit 216 for any category of estimation and / or prediction, such as intra-frame prediction.

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

The loop filter unit 220 (or simply "loop filter" 220) is configured to filter the reconstructed block 215 to obtain the filtered block 221, so as to smoothly perform pixel conversion or improve video quality. The 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, Adaptive loop filters (adaptive loop filters, ALF), or sharpening or smoothing filters, or cooperative filters. Although the loop filter unit 220 is shown as an in-loop filter in FIG. 2, in other configurations, the 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.

An embodiment of the encoder 20 (correspondingly, the loop filter unit 220) may be used to output loop filter parameters (e.g., sample adaptive offset information), for example, directly output or by the entropy coding unit 270 or any other The entropy coding unit outputs after entropy coding, for example, so that the decoder 30 can receive and apply the same loop filter parameters for decoding.

The decoded picture buffer (DPB) 230 may be a reference picture memory that stores reference picture data for the video encoder 20 to encode video data. DPB 230 can be formed by any of a variety of memory devices, such as dynamic random access (DRAM) (including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), and resistive RAM (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 the filtered block 221. The decoded picture buffer 230 may be further used to store other previous filtered blocks of the same current picture or different pictures such as previously reconstructed pictures, such as the previously reconstructed and filtered block 221, and may provide a complete previous Reconstruction is the decoded picture (and corresponding reference blocks and samples) and / or part of the reconstructed current picture (and corresponding reference blocks and samples), for example for inter prediction. In a certain example, if the reconstructed block 215 is reconstructed without in-loop filtering, a decoded picture buffer (DPB) 230 is used to store the 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, such as a reference to the same (current) picture from buffer 216 Samples and / or reference picture data 231 from one or more previously decoded pictures from the decoded picture buffer 230, and used to process such data for prediction, i.e., may be provided as inter-predicted blocks 245 or intra- Prediction block 265 of prediction block 255.

The mode selection unit 262 may be used to select a prediction mode (such as an 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.

An embodiment of the mode selection unit 262 may be used to select a prediction mode (e.g., selected from those prediction modes supported by the prediction processing unit 260) that provides the best match or minimum residual (minimum residual means Better compression in transmission or storage), or provide minimal signaling overhead (minimum signaling overhead means better compression in transmission or storage), or consider or balance both. The mode selection unit 262 may be used to determine a prediction mode based on rate distortion optimization (RDO), that is, to select a prediction mode that provides the minimum code rate distortion optimization, or to select a prediction mode whose related code rate distortion meets the prediction mode selection criteria .

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

As described above, the encoder 20 is used 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, an intra prediction mode and / or an inter prediction mode.

The intra prediction mode set may include 35 different intra prediction modes, or may include 67 different intra prediction modes, or may include intra prediction modes defined in the developing H.266.

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

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

The prediction processing unit 260 may be further configured to divide the block 203 into smaller block partitions or sub-blocks, for example, using a quad-tree (QT) partition, a binary-tree (BT) partition, or Triple-tree (TT) segmentation, or any combination thereof, and for performing predictions, for example, for each of block partitions or sub-blocks, where the mode selection includes selecting the tree structure of the partitioned block 203 and the selection applied to the block The prediction mode for each of the 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 configured 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, for example, one or more other / different previous The reconstructed block of picture 231 is decoded for motion estimation. For example, the video sequence may include the current picture and the previously decoded picture 31, or in other words, the current picture and the previously decoded picture 31 may be part of the picture sequence forming the video sequence or form the picture sequence.

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

The motion compensation unit is used for obtaining, for example, receiving inter prediction parameters, and performing inter prediction based on or using the inter prediction parameters to obtain the inter prediction block 245. Motion compensation performed by a motion compensation unit (not shown in FIG. 2) may include taking out or generating a prediction block based on a motion / block vector determined through motion estimation (possibly performing interpolation on sub-pixel accuracy). Interpolation filtering can generate additional pixel samples from known pixel samples, potentially increasing the number of candidate prediction blocks that can be used to encode picture blocks. Upon receiving the motion vector of the PU for the current picture block, the motion compensation unit 246 may locate the prediction block pointed to by the motion vector in a reference picture list. Motion compensation unit 246 may also generate syntax elements associated with blocks and video slices for use by video decoder 30 when decoding picture blocks of video slices.

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

Embodiments of the encoder 20 may be used to select an intra-prediction mode based on an optimization criterion, such as based on a minimum residual (eg, an intra-prediction mode that provides a prediction block 255 most similar to the 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 of the intra prediction mode as selected. In any case, after selecting the intra prediction mode for the block, the intra prediction unit 254 is further configured to provide the intra prediction parameters to the entropy encoding unit 270, that is, to provide an indication of the selected intra prediction mode for the block. Information. In one example, the intra prediction unit 254 may be used to perform any combination of intra prediction techniques described below.

