KR101718830B1 - Method and apparatus of parallel video decoding using the encoding mode - Google Patents

Abstract

A video decoding method and apparatus are disclosed. The image decoding method includes parsing encoding mode information from a received bitstream and parallelly restoring blocks in a current image based on the parsed encoding mode information. In the step of restoring the blocks in the current image in parallel, the intra-picture coding mode block and the intra-picture coding mode block are divided into the inter picture coding mode block and the intra picture coding mode block according to whether the parsed coding mode is an inter picture coding mode or an intra picture coding mode And restores the current intra-picture intra-picture coding mode blocks in parallel and restores the current intra-picture intra-picture coding mode blocks in a row-by-row manner.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method and an apparatus for decoding high-speed video to which an adaptive parallel processing according to an encoding mode is applied,

The present invention relates to image processing, and more particularly, to a high-speed video decoding method and apparatus using parallel processing.

Recently, broadcasting service having high definition (HD) resolution has been expanded not only in domestic but also in the world, so that many users are accustomed to high definition and high definition video, and accordingly, many organizations are spurring development for next generation video equipment. In addition, with the increase of interest in UHD (Ultra High Definition) having resolution more than 4 times of HDTV in addition to HDTV, a compression technique for a higher resolution and a higher image quality is required.

An inter prediction technique for predicting pixel values included in a current picture from temporally preceding and / or following pictures for image compression, prediction of pixel values included in a current picture using pixel information in the current picture An intra prediction technique, an entropy coding technique in which a short code is assigned to a symbol having a high appearance frequency and a long code is assigned to a symbol having a low appearance frequency.

The present invention provides an image encoding / decoding method and apparatus capable of improving encoding / decoding efficiency.

The present invention provides a high-speed video decoding method and apparatus using parallel processing capable of improving encoding / decoding efficiency.

According to one aspect of the present invention, a video decoding method is provided. The image decoding method includes parsing encoding mode information from a received bitstream and parallelly restoring blocks in a current image based on the parsed encoding mode information.

In the step of restoring the blocks in the current image in parallel, the intra-picture coding mode block and the intra-picture coding mode block are divided into the inter picture coding mode block and the intra picture coding mode block according to whether the parsed coding mode is an inter picture coding mode or an intra picture coding mode And restoring the current intra-picture intra-picture coding mode blocks in parallel and restoring the intra-picture intra-picture coding mode blocks in parallel.

The present invention can enhance image decoding speed by applying image restoration differently according to an encoding mode. Conventional video decoders use entropy decoding and image restoration simultaneously in parallel, which results in overhead due to frequent communication between parallel processors. Therefore, the conventional image decoder has a disadvantage in that the efficiency of parallel processing is lowered. On the other hand, the image decoding method and apparatus using the parallel processing according to the present invention can reduce the waiting time for reducing interprocessor communication, thereby improving the speed of the image decoding apparatus.

1 is a block diagram illustrating a configuration of an image encoding apparatus according to an embodiment of the present invention.
2 is a block diagram illustrating a configuration of an image decoding apparatus according to an embodiment of the present invention.
3 is a diagram schematically illustrating the WPP technique.
4 is a view for explaining a video decoding method applied with parallel processing according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating an example in which blocks in an inter picture coding mode are restored in parallel when blocks are divided into blocks in an inter picture coding mode and blocks in an intra picture coding mode according to an embodiment of the present invention. to be.
6 is a diagram illustrating an example of restoring blocks in an intra-picture coding mode in parallel when reconstructing blocks divided into blocks of an inter picture coding mode and a picture intraframe coding mode according to an embodiment of the present invention to be.
7 is a flowchart schematically illustrating a video decoding method according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In describing the embodiments of the present invention, if the detailed description of related known structures or functions is deemed to obscure the subject matter of the present specification, the description may be omitted.

When an element is referred to herein as being "connected" or "connected" to another element, it may mean directly connected or connected to the other element, Element may be present. In addition, the content of " including " a specific configuration in this specification does not exclude a configuration other than the configuration, and means that additional configurations can be included in the scope of the present invention or the scope of the present invention.

The terms first, second, etc. may be used to describe various configurations, but the configurations are not limited by the term. The terms are used for the purpose of distinguishing one configuration from another. For example, without departing from the scope of the present invention, the first configuration may be referred to as the second configuration, and similarly, the second configuration may be named as the first configuration.

In addition, the constituent elements shown in the embodiments of the present invention are shown independently to represent different characteristic functions, which do not mean that each constituent element is composed of separate hardware or a single software constituent unit. That is, each constituent unit is included in each constituent unit for convenience of explanation, and at least two constituent units of each constituent unit may form one constituent unit or one constituent unit may be divided into a plurality of constituent units to perform a function. The integrated embodiments and the separate embodiments of each component are also included in the scope of the present invention unless they depart from the essence of the present invention.

