Method and device for video encoding and decoding using improved intra prediction structure

Abstract

The present invention relates to the encoding and decoding of digital videos, and more specifically, to a method for encoding and decoding digital videos, a method for recording such data, and components, devices, and systems for carrying out such a method. An image decoding method according to an embodiment of the present invention comprises the steps of: obtaining information on a current block from a bit string; determining a template located in an adjacent region of the current block; deriving a primary reference vector of the current block using the template; correcting the primary reference vector to derive a corrected primary reference vector; generating a prediction block for the current block using a region indicated by the corrected primary reference vector; and restoring the current block using the prediction block, wherein the correction of the primary reference vector is achieved by performing template matching within a predetermined range around the primary reference vector.

Description

Method and device for video encoding and decoding using an improved intra prediction structure

[0001] The present invention relates to the field of encoding and decoding of digital video, and relates to a method for encoding and decoding digital video, a method for recording such data, and components, devices, and systems for realizing such a method.

[0002] The present invention may be in the same technical field as at least one of the digital video compression technology standards known by the names of standards such as MPEG-2, MPEG-4 Video, H.263, H.264 / AVC, H.265 / HEVC, H.266 / VVC, VC-1, AV1, QuickTime, VP-9, VP-10, and Motion JPEG, or may be in the technical field for improving the inherent efficiency of the standards, or may be in the technical field for improving or replacing the standards.

[0003] Digital video encoding and decoding are widely used in various digital video applications. For example, digital television broadcasting, video transmission over communication networks, video calls / video conversations / video chats, recording and providing video content using optical media including video compact discs (VCDs), digital versatile discs (DVDs), and Blu-Rays, all processes for producing, editing, collecting, and distributing video content, and devices such as video recording devices and camcorders for various purposes, including personal, commercial, industrial, and security purposes, all depend on video encoding and decoding technologies.

[0004] Accordingly, implementations that may be referred to as digital video encoders and decoders may form part of a wide range of devices related to the generation, recording, and provision of digital video, including digital televisions, digital broadcasting systems, wireless broadcasting systems, computers in the form of notebooks / desktops / tablets, e-book readers, digital cameras, digital recording devices, digital multimedia playback devices, video game devices / terminals / consoles, mobile phones (including smartphones) with multimedia playback capabilities, equipment for video conferencing, and other devices.

[0005] The above digital video encoders and decoders can be implemented by a digital video compression standard that is widely used and understood by those skilled in the art. The digital video compression standard may include at least one of compression standards known by a standard name such as MPEG-2, MPEG-4 Video, H.263, H.264 / AVC, H.265 / HEVC, H.266 / VVC, VC-1, AV1, QuickTime, VP-9, VP-10, and Motion JPEG.

[0006] Video encoders and decoders can be implemented to more efficiently encode or decode digital video information while complying with the above standards, or by improving or modifying the above standards. Attempts to modify the above standards can also lead to the development of new standards. A well-known example is the so-called enhanced compression model (ECM), an attempt to improve and replace the existing H.266 / VVC standard, currently being developed by the Joint Video Experts Team (JVET), a joint international standardization group of ISO, IEC, and ITU-T.

[0007] Digital video is known to require a significant amount of information to describe its content in its uncompressed state. Therefore, recording or transmitting this information in its original form can be inefficient. Therefore, digital video is compressed using various methods prior to recording or transmission. These compression methods include lossy and lossless encoding. Lossy encoding sacrifices some image quality to achieve high compression performance, while lossless encoding sacrifices some compression performance to prevent image quality degradation. Regardless of the encoding method, there is a need to implement a technology that achieves a high compression ratio while minimizing image quality degradation to meet the growing demand for high-quality digital video within the constraints of limited memory storage capacity and communication transmission bandwidth.

[0008] As described above, the encoding process for compression requires various operations, such as spatial segmentation of digital video, segmentation and / or processing in color channels, removal of spatial redundancy, removal of temporal redundancy, tracking of motion vectors within the video, encoding of differential images, quantization, coefficient scan, run-length coding, entropy coding, and loop filtering. These encoding operations generally consume computing resources and take a certain amount of time to complete. Similarly, the decoding operation for the encoding operation also requires certain computing resources and a certain amount of time. The main goal of video encoding and decoding technology is to ensure that the above resource consumption and time consumption do not interfere with the production, recording, distribution, and viewing of digital videos.

[0009] Accordingly, the present invention provides a new technology that can contribute to at least one of the following: improvement of encoding efficiency, improvement of decoding efficiency, improvement of video quality, reduction of computational amount, reduction of software size, reduction of hardware size, and improvement of other performances related to encoding and decoding in the technical tasks in the field of video encoding and decoding.

[0010] The present invention provides a method and apparatus for video encoding and decoding using an improved intra prediction structure that can be used in the video encoding and decoding area described above.

[0011] According to an embodiment of the present invention for solving the above-described technical problem, a video decoding method includes the steps of obtaining information about a current block from a bit string, determining a template located in an adjacent area of ​​the current block, deriving a primary reference vector of the current block using the template, performing correction on the primary reference vector to derive a corrected primary reference vector, generating a prediction block for the current block using an area indicated by the corrected primary reference vector, and restoring the current block using the prediction block, wherein the correction on the primary reference vector may be performed by performing template matching within a predetermined range around the primary reference vector.

[0012] The method may further include a step of obtaining a secondary reference vector from an area pointed to by the corrected primary reference vector, a step of performing correction on the secondary reference vector to derive a corrected secondary reference vector, and a step of generating a prediction block for the current block using the area pointed to by the corrected secondary reference vector.

[0013] The correction for the first reference vector and the correction for the second reference vector may be characterized in that they are performed using different correction sample ranges.

[0014] The above method may be characterized in that correction for the first reference vector is performed using a 1×1 sample range, and correction for the second reference vector is performed using a 3×3 sample range.

[0015] The step of obtaining the secondary reference vector may be characterized in that, if there are multiple reference vectors within the area pointed to by the corrected primary reference vector, template matching is performed on each of the multiple reference vectors and the results are compared with each other to obtain the secondary reference vector.

[0016] The method may further include a step of obtaining information indicating whether the image is screen content from the bit string, and, based on the information, determining whether correction for the primary reference vector is to be performed in integer pixel units or in subpixel units.

[0017] The method may be characterized in that, when the image is a screen content, correction for the primary reference vector is performed in integer pixel units, and when the image is not a screen content, correction for the primary reference vector is performed in at least one of integer pixel and subpixel units.

[0018] The above template matching is performed using at least one of a plurality of calculation methods for calculating differences between templates for the template matching, and the plurality of calculation methods may include at least one of a simple difference method, a calculation method for adding absolute values ​​of differences between pixels (SAD), a calculation method based on differences using a transformation matrix (SATD), a mean absolute difference (MAD), and a sum of squared differences (SSD).

[0019] The step of deriving the primary reference vector of the current block using the template may be characterized by including the step of constructing a list of reference vector candidates for deriving the primary reference vector, and the step of removing at least one reference vector from the list of reference vector candidates through comparison between reference vectors.

[0020] The step of deriving the primary reference vector of the current block using the template may be characterized by including the steps of configuring a list of reference vector candidates for deriving the primary reference vector, the step of reading information for selecting at least one of the list of reference vector candidates from a bit string, and the step of deriving the primary reference vector based on the information.

[0021] The difference vector generated as a result of correction for the above primary reference vector may be expressed as a combination of direction information and size information, and the direction information may indicate one of a limited number of directions, and the size information may indicate one of a limited number of size values.

[0022] The method may be characterized in that the search range for the template matching is set with reference to a reference vector for a surrounding block of the current block, and the surrounding block includes at least one of a left block and an upper block of the current block.

[0023] The above method may be characterized in that at least one of the horizontal size, vertical size, area, or number of pixels within the current block is compared with a predetermined threshold value, and at least one of whether to apply the template matching prediction technology and the method of applying the technology is determined based on the result of the comparison.

[0024] The method further includes a step of obtaining a first reference reference vector from an area pointed to by the corrected primary reference vector, a step of updating the first reference reference vector by performing correction on the first reference reference vector, and a step of generating a prediction block for the current block using the area pointed to by the first reference reference vector, wherein the step of updating the first reference reference vector is performed recursively a plurality of times, and a method of correcting the reference vector is different in at least one of the recursive performances.

[0025] According to an embodiment of the present invention for solving the above-described technical problem, a video encoding method includes the steps of: determining a template located in an adjacent area of ​​a current block; deriving a primary reference vector of the current block using the template; performing correction on the primary reference vector to derive a corrected primary reference vector; generating a prediction block for the current block using an area indicated by the corrected primary reference vector; generating a residual signal using the current block and the prediction block; and encoding the residual signal to generate a bit string, wherein the correction on the primary reference vector may be performed by performing template matching within a predetermined range around the primary reference vector.

[0026] The method may further include a step of obtaining a secondary reference vector from an area pointed to by the corrected primary reference vector, a step of performing correction on the secondary reference vector to derive a corrected secondary reference vector, and a step of generating a prediction block for the current block using the area pointed to by the corrected secondary reference vector.

[0027] The method may further include a step of determining whether the current encoding target image is screen content, and a step of including information indicating the result of the determination in the bit string, and may be characterized in that, based on whether the image is screen content, it is determined whether correction for the primary reference vector is to be performed in integer pixel units or in subpixel units.