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

Other structural variations of video encoder 20 may be used to encode a video stream. For example, the non-transform-based encoder 20 may directly quantize the residual signal without a transform processing unit 206 for certain blocks or frames. In another embodiment, the encoder 20 may have a quantization unit 208 and an 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. The video decoder 30 is configured to receive, for example, encoded picture data (eg, an encoded bit stream) 21 encoded by the encoder 20 to obtain a decoded picture 231. During the decoding process, video decoder 30 receives video data from video encoder 20, such as an encoded video bitstream and associated syntax elements representing picture blocks of encoded video slices.

In the example of FIG. 3, the decoder 30 includes an entropy decoding unit 304, an inverse quantization unit 310, an inverse transform processing unit 312, a reconstruction unit 314 (such as a summer 314), a buffer 316, a loop filter 320, The decoded picture buffer 330 and the 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 inverse to the encoding pass described with reference to video encoder 20 of FIG. 2.

The entropy decoding unit 304 is configured to perform entropy decoding on the encoded picture data 21 to obtain, for example, quantized coefficients 309 and / or decoded encoding parameters (not shown in FIG. 3), for example, inter prediction, intra prediction parameters , (Filtered) any or all of the loop filter parameters and / or other syntax elements. The entropy decoding unit 304 is further configured to forward 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.

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

The prediction processing unit 360 may include an inter prediction unit 344 and an intra prediction unit 354. The inter prediction unit 344 may be functionally similar to the inter prediction unit 244 and the intra prediction unit 354 may be functionally similar to the intra prediction unit 254. . The prediction processing unit 360 is generally used to perform block prediction and / or obtain prediction blocks 365 from the encoded data 21, and to receive or obtain prediction-related parameters and / or Information about the selected prediction mode.

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

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

The inverse quantization unit 310 may be used for inverse quantization (ie, inverse quantization) of the quantized transform coefficients provided in the bitstream and decoded by the entropy decoding unit 304. The inverse quantization process may include using the 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 also to determine the degree of inverse quantization that should be applied.

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

Reconstruction unit 314 (e.g., summer 314) is used to add inverse transform block 313 (i.e., reconstructed residual block 313) to prediction block 365 to obtain reconstructed block 315 in the sample domain, such as by The sample values of the reconstructed residual block 313 are added to the sample values of the prediction block 365.

The loop filter unit 320 (during or after the encoding cycle) is used to filter the reconstructed block 315 to obtain the filtered block 321 so as to smoothly perform pixel conversion or improve video quality. In one example, the loop filter unit 320 may be used to perform any combination of filtering techniques described below. The 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, Adaptive loop filter (ALF), or sharpening or smoothing filter, or cooperative filter. Although the loop filter unit 320 is shown as an in-loop filter in FIG. 3, in other configurations, the loop filter unit 320 may be implemented as a post-loop filter.

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

The decoder 30 is used, for example, to output a decoded picture 31 through an output 332 for presentation to or review by a user.

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

FIG. 4 is a schematic structural diagram of a video decoding device 400 (such as a video encoding device 400 or a video decoding device 400) according to an embodiment of the present invention. Video coding device 400 is adapted to implement the embodiments described herein. In one embodiment, the video coding device 400 may be a video decoder (such as video decoder 30 of FIG. 1A) or a video encoder (such as video encoder 20 of FIG. 1A). In another embodiment, the video decoding device 400 may be one or more of the video decoder 30 of FIG. 1A or the video encoder 20 of FIG. 1A described above.

The video decoding device 400 includes: an entry port 410 and a receiving unit (Rx) 420 for receiving data, a processor, a logic unit or a central processing unit (CPU) 430 for processing data, and a transmitter unit for transmitting data (Tx) 440 and egress port 450, and a memory 460 for storing data. The video decoding device 400 may further include a photoelectric conversion component and an electro-optic (E0) component coupled with the entrance port 410, the receiver unit 420, the transmitter unit 440, and the exit port 450, for the exit or entrance of an optical signal or an electric signal.

The processor 430 is implemented by hardware and software. The processor 430 may be implemented as one or more CPU chips, cores (eg, multi-core processors), FPGAs, ASICs, and DSPs. The processor 430 is in communication with the ingress port 410, the receiver unit 420, the transmitter unit 440, the egress port 450, and the memory 460. The processor 430 includes a decoding module 470 (eg, an encoding module 470 or a decoding module 470). The encoding / decoding module 470 implements the embodiments disclosed above. For example, the encoding / decoding module 470 implements, processes, or provides various encoding operations. Therefore, the function of the video decoding device 400 is substantially improved through the encoding / decoding module 470, and the transition of the video decoding device 400 to different states is affected. Alternatively, the encoding / decoding module 470 is implemented with instructions stored in the memory 460 and executed by the processor 430.

The memory 460 includes one or more magnetic disks, tape drives, and solid-state hard disks, which can be used as overflow data storage devices for storing programs when these programs are selectively executed, and for storing instructions and data read during program execution. The memory 460 may be volatile and / or non-volatile, and may be a read-only memory (ROM), a random access memory (RAM), a random content-addressable memory (TCAM), and / or a static state. Random access memory (SRAM).

