KR20130118798A - Method and apparatus for image decoding - Google Patents

Method and apparatus for image decoding Download PDF

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KR20130118798A
KR20130118798A KR1020130042866A KR20130042866A KR20130118798A KR 20130118798 A KR20130118798 A KR 20130118798A KR 1020130042866 A KR1020130042866 A KR 1020130042866A KR 20130042866 A KR20130042866 A KR 20130042866A KR 20130118798 A KR20130118798 A KR 20130118798A
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South Korea
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slice
reference picture
picture set
decoding
information
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KR1020130042866A
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Korean (ko)
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이하현
강정원
최진수
김진웅
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한국전자통신연구원
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
    • H04N19/174—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a slice, e.g. a line of blocks or a group of blocks

Abstract

PURPOSE: An image decoding method and an apparatus thereof are provided to decode information about a reference picture set which is described in a slice header depending on a type of a slice, thereby removing unnecessary reference picture set information about an intra-slice. CONSTITUTION: A decoding apparatus parses header information about a current slice (S310). The decoding apparatus decodes the current slice without constructing a reference picture set about the current slice depending on a type of the current slice based on the parsed header information (S340). If the current slice is an intra-slice, the decoding apparatus does not constructs a reference picture set about the current slice. [Reference numerals] (S310) Constructing a reference picture set by slice header parsing; (S320) Marking restoration picture not existing in reference picture set as unused for reference; (S330) Perform bumping; (S340) Slice decoding; (S350) Marking decoded slice as used for reference when the slice is reference picture

Description

Image decoding method and apparatus {METHOD AND APPARATUS FOR IMAGE DECODING}

The present invention relates to image encoding / decoding, and more particularly, to a technique for efficiently encoding / decoding reference picture set information.

Recently, the demand for high resolution and high quality images such as high definition (HD) image and ultra high definition (UHD) image is increasing in various applications. As the image data has high resolution and high quality, the amount of data increases relative to the existing image data. Therefore, when image data is transmitted using a medium such as a wired / wireless broadband line or image data is stored using an existing storage medium , Transmission cost and storage cost are increased. High-efficiency image compression techniques can be utilized to solve such problems as image data becomes high-resolution and high-quality.

An image compression technique includes an inter-picture prediction technique for predicting a pixel value included in a current picture from a previous or a subsequent picture of a current picture, an intra prediction technique for predicting a pixel value included in a current picture using pixel information in the current picture , And entropy encoding technology for assigning a short code to a value having a high appearance frequency and assigning a long code to a value having a low appearance frequency. Such image compression techniques can effectively compress image data and transmit or store the image data .

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

The present invention provides a method and apparatus for encoding / decoding reference picture set information capable of improving image encoding / decoding efficiency.

According to one aspect of the present invention, an image decoding method is provided. The image decoding method may include parsing header information of a current slice and decoding the current slice without configuring a reference picture set for the current slice according to the type of the current slice based on the parsed header information. It includes.

In the decoding of the current slice, if the type of the current slice is an intra slice, the reference picture set for the current slice may not be configured.

By encoding / decoding information on the reference picture set described in the slice header according to the slice type, unnecessary reference picture set information on the intra slice can be removed. In addition, by eliminating unnecessary reference picture set construction for the intra slice, the coding efficiency may be increased and the complexity may be reduced.

1 is a block diagram showing 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 flowchart schematically illustrating a decoding method for constructing a reference picture list in current HEVC.
4 is a flowchart schematically illustrating a decoding method for constructing a reference picture set 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 specification, when it is determined that a detailed description of a related well-known configuration or function may obscure the gist of the present specification, the description may be omitted.

When a component is referred to herein as being "connected" or "connected" to another component, it may mean that it is directly connected to or connected to that other component, and another component in between. It may also mean that an element exists. In addition, the description "includes" a specific configuration in this specification does not exclude a configuration other than the configuration, it means that additional configuration may be included in the scope of the technical spirit of the present invention or 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 to distinguish 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 also be referred to as the first configuration.