[0028] The method may further include a step of determining a calculation method to be used for the template matching, and a step of including information indicating the determined calculation method in the bit string, wherein the calculation method may include at least one of a simple difference method, a calculation method of adding the absolute value of the difference between pixels (SAD), a calculation method based on a difference using a transformation matrix (SATD), a mean absolute difference (MAD), and a sum of squared differences (SSD).

[0029] The method may further include a step of generating a difference vector representing a difference between the primary reference vector and the corrected primary reference vector, and a step of including the difference vector in the bit string, wherein the difference vector is expressed as a combination of direction information and magnitude information, and the direction information indicates one of a limited number of directions, and the magnitude information indicates one of a limited number of magnitude values.

[0030] The step of deriving the primary reference vector of the current block using the template may include the steps of configuring a reference vector candidate list for deriving the primary reference vector, calculating an encoding cost for the current block based on a prediction block obtained by at least one reference vector included in the reference vector candidate list, selecting at least one reference vector candidate from the candidate list based on the encoding cost calculation to derive the primary reference vector, and generating a bit string including information related to identifying the selected candidate from the candidate list.

[0031] The method further includes a step of obtaining a first reference reference vector from an area pointed to by the corrected primary reference vector, a step of updating the first reference reference vector by performing correction on the first reference reference vector, and a step of generating a prediction block for the current block using the area pointed to by the first reference reference vector, wherein the step of updating the first reference reference vector is performed recursively a plurality of times, and a method of correcting the reference vector is different in at least one of the recursive performances.

[0032] According to an embodiment of the present invention for solving the above-described technical problem, a video decoding device includes a processor, a memory connected to the processor, a receiving unit for receiving a bit stream, and an image decoding unit, wherein the image decoding unit is configured to obtain information on a current block from the bit stream, determine a template located in an adjacent area of ​​the current block, derive a primary reference vector of the current block using the template, perform correction on the primary reference vector to derive a corrected primary reference vector, generate a prediction block for the current block using an area indicated by the corrected primary reference vector, and restore the current block using the prediction block, and the correction on the primary reference vector may be characterized in that it is performed by performing template matching within a predetermined range around the primary reference vector.

[0033] The 'reference vector' used in the present invention is a concept that includes both a block vector in intra-screen prediction and a motion vector in inter-screen prediction, and the derivation and correction method related to the reference vector provided by the present invention can be applied to both a block vector and a motion vector.

[0034] According to the present invention, the complexity of template matching for performing intra prediction in a video encoder and decoder is reduced, thereby enabling efficient and high-speed video encoding and decoding.

[0035] According to the present invention, by constructing recursive reference vectors using a chained reference vector structure and applying a differentiated correction method, prediction accuracy can be significantly improved compared to existing template matching methods. In particular, by applying different correction sample ranges and calculation methods for each order of various reference vector corrections, from the first to the Nth order, optimized prediction is possible according to the regional characteristics and complexity of the image. This ultimately leads to increased encoding efficiency and a reduction in bitstream size.

[0036] Figure 1 is a conceptual diagram of a video communication system according to one embodiment of the present invention;

[0037] FIG. 2 is a conceptual diagram of the arrangement of an encoder and decoder in a real-time video streaming environment according to one embodiment of the present invention.

[0038] Figure 3 is a functional unit conceptual diagram of a video decoder according to one embodiment of the present invention;

[0039] Figure 4 is a functional unit conceptual diagram of a video encoder according to one embodiment of the present invention;

[0040] Figure 5 is a conceptual diagram of a frame type according to one embodiment of the present invention;

[0041] FIG. 6 is a conceptual diagram showing the structure of a video encoder according to another embodiment of the present invention;

[0042] Figure 7 is a conceptual diagram illustrating a template matching prediction method according to one embodiment;

[0043] FIG. 8 is a conceptual diagram of the storage and use of block vectors in a template matching prediction method according to one embodiment.

[0044] FIG. 9 is an example diagram for setting a search range of a block vector according to one embodiment of the present invention.

[0045] FIG. 10 is an exemplary diagram of a method for determining a corrected block vector according to one embodiment of the present invention;

[0046] FIG. 11 is an exemplary diagram of a second block vector template matching method according to one embodiment of the present invention, and

[0047] FIG. 12 is an exemplary diagram of a plurality of block vectors according to one embodiment of the present invention.

[0048] The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated and described in detail in the drawings. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0049] Although terms such as “first,” “second,” etc. may be used to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present invention, the first component could be referred to as the second component, and similarly, the second component could also be referred to as the first component. The term “and / or” includes any combination of multiple related listed items or any of multiple related listed items, and is non-exclusive unless otherwise indicated. The listing of items in this specification is merely an exemplary description to easily explain the spirit and possible implementation methods of the invention herein, and therefore is not intended to limit the scope of embodiments of the present invention.

[0050] As used herein, "A or B" can mean "only A," "only B," or "both A and B." In other words, as used herein, "A or B" can be interpreted as "A and / or B." For example, as used herein, "A, B or C" can mean "only A," "only B," "only C," or "any combination of A, B and C."

[0051] As used herein, a slash ( / ) or a comma can mean "and / or." For example, "A / B" can mean "A and / or B." Accordingly, "A / B" can mean "only A," "only B," or "both A and B." For example, "A, B, C" can mean "A, B, or C."

[0052] In this specification, "at least one of A and B" may mean "only A", "only B" or "both A and B". Additionally, in this specification, the expressions "at least one of A or B" or "at least one of A and / or B" may be interpreted identically to "at least one of A and B".

[0053] Additionally, in this specification, “at least one of A, B and C” can mean “only A,” “only B,” “only C,” or “any combination of A, B and C.” Additionally, “at least one of A, B or C” or “at least one of A, B and / or C” can mean “at least one of A, B and C.”

[0054] When a component is referred to as being "connected" or "connected" to another component, it should be understood that it may be directly connected or connected to that other component, but that there may be other components intervening. Conversely, when a component is referred to as being "directly connected" or "connected" to another component, it should be understood that there are no other components intervening.

[0055] The terminology used herein is merely used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, it should be understood that the terms "comprises" or "has" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0056] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by those of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0057] In describing the invention herein, embodiments may be described or illustrated in terms of unit blocks that perform the described function or functions. The blocks may be expressed herein as one or more devices, units, modules, parts, etc. The blocks may be implemented in hardware by one or more logic gates, integrated circuits, processors, controllers, memories, electronic components, or information processing hardware implementation methods, but not limited thereto. Alternatively, the blocks may be implemented in software by application software, operating system software, firmware, or information processing software implementation methods, but not limited thereto. A single block may be implemented by being separated into multiple blocks that perform the same function, or conversely, a single block may be implemented to perform the functions of multiple blocks simultaneously. The blocks may also be implemented by being physically separated or combined according to any criteria. The blocks may be implemented to operate in an environment where their physical locations are not specified and are separated from each other by a communication network, the Internet, a cloud service, or a communication method, but not limited thereto. All of the above implementation methods are within the scope of various embodiments that can be taken by a person skilled in the field of information and communication technology to implement the same technical idea, and therefore, any detailed implementation method should be interpreted as being included within the scope of the technical idea of ​​the invention in this specification.

[0058] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings. To facilitate a comprehensive understanding of the present invention, the same reference numerals will be used for identical components in the drawings, and redundant descriptions of identical components will be omitted. Furthermore, the multiple embodiments are not mutually exclusive, and it is assumed that some embodiments may be combined with one or more other embodiments to form new embodiments.

[0059]

[0060] digital video codec

[0061] Figure 1 is a conceptual diagram of a video communication system according to one embodiment of the present invention. The video communication system (100) may be configured to include at least two terminals (110, 120) connected to each other via a network (105).

[0062] In one embodiment of the present invention, the above-described FIG. 1 may refer to a block diagram for configuring a unidirectional video communication network. A first terminal (110) among the terminals may encode video data in order to transmit (111) the video data via a network (105). A second terminal (120) among the terminals may be configured to receive (121) the encoded video data via a network and decode and display the same.

[0063] In another embodiment of the present invention, the above-described FIG. 1 may refer to a block diagram for configuring a two-way video communication network. For the two-way video communication, each terminal (110, 120) may be configured to encode video data acquired by itself for video transmission (112, 122) to each other terminal via the network. Each terminal may also be configured to receive (113, 123) video data transmitted by another terminal via the network, decode the same, and display the decoded video data.

[0064] The terminals (110, 120) shown in Fig. 1 may be exemplified as devices such as server computers, personal computers, portable computers, and smartphones, depending on the embodiment, but are not limited thereto. The present invention is applicable to all environments for establishing a one-way or two-way video communication network, and it should be understood that the network (105) may be established by any means for transporting encoded video data between the terminals (110, 120).

[0065] In one embodiment of the present invention, the network (105) may refer to a wired or wireless communication network. Depending on the embodiment, the network may be configured to communicate information using any communication standard, which may include packet-based communication. The packet communication may be understood to include packets, for example, known as TCP or UDP.

[0066] However, in another embodiment of the present invention, the network (105) may be understood to include a process of information transmission using a recording medium. In this case, the configuration of the network is not limited to a communication medium, and should be understood to include a process of temporarily storing and physically transporting information on a hard disk, a solid state disk (SSD), a flash memory, a compact disc (CD), a digital versatile disc (DVD), a Blu-ray disc, and other mechanical, electronic, or optical recording media.

