WO2013063800A1 - Methods and apparatuses of solving mdcs parsing issue - Google Patents

Methods and apparatuses of solving mdcs parsing issue Download PDF

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Publication number
WO2013063800A1
WO2013063800A1 PCT/CN2011/081819 CN2011081819W WO2013063800A1 WO 2013063800 A1 WO2013063800 A1 WO 2013063800A1 CN 2011081819 W CN2011081819 W CN 2011081819W WO 2013063800 A1 WO2013063800 A1 WO 2013063800A1
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Prior art keywords
scan
scanning order
predetermined scanning
order
mdcs
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PCT/CN2011/081819
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French (fr)
Inventor
Chih-Wei Hsu
Xun Guo
Tzu-Der Chuang
Xin Zhao
Yu-Wen Huang
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Mediatek Inc.
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Priority to PCT/CN2011/081819 priority Critical patent/WO2013063800A1/en
Publication of WO2013063800A1 publication Critical patent/WO2013063800A1/en

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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
    • H04N19/18—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 a set of transform coefficients
    • 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
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/129—Scanning of coding units, e.g. zig-zag scan of transform coefficients or flexible macroblock ordering [FMO]
    • 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
    • H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
    • H04N19/157—Assigned coding mode, i.e. the coding mode being predefined or preselected to be further used for selection of another element or parameter
    • H04N19/159—Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
    • 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
    • H04N19/90—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using coding techniques not provided for in groups H04N19/10-H04N19/85, e.g. fractals
    • H04N19/91—Entropy coding, e.g. variable length coding [VLC] or arithmetic coding

