KR102646642B1 - Method and apparatus of video decoder with extended intra block copy - Google Patents

Abstract

The present invention relates to a method and device for improving the performance of IBC technology, among video compression technologies, by effectively determining a prediction block in a current picture and performing a BV prediction process.

Description

Video decoding method and device using extended Intra Block Copy method {METHOD AND APPARATUS OF VIDEO DECODER WITH EXTENDED INTRA BLOCK COPY}

The present invention relates to video encoding and decoding technology, and more specifically, to a video decoding method and device using extended Intra Block Copy technology.

Market demand for high-resolution video is increasing, and accordingly, technology that can efficiently compress high-resolution video is needed. In response to these market demands, ISO/IEC's MPEG (Moving Picture Expert Group) and ITU-T's VCEG (Video Coding Expert Group) jointly formed JCT-VC (Joint Collaborative Team on Video Coding) to develop HEVC (High The development of the Efficiency Video Coding (Efficiency Video Coding) video compression standard was completed in January 2013, and research and development on next-generation compression standards are being actively conducted.

Some embodiments of the present invention aim to provide a method and apparatus for using IBC technology as an extension of video compression technology.

However, the technical challenges that this embodiment aims to achieve are not limited to the technical challenges described above, and other technical challenges may exist.

As a technical means for achieving the above problem, a video decoding apparatus and method according to an embodiment of the present invention includes the steps of obtaining information for IBC performance from a bitstream, and deriving a BVP using the obtained IBC performance information. Step, deriving a filter coefficient for generating a prediction block using the obtained IBC performance information, generating a prediction block through filtering using the determined BVP and filter coefficient, using the generated prediction block It includes steps for performing IBC.

According to the solution of the present invention described above, video encoding and decoding efficiency can be improved through the expanded IBC method and device in the decoder.

Figure 1 shows a decoding device including an IBC unit according to an embodiment of the present invention.
Figure 2 is a diagram illustrating a method of using a filtered prediction block when performing IBC according to an embodiment of the present invention.
Figure 3 is a flowchart showing the order of performing filtering when performing IBC according to an embodiment of the present invention.
Figure 4 is a diagram illustrating a method of determining a prediction block by scaling a block in the process of determining a prediction block when performing IBC according to an embodiment of the present invention.
Figure 5 is a diagram illustrating a method of determining a prediction block by rotating a block in the process of determining a prediction block when performing IBC according to an embodiment of the present invention.
Figure 6 is a flowchart showing the procedure for calculating BV through deriving BVP using template matching when performing IBC according to an embodiment of the present invention.
Figure 7 shows that when performing IBC according to an embodiment of the present invention, when the block performing IBC is a block in an IRAP (Intra Random Access Point) picture, frequently occurring BVs are managed in a list and used for BV prediction. This is a flowchart showing the order of the method.
Figure 8 is a diagram showing the range of BVs that can be stored in the BV list when BVP is determined by managing frequently occurring BVs in a list when performing IBC according to an embodiment of the present invention.
FIG. 9 is a diagram illustrating an IBC performance method when performing IBC according to an embodiment of the present invention when a picture is divided into square, rectangular, mixed block division, or any block division method. More generally, arbitrary shapes can be predicted by copying them in blocks.

Below, with reference to the drawings attached to the present specification, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts that are not related to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

Throughout this specification, when a part is said to be connected to another part, this includes not only the case where it is directly connected, but also the case where it is electrically connected with another element in between.

In addition, throughout the specification, when a part includes a certain element, this does not mean excluding other elements, but may further include other elements, unless specifically stated to the contrary.

As used throughout this specification, the term ~ (doing) step or step of ~ does not mean a step for ~.

Additionally, terms such as first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another.

In addition, the components appearing in the embodiments of the present invention are shown independently to represent different characteristic functions, and this does not mean that each component is comprised of separate hardware or one software component. That is, for convenience of explanation, each component is listed and described as each component, and at least two of each component may be combined to form one component, or one component may be divided into a plurality of components to perform a function. Integrated embodiments and separate embodiments of each of these components are also included in the scope of the present invention as long as they do not deviate from the essence of the present invention.