[0067] Any other means of information communication or transport, regardless of the method employed, can be considered within the scope of the present invention as long as it has a structure that supports the transmission and decoding of video data in an encoded state. Therefore, in addition to the examples listed above, any means of information communication or transport, whether known in the past or newly available, can fall within the scope of application of the present invention.

[0068] FIG. 2 is a conceptual diagram illustrating the arrangement of an encoder and decoder in a real-time video streaming environment according to one embodiment of the present invention. The streaming system (200) illustrated in FIG. 2 can be applied to video data communication networks, including, for example, digital broadcasting, video telephony, and video conferencing. However, it should be noted that technical structures identical or similar to the streaming system can be equally applied even when information is transmitted via a recording medium, as described above.

[0069] According to one embodiment of the present invention, the streaming system may include a video source (210) that generates a video stream. The video source may include a digital video acquisition means (212), which may be, for example, a digital camera or other device, for acquiring uncompressed raw video. The raw video stream (215) may have a large capacity and may therefore be compressed by a video encoder (217) coupled or connected to the video source.

[0070] The above encoder (217) may be configured as a means including hardware, software, or a combination of the two, configured to implement an image encoding method and / or an implementation method thereof according to one embodiment of the present invention.

[0071] Through the encoder (217), an encoded bitstream (219) having a reduced capacity compared to the original video stream can be output. The bitstream (219) can be provided in real time via a relay device, which may be referred to as a streaming server (220), and / or can be stored in a recording medium (225) of the streaming server (220) for subsequent use.

[0072] The streaming system (200) may include at least one streaming client (230, 240) that connects to the streaming server (220) to receive the encoded bit string (229) in real time or obtain it later. The streaming client may include a video decoder (232) that obtains the encoded bit string (229) (which may also be regarded as a copy of the bit string (219) received by the streaming server), decodes the bit string (229), and outputs the resulting video data as video data in a form that can be displayed by a display (235) or other visual, auditory, or other sensory display means.

[0073] As described above, the functions for encoding and decoding video data are collectively called a coder-and-decoder, or video codec.

[0074] FIG. 3 is a conceptual diagram of a functional unit of a video decoder according to an embodiment of the present invention. As shown in FIG. 3, a receiving unit (310) can receive at least one encoded video data to be decoded by a decoder (305). In an embodiment of the present invention, the encoded video data may be independent for each reception, and the decoding procedure of each independent video data may be independent from the decoding procedure of other video data. The encoded video data may be received by the receiving unit (310) through a hardware or software connection (315) to a device storing the same, and as described above, the storing device may be a type of streaming server located at the other end of a communication network, or may mean a physical recording medium, but is not limited thereto.

[0075] The above-described receiving unit (310) can receive the encoded video data together with other data accompanying it, such as encoded audio data or other auxiliary data, and each of the data can be separated from the video data and provided to an appropriate processing function unit (312) other than the video decoder.

[0076] When the video data is provided through a communication network, a buffer memory (320) may be coupled between the receiving unit (310) and the decoder (305) to minimize delay and disconnection according to the network environment. The buffer memory (320) may refer to a computer-readable recording medium that temporarily stores the received video data and stably supplies it to a parser (330) corresponding to the input terminal of the decoder (305). However, if the bandwidth of the communication network is sufficient, if video data is read from a recording medium in a local location that is not physically separated, or if the possibility of communication delay is not predicted in other environments, the buffer memory may be unnecessary.

[0077] The video decoder (305) may include the parser (330) as its input terminal to interpret the encoded video data. The parser may perform a function of separating (parsing) a plurality of pieces of information stored in the form of a bit string in the encoded video data according to a predetermined rule, and, if necessary, performing an entropy decoding (335) of entropy-coded video data, thereby performing a function of reconstructing symbols (338), which are paragraphs of video encoding information. The symbols (338) may include all information for controlling the operation of the decoder (305), and / or may further include information for controlling a device that is attached to and operable with the decoder (305), such as a display device. Control information for controlling the above display device may include information in a format called supplementary enhancement information (SEI) or video usability information (VUI).

[0078] As described above, the parser (330) may be configured to perform entropy decoding (335) of the encoded video data. The entropy encoding method of the encoded video data may vary depending on the encoding standard, and decoding may be performed accordingly. Representative examples of the entropy encoding standard may include variable length coding, Huffman coding, and arithmetic coding, and each of the encoding methods may be a context-adaptive or context-sensitive method depending on the standard, and may also be based on principles widely known to those skilled in the art.

[0079] The parser (330) may be configured to extract at least one picture from the encoded video data. The definition of the picture may vary depending on the encoding standard, and depending on the standard, one or more of the examples listed below may correspond simultaneously and overlappingly. The picture may be grouped, defined, and / or divided into encoding / decoding units such as, for example, groups of pictures (GOPs), pictures / frames, tiles, slices, macroblocks, blocks, subblocks, transform units (TUs), and prediction units (PUs).

[0080] The parser (330) may be configured to extract encoding information, such as transform coefficients, quantization parameters (QPs), and / or motion vectors, from the encoded video data. The parser (330) may be configured to perform entropy decoding (335) and parsing operations on the video data received from the buffer memory, and to selectively decode symbols (338) representing the encoding information. In addition, the parser (330) may be configured to selectively supply a specific symbol (338) to a specific decoding function unit within the decoder (305), such as an inverse quantization and inverse transform unit (340), an intra prediction unit (350), an inter prediction unit (355), or a loop filter unit (360). Control of such information supply can be determined by the information sequence contained in the encoded video, and may vary depending on the encoding standard, and is not limited within the scope of the embodiments of the present invention, and is not described in detail in this conceptual diagram.

[0081] The decoder (305) may be comprised of a number of conceptual functional units that receive and process the encoded information provided by the parser (330). It should be readily apparent that these conceptual functional units may be combined or further subdivided, depending on implementation needs. For example, they may be further separated for ease of implementation, or integrated into one for operational efficiency. In any case, each functional unit may be configured to perform close interaction with each other. However, despite the possibility of such integration or separation, the following description will be given as a combination of conceptual functional units to illustrate the video data decoding procedure applied as an embodiment of the present invention.

[0082] The decoder may include an inverse quantization and inverse transformation unit (340). The inverse quantization and inverse transformation unit (340) may be configured to receive encoding information including a method to be used for numerical transformation (transform), a block size, quantization coefficients for recovering quantized information, and distinction information of a quantization matrix that simplifies and represents the quantized coefficients from the parser (330), and may be configured to output block values ​​(341) that can be input to an aggregator (370) as a result of processing the encoding information.

[0083] In one embodiment of the present invention, the output values ​​of the inverse quantization and inverse transformation unit (340) may include intra-prediction encoded block values. The intra-predicted block values ​​may refer to values ​​that can be decoded using prediction information within a picture currently being decoded, for example, the current frame, but not using prediction information from a previously decoded picture, for example, the previous frame.

[0084] The prediction information within the current picture may be provided by the intra prediction unit (350). According to an embodiment of the present invention, the intra prediction unit (350) generates a block value of the same form as the block being decoded as the prediction information by using picture information of a spatially adjacent area derived from a picture currently being decoded and of which decoding has been partially completed. The picture information may be provided (381) from a buffer for the current picture, a so-called line buffer (380). The merging unit (370), according to an embodiment, may be configured to merge the prediction information (351) generated by the intra prediction unit (350) with the block values ​​(341) provided by the inverse quantization and inverse transformation unit (340).

[0085] In another embodiment, the output values ​​of the inverse quantization and inverse transformation unit (340) may include block values ​​subjected to motion compensation as inter-prediction encoded block values, and in some cases, block values ​​subjected to motion compensation. In this case, the inter-prediction unit (355) may extract and use sample information (386) used for motion-based prediction from a reference picture buffer (385). The information (356) derived by performing motion compensation on the sample information based on the symbols (338) included in the block values ​​as the output values ​​may be configured to be merged with the block values ​​(341) provided by the inverse quantization and inverse transformation unit (340) by the merger unit (370). In this case, the block values ​​(341) may be referred to as so-called differential or residual values.

[0086] The position information within the memory used by the inter prediction unit (355) to extract the sample information from the reference picture may be determined by a motion vector provided to the inter prediction unit (355) and composed of a combination of symbols (338) for indicating, for example, X, Y, and other specific points of the reference picture. The inter prediction unit (355) may also include a function for interpolating and using the sample values ​​when a so-called 'subsampling'-capable motion vector is provided, and may further include a function for predicting and reinforcing the value of the motion vector.

[0087] The output values ​​(371) of the above merging unit (370) may be provided to the loop filter unit (360) and processed by various loop filtering methods. The loop filter unit (360) may be configured to receive not only the block unit output (371) of the merging unit (370) but also the symbol (338) provided from the parser (330) to control its operation. The output of the loop filter unit (360) may be output to an external display means such as the display device through an output connection (390), but may be stored (361) in a line buffer (380) for use in prediction for interpreting a subsequent intra or inter coded block value, and may also be stored in a reference picture buffer (385) through this.