Definitions

  • the invention relates generally to video processing.
  • the present invention relates to methods and apparatuses for solving MDCS parsing issue in High Efficiency Video Coding (HEVC).
  • HEVC High Efficiency Video Coding
  • HEVC High Efficiency Video Coding
  • JCT- VC Joint Collaborative Team on Video Coding
  • HM-4.0 mode-dependent coefficient scan
  • CABAC CABAC
  • three scan patterns, including diagonal, horizontal, and vertical scanning, as illustrated in Fig. 1, are used to code the significance map and coefficient levels backward.
  • CAVLC diagonal scanning is replaced by zigzag scanning, as illustrated in Fig. 2.
  • the selection of the scanning patterns for each transform unit (TU) size is based on the intra prediction modes, as shown in Table 1, where 0, 1 , and 2 stand for diagonal/zigzag, horizontal, and vertical scanning, respectively.
  • MDCS is only used for TU sizes of 4x4 and 8x8.
  • encoder When using MDCS, encoder will generate the coded bitstream for the transform coefficients following the selected scanning order, which depends on the intra prediction mode as described in the previous section. On the decoder side, decoder will parse the coded bitstream following the same scanning order as derived at the encoder side using the intra prediction mode.
  • MPM most probable mode
  • MPM indices MPM indices
  • remaining modes is coded in the bitstream instead of signaling real intra prediction modes. That is to say, reconstruction procedure should be performed to acquire the real intra mode at the parsing stage, which may reduce the parsing throughput of the decoder. It is what is concerned as the MDCS parsing issue for the decoder.
  • a pre-scan method is used to solve the parsing issue of MDCS.
  • Coefficient blocks are remapped from a mode dependent scanning order to a first predetermined scanning order, and the remapped coefficient blocks are coded using a second predetermined scanning order to generate coded coefficients.
  • the first and second predetermined scanning order may be selected to be the same or different.
  • a context determination method for significance map and a coding method for the last significant coefficient position are used to solve the same parsing issue of MDCS.
  • the context modeling of the significant map is determined by a scan position or absolute position of each scanned bits for video coding.
  • Fig. 1 is a diagram illustrating the three scanning patterns for CABAC including diagonal (left), horizontal (middle) and vertical (right);
  • FIG. 2 is a diagram illustrating the three scanning patterns for CAVLC including zigzag (left), horizontal (middle) and vertical (right);
  • FIG. 3 is a diagram illustrating a pre-scan procedure for intra coded coefficients according to an embodiment of the invention.
  • FIG. 4 is a diagram illustrating a post-scan procedure for intra coded coefficients according to an embodiment of the invention.
  • a pre-scan method is used to solve the parsing issue of MDCS.
  • the scanning order for the intra coded coefficients is still selected based on the intra prediction mode as MDCS does.
  • those scanned coefficients are remapped into another coded block using a first predetermined scanning order.
  • the above-mentioned procedure is called pre-scan and is illustrated in Fig. 3 as an example, where the diagonal scanning is selected in MDCS for the 8x8 intra coded block and the horizontal scanning is the first predetermined scanning order for the pre-scan.
  • the remapped coefficient blocks are coded using the default scanning order, which is diagonal scanning for CABAC and zigzag scanning for CAVLC in current HM-4.0.
  • the bitstream for the transform coefficients of the intra coded block can be parsed using the default scanning order without knowing the real intra prediction mode.
  • the parsed coefficients can be remapped from the same first predetermined scanning order as that of the encoder to find the original scanning position using the selected scanning order in MDCS.
  • the above-mentioned procedure is called post-scan and is illustrated in Fig 4 as an example, where the horizontal scanning is the first predetermined scanning order for the post-scan and the diagonal scanning is selected in MDCS for the 8x8 intra coded block. In this way, there is no need to perform reconstruction procedure to acquire the intra prediction mode at the parsing stage, which will not decrease the parsing throughput of the decoder.
  • a context determination method for the significance map and a coding method for the last significant coefficient position are used to solve the parsing issue of MDCS.
  • significance map the context modeling of each bit is determined according to its absolute position, which needs the real scan order for derivation.
  • the scan order is also needed to derive the number of the coded coefficients.
  • the context modeling for each bit can be determined according to its scan position or absolute position. If the absolute position is used, the significance map should be remapped using the method described in the previous embodiment.
  • the context index is derived using a function of the scan position or absolute position as the following equation:
  • ctxIdx[scanPos] F (Pos), (1) where ctxidx is the context index; scanPos is the scan position of the significance map for different scan orders; and Pos is scan position or absolute position. Two examples are provided in equation (1) and (2) when Pos is a scan position
  • ctxIdx[scanPos] scanPos » 2
  • ctxIdx[scanPos] F H M4 . o(scanPos), (3)
  • FH M 4 . o is the context modeling function in HM4.0, which uses absolute position as the input.
  • the coordinates (x, y) can be derived using any possible scan orders such as diagonal, horizontal, vertical and zigzag.
  • the coding of the last significant coefficient position can use the same scan order with the significance map. It can also use a scan order other than that of the significance map.
  • an embodiment of the present invention can be a circuit integrated into a video compression chip or program codes integrated into video compression software to perform the processing described herein.
  • An embodiment of the present invention may also be program codes to be executed on a Digital Signal Processor (DSP) to perform the processing described herein.
  • DSP Digital Signal Processor
  • the invention may also involve a number of functions to be performed by a computer processor, a digital signal processor, a microprocessor, or field programmable gate array (FPGA).
  • processors can be configured to perform particular tasks according to the invention, by executing machine-readable software code or firmware code that defines the particular methods embodied by the invention.
  • the software code or firmware codes may be developed in different programming languages and different format or style.
  • the software code may also be compiled for different target platform.
  • different code formats, styles and languages of software codes and other means of configuring code to perform the tasks in accordance with the invention will not depart from the spirit and scope of the invention.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Compression Or Coding Systems Of Tv Signals (AREA)

Abstract

Methods of solving the parsing issue of MDCS are disclosed. In one embodiment, a pre-scan method is used to solve the parsing issue of MDCS. In another embodiment, a context determination method for significance map and a coding method for the last significant coefficient position are used to solve the same parsing issue of MDCS.