In addition, the components shown in the embodiments of the present invention are independently shown to represent different characteristic functions, and do not mean that each component is made of separate hardware or one software component unit. In other words, each component is listed as a component for convenience of description, and at least two of the components may form one component, or one component may be divided into a plurality of components to perform a function. The integrated and separated embodiments of each component are also included in the scope of the present invention without departing from the spirit of the present invention.

1 is a block diagram showing a configuration of an image encoding apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the image encoding apparatus 100 may include an inter predictor 110, an intra predictor 120, a switch 125, a subtractor 130, a transformer 135, a quantizer 140, and entropy. The encoder 150, an inverse quantizer 160, an inverse transformer 170, an adder 175, a filter 180, and a picture buffer 190 are included.

The image encoding apparatus 100 may encode an input image in an intra mode or an inter mode and output a bitstream. In the intra mode, the switch 125 is switched to intra, and in the inter mode, the switch 125 is switched to inter. 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.

In the intra mode, the intra predictor 120 may generate a prediction block by performing spatial prediction using pixel values of blocks that are already encoded around the current block.

In the inter mode, the inter prediction unit 110 may obtain a motion vector by searching for a region corresponding to an input block in a reference image stored in the picture buffer 190 during a motion prediction process. The inter prediction unit 110 may generate a prediction block by performing motion compensation using the motion vector and the reference image stored in the picture buffer 190.

The subtractor 130 may generate a residual block by the difference between the input block and the generated prediction block.

The transformer 135 may perform transform on the residual block and output a transform coefficient.

The quantization unit 140 may output a quantized coefficient by quantizing the input transform coefficient according to the quantization parameter.

The entropy encoder 150 may output a bitstream by performing entropy encoding on the basis of the values calculated by the quantizer 140 or the encoding parameter values calculated in the encoding process. For example, when entropy coding 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, The size of the bit string 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 Code, Context-Adaptive Variable Length Coding (CAVLC), and Context-Adaptive Binary Arithmetic Coding (CABAC) for entropy encoding.

Since the image encoding apparatus 100 performs inter prediction encoding, the current encoded image needs to be decoded and stored to be used as a reference image. Accordingly, the quantized coefficient may be inversely quantized by the inverse quantizer 160 and inversely transformed by the inverse transformer 170. The inverse quantized and inverse transformed coefficients can be added to the prediction block through the adder 175 and a reconstruction block can be generated.

The reconstruction block passes through the filter unit 180, and the filter unit 180 applies at least one or more of a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) to the reconstructed block or reconstructed picture. can do. 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 filter unit 180 may be called an in-loop filter. The restoration block having passed through the filter unit 180 may be stored in the picture buffer 190.

2 is a block diagram illustrating a configuration of an image decoding apparatus according to an embodiment of the present invention.

2, the image decoding apparatus 200 may include an entropy decoder 210, an inverse quantizer 220, an inverse transformer 230, an intra predictor 240, an inter predictor 250, and a filter ( 260 and picture buffer 270.

The video decoding apparatus 200 receives the bit stream output from the encoding apparatus 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 generate a reconstructed block, that is, a reconstructed block by obtaining a residual block reconstructed from the received bitstream, generating a prediction block, and adding the reconstructed residual block and the prediction block.

The entropy decoder 210 entropy decodes the input bitstream according to a probability distribution. By entropy decoding, quantized (transform) coefficients can be generated. The entropy decoding method is similar to the entropy encoding method described above. 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 using the quantization parameters in the inverse quantization unit 220 and inversely transformed in the inverse transformation unit 230. The reconstructed residual blocks are 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 values of the already coded blocks around the current block.

In the inter mode, the inter predictor 250 may generate a predictive block by performing motion compensation using a motion vector and a reference image stored in the picture buffer 270.

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

Meanwhile, in H.264 / AVC, a slice window method or a memory management control operation (MMCO) is used as a method of managing a reference picture list. In High Efficiency Video Coding (HEVC), a reference picture set (RPS) technique is adopted, which transmits information about reference pictures directly in a slice header. By directly transmitting the information on the reference pictures, implementation in the encoder and / or decoder is simpler than the conventional scheme, and there is an advantage that the detection of the loss of the reference picture is more efficient.

Table 1 is a syntax illustrating an example of configuring information about a reference picture set in a slice header of a current HEVC.