FIG. 5 is a simplified block diagram of an apparatus 500 that can be used as either or both of the source device 12 and the destination device 14 in FIG. 1A according to an exemplary embodiment. The device 500 may implement the technology of the present application. The device 500 for implementing chroma block prediction may be in the form of a computing system including a plurality of computing devices, or in a mobile phone, tablet computer, laptop computer, notebook computer, desktop The form of a single computing device, such as a computer.

The processor 502 in the apparatus 500 may be a central processing unit. Alternatively, the processor 502 may be any other type of device or multiple devices capable of manipulating or processing information, existing or to be developed in the future. As shown, although a single processor such as the processor 502 can be used to practice the disclosed embodiments, speed and efficiency advantages can be achieved using more than one processor.

In one embodiment, the memory 504 in the device 500 may be a read-only memory (ROM) device or a random access memory (RAM) device. Any other suitable type of storage device can be used as the memory 504. The memory 504 may include code and data 506 accessed by the processor 502 using the bus 512. The memory 504 may further include an operating system 508 and an application program 510, which contains at least one program that permits the processor 502 to perform the methods described herein. For example, the application program 510 may include applications 1 to N, and applications 1 to N further include a video encoding application that performs the methods described herein. The device 500 may also include additional memory in the form of a slave memory 514, which 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.

The apparatus 500 may also include one or more output devices, such as a display 518. In one example, the display 518 may be a touch-sensitive display combining a display and a touch-sensitive element operable to sense a touch input. The display 518 may be coupled to the processor 502 through a bus 512. In addition to the display 518, other output devices may be provided that allow the user to program or otherwise use the device 500, or provide other output devices as an alternative to the display 518. When the output device is a display or contains a display, the display can be implemented in different ways, including through a liquid crystal display (LCD), a cathode-ray tube (CRT) display, a plasma display, or a light emitting diode (ligbt) emitting diode (LED) displays, such as organic LED (OLED) displays.

The apparatus 500 may further include or be in communication with an image sensing device 520, such as a camera or any other image sensing device 520 that can or will be developed in the future to sense an image, such as An image of a user running the device 500. The image sensing device 520 may be placed directly facing a user of the running apparatus 500. In an example, the position and optical axis of the image sensing device 520 may be configured such that its field of view includes an area immediately adjacent to the display 518 and the display 518 is visible from the area.

The device 500 may also include or be in communication with a sound sensing device 522, such as a microphone or any other sound sensing device that can or will be developed in the future to sense the sound near the device 500. The sound sensing device 522 may be placed directly facing the user of the operating device 500 and may be used to receive a sound, such as a voice or other sound, emitted by the user when the device 500 is running.

Although the processor 502 and the memory 504 of the apparatus 500 are shown in FIG. 5 as being integrated in a single unit, other configurations may be used. The operation of the processor 502 may be distributed among a plurality of directly coupleable machines (each machine having one or more processors), or distributed in a local area or other network. The memory 504 may be distributed among multiple machines, such as a network-based memory or a memory among multiple machines running the apparatus 500. Although only a single bus is shown here, the bus 512 of the device 500 may be formed by multiple buses. Further, the slave memory 514 may be directly coupled to other components of the device 500 or may be accessed through a network, and may include a single integrated unit, such as one memory card, or multiple units, such as multiple memory cards. Therefore, the apparatus 500 can be implemented in various configurations.

As described earlier in this application, a color video contains a chrominance component (U, V) in addition to a luminance (Y) component. Therefore, in addition to encoding the luminance component, it is also necessary to encode the chrominance component. According to different sampling methods of the luminance component and the chrominance component in a color video, there are generally YUV4: 4: 4, YUV4: 2: 2, and YUV4: 2: 0. As shown in FIG. 6, where a cross represents a sampling point of a luminance component, and a circle represents a sampling point of a chrominance component.

-4: 4: 4 format: indicates that the chrominance component is not down-sampled;

-4: 2: 2 format: indicates that the chrominance component is down-sampled horizontally with respect to the luminance component at 2: 1, without vertical down-sampling. For every two U sampling points or V sampling points, each line contains four Y sampling points;

-4: 2: 0 format: indicates that the chrominance component is subjected to a horizontal downsampling of 2: 1 relative to the luminance component and a vertical downsampling of 2: 1.

Among them, YUV4: 2: 0 is the most common. In the case where the video image uses the YUV4: 2: 0 sampling format, if the luminance component of the image block is an image block of size 2Mx2N, the chrominance component of the image block is an image block of size MxN. Therefore, the chrominance component of an image block is also referred to as a chrominance block or a chrominance component block in this application. This application is described with YUV4: 2: 0, but it can also be applied to other sampling methods of luminance components and chrominance components.

