KR101373759B1 - Apparatus and method for decoding - Google Patents

Abstract

The decoding apparatus entropy decodes the bitstream to extract syntax information and quantization coefficients, a pixel reconstruction unit generating a reconstructed image according to the quantization coefficients by referring to the syntax information, and extracts unit information from the division information. When the unit information indicates that the target block corresponds to the same filtering region as the previous block, the threshold that calculates the threshold offset of the target block by summing the threshold offset difference signal included in the syntax information and the threshold offset of the previous block. The deblocking filter and the reconstructed image for performing deblocking filtering on the target block of the reconstructed image using the value offset calculator, a threshold offset corresponding to the threshold offset of the previous block or the target block according to the unit information. It includes an image output unit for outputting.

Description

Decoding device and method {APPARATUS AND METHOD FOR DECODING}

The present invention relates to an image processing technique, and more particularly, to a decoding apparatus and method for adaptively determining a difference signal of a threshold offset of performing a deblocking filter, which is an in-loop filter of decoding.

Recently, as the demand for high resolution and high definition video has increased, there has been a need for a highly efficient video compression technology for the next generation video service. In response to these market demands, MPEG and VCEG, which jointly standardized the MPEG-2 Video and H.264 / AVC codecs, have been jointly standardized on new video compression technologies since 2010. MPEG and VCEG have established Joint Collaborative Team on Video Coding (JCT-VC) for the development of new standard technologies and are now developing next generation video standard technology called HEVC (High Efficiency Video Coding) through JCT-VC. These HEVCs are standardizing to improve compression efficiency by more than 50% compared to H.264 / AVC High profile, which is known to have the highest compression efficiency in the past, and support full-HD and 4K-resolution video .

Similar to H.264 / AVC, HEVC uses an in-loop deblocking filter to improve coding efficiency and subjective picture quality. HEVC uses a number of in-loop filters, such as a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF), among which the deblocking filter performs filtering using a threshold offset.

According to the present invention, a threshold offset for deblocking filtering is determined according to syntax information included in a bitstream in which a threshold offset difference signal is set for each filtering region of an adaptively sized size for a deblocking filter. An object of the present invention is to provide a decoding apparatus and method.

According to an aspect of the invention, the entropy decoding unit for extracting syntax and quantization coefficients by entropy decoding the bitstream; A pixel reconstruction unit configured to generate a reconstructed image according to the quantization coefficients with reference to the syntax information; Extracting unit information from the division information, and when the unit information indicates that the target block of the reconstructed image corresponds to the same filtering region as the previous block, the threshold offset difference signal included in the syntax information and the previous block are included. A threshold offset calculator configured to calculate a threshold offset of the target block by summing threshold offsets; A deblocking filter performing deblocking filtering on the target block using a threshold offset corresponding to the threshold offset of the previous block or the threshold offset of the target block according to the unit information; And an image output unit configured to output the reconstructed image.

The deblocking filter may perform deblocking filtering on the target block when a pixel located within a predetermined distance at a boundary between the target block and an adjacent block satisfies a predetermined conditional expression including the threshold.

The syntax information may include one or more of the unit information for each block and the threshold offset difference signal.

The filtering area may be an area including a block in which deblocking filtering is performed according to the same threshold offset.

According to another aspect of the present invention, a method for decoding a bitstream by a decoding apparatus, the method comprising: extracting syntax information and quantization coefficients by entropy decoding the bitstream; Generating a reconstructed image according to the quantization coefficients with reference to the syntax information; Extracting unit information from the division information; When the unit information indicates that the target block of the reconstructed image corresponds to the same filtering region as the previous block, the threshold offset of the target block is added by adding the threshold offset difference signal included in the syntax information and the threshold offset of the previous block. Calculating a value offset; Performing deblocking filtering on the target block using a threshold offset corresponding to the threshold offset of the previous block or the threshold offset of the target block according to the unit information; And outputting the reconstructed image.

The deblocking filtering may include performing deblocking filtering on the target block when a pixel located within a predetermined distance at a boundary between the target block and an adjacent block satisfies a predetermined conditional expression including the threshold. It may be a step.

The syntax information may include one or more of the unit information for each block and the threshold offset difference signal.

The filtering area may be an area including a block in which deblocking filtering is performed according to the same threshold offset.

According to the present invention, it is possible to decode a bitstream set for each filtering region whose size and shape may change from case to case, instead of being set for each region of a fixed size.