[0088] Certain pictures, such as frames, after their decoding is completed, can be utilized as reference pictures for performing predictive decoding in a subsequent decoding process. A picture (or frame) can be gradually accumulated in a line buffer (380) and decoded. When the decoding of a frame is completed, the contents of the line buffer (380) are transferred (383) to the reference picture buffer (385), and a new line buffer (380) can be allocated for decoding the new frame.

[0089] The above video decoder (305) may be configured to perform a decoding operation according to a predetermined video compression technique that may be documented by various international standards or commercial standards. The standards may include, for example, international standard recommendations such as H.264, H.265, and H.266 defined by the International Telecommunication Union Standardization Sub-Division (ITU-T). Those skilled in the art will understand that each of the above recommendations is equivalent to an international standard jointly defined by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). The encoded video data may comply with a specific bitstream syntax defined by the relevant standards, as defined and required by the video compression standard documents and standard documents, and specifically by the profiles and levels specified within such documents. In addition, the complexity of the encoded video data may be limited to a certain level to comply with the profiles and levels. For example, a profile or level may be configured to limit a maximum picture size, a maximum decoding speed, and a maximum reference picture size. These limitations may, in some embodiments, also be further limited by metadata signals for a hypothetical reference decoder (HRD) and HRD buffer management included in the encoded video data.

[0090] According to one embodiment of the present invention, the receiver (310) may receive additional redundant data along with the encoded video. The additional data may be considered as part of the encoded video data. The additional data may include information that may be used by the decoder (305) to properly decode the data or to more accurately reconstruct an image that approximates the original image. The additional data may be provided in the form of, for example, layers for temporal, spatial, or signal-to-noise ratio (SNR) enhancement, redundant slices, redundant pictures, and forward error correction codes.

[0091] Figure 4 is a functional unit conceptual diagram of a video encoder according to one embodiment of the present invention. The encoder (405) may be configured to receive original video information (402) from a video source (401) and perform encoding.

[0092] The original video information (402) may have any suitable bit depth, for example, 8 bits, 10 bits, 12 bits, etc. In addition, the original video information (402) may have any suitable color space, for example, R / G / B, Y / U / V, Y / Cb / Cr, etc. In addition, the original video information (402) may have any suitable sampling structure corresponding to the color space, for example, Y / Cb / Cr 4:2:0, Y / Cb / Cr 4:4:4, etc. The original video information (402) having such a predetermined format may be provided to the encoder in the form of a digital video stream.

[0093] In a one-way video communication network, the original video information (402) can be obtained from a recording medium storing a previously prepared video source. In a two-way video communication network, the original video information (402) can be obtained from an image acquisition device, such as a camera, that generates at least one video transmission stream included in the two-way video communication.

[0094] The video data including the above original video information (402) may be configured as a plurality of pictures configured to simulate motion by playing them in chronological order. In addition to pictures, the pictures may also be expressed in concepts such as frames. The pictures may include one or more samples depending on the type of sampling structure, color space, etc. being used. Those skilled in the art will understand that the samples are closely related terms to pixels in digital images. The operation of the encoder will be described below with reference to such samples.

[0095] According to one embodiment of the present invention, the encoder (405) may be configured to encode and compress pictures (and / or grouped or segmented information) constituting the original video information (402) in real time (or according to other temporal requirements required according to the implementation method) into the form of encoded video information.

[0096] In the encoder (405), the control unit (450) may be a functional unit configured to control an appropriate encoding speed. The control unit (450) may be configured to control other functional units and be functionally coupled to the following functional units as described below. The parameters set by the control unit (450) may include parameters related to bitrate control, such as picture skip, quantizer, and variable values ​​for applying image quality optimization techniques, and may also include values ​​such as picture size, group of pictures (GOP) structure, and maximum search range of motion vectors. A person skilled in the art will be able to understand various other functions that the control unit (450) may have, and such other functions may be added or removed according to the design of a video encoder optimized for individual system design.

[0097] According to an embodiment of the present invention, the encoder (405) may be configured to operate in a structure such as a "coding loop" well known to those skilled in the art. To simplify the description by way of example, the coding loop may be configured with an internal encoder (so-called "source coder") (410) which is responsible for receiving a picture to be encoded and generating symbols based on at least one reference picture that has been encoded in the past, and a local decoder (420) configured to be connected to the internal encoder. The local decoder (420) may be configured to perform an operation to reproduce sample data to be generated by a decoder (490) located at an actual remote location that will receive encoded video information from the encoder (405) by receiving an output of the internal encoder (410).

[0098] Video data composed of sample data reconstructed by the internal decoder (420) may be configured to be input to the reference picture buffer of the encoder (405). As described above, the internal decoder (420) is implemented to reproduce the result output by the encoder (405) and to be decoded by a remote decoder, so the video data recorded in the reference picture buffer may also be identical in bit unit to the information of the reference picture buffer of the remote decoder. That is, the prediction function unit that may be included in the encoder (405) may read the same values ​​as the sample values ​​of the previous frame that the decoder will later refer to in the decoding process from the reference picture buffer of the encoder (405).

[0099] As described above, the principle of achieving matching of the reference picture buffers between the encoder (405) and the decoder (490) by means of the internal decoder (420) on the encoder (405) side is well known to those skilled in the art, and a method of responding to an environment in which such an environment is not guaranteed (e.g., information loss due to communication failure, etc.) can also follow what is known to those skilled in the art.

[0100] An embodiment of the operation method of the internal decoder (420) has been described in detail above with reference to FIG. 3. The decoder of FIG. 3 may be regarded as the aforementioned "remote" decoder (490). The internal decoder (420) may be implemented excluding lossless encoding and decoding sections such as the parser (330) or entropy decoding (335). This is because the internal encoder (405) is implemented to simply reproduce the operation of a decoder located at a remote location, and thus may directly decode symbols without requiring a process of compressing and then decompressing symbols. Accordingly, the functional units preceding the parser and entropy decoder as shown in FIG. 3 may not be provided or may be implemented at least partially.

[0101] As described above, according to a preferred embodiment of the present invention, any decoder function (excluding a parser and an entropy decoder) present in the decoder can naturally exist as a substantially identical function in the corresponding encoder (405).

[0102] The operation of the encoding function unit that may be included in the above encoder (405) can be considered as the reverse operation of the decoder function unit. Therefore, the embodiment can be explained by performing the operation of the decoder function unit in reverse. For example, a quantization and transform function unit corresponding to the inverse quantization and inverse transform unit may be provided, and an inter prediction encoding unit corresponding to the inter prediction unit may be provided. In addition, some additional explanations will be added.

[0103] The internal encoder (410) may be configured to perform encoding on input picture information, for example, an input frame, by a prediction encoding method executed by a prediction encoding unit (440) that operates by referencing at least one reference picture information, for example, at least one temporally previous encoded picture (or frame) from a reference picture buffer (430) from video data designated as a reference frame. In this case, the encoder (405) may be configured to encode a differential between blocks of samples constituting the input picture and blocks of samples constituting the reference picture.

[0104] The internal decoder (420) can decode video data that can be designated as the reference picture from symbols generated by the internal encoder (410). As described above, since the video data is identical to the decoding operation performed by the remote decoder, the video data used as the reference picture may be provided to the encoder (405) in a form that has undergone lossy compression and has been partially damaged, and this operation may be intended to ensure operational consistency with the decoder.

[0105] The prediction encoding unit (440) may be configured to perform a prediction search operation within the encoder (405). The prediction search operation may refer to an operation corresponding to the inter prediction or intra prediction described in the description of the decoder. For picture information that is input and scheduled to be newly encoded, the prediction unit may access the reference picture buffer (430) to retrieve information such as a motion vector, a block shape, and metadata that may include the same, which are information indicating a point of a reference picture that can function as prediction reference information suitable for the new picture information, and a sample block to be actually referenced. The above prediction encoding unit (440) may operate on the basis of the so-called "sample block by pixel block" criteria in order to obtain appropriate prediction reference information. According to one embodiment of the present invention, at least one prediction reference information designating at least one reference picture information stored in the reference picture buffer (430) may be designated for the input picture, as determined based on the search results obtained by the prediction encoding unit (440).

[0106] In one embodiment of the present invention, the control unit (450) may be configured to manage the overall encoding operation of the internal encoder (410), including setting parameters used to encode video data.

[0107] All outputs of the above-described functional units may be subjected to entropy encoding (460) in order to be finally output. The entropy encoding (460) may include various entropy coding techniques, such as variable length coding, Huffman coding, and arithmetic coding, for the symbols generated by the various functional units as described above, and each encoding method may be a context-adaptive or context-sensitive method according to the standard, or may be based on principles widely known to those skilled in the art. Such entropy encoding (460) can typically achieve lossless compression, and thus can be configured to convert at least one symbol generated by the functional units into encoded video data.

[0108] The above control unit (450) may, when controlling the operation of the encoder (405), apply to each picture (or frame) the type of encoding in which a specific picture is encoded during the encoding period. Depending on the type, the method by which the picture is encoded may be affected. Depending on the embodiment, the type may include what is categorized as the following "frame type."

[0109] Fig. 5 is a conceptual diagram of a frame type according to one embodiment of the present invention. The following description will be made with reference to Fig. 5.