In this application, the pixels in the chroma image are referred to as chroma samples, or chroma points; the pixels in the luminance image are referred to as luma samples, or brightness. point.

Similar to the luminance component, chroma intra prediction also uses the boundary pixels of adjacent reconstructed blocks around the current chroma block as the reference pixels of the current block, and maps the reference pixels to the pixels in the current chroma block according to a certain prediction mode. , As the predicted value of pixels in the current chroma block. The difference is that since the texture of the chroma component is generally simple, the number of intra prediction modes of the chroma component is generally less than the luminance component.

Linear mode (LM) is a chroma intra prediction method that uses texture correlation between luminance and chroma. LM uses the reconstructed luminance component to derive the current chrominance block prediction value according to a linear model, which can be expressed as the following formula:

pred _C (i, j) = α * rec _L ′ (i, j) + β (1)

Among them, α and β are linear model coefficients, pred _C (i, j) is the predicted value of the chroma pixel at the position (i, j), and rec _L ′ (i, j) is the luminance reconstruction block corresponding to the current chroma block. (Hereinafter referred to as the corresponding luminance block) the luminance reconstruction pixel value at the (i, j) position after being down-sampled to the chroma component resolution.

The linear model coefficients do not need to be coded for transmission, but use the edge pixels of adjacent reconstructed blocks of the current chrominance block and the luminance component pixels at corresponding positions of the edge pixels to derive α, β. Let the number of adjacent reference pixels be N, where L _n and C _n are the values of the nth luma pixel and the value of the chroma pixel, 0 ≦ n ≦ N-1. L _n and C _n can form pixel value pairs, so a set of pixel value pairs can be obtained: {(L ₀ , C ₀ ), (L ₁ , C ₁ ), (L ₂ , C ₂ ) ... (L _n , C _n ) ... (L _N-1 , C _N-1 )}, where N is the number of adjacent pixel points of the current chroma block used to determine the coefficients of the linear model. As shown in FIG. 7, a value pair corresponding to the maximum brightness value L _max and the minimum brightness value L _min is found in the pixel value pair set, and the i-th pixel point B corresponds to the maximum brightness value point, that is, L _i = L _max , Let the j-th pixel point A correspond to the minimum brightness value point, that is, L _j = L _min . then

β = C _j -α * L _j (3)

For the sake of simplicity, the method of determining the linear model coefficient using the value pair corresponding to the maximum brightness value L _max and the minimum brightness value L _min is referred to as an extreme value method, and the maximum brightness value L _max is also referred to as a maximum brightness value or The maximum value or brightness maximum value, the corresponding value pair is called the maximum value pair; the minimum brightness value L _min is also called the minimum brightness value or the minimum value or the brightness minimum value, and the corresponding value pair is called the minimum value pair .

The LM mode can effectively use the correlation between the luminance component and the chrominance component. Compared with the directional prediction mode, the LM method is more flexible, thereby providing a more accurate prediction signal for the chrominance component.

In addition, there is also a multiple model linear model (MMLM), and there are multiple α and β. Taking two linear models as an example, there are two sets of linear model coefficients, α ₁ , β ₁ and α ₂ , β ₂ . MMLM uses the reconstructed luminance component to derive the current chrominance block prediction value according to a linear model, which can be expressed as the following formula:

For convenience of explanation, the adjacent upper and left sides used to calculate the linear model coefficients are referred to as templates in this application. The adjacent upper side is called the upper template, and the adjacent left side is called the left template. The chrominance sampling points in the upper template are referred to as the upper template chroma points, and the luminance sampling points in the upper template are referred to as the upper template luma points. Similarly, the left template chroma point and the left template luma point are known. The template luminance point and the template chrominance point correspond one-to-one, and the values of the sampling points constitute a value pair.

In the embodiment of the present application, the template represents a set of luminance points or chrominance points used to calculate linear model coefficients. The luminance points generally need to be obtained by resampling (because the resolution of the luminance component is different from the chrominance). Chroma points are generally one or two rows of pixels adjacent to the current chroma block and one or two columns of pixels on the left. Figure 8 (a) is a schematic diagram of the template using one row and one column, and Figure 8 (b) is a schematic diagram of the template using two rows and two columns. A template or a template region refers to an adjacent region of the luminance block.

In the specific encoding process, the current chroma block uses the RDO criterion to select the best mode from the LM mode and other chroma modes.

An embodiment of the present application proposes a linear model coefficient derivation method for reducing LM complexity. Specifically, after searching for extreme values in the template luminance points, the corresponding chromaticity values are determined. Then determine a luminance value and chrominance value, and combine the obtained luminance extreme value and corresponding chrominance value to derive two linear models for the construction of chrominance prediction blocks.

It should be noted that the embodiments of the present application do not limit the positions, numbers, and acquisition methods of the template luminance points and template chrominance points. For example, one row and one column of pixels can be used, or two rows and two columns of pixels can be used. The template brightness points can be obtained by downsampling or non-downsampling.