First, the terms used in this application are briefly explained as follows.

The video decoding apparatus (Video Decoding Apparatus), which will be described below, is used in personal computers (PCs), laptop computers, portable multimedia players (PMPs), wireless communication terminals, and smart phones. , may be devices included in server terminals such as TV application servers and service servers, user terminals such as various devices, communication devices such as communication modems for communicating with wired and wireless communication networks, and decoding of images or between screens for decoding. It can refer to a variety of devices equipped with various programs for prediction within the screen, memory for storing data, and a microprocessor for executing programs to perform operations and control.

In addition, the video encoded into a bitstream by the encoder is transmitted in real time or non-real time through wired and wireless communication networks such as the Internet, wireless short-range communication networks, wireless LAN networks, WiBro networks, and mobile communication networks, or through cables, universal serial buses (USB, It can be transmitted to a video decoding device through various communication interfaces such as Universal Serial Bus, decoded, restored to video, and played back.

Typically, a video may be composed of a series of pictures, and each picture may be divided into coding units such as blocks. In addition, those skilled in the art will understand that the term picture described below can be used in place of other terms with equivalent meaning, such as image, frame, etc. will be.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the attached drawings. In describing the present invention, duplicate descriptions of the same components will be omitted.

In video compression technology, IBC (Intra Block Copy) technology is a prediction method that finds blocks similar to the current block to be encoded or decoded in the restored area of the current frame. Information on blocks similar to the current block is expressed as a block vector (BV), and the encoder performs block vector prediction with adjacent blocks to reduce the amount of BV data transmitted to the decoder. Block vector prediction is a method of obtaining the block vector prediction value (BVP) that has the smallest difference value with the current BV among the BVs of adjacent blocks, and the encoder uses the block vector difference value (BVP), which is the difference value between the BV and BVP. Vector Difference (BVD) is transmitted to the decoder. In the decoder, the BVP obtained in the same manner as the encoder is combined with the transmitted BVD to obtain the BV, find the prediction block, and perform decoding.

Figure 1 shows a decoding device including an IBC unit according to an embodiment of the present invention.

The decoding device including the IBC unit includes an entropy decoding unit 120, an inverse quantization unit 130, an inverse transform unit 140, an intra-screen prediction unit 150, an inter-screen prediction unit 160, an IBC unit 170, and an IBC unit 170. It may include at least one of a loop filter unit 180 and a restored image storage unit 190.

The entropy decoder 120 decodes the input bitstream 110 and outputs decoding information such as syntax elements and quantized coefficients. The output information may include information for global motion compensation.

The inverse quantization unit 130 and the inverse transform unit 140 receive quantization coefficients, sequentially perform inverse quantization and inverse transformation, and output a residual signal.

The intra-screen prediction unit 150 generates a prediction signal by performing spatial prediction using pixel values of previously decoded neighboring blocks adjacent to the current block to be decoded.

The inter-screen prediction unit 160 performs motion compensation using the motion vector and the restored image stored in the restored image storage unit 190 to generate a prediction signal.

The IBC unit 170 generates a prediction signal with reference to an already decoded block within the same frame as the current block to be decoded. A prediction signal is generated by performing motion compensation using the block vector and the already decoded block image in the same frame stored in the reconstructed image storage unit 190.

When generating a prediction signal, a prediction block can be generated by performing filtering on a block image within the same frame that has already been decoded.

The prediction signals output from the intra-screen prediction unit 150, the inter-screen prediction unit 160, and the IBC unit 170 are summed with the residual signal, and the restored image generated through the summation is sent to the in-loop filter unit 180. It is delivered.

The restored picture to which filtering has been applied in the in-loop filter unit 180 is stored in the restored image storage unit 190 and can be used as a reference picture in the inter-screen prediction unit 160.