[0110] An intra (“I”) picture (510) may refer to a picture that can be encoded and decoded using only its own information without referring to other picture information in video data through predictive encoding. The “I” picture may be designated by names such as a key frame, an independent / instantaneous decoder referh (IDR) frame, and a clean random-access (CRA) frame, depending on the video encoding standard, and the “I” pictures designated by the various names as described above may have various modifications and application methods as permitted by each standard and may be partially different from each other. In addition to those listed above, various application methods for implementing the “I” picture may be by various methods that are already known to those skilled in the art or may be newly provided.

[0111] A prediction ("P") picture (520) may refer to a picture that can be encoded and decoded through intra or inter prediction based on at least one prediction information and / or a motion vector that designates at least one reference picture to predict sample values ​​of a block constituting the picture. The "P" picture may be configured to refer to only one reference frame, or may be configured to refer to one or more reference frames, according to a video encoding standard. When referring to more than one reference frame, sample information and / or associated metadata derived from multiple reference pictures may be used to reconstruct a single block. However, in common cases, a picture designated as a "P" picture may be understood as a picture that performs reference only to a temporally preceding picture.

[0112] A bidirectional prediction ("B") picture (530) may refer to a picture that can be encoded and decoded through intra or inter prediction based on at least one piece of prediction information and / or a motion vector that designates at least two reference pictures in order to predict sample values ​​of blocks constituting the picture. In a common case, a picture designated as the "B" picture is distinguished from a picture designated as the "P" picture, and may be understood as a picture that performs a reference without being limited to a temporally preceding picture.

[0113] Video data may be spatially divided into a plurality of sample blocks during the encoding and decoding process, and encoding may be performed in units of the blocks. The block units may include, but are not limited to, sizes such as 4x4, 8x8, 4x8, or 16x16 in units of horizontal / vertical pixels, as is widely known. The block may be encoded using a predictive encoding method with reference to any other (already encoded) blocks, as permitted and / or restricted by the type specified for each picture in which the block is included. For example, the blocks of the "I" picture (510) may be encoded without using a predictive encoding method, or with reference to blocks that have already been encoded within the same partial picture. That is, only the so-called intra prediction method may be used. In contrast, the "P" picture (520) may further reference a reference picture encoded in at least one previous time unit, and thus, inter prediction may also be used for encoding along with intra prediction. In the case of a "B" picture (530), reference can be made not only to a previously encoded picture in the encoding order but also to a later reference picture in terms of time unit. However, it is widely known that there may be blocks within a "P" picture or a "B" picture that are encoded without relying on predictive encoding.

[0114] The above video encoder (405) may be configured to perform encoding operations according to a predetermined video compression technique that may be documented by various international standards or commercial standards. Examples of the above standards may include all of those described in the above decoder.

[0115] According to one embodiment of the present invention, the transmitter (470) may buffer the encoded video data generated by the entropy encoding in order to provide / transmit the video data (ultimately to a remote decoder (490)) to a device storing the encoded video data via a hardware or software connection (495). According to an embodiment, when providing / transmitting the encoded video data from the video encoder (405), the transmitter (470) may receive and merge other data accompanying the encoded video data, for example, encoded audio data or other auxiliary data, from a separate source (480).

[0116] According to one embodiment of the present invention, the transmitter (470) may be configured to transmit additional data along with the encoded video. The additional data may be considered part of the encoded video data. The additional data may include information that can be used by a decoder to properly decode the data or to more accurately reconstruct an image that approximates the original image. Examples of the additional data may include all of the examples previously presented with respect to the receiver (310) of the decoder.

[0117] The present invention can be implemented by a digital video compression standard that is widely used and understood by those skilled in the art as described above. The digital video compression standard may include at least one of compression standards known by the standard name such as MPEG-2, MPEG-4 Video, H.263, H.264 / AVC, H.265 / HEVC, H.266 / VVC, VC-1, AV1, QuickTime, VP-9, VP-10, and Motion JPEG.

[0118] Fig. 6 is a conceptual diagram illustrating the structure of a video encoder according to another embodiment of the present invention. What is depicted in Fig. 6 may be a rough structure of a video encoder widely known as a standard code such as ITU-T H.266 and ISO / IEC 23090-3, and also known as MPEG-I Part 3 or versatile video coding (VVC).

[0119] According to FIG. 6, a video encoder (605) may be configured to receive uncompressed and unencoded original video data (601) as input and output an encoded bit stream (602). The video data (601) may be supplied directly to a luma mapping unit (610a) when intra-encoded, or may be supplied to a luma mapping unit (610b) via an inter-prediction unit (620) including motion vector extraction. In the intra-encoded case, the mapped luma signal may be supplied to an output merger (606) by selecting (608) at least one of an intra-prediction encoded signal via an intra-prediction unit (625) or an inter-prediction encoded signal output from the luma mapping unit (610b) via the inter-prediction unit (620). The result of the above output merger can be applied to a chroma scaling unit (615). (The operation of the luminance signal mapping unit (610) and the operation of the chroma scaling unit (615) are collectively referred to as a luma mapping / chroma scalaing (LMCS) process.) The reduced chroma signal can be provided to a transform unit (630), and the transform unit (630) can perform an adaptive color transform, particularly on the chroma signal. The coefficients derived as a result of the transform are applied to a quantization unit (640) and quantized. As a result, lossy compression is achieved, and the result of the lossy compression can be output as a bit string (602) through a multi-hypothesis CABAC (650), which is a lossless compression method.

[0120] Meanwhile, the result of the lossy compression may actually enter the decoding process by going through the processes of inverse quantization (645), inverse transform (635), and luminance signal expansion (617) to generate a coding loop. The result of the luminance signal expansion may be supplied to the internal merger (607) together with the result of selecting (608) at least one of the previously generated intra prediction encoding signal or inter prediction encoding signal. The result of the internal merger may go through inverse luma mapping (618), and then may go through processing such as a deblocking filter (660), sample adaptive offset (SAO) (670), and an adaptive loop filter (ALF) to reproduce the image quality improvement process in the decoder. The result of reproducing the operation in the decoder as described above is applied to the reference picture buffer (690) and can be reused for prediction encoding by the inter prediction unit (620).

[0121] The present invention can also be utilized by or incorporated into an enhanced compression model (ECM), which is an implementation of a next-generation video codec currently being developed by the Joint Video Experts Team (JVET), an international standardization expert organization. The enhanced compression model can include an enhanced intra prediction coding method, an enhanced inter prediction coding method, an enhanced transform and transform coefficient coding method, an enhanced adaptive loop filtering method, a bilateral filtering method, a new sample adaptive offset (SAO) method for improving image quality, an extended entropy coding method, and an improved gradual decoding refresh (GDR) technique.

[0122]

[0123] Template Matching Prediction

[0124] The present invention relates to a video encoding and decoding method and a device using an improved intra prediction method that can be used in the video encoding and decoding field including the embodiments described above.

[0125] Fig. 7 is a conceptual diagram illustrating a template matching prediction method according to one embodiment. The template matching prediction method according to the present embodiment can be performed by a video decoder and / or video encoder disclosed herein.

[0126] Referring to FIG. 7, a current picture may include a reconstructed area (790), which is a previously decoded (or encoded) area therein, and a current block (710), which means an encoding / decoding unit in which decoding (or encoding) is currently in progress. Here, the current picture may be understood to mean at least one concept among a slice, a frame, a subpicture, and a tile, depending on the embodiment, and the current block may be understood to mean a concept such as a block, a subblock, a prediction unit, or a coding unit, depending on the embodiment.

[0127] Meanwhile, among the samples (i.e., pixels) constituting the above restoration area (790), a set of samples adjacent to the current block (710) can be defined as a template (715).

[0128] The above template (715) may include samples belonging to the left block, the upper block, and the upper left block of the current block (710) and adjacent to the current block (710), and may be understood to mean a set of L-shaped samples having a predetermined sample thickness (717) that are directly adjacent to the current block (710) among the samples. The sample thickness (717) may be designated as any number greater than or equal to 1 pixel. However, for the convenience of technical understanding, it is described herein as being considered as 1 pixel, but it will be easily understood that the present invention may be substantially equally modified and applied to templates having various sample thicknesses (717) configured to include 2 pixels or more, 1 pixel or less, and in some cases, sub-pixel units. In addition, the sample thickness (717) may not be constant, may be variable, or may vary depending on the direction or section of the template. Additionally, the template (715) may further include samples included in the lower left block and / or upper right block of the current block (710).

[0129] The template matching prediction method according to the present embodiment may search for a block (720) corresponding to the current block (710) within the restoration area (790) and use the corresponding block (720) as a prediction block. Specifically, the template matching prediction method according to the present embodiment may include a step of performing template matching (735) by searching for an appearance location of a sample similar to the samples constituting the template (715) within the restoration area (790), a step of deriving a prediction template (725) based on the template matching (735), and a step of using a block (or an arbitrary set of samples corresponding thereto) corresponding to the current block (710) as a prediction block (720) by making the prediction template (725) adjacent thereto.

[0130] At this time, information indicating the direction and distance of the prediction block (720) from the current block (710) can be defined as a block vector, which is a type of reference vector. The pixel information of the prediction block (720) can be used in combination with various conventional encoding methods during the subsequent encoding process of the current block (710). For example, it can be utilized in differential coding.

[0131] FIG. 8 is a conceptual diagram illustrating the storage and use of block vectors in a template matching prediction method according to one embodiment. The template matching prediction method according to the present embodiment can be performed by a video decoder and / or video encoder disclosed herein.