In addition, according to the present invention, it is possible to reduce the image quality degradation caused by the deblocking filter or the phenomenon in which the deblocking filter does not prevent the deblocking phenomenon.

In addition, according to the present invention, the number of bits to be inserted into syntax information of a bitstream in order to allocate a threshold offset for a block can be reduced to an appropriate level.

1 is a block diagram illustrating a decoding apparatus according to an embodiment of the present invention.
2 is a diagram illustrating a table referenced by a decoding apparatus according to an embodiment of the present invention to calculate a threshold value according to a threshold offset.
3 is a flowchart illustrating a decoding process of a decoding apparatus according to an embodiment of the present invention.
4 is a diagram illustrating syntax information extracted from a bitstream by a decoding apparatus according to the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present disclosure rather unclear.

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

In addition, the components shown in the embodiments of the present invention are shown independently to represent different characteristic functions, which does not mean that each component is composed of separate hardware or software constituent units. That is, each constituent unit is included in each constituent unit for convenience of explanation, and at least two constituent units of the constituent units may be combined to 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 separate embodiments of the components are also included within 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 decoding apparatus according to an embodiment of the present invention, and FIG. 2 illustrates a table referenced by the decoding apparatus according to an embodiment of the present invention to calculate a threshold value according to a threshold offset. One drawing.

Hereinafter, a region to be the current filtering target among the filtering regions, which are regions that are consecutively positioned with each other and are filtered according to the same threshold offset difference signal, will be referred to as a current region.

The decoding apparatus includes an entropy decoder 110, a pixel reconstructor 120, a threshold offset calculator 130, a deblocking filter 140, and an image output unit 150.

The entropy decoder 110 parses and decodes the bitstream to extract syntax information and quantization coefficients. In this case, the syntax information may include unit information for each filtering region and a threshold offset difference signal. The unit information indicates a range of the filtering area. The unit information will be described in detail later with reference to FIG. 3. The threshold offset differential signal is a difference between a threshold offset of a filtering area (hereinafter, referred to as a previous area) that was a filtering target before the current area and a threshold offset of the current area.

The pixel reconstruction unit 120 generates a reconstructed image by performing inverse quantization, inverse transformation, and prediction on quantization coefficients with reference to syntax information. The pixel reconstruction unit 120 transmits a reconstruction image to the deblocking filter 305. According to an implementation method, other in-loop filters SAO and ALF may be provided before the deblocking filter, and the reconstructed image filtered by the in-loop filter may be transmitted to the deblocking filter 305.

The threshold offset calculator 303 extracts a quantization parameter, unit information, and a threshold offset difference signal from syntax information. The threshold offset calculator 130 calculates a threshold offset for the current region by summing a threshold offset difference signal and a threshold offset corresponding to the previous region. The threshold offset calculator 130 transmits one or more of a quantization parameter, unit information, and a threshold offset for the current region to the deblocking filter 140. The threshold offset calculator 130 may temporarily store the calculated threshold offset, and then use the previously stored threshold offset to calculate the threshold offset of the current region when the current region is changed.

The deblocking filter 140 performs deblocking filtering on the current region according to the unit information. The deblocking filter 140 calculates a threshold value according to the threshold offset, and compares a difference between pixel values adjacent to a horizontal boundary of each block included in the current region with a threshold value. For example, the deblocking filter 140 may previously store a table as shown in FIG. 2, and calculate a threshold value corresponding to the threshold offset with reference to the table below.

Referring to FIG. 2, row A represents an index, and the index is a value obtained by scaling (normalizing) a sum of a threshold offset and a quantization parameter according to a predetermined criterion. Also, rows B and C are thresholds for each index. 2 illustrates assuming that the deblocking filter 140 performs deblocking filtering using two threshold values. Accordingly, it will be apparent to those skilled in the art that the deblocking filter 140 may refer to a table different from that of FIG. 2 according to the method of deblocking filtering of the deblocking filter 140.

The deblocking filter 140 may determine that a pixel located within a predetermined distance from a boundary between each block included in the current region and an adjacent block (hereinafter referred to as a boundary pixel) satisfies a predetermined conditional expression including a threshold value. Deblocking filtering is performed on the horizontal boundary. At this time, since the deblocking filter 140 performs a deblocking filtering on a specific block using a threshold value, a detailed description thereof will be omitted.

The deblocking filter 140 also determines whether the boundary pixel) satisfies a predetermined conditional expression including a threshold. When the deblocking filter 140 satisfies a predetermined conditional expression including a threshold value, the deblocking filter 140 performs deblocking filtering on the vertical boundary of the block.