Description

METHODS AND APPARATUSES OF SOLVING MDCS
PARSING ISSUE
TECHNICAL FIELD
[0001] The invention relates generally to video processing. In particular, the present invention relates to methods and apparatuses for solving MDCS parsing issue in High Efficiency Video Coding (HEVC).
BACKGROUND
[0002] HEVC (High Efficiency Video Coding) is an advanced video coding system being developed under the Joint Collaborative Team on Video Coding (JCT- VC) group of video coding experts from ITU-T Study Group. In HEVC test model version 4.0 (HM-4.0), mode-dependent coefficient scan (MDCS) method is adopted for intra coded coefficients. For CABAC, three scan patterns, including diagonal, horizontal, and vertical scanning, as illustrated in Fig. 1, are used to code the significance map and coefficient levels backward. For CAVLC, diagonal scanning is replaced by zigzag scanning, as illustrated in Fig. 2. The selection of the scanning patterns for each transform unit (TU) size is based on the intra prediction modes, as shown in Table 1, where 0, 1 , and 2 stand for diagonal/zigzag, horizontal, and vertical scanning, respectively. In current HM-4.0, MDCS is only used for TU sizes of 4x4 and 8x8.
Table 1. LUT of scanning patterns for intra luma block in HM4.0
Figure imgf000002_0001
[0003] When using MDCS, encoder will generate the coded bitstream for the transform coefficients following the selected scanning order, which depends on the intra prediction mode as described in the previous section. On the decoder side, decoder will parse the coded bitstream following the same scanning order as derived at the encoder side using the intra prediction mode. However, in HM-4.0, only information of most probable mode (MPM) flags, MPM indices, and remaining modes is coded in the bitstream instead of signaling real intra prediction modes. That is to say, reconstruction procedure should be performed to acquire the real intra mode at the parsing stage, which may reduce the parsing throughput of the decoder. It is what is concerned as the MDCS parsing issue for the decoder.
SUMMARY [0004] In light of the previously described problems, there exists a need for an apparatus and method, in which the coding of the transform coefficients does not depend on the real scan orders at parsing stage.
[0005] In one embodiment, a pre-scan method is used to solve the parsing issue of MDCS. Coefficient blocks are remapped from a mode dependent scanning order to a first predetermined scanning order, and the remapped coefficient blocks are coded using a second predetermined scanning order to generate coded coefficients. The first and second predetermined scanning order may be selected to be the same or different. In another embodiment, a context determination method for significance map and a coding method for the last significant coefficient position are used to solve the same parsing issue of MDCS. The context modeling of the significant map is determined by a scan position or absolute position of each scanned bits for video coding.
BRIEF DESCRIPTION OF DRAWINGS The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
[0006] Fig. 1 is a diagram illustrating the three scanning patterns for CABAC including diagonal (left), horizontal (middle) and vertical (right);
[0007] Fig. 2 is a diagram illustrating the three scanning patterns for CAVLC including zigzag (left), horizontal (middle) and vertical (right);
[0008] Fig. 3 is a diagram illustrating a pre-scan procedure for intra coded coefficients according to an embodiment of the invention.
[0009] Fig. 4 is a diagram illustrating a post-scan procedure for intra coded coefficients according to an embodiment of the invention.
DETAILED DESCRIPTION
[0010] The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.
[0011] In the first embodiment, a pre-scan method is used to solve the parsing issue of MDCS. On the encoder side, the scanning order for the intra coded coefficients is still selected based on the intra prediction mode as MDCS does. However, instead of coding the scanned coefficients into bitstream, those scanned coefficients are remapped into another coded block using a first predetermined scanning order. The above-mentioned procedure is called pre-scan and is illustrated in Fig. 3 as an example, where the diagonal scanning is selected in MDCS for the 8x8 intra coded block and the horizontal scanning is the first predetermined scanning order for the pre-scan. Then the remapped coefficient blocks are coded using the default scanning order, which is diagonal scanning for CABAC and zigzag scanning for CAVLC in current HM-4.0. On the decoder side, the bitstream for the transform coefficients of the intra coded block can be parsed using the default scanning order without knowing the real intra prediction mode. However, after the real intra prediction mode is reconstructed and is available, the parsed coefficients can be remapped from the same first predetermined scanning order as that of the encoder to find the original scanning position using the selected scanning order in MDCS. The above-mentioned procedure is called post-scan and is illustrated in Fig 4 as an example, where the horizontal scanning is the first predetermined scanning order for the post-scan and the diagonal scanning is selected in MDCS for the 8x8 intra coded block. In this way, there is no need to perform reconstruction procedure to acquire the intra prediction mode at the parsing stage, which will not decrease the parsing throughput of the decoder.
[0012] In another embodiment, a context determination method for the significance map and a coding method for the last significant coefficient position are used to solve the parsing issue of MDCS. There are two syntax elements which would depend on scan order at the parsing stage: significance map and last significant coefficient position. For significance map, the context modeling of each bit is determined according to its absolute position, which needs the real scan order for derivation. And for last significant coefficient position, the scan order is also needed to derive the number of the coded coefficients.
[0013] For the significance map, the context modeling for each bit can be determined according to its scan position or absolute position. If the absolute position is used, the significance map should be remapped using the method described in the previous embodiment. The context index is derived using a function of the scan position or absolute position as the following equation:
ctxIdx[scanPos] = F (Pos), (1) where ctxidx is the context index; scanPos is the scan position of the significance map for different scan orders; and Pos is scan position or absolute position. Two examples are provided in equation (1) and (2) when Pos is a scan position
ctxIdx[scanPos] = scanPos » 2, (2) ctxIdx[scanPos] = FHM4.o(scanPos), (3) where FHM4.o is the context modeling function in HM4.0, which uses absolute position as the input.
[0014] For the last significant coefficient position, the coordinates (x, y) can be derived using any possible scan orders such as diagonal, horizontal, vertical and zigzag. The coding of the last significant coefficient position can use the same scan order with the significance map. It can also use a scan order other than that of the significance map.
[0015] The methods described above can be used in a video encoder as well as in a video decoder. Embodiments of the methods according to the present invention as described above may be implemented in various hardware, software codes, or a combination of both. For example, an embodiment of the present invention can be a circuit integrated into a video compression chip or program codes integrated into video compression software to perform the processing described herein. An embodiment of the present invention may also be program codes to be executed on a Digital Signal Processor (DSP) to perform the processing described herein. The invention may also involve a number of functions to be performed by a computer processor, a digital signal processor, a microprocessor, or field programmable gate array (FPGA). These processors can be configured to perform particular tasks according to the invention, by executing machine-readable software code or firmware code that defines the particular methods embodied by the invention. The software code or firmware codes may be developed in different programming languages and different format or style. The software code may also be compiled for different target platform. However, different code formats, styles and languages of software codes and other means of configuring code to perform the tasks in accordance with the invention will not depart from the spirit and scope of the invention.
[0016] The invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described examples are to be considered in all respects only as illustrative and not restrictive. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.