[0132] When the prediction block is used in the template matching prediction method according to the present embodiment, the distance between the current block (810) and the prediction block (820) is defined as a block vector (830), which can be used in subsequent encoding and decoding. The block vector (830) can be stored for use in the template matching prediction method, as well as in copy encoding and decoding methods of intra blocks. In addition, the decoding (or encoding) of the next block (e.g., 840) of the current block (810) can be configured to refer to (850) the block vector. According to one embodiment of the present invention, the block vector may be a value determined by an operation in the same manner in the encoder and the decoder, respectively. In this case, the block vector may not be included in the encoded bit string.

[0133] Meanwhile, when template matching is performed, excessive computation in the restoration area can increase the complexity of the encoder / decoder. This can be due to the search range for template matching in the restoration area being too large, the number of pixels within the template being too large, or the number of block vectors referenced in the candidate list for block vector search being too large. Therefore, to perform template matching prediction with low complexity, definitions for the calculation method, search range, and block vector composition method for the template matching task are required.

[0134]

[0135] Composition of the present invention

[0136] According to one embodiment of the present invention, when performing template matching on block vectors in a block vector candidate list, the system may be configured to compare multiple calculation results and terminate template matching on the remaining block vectors early. For example, in one embodiment, if a specific calculation result is smaller than a predetermined value, the system may be configured to terminate the remaining template matching early. For another example, in one embodiment, if a specific calculation result is significantly smaller than other calculation results, the system may be configured to terminate the remaining template matching early.

[0137] According to one embodiment of the present invention, template matching of sub-pixel units may be configured to be terminated early based on a calculation result of an integer pixel unit. For example, in one embodiment, if the calculation result of an integer pixel unit is less than a predetermined value, template matching of the remaining sub-pixel units may be configured to be terminated early. For another example, in one embodiment, if the calculation result of an integer pixel unit is less than some of the sub-pixel calculation results, the remaining template matching may be configured to be terminated early. For another example, in one embodiment, template matching of a certain area pointed to by a block vector may be configured to be terminated early based on a calculation result of another area.

[0138] According to one embodiment of the present invention, template matching may be configured to terminate early when the calculation result increases gradually when performed from an area close to the current block. However, depending on the embodiment, early termination may not be applied, and various configurations and methods described below may be separately included.

[0139] According to one embodiment of the present invention, when performing template matching on block vectors in a block vector candidate list, the number of block vectors may be reduced or specific block vectors may be removed through comparison between block vectors in the candidate list. For example, in one embodiment, the remaining block vectors may be removed through comparison between calculation results of specific block vectors in the candidate list. For another example, in one embodiment, the present invention may be configured to determine whether to perform template matching on the remaining block vectors through comparison between specific block vectors or comparison between calculation results of block vectors. For another example, in one embodiment, the number of block vectors may be reduced or specific block vectors may be removed according to compression information of surrounding blocks.

[0140] According to one embodiment of the present invention, when a calculation for template matching is performed on block vectors in a block vector candidate list, the calculation method may be configured to be performed differently depending on the characteristics of the pixel unit, sub-pixel unit, and / or block vector. In one embodiment, the calculation method may be transmitted from the encoder to the decoder, preferably through a symbol included in the syntax information of a bitstream. If only one calculation method is used, transmission may be unnecessary. However, if various different calculation methods are applied, the calculation method may be transmitted, for example, through a flag and / or index indicating the calculation method, and a combination of such expressions. The various calculation methods are not limited.

[0141] According to one embodiment of the present invention, the calculation method may include a simple difference method. According to another embodiment of the present invention, the calculation method may include a calculation method that adds the absolute values ​​of the differences between pixels (e.g., sum of absolute differences (SAD)). According to another embodiment of the present invention, the calculation method may include a calculation method based on differences using a transformation matrix including a Hadamard transform (e.g., sum of absolute transformed differences (SATD)). According to another embodiment of the present invention, the calculation method may be based on other functions or algorithms used for calculating other cost weights or difference values, and may include various methods including, but not limited to, mean absolute difference (MAD), mean removed sum of absolute differences (MRSAD), and sum of squared differences (SSD).

[0142] According to one embodiment of the present invention, the calculation method may be configured to be set to be the same or different for each compression unit such as a video sequence, frame, slice, subpicture, tile, macroblock, or coding tree unit (CTU) and transmitted. When a plurality of template matching calculation methods are implemented as described above, the encoder may record which of the calculation methods was applied to a specific sequence, frame, slice, subpicture, or tile in a bit string as a symbol included in the syntax information, and the decoder may be configured to read the symbol to derive and use the calculation method.

[0143] According to one embodiment of the present invention, when setting a search range for template matching prediction, the search range may be set to perform a search centered on a search range block vector generated from block vectors of surrounding blocks or block vectors in a block vector candidate list. In this case, the search range may be set in integer pixel units or in subpixel units.

[0144] FIG. 9 is an exemplary diagram illustrating a method for setting a search range for a block vector according to an embodiment of the present invention. Referring to FIG. 9, the adjacent blocks adjacent to the current block (930) may include at least one left block (932) and an upper block (934). For example, each of the adjacent blocks (932, 934) may have a block vector and / or may be a block having a candidate list for calculating a block vector.

[0145] A method for searching a block vector according to one embodiment of the present invention may include a step of generating a search range block vector (910) based on a current block (930) by referencing a block vector (915) of a left block (for example, by replicating it so that the direction and distance are the same by reflecting the distance between blocks). Then, a search range (940) of a constant size in the up / down / left / right directions may be calculated based on a point (917) indicated by the search range block vector (910) (or centered on the point).

[0146] A method for searching a block vector according to another embodiment of the present invention may include a step of generating a search range block vector (920) by referring to a block vector (925) of an upper block, and a step of calculating a search range (945) of a certain size based on a point (927) pointed to by the block vector (920). Through this, complexity can be reduced by not performing search calculations for all pixels of a frame, and it can also be made possible to ensure prediction accuracy by referring to adjacent block vectors.

[0147] FIG. 10 is an exemplary diagram of a method for determining a corrected block vector according to an embodiment of the present invention. Referring to FIG. 10, a current block (1020) and an adjacent template (1025) are located within a restoration area (1010). An initial block vector (1030) selected from a block vector candidate list points to a specific location within the restoration area (1010). According to the present invention, a corrected block vector (1040) can be derived by applying correction to the initial block vector (1030). The correction can be performed by performing template matching within a predetermined range (1035) around the initial block vector (1030). The corrected block vector (1040) can be expressed as a differential vector (1045) from the initial block vector (1030), and the differential vector (1045) can be signaled through a bit string. Based on the above-mentioned corrected block vector (1040), a reference block (1050) and a template (1055) that serve as reference targets can be determined.

[0148] According to another embodiment of the present invention, the prediction vector for the template matching may be configured to use a block vector in a surrounding block or a block vector candidate list with a separate correction applied. When correcting a block vector in a surrounding block or a block vector candidate list as described above, according to one embodiment of the present invention, the difference between the block vector and the corrected block vector may be configured to be transmitted. The correction may preferably be performed in a search range set based on the block vector, and the search range may include a sub-pixel unit. For example, according to one embodiment of the present invention, template matching may be configured to additionally perform for eight 1 / 4 pixel units surrounding the block vector. In addition, various sub-pixel units such as 1 / 2 pixel and 1 / 8 pixel may be applied, and various search patterns for correction may also be defined. For example, various search patterns such as a diamond pattern, a cross pattern, and a square pattern may be used.

[0149] According to one embodiment of the present invention, the information indicating the difference may be expressed as information by a combination of a size of a vector, flag information, index information, and at least one of the information listed above, and the information may be configured to be transmitted from an encoder to a decoder, preferably through a symbol included in the syntax of a bit string. For example, when expressed by a size of a vector, information describing a differential vector may be transmitted as a symbol. For another example, when expressed by a flag, the flag information may be transmitted as a symbol. For another example, when expressed by the index, index information for a table indicating multiple possibilities for the differential vector may be transmitted as a symbol.

[0150] According to one embodiment of the present invention, correction information for a block vector of the present invention may be implemented by a method that is substantially the same as or similar to a conventional MMVD (merge mode with motion vector difference) method, and may include a technique that may be called MBVD (merge mode with block vector difference). For example, according to one embodiment of the present invention, a more accurate block vector may be generated by adding the difference vector to an initial block vector, and the difference vector may be designed to have a limited direction (e.g., 4 directions or 8 directions) and a limited size value.

[0151] FIG. 11 is an exemplary diagram of a secondary block vector template matching method according to an embodiment of the present invention. Referring to FIG. 11, a current block (1120) and its adjacent template (1125) are located within a restoration area (1110). A primary block vector (1130) for the current block (1120) points to a primary reference block (1140) within the restoration area (1110). According to an embodiment of the present invention, a secondary reference block (1160) can be searched for using a secondary block vector (1150) associated with the primary reference block (1140). The secondary reference block (1160) can be used as another candidate for template matching, thereby enabling more accurate prediction.