Figure 2 is a diagram illustrating a method of using a filtered prediction block when performing IBC according to an embodiment of the present invention.

The prediction block 220 to be used in IBC performance may be a block made of integer pixels of the already reconstructed area 210 within the same picture, as well as a block generated by performing filtering on the already reconstructed area.

The encoder can filter the already reconstructed area 210 in the same picture to determine the block most similar to the current block 210 and use it as a prediction block. The decoder can obtain the prediction block 220 by performing filtering in the same way as the encoder using the information received from the encoder.

Filtering methods may include applying a fixed coefficient filter or an adaptive coefficient filter, and using a block made up of integer pixels changed by the filter as a prediction block or using a block made up of subpixels generated by filtering as a prediction block. It can be used as

When using a fixed coefficient for filtering, filtering can be performed using a fixed coefficient determined according to the position of an integer pixel or subpixel. When using adaptive coefficients for filtering, the decoder can use adaptive filter coefficients transmitted from the encoder or the decoder can use adaptive filter coefficients directly derived using surrounding pixel values.

The precision of subpixel generation through filtering can be selectively set to 1/2 position or 1/4 position. If 1/2 position precision is selected, a prediction block consisting of pixels at 1/2 positions of two integer pixels is created and used, and if 1/4 position precision is selected, a prediction block consisting of pixels at 1/4 positions of two integer pixels is created and used. Use prediction blocks.

In FIG. 2, pixels 240, 250, 260, and 270 are integer pixels, and pixels 241, 242, and 243 are subpixels between the two integer pixels 240 and 250. If the precision of the subpixel is to use the subpixel at the 1/2 position, 242, which is the subpixel at the 1/2 position between integer pixels 240 and 250, can be obtained and used by filtering the surrounding pixels. If the precision of the subpixel is to use the subpixel at the 1/4 position, 241 or 243, which is the subpixel at the 1/4 position between the integer pixels 240 and 250, can be obtained and used by filtering the surrounding pixels.

Figure 3 is a flowchart showing the order of performing filtering when performing IBC according to an embodiment of the present invention.

If filtering is performed in the block that performs IBC, the subpixel can be determined through information indicating whether to use a block made up of subpixels at 1/2 positions as a prediction block or whether to use a block made up of subpixels at 1/4 positions as a prediction block. Determine the accuracy (310). Then, it is determined (320) whether an adaptive coefficient filter is used, and if an adaptive coefficient filter is used, an adaptive coefficient is derived (330) using surrounding pixels, and then filtering (340) is performed. If an adaptive coefficient filter is not used, filtering (340) is performed with a set coefficient without an adaptive coefficient derivation step.

FIG. 4 is a diagram illustrating a method of determining a prediction block by scaling a block in the process of determining a prediction block when performing IBC according to an embodiment of the present invention.

When determining a prediction block in the already decoded area 410 within the same frame during the IBC performance process, a scaled block 420 of a similar form to the current block 430 can be determined and used as a prediction block.

Figure 5 is a diagram illustrating a method of determining a prediction block by rotating a block in the process of determining a prediction block when performing IBC according to an embodiment of the present invention.

When determining a prediction block in the already decoded area 510 within the same frame during the IBC performance process, a rotated block 520 having a similar form as the current block 530 can be determined and used as a prediction block.

Figure 6 is a flowchart showing the procedure for calculating BV through deriving BVP using template matching when performing IBC according to an embodiment of the present invention.

In the case of a block that performs IBC, BVP can be calculated through template matching in the process of calculating BV, and the process is shown in Figure 6.

The decoder extracts intra_bc_flag in block units from the bitstream (610). If the extracted intra_bc_flag means 0 (620), the corresponding block is a block that does not perform IBC. If the extracted intra_bc_flag means 1, the corresponding block is a block that performs IBC, so the BVD is obtained through the BVD decoding process (630). In the BV prediction process, template matching is performed to derive the BVP (640). The BV is calculated by adding the derived BVP and the decrypted BVD (650).