In addition, some of the components are not essential components to perform essential functions in the present invention, but may be optional components only to improve performance. The present invention can be implemented only with components essential for realizing the essence of the present invention, except for the components used for the performance improvement, and can be implemented by only including the essential components except the optional components used for performance improvement Are also included in the scope of the present invention.

1 is a block diagram illustrating a configuration of an image encoding apparatus according to an embodiment of the present invention. The image encoding apparatus of FIG. 1 may be a structure to which HEVC (High Efficiency Video Coding) encoding technology is applied, and may be structurally identical to the existing AVC / H.264 video encoding technology.

1, the image encoding apparatus 100 includes a motion prediction unit 111, a motion compensation unit 112, an intra prediction unit 120, a switch 115, a subtractor 125, a transform unit 130, A quantization unit 140, an entropy encoding unit 150, an inverse quantization unit 160, an inverse transformation unit 170, an adder 175, a filter unit 180, and a reference image buffer 190.

The image encoding apparatus 100 may encode an input image in an intra mode or an inter mode and output a bit stream. In the intra mode, the switch 115 is switched to the intra mode, and in the inter mode, the switch 115 can be switched to the inter mode. Intra prediction is intra prediction, and inter prediction is inter prediction. The image encoding apparatus 100 may generate a prediction block for an input block of an input image, and then may code a residual between the input block and the prediction block. At this time, the input image may mean an original picture.

In the intra mode, the intraprediction unit 120 may generate a prediction block by performing spatial prediction using the pixel values of the already coded / decoded blocks around the current block.

In the inter mode, the motion predicting unit 111 can obtain a motion vector by searching an area of the reference picture stored in the reference picture buffer 190 that is best matched with the input block. The motion compensation unit 112 may generate a prediction block by performing motion compensation using a motion vector. Here, the motion vector is a two-dimensional vector used for inter prediction, and can represent the offset between the current image to be encoded / decoded and the reference image.

The subtractor 125 may generate a residual block by a difference between the input block and the generated prediction block.

The transforming unit 130 may perform a transform on the residual block to output a transform coefficient. The quantization unit 140 may quantize the input transform coefficients according to a quantization parameter (or a quantization parameter) to output a quantized coefficient.

The entropy encoding unit 150 may output a bit stream by performing entropy encoding based on the values calculated by the quantization unit 140 or the encoding parameter values calculated in the encoding process. When entropy encoding is applied, a small number of bits are allocated to a symbol having a high probability of occurrence, and a large number of bits are allocated to a symbol having a low probability of occurrence, thereby expressing symbols, The size of the column can be reduced. Therefore, the compression performance of the image encoding can be enhanced through the entropy encoding. The entropy encoding unit 150 may use an encoding method such as Exponential-Golomb, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) for entropy encoding.

Since the image encoding apparatus 100 according to the embodiment of FIG. 1 performs inter-prediction encoding, that is, inter-view prediction encoding, the currently encoded image needs to be decoded and stored for use as a reference image. Accordingly, the quantized coefficients are inversely quantized in the inverse quantization unit 160 and inversely transformed in the inverse transformation unit 170. The inverse quantized and inverse transformed coefficients are added to the prediction block through the adder 175 and a reconstruction block is generated.

The restoration block passes through the filter unit 180 and the filter unit 180 applies at least one of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) can do. The filter unit 180 may be referred to as an adaptive in-loop filter. The deblocking filter can remove block distortion occurring at the boundary between the blocks. The SAO may add a proper offset value to the pixel value to compensate for coding errors. ALF can perform filtering based on the comparison between the reconstructed image and the original image. The reconstruction block having passed through the filter unit 180 can be stored in the reference picture buffer 190.

2 is a block diagram illustrating a configuration of an image decoding apparatus according to an embodiment of the present invention. The video decoding apparatus of FIG. 2 may be a structure to which the HEVC decoding technology is applied, and may be structurally identical to the existing AVC / H.264 video decoding technology.

2, the image decoding apparatus 200 includes an entropy decoding unit 210, an inverse quantization unit 220, an inverse transform unit 230, an intra prediction unit 240, a motion compensation unit 250, an adder 255 A filter unit 260, and a reference picture buffer 270.

The video decoding apparatus 200 receives the bit stream output from the encoder and decodes the video stream into the intra mode or the inter mode, and outputs the reconstructed video, that is, the reconstructed video. In the intra mode, the switch is switched to the intra mode, and in the inter mode, the switch can be switched to the inter mode.