[0152] According to one embodiment of the present invention, when finding a block vector for template matching or constructing a list of block vectors, it may be configured to use a secondary block vector stored in a block pointed to by a primary block vector. The primary and secondary block vectors may be recursed in the same manner, and may be configured to use, for example, a tertiary block vector of a block pointed to by a secondary block vector stored in a block pointed to by the primary block vector. The recursive block vector reference may be referred to as a chained motion vector, and should be understood as a technical configuration compatible with various block vector re-reference configurations encompassed by such a name or concept. The number of recursion is not limited in the present invention, and it may be determined to use an Nth-order block vector according to any condition. According to one embodiment of the present invention, for any order N, whether to use an Nth-order block vector may be determined based on an N-1st-order block vector or a calculation result of a block vector. According to one embodiment of the present invention, for any order N, the correction process, calculation method, or template matching of sub-pixel units can be configured to operate differently starting from the Nth order block vector.

[0153] According to one embodiment of the present invention, the block vector can be corrected up to two times, and can be configured to be corrected with a 1×1 sample range in the first time and a 3×3 sample range in the second time. However, the present invention does not limit the number of recursion times of the N-th block vector as described above, and it is obvious that the specific method of block vector correction can be changed for each block vector re-correction order. For example, different correction sample ranges can be applied for each order, and at least some correction sample ranges can be applied differently for corrections of the 3rd, 4th, and Nth orders or higher. In addition, the reference orders are expressed in the order of 1st, 2nd, 3rd… for easy understanding, but the order can be enumerated in another sequential manner, for example, 1st, 2nd, 3rd… , 0th, 1st, 2nd… , or BV0, BV1, BV2… It is usually self-evident that the invention can be expressed by various enumeration methods, and therefore, as long as the technical idea of ​​the invention is maintained, the difference in the expression method does not limit the scope of the invention.

[0154] That is, according to one embodiment of the present invention, it should be understood that the template matching prediction method can be configured to enable continuous reference and correction for the primary block vector. Specifically, the first reference block vector derived from the primary block vector can be updated through a correction process, and this reference and update process can be recursively performed multiple times. It can be understood that the first reference block vector encompasses any N-th or higher order block vector obtained from the area pointed to by the primary block vector in the description of the above-described embodiment. In at least one of these recursive performances, the correction method of the block vector can be changed, which can mean various changes in the correction method, including differentiation of the correction sample range, change of the integer pixel and sub-pixel unit processing method, switching of the calculation algorithm, or adjustment of the template matching parameter.

[0155] According to one embodiment of the present invention, whether to perform integer-unit or sub-pixel-unit block vector correction can be determined based on whether an image to be encoded / decoded is screen content. Here, screen content may refer to artificial image content such as a computer screen or a game image rather than a natural image, but is not limited thereto. Preferably, in the case of screen content, sub-pixel re-correction may not be performed, but may be configured in a different manner depending on the characteristics of the image or the configuration method of the encoder / decoder. Depending on the embodiment, whether the image is screen content can be transmitted as a signal included in high-level bitstream syntax information (HLS), or can be transmitted as a signal included in a bitstream syntax of another unit, or can be implicitly inferred from another signal of the bitstream syntax or the characteristics of the image to be encoded / decoded.

[0156] FIG. 12 is an exemplary diagram of a plurality of block vectors according to one embodiment of the present invention. Referring to FIG. 12, a current block (1220) and its adjacent template (1225) are located in a restoration area (1210). An N-th block vector (1230) points to an N-th reference block (1240) within the restoration area (1210). (As described above, the N-th block vector (1230) may be derived by concatenating block vectors multiple times.) Another feature of the present invention is to provide a method of utilizing a plurality of block vectors (1250) that may exist within the N-th reference block (1240). Each of the plurality of block vectors points to a different location and may be utilized selectively or integrally as needed.

[0157] According to one embodiment of the present invention, when there are multiple block vectors in a block pointed to by an N-th block vector for an arbitrary order N, it can be configured to select and operate at least one specific block vector among them. That is, when multiple block vectors are extracted by template matching in a block pointed to by an N-th block vector, it can be configured to compensate each vector and compare it with each other to calculate. For example, according to one embodiment, it can be configured to use them sequentially in an arbitrary order. For example, according to another embodiment, it can be configured to determine whether to use the remaining block vectors by utilizing the calculation results for an arbitrary number of block vectors. For example, according to another embodiment, it can be configured to perform template matching up to the sub-pixel unit only for an arbitrary number of block vectors. For example, according to another embodiment, it can be configured to use only the block vectors stored in the area closest to the pixel pointed to by the block vector.

[0158] In one embodiment of the present invention, it may be configured to determine whether to apply a template matching prediction technique to the Nth block by considering at least one of the horizontal or vertical size of the block, the area, the number of pixels within the block, and / or information about the surrounding blocks. In this case, it may be configured to select and use a template corresponding to the left, top, or left and top of the Nth block.

[0159] For example, according to one embodiment, when the width of a block is greater than a first threshold value and the height is greater than a second threshold value, template matching may be performed only up to the Nth block by specifying an arbitrary N. For another example, when the width of a block is less than a third threshold value and the height is less than a fourth threshold value, template matching may be performed only up to the Nth block by specifying an arbitrary N. For another example, when the number of pixels in a block is greater than or less than a fifth threshold value, template matching may be performed only up to the Nth block by specifying an arbitrary N. For another example, when the area of ​​a block is greater than or less than a sixth threshold value, template matching may be performed only up to the Nth block by specifying an arbitrary N.

[0160] According to one embodiment of the present invention, when a plurality of calculation methods are used in template matching prediction, and / or when a comparison between a current block and a predicted block is performed for a plurality of block vectors in template matching prediction, and / or when a maximum number of block vectors is set in template matching prediction, and / or when whether to perform integer pixel or sub-pixel unit in template matching prediction, and / or when a search range area is set in template matching prediction, the set information may be transmitted as a combination of a flag or an index, and the set information may be set and transmitted for each sequence, tile, subpicture, frame, slice, or block.

[0161] In the above-described embodiments of the present invention, for the convenience of explanation, the types of reference vectors have been described based on block vectors in intra-prediction. However, those skilled in the art will understand that the various application methods for the above-described block vectors can be equally applied to motion vectors in inter-prediction. That is, similar to block vectors, motion vectors can also be derived, recursively derived, and / or corrected by the methods disclosed in the present invention. Furthermore, it is self-evident that block vectors and motion vectors can be derived interchangeably, recursively derived, and / or corrected. Therefore, the present invention can be applied to both intra-prediction methods and inter-prediction methods, and should be understood as a technical idea that is commonly applied to general reference vectors.

[0162] Encoder and decoder

[0163] It is self-evident that the method according to the present invention can be applied equally to both encoders and decoders. Additionally, as illustrated in FIG. 4 through the internal decoder (420) and the coding loop including it, this decoding process can be implemented identically within the encoder to predict the state of the decoder.

[0164] The encoding method according to the present invention described above can be implemented through an encoder as a device. The encoder as a device can be implemented in a form that maintains the conventional encoder structure exemplified through FIGS. 1 to 6 above or applies a predetermined change thereto. However, the form of implementation is not necessarily limited to that exemplified, and any form of encoder structure that can function as a video encoder should be considered an encoder established by the present invention as long as it implements the technical idea of ​​the present invention.

[0165] In addition, the method for decoding the encoding result according to the present invention described above can be implemented through a decoder as a device. The decoder as a device can be implemented in a form that maintains the conventional decoder structure exemplified through FIGS. 1 to 6 above or applies a predetermined change thereto. However, the form of implementation is not necessarily limited to that exemplified, and any form of decoder structure that can function as a video decoder should be considered a decoder established according to the present invention as long as it implements the technical idea of ​​the present invention.

[0166] A person skilled in the art will readily understand that a bit string encoded by the above-described method and device can be decoded by applying a method symmetrical and / or reverse to the encoding method. In one embodiment, when reading information for decoding from the encoded bit string, at least one variable length coded phrase included in the encoded bit string can be interpreted, and furthermore, in one embodiment, the variable length coding can be performed by an entropy coding method. The technical details and application method of implementing such a decoding procedure can be readily understood from the above-described encoding procedure.

[0167] The processor that may be included in the encoder and / or decoder described herein may mean one or more general purpose computers or special purpose computers, such as a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable array (FPA), a programmable logic unit (PLU), a microprocessor, or any other device capable of executing instructions and responding.

[0168] Even if the processor is expressed singularly for ease of understanding, those skilled in the art will appreciate that the processor may include multiple processing elements and / or multiple types of processing elements. For example, a device according to one embodiment of the present invention may include multiple processors or one processor and one controller as the processor. Furthermore, the processor may be implemented using various processing configurations, such as a parallel processor or a multi-core processor.

[0169] The processor may be configured to execute an operating system (OS) and one or more software programs running on the operating system. Furthermore, the processor may access, store, manipulate, process, and generate data in response to the execution of the software.

[0170] The software may include a computer program, code, instructions, or a combination of one or more of these, and may be configured to control the processor to perform a desired operation and to issue commands to the processor, either independently or collectively. The software may be permanently or temporarily embodied in any type of machine, component, physical device, virtual equipment, computer storage medium or device, or transmitted signal wave, for interpretation by the processor or for providing commands or data to the processor. The software may also be distributed over networked computer systems, and stored or executed in a distributed manner.