The deblocking filter 140 transmits the reconstructed image including the filtered blocks to the image output unit 150. In addition, when the difference between the pixels of each block included in the current area and the pixels included in the area of the adjacent block is less than the threshold value, the deblocking filter 140 omits the deblocking filtering for the corresponding block and displays the reconstructed image. The output unit 150 transmits.

In this case, the deblocking filtering method performed by the deblocking filter 140 is well known in the MPEG standard, and thus a detailed description thereof will be omitted.

Hereinafter, the decoding apparatus described above will be described in detail with reference to FIG. 3.

3 is a flowchart illustrating a decoding process of a decoding apparatus according to an embodiment of the present invention. Hereinafter, the decoding apparatus will refer to a block to which the current deblocking filtering is to be performed as a target block. In addition, the block in which the decoding apparatus performs deblocking filtering before the target block is referred to as a previous block.

Referring to FIG. 3, in step 310, the decoding apparatus receives a bitstream.

In operation 320, the decoding apparatus performs entropy decoding, inverse transformation, and inverse quantization on the bitstream to generate a reconstructed image.

In operation 330, the decoding apparatus selects one of the blocks not previously selected as the target block included in the reconstructed image, and extracts unit information about the target block from syntax information included in the bitstream.

In operation 340, the decoding apparatus determines whether the target block is included in the same filtering region as the previous block by referring to the unit information. 4, a process of determining whether a decoding block is included in the same filtering region as the previous block will be described in detail with reference to FIG. 4.

If the target block is included in the same filtering area as the previous block in operation 340, the decoding apparatus sets the threshold offset of the previous block as the threshold offset of the target block in operation 350.

In operation 360, the decoding apparatus calculates a threshold value according to the threshold offset of the target block. The process of calculating the threshold value according to the threshold offset is described above with reference to FIG. 2.

If the target block is included in a filtering region different from the previous block in step 340, the decoding apparatus extracts a threshold offset difference signal for the target block from syntax information of the bitstream in step 355.

In operation 357, the decoding apparatus calculates the threshold offset of the target block by summing the threshold offset of the previous block and the threshold offset difference signal of the target block. Thereafter, the decoding apparatus performs the process from step 360 described above.

In operation 370, the decoding apparatus determines whether a difference between pixel values adjacent to the boundary of the target block is greater than or equal to the threshold.

If the boundary pixel satisfies a predetermined conditional expression including a threshold in operation 370, the decoding apparatus performs deblocking filtering on the target block in operation 380.

If the boundary pixel does not satisfy a predetermined conditional expression including a threshold in operation 370, in operation 390, the decoding apparatus determines whether a block that is not selected as a target block exists.

If there is a block that is not selected as the target block in step 390, the decoding apparatus performs the process from step 330 described above.

If there is no block selected as the target block in operation 390, the decoding apparatus outputs a reconstructed image in operation 395.

4 is a diagram illustrating syntax information extracted from a bitstream by a decoding apparatus according to the present invention.

Referring to FIG. 4, Sequence Parameter Set (SPS) syntax information 801 represents syntax information for the entire bitstream, and slice header syntax information 802 represents syntax information commonly used in one slice.

In the SPS syntax information 801, deblocking_filter_adaptive_offset_enabled_flag is a flag indicating whether to perform a decoding process for determining whether to use deblocking filtering according to the present invention. For example, when deblocking_filter_adaptive_offset_enabled_flag is 1, this indicates that a decoding process for determining whether the corresponding bitstream performs deblocking filtering according to the present invention should be applied.

 When deblocking_filter_adpative_offset_flag is 1, it indicates that the syntax of deblocking_filter_region_offset_flag and deblocking_filter_LCU_offset_flag, which indicates a unit for allocating a threshold offset difference value, is further included. Through this, it is possible to indicate whether to allocate the threshold offset difference value in units of slice, area, and LCU. For example, when deblocking_filter_region_offset_flag is 1, it indicates that deblocking filtering is applied according to a threshold offset equal to a previous block and a current block. If deblocking_filter_LCU_offset_flag is 1, a threshold offset difference value is assigned to the current block. If both statements are 0, this may indicate that a threshold offset difference value is allocated in units of slices. There is no case where both the syntaxes of deblocking_filter_region_offset_flag and deblocking_filter_LCU_offset_flag become 1. The foregoing may be expressed as shown in Table 1 below.

deblocking_filter_region_flag deblocking_filter_LCU_flag meaning One 0 Indicates that the current LCU corresponds to the same filtering area with deblocking filtering applied according to the same threshold offset as the previous LUC. 0 One The new threshold offset differential signal for the current LCU is included in the bitstream 0 0 One threshold offset differential signal is included for the entire slice.