For the convenience of description, the set of value pairs composed of the template luminance point value and the template chrominance point value is Ω, the set of the template luminance point value is Ψ, and the set of the template chrominance point value is Ф.

Ω = {(L ₀ , C ₀ ), (L ₁ , C ₂ ) ... (L _n , C _n ) ... (L _N-1 , C _N-1 )}

Ψ = {L ₀ , L ₁ , ... L _n , ... L _N-1 }

Ф = {C ₀ , C ₁ , ... C _n , ... C _N-1 }

Here N is the number of template pixels used to determine the coefficients of the linear model.

It should be noted that the embodiments of the present application are mainly used for an intra prediction process, and this process exists at both the encoding end and the decoding end. With reference to the following first to fifth embodiments, a prediction method of a chroma block is described. Specifically, the following embodiments 1 to 5 can be performed by the system or device in the embodiment of FIGS. 1A-5.

Example one

As shown in FIG. 9, in the first embodiment, after searching for extreme values in the template brightness points, the corresponding chromaticity values are determined. Then determine a luminance value and chrominance value, and combine the obtained luminance extreme value and corresponding chrominance value to derive two linear models for the construction of chrominance prediction blocks.

Step 902: Obtain an extreme value of brightness

First you need to get the extreme brightness. The value of the brightness point in the template of the brightness block corresponding to the current chroma block is searched to obtain the brightness extreme value. The search range here is the template region of the luma block corresponding to the current chroma block, and the template region includes an upper template and / or a left template. As shown in Figures 8 (a) and 8 (b), you can search one row of the upper template, one row of the upper template and one column of the left template, or two rows of the upper template, or two rows of the upper template. Row and two columns of the left template.

In the set of template brightness point values, search for extreme values. The brightness extreme value includes a brightness maximum value and a brightness minimum value. Let 找到 = {L ₀ , L ₁ , ... L _n , ... L _N-1 } find the maximum brightness value L _i and the minimum brightness value L _j .

Step 904: Obtain the value of the chrominance point corresponding to the brightness extreme value.

After obtaining the extreme value of brightness, the value of the corresponding chromaticity point needs to be determined. The position of the corresponding chrominance point is the position of the chrominance point closest to the position of the extreme point of luminance. When the brightness extreme value includes a brightness maximum value and a brightness minimum value, a value of a chroma point corresponding to the brightness maximum value and a value of a chroma point corresponding to the brightness minimum value are obtained. For example, if the maximum luminance value is L _i , then the value of the chroma point corresponding to L _i (referred to as the chroma value) is C _i ; if the minimum luminance value is L _j , the chroma value corresponding to L _j is C _j .

Step 906: Determine the third brightness value.

Multiple methods can be used to determine the third brightness value. For example, the average value of the brightness points in the template of the brightness block can be used as the third brightness value; or the value closest to the average value of the brightness points in the template of the brightness block can be used as the third value. The brightness value; the values of the brightness points in the template of the brightness block can also be sorted, and the sorted intermediate value is used as the third brightness value; this is not limited in the first embodiment of the present invention.

Step 908: Determine the value of the chroma point corresponding to the third brightness value

Similar to step 904, after obtaining the third luminance value, the value of the corresponding chrominance point needs to be determined. The position of the corresponding chromaticity point is the position of the luminance point closest to the third luminance value.

Step 910: Obtain two sets of linear model coefficients according to the brightness extreme value and the value of the chromaticity point corresponding to the brightness extreme value, the third brightness value and the value of the chromaticity point corresponding to the third brightness value. .

Specifically, according to the luminance maximum value and the value of the chroma point corresponding to the luminance maximum value, the third luminance value and the value of the chroma point corresponding to the third luminance value, a first group is obtained. A linear model coefficient; obtaining a second value according to the minimum luminance value and a value of a chroma point corresponding to the minimum luminance value, the third luminance value and a value of a chroma point corresponding to the third luminance value Set of linear model coefficients.

Step 912: Obtain the predicted value of the current chroma block

According to the reconstructed value of the luma block, and then obtain the predicted value of the current chroma block according to formula (4).

According to the method in Embodiment 1 of the present invention, according to the brightness extreme value and a value of a chromaticity point corresponding to the brightness extreme value, the third brightness value and a value of a chromaticity point corresponding to the third brightness value, By the extreme method, two sets of linear model coefficients are obtained. Compared with the prior art, which obtains two sets of linear model coefficients by the method of least squares, the embodiment of the present invention can reduce the complexity of the MMLM mode and improve the efficiency of chroma encoding and decoding.

Example two

In the second embodiment, first, the extreme value points in the template brightness points are obtained, and the corresponding chrominance value points are determined. Then determine the average value of the brightness points in the template of the brightness block, find the value of the brightness point closest to the average value of the brightness points in the template among the template brightness points, and determine the value of the corresponding chrominance point. Using the determined three points, two linear models are derived for prediction of chrominance blocks.