The image decoding apparatus 200 may obtain a reconstructed residual block from the input bitstream, generate a prediction block, and add the reconstructed residual block and the prediction block to generate a reconstructed block, i.e., a reconstructed block .

The entropy decoding unit 210 may entropy-decode the input bitstream according to a probability distribution to generate symbols including a symbol of a quantized coefficient type.

When the entropy decoding method is applied, a small number of bits are assigned to a symbol having a high probability of occurrence, and a large number of bits are assigned to a symbol having a low probability of occurrence, so that the size of a bit string for each symbol is Can be reduced.

The quantized coefficients are inversely quantized in the inverse quantization unit 220 and inversely transformed in the inverse transformation unit 230. The reconstructed residual block can be generated as a result of inverse quantization / inverse transformation of the quantized coefficients.

In the intra mode, the intraprediction unit 240 may generate a prediction block by performing spatial prediction using the pixel value of the already decoded block around the current block. In the inter mode, the motion compensation unit 250 may generate a prediction block by performing motion compensation using a motion vector and a reference image stored in the reference picture buffer 270. [

The residual block and the prediction block are added through the adder 255, and the added block can be passed through the filter unit 260. [ The filter unit 260 may apply at least one of a deblocking filter, SAO, and ALF to a restoration block or a restored picture. The filter unit 260 may output a reconstructed image, that is, a reconstructed image. The reconstructed image is stored in the reference picture buffer 270 and can be used for inter prediction.

The image decoder of FIG. 2 can be roughly divided into a process of receiving an encoded bitstream, parsing encoding information from the received bitstream, and restoring an image using parsed encoding information. According to the image decoder shown in FIG. 2, the parsing process can be performed mainly in the entropy decoding unit. After the encoded bit stream passes through the entropy decoding unit, the encoded information for the bit stream can be known. Since the reconstruction process is an inverse process of the encoding process, if the encoding information is obtained, the image can be reconstructed in the reverse order of the encoding process.

As described above, since the entropy decoding is used for decoding the encoded information, it is impossible to parse the encoded information in parallel unless entropy coding is performed in parallel during the encoding process. On the other hand, the reconstruction process for reconstructing an image can be divided into modules having no dependency, and each of the modules can reconstruct the image in parallel. If the time required for each module of the decoder is measured, more time is required for the restoration process than the parsing process. Therefore, in order to develop a high-speed decoding apparatus, it is an important factor to efficiently perform the restoration process in parallel.

Accordingly, the present invention provides a method and apparatus for recovering an image at a high speed by processing an image restoration process in parallel.

On the other hand, the image reconstruction process can be performed differently according to the encoding method performed by the encoder. For example, the image reconstruction process may be performed differently depending on the encoding mode. The coding mode includes an intra-picture coding mode (intra mode) and an inter-picture coding mode (inter mode) as described above. The intra-picture coding mode refers to a mode in which a neighboring block located in the periphery of the current block is referred to in an image including a current block to be encoded when an image is encoded. The inter-picture coding mode refers to a mode in which coding is performed with reference to a previous or subsequent image of an image including a current block to be coded. Since the method of encoding an image differs according to the encoding mode, the process of reconstructing an image is also different.

In other words, in order to restore the current block (current block to be decoded) encoded in the intra-picture coding mode, the block referenced by the current block in the image including the current block must be restored to restore the current block can do. In order to recover the current block (current block to be decoded) encoded in the inter-picture mode, the motion information and reference pictures for the current block must be restored in order to recover the current block.

In the process of restoring an image for the above reason, inter-block dependency may also exist. Therefore, in order to process the image restoration process in parallel, it is necessary to distinguish the restoration process depending on dependency. WPP (Wavefront Parallel Processing) is a technique for parallel processing of the decoding process. Blocks in one image can be processed in parallel by WPP.

3 is a diagram schematically illustrating the WPP technique.

Referring to FIG. 3, the image 300 may be decoded based on the divided blocks B1, B2,..., B63 as shown in FIG. Here, B1 denotes a block denoted by '1' in FIG. 3, and B2 denotes a block denoted by '2' in FIG. The image 300 shown in FIG. 3 may be a whole area of the current image or a part of the current image.

In the embodiment of FIG. 3, it is assumed that there are four processors (P1 to P4) that can be processed in parallel for convenience of explanation. Each processor can be processed in parallel for each row. For example, the first row 310 may be processed by processor P1, the second row 320 may be processed by processor P2, the third row 330 may be processed by processor P3, and the fourth row 340 may be processed by processor P4.