Accordingly, when the decoding apparatus extracts each syntax information from the bitstream, the decoding apparatus sets a filtering region to be deblocking filtering target using one threshold offset difference signal using unit information about each block including deblocking_filter_region_offset_flag and deblocking_filter_LCU_offset_flag. Can be.

In this case, the above-described block may be a large coding unit (LCU) specified in the MPEG standard or a block having a predetermined size.

As described above, the decoding apparatus according to an embodiment of the present invention can decode the bitstream set for each filtering region whose size and shape can be changed every time, rather than the threshold offset differential signal being set for each region of a fixed size. have.

Therefore, the decoding apparatus according to an embodiment of the present invention is more detailed for each block constituting each slice of the reconstructed image in some cases, as compared with the decoding apparatus using a deblocking filter using a threshold offset set for each slice. You can set the threshold offset with. Accordingly, the decoding apparatus according to the embodiment of the present invention can reduce the image quality degradation caused by the deblocking filter or the phenomenon in which the deblocking filter does not prevent the deblocking phenomenon.

In addition, since the threshold offset may be set for each filtering area whose size and shape change from case to case, the decoding apparatus according to an embodiment of the present invention performs deblocking filtering by using the same threshold offset among blocks included in the slice. The same threshold offset may be set for blocks that may be applied. Therefore, the decoding apparatus may lower the number of bits to be inserted into the syntax information of the bitstream in order to allocate the threshold offset to the block.

In the above-described embodiments, methods are described based on 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 in a different order than the steps described above have. It will also be understood by those skilled in the art that the steps depicted in the flowchart illustrations are not exclusive, that other steps may be included, or that one or more steps in the flowchart may be deleted without affecting the scope of the present invention. You will understand.

The above-described embodiments include examples of various aspects. While it is not possible to describe every possible combination for expressing various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, it is intended that the invention include all alternatives, modifications and variations that fall within the scope of the following claims.

Claims (8)

An entropy decoder configured to extract syntax information and quantization coefficients by entropy decoding the bitstream;
A pixel reconstruction unit configured to generate a reconstructed image according to the quantization coefficients with reference to the syntax information;
Extracting unit information from the syntax information, and when the unit information indicates that the target block of the reconstructed image corresponds to the same filtering region as the previous block, the threshold offset difference signal included in the syntax information and the previous filtering region are included. A threshold offset calculator configured to calculate a threshold offset of the target block by summing threshold offsets;
A deblocking filter performing deblocking filtering on the target block using a threshold offset corresponding to the threshold offset of the previous block or the threshold offset of the target block according to the unit information; And
Image output unit for outputting the restored image
, ≪ / RTI &
And the filtering area is an area including blocks consecutively located with each other and filtered according to the same threshold offset difference signal.
The method according to claim 1,
The deblocking filter performs deblocking filtering on the target block when a pixel located within a predetermined distance at a boundary between the target block and an adjacent block satisfies a predetermined conditional expression including the threshold. Decryption device.
The method according to claim 1,
And the syntax information includes one or more of the unit information for each block and the threshold offset difference signal.
delete In the decoding apparatus decodes the bitstream,
Entropy decoding the bitstream to extract syntax information and quantization coefficients;
Generating a reconstructed image according to the quantization coefficients with reference to the syntax information;
Extracting unit information from the syntax information;
When the unit information indicates that the target block of the reconstructed image corresponds to the same filtering region as the previous block, the threshold offset difference signal included in the syntax information and the threshold offset of the previous filtering region are added together to determine the target block. Calculating a threshold offset;
Performing deblocking filtering on the target block using a threshold offset corresponding to the threshold offset of the previous block or the threshold offset of the target block according to the unit information; And
Outputting the restored image
, ≪ / RTI &
And the filtering area is an area including blocks consecutively located with each other and filtered according to the same threshold offset difference signal.
6. The method of claim 5,
The deblocking filtering may include performing deblocking filtering on the target block when a pixel located within a predetermined distance at a boundary between the target block and an adjacent block satisfies a predetermined conditional expression including the threshold. Decoding method characterized in that the step.
The method of claim 6,
The syntax information includes at least one of the unit information for each block and the threshold offset difference signal.
delete

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