With reference to the embodiment of FIG. 10, specific steps for acquiring a prediction signal of a chroma block are described.

Step 1002 is similar to step 902 of the first embodiment, and step 1004 is similar to step 904 of the first embodiment, and details are not described again.

Step 1006: Calculate the average value of the brightness points in the template of the brightness block, and determine the value of the brightness point closest to the average value among the brightness points of the template as the third brightness value.

In an implementation manner, an average value of the brightness points in the template of the brightness block is L _mean = (L _i + L _j ) / 2. In another implementation manner, the mean value of the brightness points in the template of the brightness block is

Where N is the number of brightness points in the template, L _n is the value of the nth brightness point, and 0≤n≤N-1.

Taking FIG. 11 as an example, in Ψ = {L ₀ , L ₁ , ... L _n , ... L _N-1 }, determine the value closest to the mean L _mean , and set it to L _s , then L _s satisfies, for n in any 0≤n≤N-1:

| L _s -L _mean | ≤ | L _n -L _mean |

Step 1008: Determine the value of the chroma point corresponding to the third brightness value

The position of the corresponding chromaticity point is the position of the luminance point closest to the third luminance value. Let L _s correspond to the chromaticity value C _s .

Step 1010: Obtain two sets of linear model coefficients according to the brightness extreme value and the value of the chroma point corresponding to the brightness extreme value, the third brightness value and the value of the chroma point corresponding to the third brightness value. (α ₁ , β ₁ ), (α ₂ , β ₂ ).

For example, based on (L _i , C _i ), (L _s , C _s ), (L _j , C _j ) and formulas (2), (3), two linear models are obtained.

Step 1008: Obtain the predicted value of the chrominance block.

According to the method in Embodiment 2 of the present invention, according to the brightness extreme value and the value of the chromaticity point corresponding to the brightness extreme value, the value of the brightness point closest to the mean value is used as the third brightness value, and the third brightness The values of the chrominance points corresponding to the values are obtained through two extreme linear method coefficients through the extreme method. Compared with the two sets of linear model coefficients obtained through the least square method in the prior art, the embodiment of the present invention can reduce the complexity of the MMLM and improve the MMLM. The efficiency of chroma codec.

Example three

In this embodiment, first, an extreme value point in the template brightness point is obtained, and a corresponding chromaticity value point is determined. Then obtain the average value of the brightness in the template brightness points and the average value of the chroma in the template chromaticity points. Then two linear models are derived for obtaining the predicted values of the chrominance blocks.

With reference to the embodiment of FIG. 12, specific steps for acquiring a prediction signal of a chroma block are described.

Step 1202 is similar to step 902 of the first embodiment, and step 1204 is similar to step 904 of the first embodiment, and details are not described again.

Step 1206: Calculate the average value of the brightness points in the template of the brightness block as the third brightness value.

In an implementation manner, the average value of the brightness points in the template of the brightness block is L _mean = (L _i + L _j ) / 2, as shown in FIG. 13. In another implementation manner, the mean value of the brightness points in the template of the brightness block is

Step 1208: Determine the value of the chroma point corresponding to the third brightness value

As shown in FIG. 13, an average value of chrominance points in the template of the current chrominance block is calculated as a value of the chrominance point corresponding to the third luminance value. In an implementation manner, an average value of the chrominance points in the template of the current chrominance block is C _mean = (C _i + C _j ) / 2. In another implementation manner, the average value of the chroma points in the template of the current chroma block is

Step 1210: Obtain two sets of linear model coefficients according to the brightness extreme value and the value of the chromaticity point corresponding to the brightness extreme value, the third brightness value and the value of the chromaticity point corresponding to the third brightness value. (α ₁ , β ₁ ), (α ₂ , β ₂ ).

For example, based on (L _i , C _i ), (L _mean , C _mean ), (L _j , C _j ) and formulas (2), (3), two linear models are obtained.

Step 1208: Obtain the predicted value of the chroma block

According to the method in Embodiment 3 of the present invention, according to the brightness extreme value and the value of the chromaticity point corresponding to the brightness extreme value, the average value is used as the third brightness value, and the value of the chromaticity point corresponding to the third brightness value is Value, two sets of linear model coefficients are obtained by the extreme value method. Compared with the two sets of linear model coefficients obtained by the least square method in the prior art, the embodiment of the present invention can reduce the complexity of MMLM and improve the efficiency of chroma coding .

Embodiment 4

In this embodiment, first, an extreme value point in the template brightness point is obtained, and a corresponding chromaticity value point is determined. Then find the median brightness point in the template brightness point and determine the value of its corresponding chromaticity point. Using the above three points, two linear models are derived for obtaining the predicted value of the chrominance block.

With reference to the embodiment of FIG. 14, specific steps for acquiring a prediction signal of a chroma block are described.

Step 1402 is similar to step 902 of the first embodiment, and step 1404 is similar to step 904 of the first embodiment, and details are not described again.