Figure pat00001

Referring to Table 1, short_term_ref_pic_set_sps_flag indicates whether to use reference picture set related syntax information in a sequence parameter set (SPS). For example, if the value of short_term_ref_pic_set_sps_flag is 1, the reference picture set related syntax information in the SPS is used. If the value of short_term_ref_pic_set_sps_flag is 0, it may mean that the reference picture set related syntax information in the SPS is not used.

short_term_ref_pic_set (num_short_term_ref_pic_sets) describes syntax information about a short term reference picture set in a slice header. For example, if the short_term_ref_pic_set_sps_flag value is 0, syntax information for the short-term reference picture set may be described in the slice header.

short_term_ref_pic_set_idx indicates the index of the reference picture set list in the SPS.

num_long_term_pics indicates the number of long-term reference pictures included in a long term reference picture set.

delta_poc_lsb_lt [i] is used to determine the Least Significant Bits (LSB) value of the Picture Order Count (POC) of the i-th long-term reference picture.

delta_poc_msb_present_flag [i] indicates whether delta_poc_msb_cycle_lt_minus1 [i] exists. For example, if the value of delta_poc_msb_present_flag [i] is 1, delta_poc_msb_cycle_lt_minus1 [i] is present. If the value of delta_poc_msb_present_flag [i] is 0, it may mean that delta_poc_msb_cycle_lt_minus1 [i] is not present.

delta_poc_msb_cycle_lt_minus1 [i] is used to determine the Most Significant Bits (MSB) value of the POC of the i-th long-term reference picture.

usded_by_curr_pic_lt_flag [i] indicates whether the i-th long-term reference picture included in the long-term reference picture set is used. For example, if the value of usded_by_curr_pic_lt_flag [i] is 0, the i-th long-term reference picture included in the long-term reference picture set is not used. If the value of usded_by_curr_pic_lt_flag [i] is 1, the i-th long-term reference picture included in the long-term reference picture set is used. Can mean.

As shown in Table 2, in the slice header of the current HEVC, encoding and / or decoding is performed by configuring reference picture set information for a case in which a network abstract layer (NAL) unit type is not an instantaneous decoding refresh (IDR) picture. do. The reference picture list configured by such reference picture set information is used for inter prediction and is information that is not necessary for an intra slice (eg, I-slice) that performs intra prediction. However, the slice header of HEVC currently distinguishes between NAL unit types, but not slice types.

Accordingly, the present invention provides a method of classifying slice types in a slice header and encoding and / or decoding reference picture set information accordingly.

Table 2 shows syntax of a slice header describing reference picture set information according to an embodiment of the present invention.

Figure pat00002

Referring to Table 2, reference picture set information may be encoded / decoded in a slice header according to a slice type. For example, in the case of an inter slice (eg, P-slice or B-slice), reference picture set information may be encoded / decoded. In the case of an intra slice (eg, I-slice), reference picture set information may not be encoded / decoded.

In this case, an I-slice may encode an image itself without inter-picture prediction, and a P-slice may predictively encode an inter-picture using a reference picture only in a forward direction, and a B-slice ( Bidirectionally Predictive slices) may be inter picture predictive encoded using a reference picture in the forward and reverse directions.

The syntax for encoding / decoding reference picture set information according to an embodiment of the present invention as shown in Table 2 may be changed in syntaxes describing the reference picture set, but other syntaxes may be used in the same manner as the existing method. .

3 is a flowchart schematically illustrating a decoding method for constructing a reference picture list in current HEVC.

Referring to FIG. 3, the decoding apparatus parses a slice header to configure a reference picture set (S310). In this case, as shown in Table 1, the decoding apparatus may parse the reference picture set information and configure the reference picture set when the decoding apparatus is not an IDR picture without distinguishing a slice type.

The decoding apparatus marks “unused for reference” which is information indicating that the reconstructed picture that does not exist in the reference picture set is not used as the reference picture (S320). In this case, the reconstructed picture stored in the decoded picture buffer (DPB) may be checked whether the picture exists in the reference picture set.

The decoding apparatus performs bumping to remove the reconstructed picture marked as “unused for reference” from the picture buffer (S330).