Claims

1. A method of solving the parsing issue of mode-dependent coefficient scan (MDCS) in video coding , comprising:
remapping coefficient blocks from a mode dependent scanning order to a first predetermined scanning order; and
coding the remapped coefficient blocks using a second predetermined scanning order to generate coded coefficients.
2. The method as claimed in claim 1, wherein the first predetermined scanning order and the second predetermined scanning order are the same.
3. The method as claimed in claim 1, wherein the first predetermined scanning order or the second predetermined scanning order is selecting from horizontal scan, vertical scan, diagonal scan, or zigzag scan.
4. The method as claimed in claim 1, further comprising parsing the coded coefficients using the second predetermined scanning order.
5. The method as claimed in claim 4, wherein the parsed coefficients are remapped from the first predetermined scanning order to the mode dependent scanning order after modes are reconstructed.
6. The method as claimed in claim 4, wherein the first predetermined scanning order and the second predetermined scanning order are the same.
7. The method as claimed in claim 4, wherein the first predetermined scanning order or the second predetermined scanning order is selecting from horizontal scan, vertical scan, diagonal scan, or zigzag scan.
8. A method of solving the parsing issue of mode-dependent coefficient scan (MDCS) in video encoding , comprising:
determining a context modeling of a significance map by a scan position or absolute position of each scanned bit; and
coding the scanned bits.
9. The method as claimed in claim 8, wherein the context modeling of the significance map is determined by the scan position of each scanned bit, and a context index is derived using a function of the scan position or a look-up table.
10. The method as claimed in claim 8, wherein coding of a last significant position according to a scan order selecting from diagonal, horizontal, vertical or zigzag.
11. The method as claimed in claim 8, wherein the context modeling of the significance map is determined by the absolute position of each scanned bit after a real scan order is remapped to a pre-defined scan order, and the pre-defined scan order is selected from diagonal, horizontal, vertical and zigzag.
PCT/CN2011/081819 2011-11-04 2011-11-04 Methods and apparatuses of solving mdcs parsing issue WO2013063800A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007046644A1 (en) * 2005-10-21 2007-04-26 Electronics And Telecommunications Research Institute Apparatus and method for encoding and decoding moving picture using adaptive scanning
CN101606391A (en) * 2007-01-18 2009-12-16 弗劳恩霍夫应用研究促进协会 Quality scalable video data stream
WO2011128303A2 (en) * 2010-04-13 2011-10-20 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Coding of significance maps and transform coefficient blocks

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007046644A1 (en) * 2005-10-21 2007-04-26 Electronics And Telecommunications Research Institute Apparatus and method for encoding and decoding moving picture using adaptive scanning
CN101606391A (en) * 2007-01-18 2009-12-16 弗劳恩霍夫应用研究促进协会 Quality scalable video data stream
WO2011128303A2 (en) * 2010-04-13 2011-10-20 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Coding of significance maps and transform coefficient blocks

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