Figure 7 shows that when performing IBC according to an embodiment of the present invention, when the block performing IBC is a block in an IRAP (Intra Random Access Point) picture, frequently occurring BVs are managed in a list and used for BV prediction. This is a flowchart showing the order of the method.

In the case of a block that performs IBC in an IRAP picture, frequently occurring BVs can be managed as a list and the BVP can be determined from the list, and the process is shown in FIG. 7.

The decoder extracts intra_bc_flag in block units from the bitstream (710), and if the flag means 1, the BVD is obtained through the BVD decoding process (720). If the current block belongs to an IRAP picture, the BVP is determined from the frequently occurring BV list (740) and added to the decoded BVD to calculate the BV (760). If the current block does not belong to the IRAP picture, the BVP is obtained from the neighboring blocks through the BV prediction process (750) and added to the decoded BVD to calculate the BV (760).

Figure 8 is a diagram showing the range of BVs that can be stored in the BV list when BVP is determined by managing frequently occurring BVs in a list when performing IBC according to an embodiment of the present invention.

When using the method of managing frequently occurring BVs as a list and determining the BVP from that list, the range of BVs that can be included in the BV list depends on the search range of IBC and whether or not WPP (Wavefront Parallel Processing) is used. It may vary.

When IBC is performed with WPP as shown in FIG. 8, BVs that can be included in the frequently occurring BV list are limited to BVs of blocks in areas 810, 820, 830, and 840 that have already been decrypted through WPP. For example, the BV list for the current block may include BVs in a region that has already been decoded prior to the current block. Additionally, after encoding/decoding of the current block is completed, the BV of the current block can be added to the BV list. Accordingly, the BV of the current block can be used for encoding/decoding of the IBC mode block following the current block.

FIG. 9 is a diagram illustrating an IBC performance method when a picture is divided using QTBT (QuadTree plus Biniary Tree) type block division or an arbitrary block division method when performing IBC according to an embodiment of the present invention. .

Even in the case of blocks divided by the QTBT block division method or any type of block division method, the IBC mode can be selected and encoded or decoded.

Blocks 910 and 930 in FIG. 9 are blocks in which the QTBT type block division method is used, and blocks 920 and 940 are blocks in which a random type block division method is used. Block 930 uses block 910 as a prediction block, and block 940 IBC can be performed using block 920 as a prediction block.

Claims (5)

In the video decoding method of decoding the current block in the current picture reference mode,
deriving a block vector of the current block based on a block vector list including block vectors of blocks in the current picture decoded before the current block; and
Generating a prediction block of the current block based on the derived block vector,
The prediction block is generated based on scaling performed depending on whether an intra block copy (IBC) mode is applied to the current block,
The derived block vector indicates a reference block included in the current picture,
The range of block vectors that can be included in the block vector list is determined according to the search range,
A video decoding method wherein the block vector of the current block is included in the block vector list. delete In the video encoding method of encoding the current block in the current picture reference mode,
determining a block vector of the current block and generating a prediction block of the current block based on the determined block vector; and
Encoding the block vector of the current block based on a block vector list including block vectors of blocks in the current picture that were encoded before the current block,
The prediction block is generated based on scaling performed depending on whether an intra block copy (IBC) mode is applied to the current block,
The block vector indicates a reference block included in the current picture,
The range of block vectors that can be included in the block vector list is determined according to the search range,
A video encoding method wherein the block vector of the current block is included in the block vector list. delete A method of transmitting a bitstream generated by a video encoding method, the video encoding method comprising:
determining a block vector of the current block and generating a prediction block of the current block based on the determined block vector; and
Encoding the block vector of the current block based on a block vector list including block vectors of blocks in the current picture that were encoded before the current block,
The prediction block is generated based on scaling performed depending on whether an intra block copy (IBC) mode is applied to the current block,
The block vector indicates a reference block included in the current picture,
The range of block vectors that can be included in the block vector list is determined according to the search range,
The block vector of the current block is included in the block vector list.