In order to restore the image 300, information on neighboring blocks adjacent to the current block to be restored (e.g., pixel information or motion information of neighboring blocks) is required. For example, in order to restore the block B22, pixel information or motion information of the neighboring blocks B21, B12, B13, and B14 adjacent to the block B22 is required. Therefore, the processor P3 can decode the block B22 when the processor P2 has completed decoding at least blocks B10 to B14 of the second row 320. [

That is, when applying the WPP technology, each processor further needs to check whether or not the previous processor restored the block located at the upper right of the current block in order to restore the current block. In other words, dependency between processors may occur when applying WPP and performing parallel restoration process for each row. In order to cut off the inter-processor dependency, it is possible to perform parallel processing by performing a restoration process with a certain time interval (time to process two blocks) between the processors. 3, blocks B8, B15, B22, and B29 are blocks that can be decoded simultaneously in each processor.

The above-described method is a general WPP method widely used for processing image decoding in parallel. Hereinafter, the present invention proposes a video decoding method capable of parallel processing at a higher speed than the conventional WPP technology.

4 is a view for explaining a video decoding method applied with parallel processing according to an embodiment of the present invention. The method of FIG. 4 can be performed in the decoding apparatus of FIG. 2 described above.

Referring to FIG. 4, the decoding apparatus receives a bitstream from an encoder and performs a parsing process for entropy decoding (entropy decoding) the received bitstream (400).

The decoding apparatus can obtain information about a current image to be restored through parsing (410). In this case, the information on the parsed current image is information for restoring all the blocks in the current image. The information on the parsed current image includes information on a coding mode for each block in the current image, information according to the mode, Case).

The decoding apparatus divides all the blocks in the current image into two groups according to the encoding mode (420). The blocks in the current image can be divided into an intra picture coding mode group and an inter picture coding mode group.

At this time, as described above, the blocks (intra-picture coding mode blocks) belonging to the intra-picture coding mode group may have inter-processor dependency when the restoration process is performed in parallel for each row by applying WPP . On the other hand, blocks (inter-picture coding mode blocks) belonging to the inter-picture coding mode group have already inter-processor dependency since they have already parsed the motion information of the neighboring blocks.

Accordingly, the decoding apparatus according to the embodiment of the present invention can restore the current intra-image inter-picture coding mode blocks by a parallel processing method (430).

In operation 440, the decoding apparatus allocates a processor to each of the remaining blocks in the current image, i.e., blocks in the current intra-picture intra-picture coding mode, as in the WPP technique described above. In this case, it is necessary to check whether there is a dependency between processors, but since the blocks in the current inter picture coding mode are restored in advance, the time required for the processor to wait for another processor is significantly reduced. Accordingly, the image decoding method to which the parallel processing according to the present invention is applied can improve the throughput and efficiency.

FIG. 5 is a diagram illustrating an example in which blocks in an inter picture coding mode are restored in parallel when blocks are divided into blocks in an inter picture coding mode and blocks in an intra picture coding mode according to an embodiment of the present invention. to be.

Referring to FIG. 5, blocks in the current image 500 may be classified into blocks of an inter picture coding mode and an intra picture coding mode according to a coding mode. In FIG. 5, for convenience of explanation, it is assumed that a block indicated by shading is a block of an inter picture coding mode.

Since the blocks in the inter picture coding mode have already been restored to motion information and reference pictures, each processor can restore blocks in parallel for each row quickly.

6 is a diagram illustrating an example of restoring blocks in an intra-picture coding mode in parallel when reconstructing blocks divided into blocks of an inter picture coding mode and a picture intraframe coding mode according to an embodiment of the present invention to be.

In FIG. 6, for convenience of explanation, it is assumed that a block indicated by shading is a block of an intra-picture coding mode in the current image 600. The blocks in the inter-picture coding mode are reconstructed blocks that have already been reconstructed in parallel as described above with reference to FIG.

As shown in FIG. 6, the rest of the blocks (blocks in the intra-picture coding mode) except the blocks (blocks in the inter-picture coding mode) that have been restored in the current image 600, P1 to P4), and each processor can perform a restoration process in parallel while confirming the inter-processor dependency. At this time, since the blocks in the inter-picture coding mode have already been restored, the time required for the processors to wait is reduced and the throughput can be improved.

For example, blocks 1, 2, 4, 5 and 6 of the inter picture coding mode among the blocks of the first row 610 in the current image 600 to be processed by the processor P1 are pre- State. Processor P1 only has to process blocks 3, 7, 8, and 9 in the intra-picture coding mode. In this case, only two blocks (blocks 3 and 7) need to be processed until block 8 is restored. In the case of block 13 of the blocks in the second row 620 in the current image 600 that the processor P2 has to process, the processor P2 identifies and processes the dependencies. However, block 14 in the second row 620 does not need to wait for the dependency release. Accordingly, the parallel processing can be efficiently performed by using the decoding method according to the present invention.