[0171] The software may also be implemented in the form of program commands that can be executed through various computer means and recorded or stored in the memory. The memory may be a computer-readable recording medium, and program commands, data files, data structures, etc. may be recorded singly or in combination in the computer-readable recording medium. The program commands stored in the memory may be based on a command system specifically designed and configured for the embodiment of the present invention, or may follow a command system known and available to those skilled in the art of computer software, such as a command system exemplified by the assembly language, C, C++, Java, Python, etc. It should be understood that the command system and the program commands therefrom include not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by the device and / or the processor according to an embodiment of the present invention using an interpreter or the like.

[0172] The computer-readable recording medium constituting the device according to one embodiment of the present invention, including the memory described in this specification, may include a temporary or volatile recording medium that is maintained only while the processor is operating, such as a processor cache, a RAM, a flash memory, or a relatively non-volatile or long-term recording medium, such as a magnetic media such as a hard disk, a floppy disk, and a magnetic tape, an optical media such as a CD-ROM, a DVD, a magneto-optical media such as a floptical disk, or a solid state memory, or may include a read-only recording medium, such as a ROM arranged on hardware, and furthermore, the hardware itself configured to perform an operation equivalent to a series of program commands by a hard-wired structure by circuit wiring, and each step for performing the operation for implementing an embodiment of the present invention can be viewed as being recorded by the connection and arrangement of the hardware components, and thus the connection and arrangement method is the memory and It is obvious to a person skilled in the art that they can be considered equivalent.

[0173] The embodiments described above with respect to the processor and the memory are not mutually exclusive and may be selected or combined and implemented as needed. For example, a single hardware device may be configured to operate as a module composed of one or more of the software to perform the operations of an embodiment of the present invention, and vice versa. As another example, in the present specification, all or part of the operations assigned to a certain functional unit may be implemented by one or more of the software stored in a device according to an embodiment of the present invention (preferably, in any one of the recording media belonging to the category of the memory) and configured to be executed by the processor. In such a case, such a functional unit may be referred to as a functional unit "included" in the processor.

[0174]

[0175] Although the present invention has been described with reference to drawings and embodiments, as already mentioned above, it does not mean that the scope of protection of the present invention is limited to the drawings or embodiments presented above, and it will be understood that a person skilled in the relevant technical field can modify and change the present invention in various ways within a scope that does not depart from the spirit and scope of the present invention described in the claims of the present invention patent.

Claims

1. In the video decryption method, A step of obtaining information about the current block from a bit string; A step of determining a template located in an adjacent area of ​​the current block; A step of deriving a primary reference vector of the current block using the above template; A step of performing correction on the above primary reference vector to derive a corrected primary reference vector; A step of generating a prediction block for the current block using the area pointed to by the above-mentioned corrected primary reference vector; and A step of restoring the current block using the predicted block; An image decoding method, characterized in that correction for the primary reference vector is performed by performing template matching within a predetermined range around the primary reference vector.

2. In paragraph 1, A step of obtaining a secondary reference vector from the area pointed to by the above-mentioned corrected primary reference vector; A step of performing correction on the above secondary reference vector to derive a corrected secondary reference vector; and An image decoding method, characterized in that it further comprises a step of generating a prediction block for the current block using the area pointed to by the corrected secondary reference vector.

3. In paragraph 2, An image decoding method, characterized in that the correction for the first reference vector and the correction for the second reference vector are performed using different correction sample ranges.

4. In paragraph 3, The correction for the above primary reference vector is performed using a 1×1 sample range, An image decoding method, characterized in that the correction for the above secondary reference vector is performed using a 3×3 sample range.

5. In paragraph 1, Further comprising a step of obtaining information indicating whether the image is screen content from the bit string; An image decoding method characterized in that, based on the above information, it is determined whether correction for the first reference vector is to be performed on an integer pixel basis or a subpixel basis.

6. In paragraph 5, If the above image is screen content, correction for the first reference vector is performed in integer pixel units, An image decoding method, characterized in that when the above image is not a screen content, correction for the first reference vector is performed by at least one of an integer pixel and a subpixel unit.

7. In paragraph 1, The above template matching is performed using at least one of a plurality of calculation methods for calculating differences between templates for the above template matching, An image decoding method, characterized in that the above-mentioned multiple calculation methods include at least one of a simple difference method, a calculation method for adding the absolute value of the difference between pixels (SAD), a calculation method based on a difference using a transformation matrix (SATD), a mean absolute difference (MAD), a mean removed sum of absolute differences (MRSAD), and a sum of squared differences (SSD).

8. In paragraph 7, The above template matching is characterized in that it is performed using two or more of the above multiple calculation methods, A step of reading information for selecting at least one of the plurality of calculation methods from a bit string; and A method for decoding an image, comprising: a step of determining a calculation method for the template matching based on the above information.

9. In paragraph 1, The step of deriving the primary reference vector of the current block using the above template is: A step of constructing a list of reference vector candidates for deriving the above first reference vector; and An image decoding method, comprising: a step of removing at least one reference vector from the above-mentioned reference vector candidate list through comparison between reference vectors.

10. In paragraph 1, The step of deriving the primary reference vector of the current block using the above template is: A step of constructing a list of reference vector candidates for deriving the above first reference vector; A step of reading information for selecting at least one of the above reference vector candidate lists from a bit string; and An image decoding method, comprising: a step of deriving the first reference vector based on the above information.

11. In paragraph 1, An image decoding method, characterized in that at least one of the horizontal size, vertical size, area, or number of pixels within a current block is compared with a predetermined threshold value, and at least one of whether to apply a template matching prediction technique and the method of applying the technique is determined based on the result of the comparison.

12. In paragraph 1, A step of obtaining a first reference reference vector from an area pointed to by the above-mentioned corrected first reference vector; A step of updating the first reference reference vector by performing a correction on the first reference reference vector; and further comprising a step of generating a prediction block for the current block using the area pointed to by the first reference reference vector; An image decoding method, characterized in that the step of updating the first reference reference vector is performed recursively multiple times, and a method of correcting the reference vector is different in at least one of the recursive performances.

13. In the video encoding method, A step of determining a template located in an adjacent area of ​​the current block; A step of deriving a primary reference vector of the current block using the above template; A step of performing correction on the above primary reference vector to derive a corrected primary reference vector; A step of generating a prediction block for the current block using the area pointed to by the above-mentioned corrected primary reference vector; A step of generating a residual signal using the current block and the prediction block; and A step of encoding the residual signal to generate a bit string; An image encoding method, characterized in that correction for the primary reference vector is performed by performing template matching within a predetermined range around the primary reference vector.

14. In paragraph 13, A step of obtaining a secondary reference vector from the area pointed to by the above-mentioned corrected primary reference vector; A step of performing correction on the above secondary reference vector to derive a corrected secondary reference vector; and A video encoding method, characterized in that it further comprises a step of generating a prediction block for the current block using the area pointed to by the corrected secondary reference vector.

15. In paragraph 13, A step of determining whether the current encoding target image is screen content; and further comprising a step of including information indicating the result of the decision in the bit string; A video encoding method characterized in that it is determined whether correction for the primary reference vector is to be performed in integer pixel units or in subpixel units based on the presence of the above screen content.

16. In paragraph 13, a step of determining a calculation method to be used for the above template matching; and Further comprising a step of including information indicating the above-determined calculation method in the bit string, A video encoding method, characterized in that the above calculation method includes at least one of a simple difference method, a calculation method for adding the absolute value of the difference between pixels (SAD), a calculation method based on a difference using a transformation matrix (SATD), a mean absolute difference (MAD), a mean removed sum of absolute differences (MRSAD), and a sum of squared differences (SSD).

17. In paragraph 13, A step of generating a difference vector representing the difference between the primary reference vector and the corrected primary reference vector; and further comprising a step of including the difference vector in the bit string; The above difference vector is expressed as a combination of direction information and magnitude information, The above direction information indicates one of a limited number of directions, A method for encoding an image, wherein the size information indicates one of a limited number of size values.

18. In paragraph 13, The step of deriving the primary reference vector of the current block using the above template is: A step of constructing a list of reference vector candidates for deriving the above first reference vector; A step of calculating an encoding cost for the current block based on a prediction block obtained by at least one reference vector included in the above reference vector candidate list; A step of deriving the primary reference vector by selecting at least one reference vector candidate from the candidate list based on the encoding cost calculation; and A method for encoding an image, comprising: generating a bit string including information related to identifying the selected candidate from the candidate list.

19. In paragraph 13, A step of obtaining a first reference reference vector from an area pointed to by the above-mentioned corrected first reference vector; A step of updating the first reference reference vector by performing a correction on the first reference reference vector; and further comprising a step of generating a prediction block for the current block using the area pointed to by the first reference reference vector; A method for encoding an image, characterized in that the step of updating the first reference reference vector is performed recursively multiple times, and a method of correcting the reference vector is different in at least one of the recursive performances.

20. In the video decryption device, processor; Memory connected to the processor; a receiving unit for receiving a bit string; and including a video decryption unit; The image decoding unit is configured to obtain information about a current block from the bit string, determine a template located in an adjacent area of ​​the current block, derive a primary reference vector of the current block using the template, perform correction on the primary reference vector to derive a corrected primary reference vector, generate a prediction block for the current block using an area pointed to by the corrected primary reference vector, and restore the current block using the prediction block. An image decoding device, characterized in that correction for the primary reference vector is performed by performing template matching within a predetermined range around the primary reference vector.

Images