Step 1406: Obtain an intermediate value of the template brightness point as the third brightness value.

As shown in FIG. 15, in the template luminance point value set Ψ = {L ₀ , L ₁ , ... L _n , ... L _N-1 }, the luminance point corresponding to the intermediate value (referred to as the median point for short) is determined. ). Specifically, the values of the brightness points in the template of the brightness block may be sorted (can be sorted from small to large, or sorted from large to small), and the sorted intermediate value is taken as the third brightness value. . Let the median point be Ls.

Step 1408: Determine the value of the chroma point corresponding to the third brightness value

The chromaticity value corresponding to Ls is Cs. For details, refer to the description of

step

908 or 1008.

Step 1410: Obtain two sets of linear model coefficients according to the brightness extreme value and the value of the chromaticity point corresponding to the brightness extreme value, the third brightness value and the value of the chromaticity point corresponding to the third brightness value. (α ₁ , β ₁ ), (α ₂ , β ₂ ).

Step 1408: Obtain the predicted value of the chroma block

According to the method in Embodiment 4 of the present invention, according to the brightness extreme value and the value of the chromaticity point corresponding to the brightness extreme value, a middle value is used as the third brightness value, and the chromaticity point corresponding to the third brightness value By using the extreme value method, two sets of linear model coefficients are obtained. Compared with the prior art, which obtains two sets of linear model coefficients by the method of least squares, the embodiment of the present invention can reduce the complexity of the MMLM and improve the chroma encoding and decoding. effectiveness.

Example 5

In this embodiment, first, an extreme value point in the template brightness point is obtained, and a corresponding chromaticity value point is determined. Then classify the points according to the mean value of the luminance points in the template of the luminance block. Each class obtains a linear model based on the extreme value method, where the minimum value class determines the minimum value, and the smaller value class determines the maximum value.

With reference to the embodiment of FIG. 16, specific steps for acquiring a prediction signal of a chroma block are described.

Step 1602 is similar to step 902 of the first embodiment, and step 1604 is similar to step 904 of the first embodiment, and details are not described again.

Step 1606: Classify the points according to the mean value of the brightness points in the template of the brightness block. First calculate the mean value of the brightness points in the template of the brightness block, and set the mean value to L _mean = (L _i + L _j ) / 2. As shown in FIG. 17, Ω = {(L ₀ , C ₀ ), (L ₁ , C ₂ ) ... (L _n , C _n ) ... (L _N-1 , C _N-1 )} Classification is performed according to the average value of the brightness points in the above-mentioned template of the brightness block to obtain a larger value class Ω _p and a smaller value class Ω _Q. Where the value of the luminance portion of each value pair in Ω _p is greater than L _mean . The value of the luminance portion of each value pair in Ω _Q is less than or equal to L _mean .

Step 1608: Determine the minimum luminance value and the corresponding chrominance value in the larger value class, and determine the maximum luminance value and the corresponding chrominance value in the smaller value class.

The minimum luminance value L _t and the chromaticity value C _t corresponding to the minimum value are determined in the larger value class Ω _p .

In the smaller value class Ω _Q , the maximum luminance value L _s and the chrominance value C _s corresponding to the maximum value are determined.

Step 1610: Obtain two sets of linear model coefficients.

Step 1612: Obtain the predicted value of the chroma block

In the method of Embodiment 5 of the present invention, the minimum luminance value and the corresponding chrominance value are determined in the larger value class, and the maximum luminance value and the corresponding chrominance value are determined in the smaller value class. Two sets of linearity are obtained by the extreme value method The model coefficients are compared with the two sets of linear model coefficients obtained by the least square method in the prior art. The embodiment of the present invention can reduce the complexity of the MMLM and improve the efficiency of chroma encoding and decoding.

It should be understood that the disclosure combined with the described method may be equally applicable to a corresponding device or system for performing the method, and vice versa. For example, if one or more specific method steps are described, the corresponding device may include one or more units such as functional units to perform the described one or more method steps (e.g., one 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 drawings. On the other hand, for example, if a specific device is described based on one or more units such as functional units, the corresponding method may include a step to perform the functionality of one or more units (e.g., a step performs one or more units Functionality, or multiple steps, where each performs the functionality of one or more of the multiple units), even if such one or more steps are not explicitly described or illustrated in the drawings. Further, it should be understood that the 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 or transmitted as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium, which corresponds to a tangible medium such as a data storage medium or a communication medium including any medium that facilitates transfer of a computer program from one place to another according to a communication protocol . In this manner, computer-readable media generally may correspond to (1) tangible computer-readable storage media that is non-transitory, or (2) a communication medium such as 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, codes, and / or data structures used to implement 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 may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage devices, flash memory, or may be used to store instructions or data structures Any other media that requires program code and is accessible by the computer. Also, any connection is properly termed a computer-readable medium. For example, if a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technology such as infrared, radio, and microwave is used to transmit instructions from a website, server, or other remote source, then Coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of the 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 temporary media, but are actually directed to non-transitory tangible storage media. As used herein, magnetic disks and compact discs include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), flexible discs and Blu-ray discs, where the discs are usually magnetic The data is reproduced, while the optical disk uses a laser to reproduce the data optically. 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 , ASIC), field programmable logic array (field programmable logic arrays, FPGA) or other equivalent integrated or discrete logic circuits. Accordingly, the term "processor" as used herein may refer to any of the above-described structures or any other structure suitable for implementing the techniques described herein. Additionally, in some aspects, the functionality described herein may be provided within dedicated hardware and / or software modules for encoding and decoding, or incorporated in a composite codec. Also, the techniques could 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 devices that include a wireless handset, an integrated circuit (IC), or a collection of ICs (eg, a chipset). The present disclosure describes various components, modules, or units to emphasize functional aspects of the device for performing the disclosed techniques, but does not necessarily need to be implemented by different hardware units. Specifically, as described above, the various units may be combined in a codec hardware unit in combination with suitable software and / or firmware, or provided by a collection of interoperable hardware units, which include as described above One or more processors.