The decoding apparatus decodes the parsed current slice (S340).

When the decoded current slice is used as the reference picture, the decoding apparatus marks the decoded current slice as “used for reference” which is information indicating that the decoded current slice is used as the reference picture (S350).

As described above, in the decoding method for constructing a reference picture list in the current HEVC, an encoder and decoding are performed by configuring a reference picture set even for an intra slice (eg, I-slice) that does not need information about the reference picture. There is a problem of reducing the efficiency and increasing the complexity in the device.

Hereinafter, a method of efficiently encoding / decoding reference picture set information according to a slice type will be described.

4 is a flowchart schematically illustrating a decoding method for constructing a reference picture set according to an embodiment of the present invention. The method of FIG. 4 may be performed by the image decoding apparatus of FIG. 2.

Referring to FIG. 4, the decoding apparatus parses a slice header (S410).

If the slice type is not an intra slice (eg, I-slice) based on the parsed slice header information (S420), the decoding apparatus configures a reference picture set (S430). That is, the decoding apparatus may configure the reference picture set when the slice type is an inter slice, for example, a P-slice or a B-slice.

In this case, the decoding apparatus marks “unused for reference” which is information indicating that the reconstructed picture that does not exist in the reference picture set is not used as the reference picture (S440). For example, the reconstructed picture stored in the decoded picture buffer (DPB) may be checked whether the picture exists in the reference picture set, and the "unused for reference" may be marked.

The decoding apparatus performs bumping to remove the reconstructed picture marked as "unused for reference" from the picture buffer (S450).

The decoding apparatus decodes the parsed current slice (S460).

When the decoded current slice is used as the reference picture, the decoding apparatus marks the decoded current slice as “used for reference” which is information indicating that the decoded current slice is used as the reference picture (S470).

Meanwhile, in the decoding method for configuring the reference picture set according to the embodiment of the present invention, when the slice type is an intra slice (eg, I-slice) based on the slice header information parsed in step S410 (S420). In operation S450, the decoding apparatus configures the above-described reference picture set and performs the process of marking “unused for reference” for the reconstructed picture that does not exist in the reference picture set (S440). Can be. Therefore, the information on the reference picture set can be efficiently decoded by omitting the process of configuring the reference picture set for the intra slice that does not need the information about the reference picture.

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, 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 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 (1)

Parsing header information for the current slice; And
Decoding the current slice without forming a reference picture set for the current slice according to the type of the current slice based on the parsed header information;
In the step of decoding the current slice,
And when the type of the current slice is an intra slice, does not constitute a reference picture set for the current slice.
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9590952B2 (en) 2014-09-05 2017-03-07 Microsoft Technology Licensing, Llc Lossy data stream decoder
WO2021088855A1 (en) * 2019-11-04 2021-05-14 Mediatek Inc. Signaling high-level information in video and image coding
WO2021132962A1 (en) * 2019-12-23 2021-07-01 엘지전자 주식회사 Nal unit type-based image or video coding
WO2021132964A1 (en) * 2019-12-23 2021-07-01 엘지전자 주식회사 Image or video coding based on nal unit-associated information
WO2021132963A1 (en) * 2019-12-23 2021-07-01 엘지전자 주식회사 Nal unit type-based image or video coding for slice or picture

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9590952B2 (en) 2014-09-05 2017-03-07 Microsoft Technology Licensing, Llc Lossy data stream decoder
WO2021088855A1 (en) * 2019-11-04 2021-05-14 Mediatek Inc. Signaling high-level information in video and image coding
US11758193B2 (en) 2019-11-04 2023-09-12 Hfi Innovation Inc. Signaling high-level information in video and image coding
WO2021132962A1 (en) * 2019-12-23 2021-07-01 엘지전자 주식회사 Nal unit type-based image or video coding
WO2021132964A1 (en) * 2019-12-23 2021-07-01 엘지전자 주식회사 Image or video coding based on nal unit-associated information
WO2021132963A1 (en) * 2019-12-23 2021-07-01 엘지전자 주식회사 Nal unit type-based image or video coding for slice or picture
US11805264B2 (en) 2019-12-23 2023-10-31 Lg Electronics Inc. NAL unit type-based image or video coding

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