7 is a flowchart schematically illustrating a video decoding method according to an embodiment of the present invention. The method of FIG. 7 can be performed in the decoding apparatus of FIG. 2 described above.

Referring to FIG. 7, the decoding apparatus receives a bitstream from an encoder and parses the received bitstream to obtain encoding information (S700).

The parsed encoding information includes information necessary for restoring the current image. For example, the parsed encoding information may include encoding mode information for current intra-image blocks, information according to the mode (motion information, information related to the reference image, etc.) have.

The decoding apparatus can restore blocks in the current image in parallel based on the parsed encoding information (S710).

More specifically, the decoding apparatus can distinguish blocks in the current image according to whether the parsed encoding mode is an intra-scene encoding mode or an intra-scene encoding mode. If the coding mode of the current intra-picture block is an inter-picture mode, the corresponding block can be classified into inter picture coding mode blocks. Otherwise, if the intra-picture coding mode of the current block is the in-picture mode, the block can be divided into intra-picture coding mode blocks.

The decoding apparatus can perform a restoration process in parallel with the intra-picture intra-picture coding mode block preceding the current inter-picture coding mode block. Upon completion of the restoration of the intra-picture coding mode block, the decoding apparatus can perform a restoration process in parallel with the intra-picture intra-picture coding mode block as in the WPP method described above. At this time, when restoring the intra-picture coding mode block, it is possible to allocate a processor for each row and restore it in parallel, but it may be necessary to check whether there is a dependency between the processors. However, as described above, in the video decoding method according to the present invention, since the inter-picture coding mode blocks are restored in advance, the time required for the processor to wait for another processor is significantly reduced. Therefore, the throughput and speed of the decoding apparatus can be improved.

In the above-described embodiments, the methods are described on the basis of a flowchart as a series of steps or blocks, but the present invention is not limited to the order of the steps, and some steps may occur in different orders or simultaneously . It will also be understood by those skilled in the art that the steps depicted in the flowchart illustrations are not exclusive and that other steps may be included or that one or more steps in the flowchart may be deleted without affecting the scope of the invention You will understand.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the claims, and all technical ideas within the scope of the claims should be construed as being included in the scope of the present invention.

Claims (10)

Parsing the encoding mode information from the received bitstream; And
And parallelly restoring blocks in the current image based on the parsed encoding mode information,
And restoring the blocks in the current image in parallel,
Dividing the current intra-picture blocks into an inter picture coding mode group and an intra picture coding mode group according to whether the parsed coding mode is an inter picture coding mode or an intra picture coding mode,
Sequentially restoring blocks included in the inter-picture coding mode group in parallel;
Checking whether there is an inter-processor dependency assigned to each block for blocks included in the intra-picture coding mode group;
And restoring the blocks included in the intra-picture coding mode group in a row-by-row manner based on the inter-processor dependency. delete delete The method of claim 1,
The process of determining whether or not the dependency exists,
And checking whether a block located at the upper right end of the current block is reconstructed. The method according to claim 1,
Wherein the blocks included in the inter-picture coding mode group have no inter-processor dependency. An entropy decoding unit for entropy decoding the received bitstream to generate a quantized coefficient;
A dequantizer for dequantizing the quantization coefficient;
An inverse transformer for inversely transforming the inversely quantized coefficient to generate a reconstructed residual block;
An intra intra prediction unit for generating a first prediction block using an already decoded block around a current block;
A motion compensation unit for generating a second prediction block by performing motion compensation using a motion vector and a reference image stored in a reference picture buffer;
An adder for adding a residual block to the first predictive block or the second predictive block to generate a restored block for a current intra-image block; And
And a filter unit for applying a deblocking filter to the restoration block to output a restored image,
Wherein the blocks in the current image include:
An inter picture coding mode group and an intra picture coding mode group based on the coding mode information generated by the entropy decoding unit,
The blocks included in the inter-picture coding mode group may be,
In parallel to the blocks included in the intra-picture coding mode group,
Wherein the blocks included in the intra-
And determining whether there is a dependency between the processors assigned to the respective rows. delete delete The method of claim 6,
The process of determining whether or not the dependency exists,
And determining whether a block located at an upper right end of the current block has been reconstructed. The method according to claim 6,
Wherein inter-processor dependencies do not exist for blocks included in the inter-picture coding mode group.

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