Claims

A prediction method for chrominance blocks includes:

Searching a value of a brightness point in a template of a brightness block corresponding to the current chroma block to obtain a brightness extreme value, the brightness extreme value including a brightness maximum value and a brightness minimum value;

Obtaining a value of a chroma point corresponding to the maximum luminance value and a value of a chroma point corresponding to the minimum luminance value;

Determining a third brightness value;

Determining a value of a chroma point corresponding to the third brightness value;

Obtaining a first set of linear model coefficients according to the luminance maximum value and a value of a chroma point corresponding to the luminance maximum value, the third luminance value and a value of a chroma point corresponding to the third luminance value ;

Obtaining the second set of linear model coefficients according to the minimum luminance value and the value of the chroma point corresponding to the minimum luminance value, the third luminance value and the value of the chroma point corresponding to the third luminance value ;with

A prediction value of the current chrominance block is obtained according to the two sets of linear model coefficients and a reconstruction value of the luminance block.
The method of claim 1, wherein determining the third brightness value comprises:

Calculating an average value of brightness points in a template of the brightness block;

In the template of the luminance block, a value closest to the average value of the luminance points is determined as the third luminance value.
The method according to claim 2, wherein if the maximum luminance value is L i , the minimum luminance value is L j , and the chromaticity value corresponding to L i is C i , and the color corresponding to L j is The degree value is C j , the mean value of the brightness points in the template of the luma block is L mean , the closest value in the template to the mean value L mean is L s , and the chromaticity value corresponding to L s is C s , Then the two sets of linear model coefficients (α 1 , β 1 ), (α 2 , β 2 ) are
The method of claim 1, wherein determining the third brightness value comprises:

Calculating an average value of the brightness points in the template of the brightness block as the third brightness value; and

An average value of chrominance points in the template of the current chrominance block is calculated as a value of a chrominance point corresponding to the third luminance value.
The method according to claim 4, wherein if the maximum luminance value is L i , the minimum luminance value is L j , and the chromaticity value corresponding to L i is C i , and the color corresponding to L j is The degree value is L j , the mean value of the luma points in the template of the luma block is L mean , and the mean value of the chroma points in the template of the current chroma block is C mean , then the two linear model coefficients (α 1 , Β 1 ), (α 2 , β 2 ) are
The method according to any one of claims 2 to 5, wherein the mean value of the brightness points in the template of the brightness block is L mean = (L i + L j ) / 2, and the brightness maximum value is L i , the minimum brightness value is L j .
The method according to any one of claims 2 to 5, wherein the mean value of the brightness points in the template of the brightness block is
Where N is the number of brightness points in the template, L n is the value of the nth brightness point, and 0≤n≤N-1.
The method according to claim 5, wherein the average value of the chrominance points in the template of the current chrominance block is C mean = (C i + C j ) / 2.
The method according to claim 5, wherein the average value of the chrominance points in the template of the current chrominance block is

Where N is the number of brightness points in the template, L n is the value of the nth brightness point, and 0≤n≤N-1.
The method according to claim 1, wherein the values of the brightness points in the template of the brightness block are sorted, and the sorted intermediate value is used as the third brightness value.
The method according to claim 10, wherein if the maximum luminance value is L i , the minimum luminance value is L j , and the chromaticity value corresponding to L i is C i , and the color corresponding to L j is The degree value is C j , the intermediate value of the brightness point in the template of the brightness block is L s , and the chromaticity value corresponding to L s is C s , then the two sets of linear model coefficients (α 1 , β 1 ), ( α 2 , β 2 ) is
An apparatus for decoding a video stream includes a processor and a memory, where the memory stores instructions, and the instructions cause the processor to execute the method according to any one of 1-11.
An apparatus for encoding a video stream includes a processor and a memory, where the memory stores instructions, and the instructions cause the processor to execute the method according to any one of 1-11.