(19)
(11)EP 2 936 816 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
29.04.2020 Bulletin 2020/18

(21)Application number: 14782773.7

(22)Date of filing:  09.04.2014
(51)International Patent Classification (IPC): 
H04N 19/176(2014.01)
H04N 19/593(2014.01)
H04N 19/186(2014.01)
H04N 19/129(2014.01)
H04N 19/157(2014.01)
(86)International application number:
PCT/CN2014/074955
(87)International publication number:
WO 2014/166381 (16.10.2014 Gazette  2014/42)

(54)

METHOD AND APPARATUS FOR NON-SQUARE INTRA MODE CODING

VERFAHREN UND VORRICHTUNG FÜR NICHTQUADRATISCHE INTRAMODALE CODIERUNG

PROCÉDÉ ET APPAREIL PERMETTANT UN CODAGE EN MODE INTRA NON CARRÉ


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 09.04.2013 US 201361810029 P

(43)Date of publication of application:
28.10.2015 Bulletin 2015/44

(73)Proprietor: MediaTek Singapore Pte. Ltd.
Singapore 138628 (SG)

(72)Inventors:
  • LIU, Shan
    San Jose, California 95125 (US)
  • CHEN, Zhenzhong
    San Jose, California 95134 (US)

(74)Representative: Habermann, Hruschka & Schnabel 
Patentanwälte Montgelasstraße 2
81679 München
81679 München (DE)


(56)References cited: : 
WO-A1-2013/160698
US-A1- 2011 243 230
US-A1- 2008 311 920
US-A1- 2012 230 412
  
  • CHEN Z ET AL: "AHG5:Intra Prediction Mode-Dependent Coefficient Scanning for 4:2:2 Chroma Extended Format", 13. JCT-VC MEETING; 104. MPEG MEETING; 18-4-2013 - 26-4-2013; INCHEON; (JOINT COLLABORATIVE TEAM ON VIDEO CODING OF ISO/IEC JTC1/SC29/WG11 AND ITU-T SG.16 ); URL: HTTP://WFTP3.ITU.INT/AV-ARCH/JCTVC-SITE/,, no. JCTVC-M0232, 9 April 2013 (2013-04-09) , XP030114189,
  • SILCOCK P ET AL: "AHG12: Extension of HM7 to Support Additional Chroma Formats", 101. MPEG MEETING; 16-7-2012 - 20-7-2012; STOCKHOLM; (MOTION PICTURE EXPERT GROUP OR ISO/IEC JTC1/SC29/WG11),, no. m25517, 25 July 2012 (2012-07-25), XP030053851,
  • PENG (USTC) X ET AL: "CE6.b Report of Test 3: Interaction between SDIP and MDCS", 97. MPEG MEETING; 18-7-2011 - 22-7-2011; TORINO; (MOTION PICTURE EXPERT GROUP OR ISO/IEC JTC1/SC29/WG11),, no. m20616, 12 July 2011 (2011-07-12), XP030049179,
  • YUNFEI ZHENG ET AL: "CE11: Mode Dependent Coefficient Scanning", 95. MPEG MEETING; 24-1-2011 - 28-1-2011; DAEGU; (MOTION PICTURE EXPERT GROUP OR ISO/IEC JTC1/SC29/WG11),, no. m19172, 26 January 2011 (2011-01-26), XP030047739,
  
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description

TECHNICAL FIELD



[0001] The present invention relates to video coding. In particular, the present invention relates to coding techniques associated with Intra prediction for non-square blocks using mode-dependent coefficient scanning (MDCS).

BACKGROUND



[0002] Intra prediction exploits spatial correlation within a picture or within a picture region. In order to improve coding efficiency, the emerging High-Efficiency Video Coding (HEVC) standard exploits block-based spatial prediction extensively. In HEVC, multiple Intra prediction modes are used to exploit spatial features and the number of Intra prediction modes depends on the block size of a Prediction Unit (PU). In the HEVC standard, angular Intra prediction supports 33 distinct prediction directions along with a Planar mode (i.e., mode 0) and a DC mode (i.e., mode 1) as shown in Fig. 1. The mode numbers from 2 through 34 are associated with angular prediction. Mode 2 through mode 18 cover prediction directions from -135° to -45°, where mode 2 corresponds to -135° direction, mode 18 corresponds to -45° direction and mode 10 corresponds to -90° direction. Mode 18 through mode 34 cover prediction directions from -45°to +45°, where mode 26 corresponds to 0° direction and mode 34 corresponds +45° direction. There are four Intra prediction block sizes including 4x4, 8x8, 16x16 and 32x32. The decoder supports 132 combinations of block size and prediction direction.

[0003] HEVC adopts Intra prediction mode-dependent coefficient scanning (MDCS) for 4x4 and 8x8 transform blocks, where the scanning order of transform coefficients is determined by the Intra prediction mode. The scanning patterns for an 8x8 transform block, including diagonal coefficient scanning, horizontal coefficient scanning and vertical coefficient scanning, are shown in Fig. 2. For Intra prediction angular modes 6-14, vertical coefficient scanning is applied to the underlying square transform block. For Intra prediction angular modes 22-30, horizontal coefficient scanning is applied to the underlying square transform block. For the rest modes, diagonal coefficient scanning is applied. Fig. 3 illustrates the mode-dependent (or mode-derived) coefficient scanning patterns for an 8x8 transform block according to the conventional MDCS of the HEVC standard, where modes in range 310 use vertical coefficient scanning, modes in range 320 use horizontal coefficient scanning, and the rest modes use diagonal coefficient scanning.

[0004] In HEVC Range Extension, 4:2:2 color subsampling pattern is supported, where a chroma block collocated with a 2Nx2N luma block has a size Nx2N. The angular Intra modes for an Nx2N chroma block are shown in Fig. 4, where the Intra modes for the non-square block are derived by mapping the Intra modes for the square block to the Intra modes (named mapped Intra modes) for the non-square block. The Intra prediction MDCS for the chroma components is the same as that for the luma component. As shown in Fig. 4, mapped Intra prediction angular modes 6-14 for the chroma components cover a much wider angle 410 than Intra prediction angular modes 22-30 for the luma component 420. This also applies to general Nx2N luma as well as chroma intra block prediction. In one example, a 2Nx2N intra coding unit (CU) may be split into two Nx2N prediction units. In some cases, a 2NxN prediction block may also be derived from a 2Nx2N coding or prediction block. For example, a 2NxN block may be generated from a 2Nx2N block in a scalable coding system, where 2:1 scaling is performed in the vertical direction. In another example, a 2Nx2N intra coding unit (CU) is split into two 2NxN intra prediction units. The MDCS method may be applied to the non-square blocks in the scalable coding system as shown in Fig. 5. As shown in Fig. 5, mapped Intra prediction angular modes 6-14 for the chroma components cover a much narrower angle 510 than Intra prediction angular modes 22-30 for the luma component 520. The original MDCS design is tailored for the Intra predictive coding of luma component with square block sizes. Therefore, if the same MDCS design is applied to the non-square blocks of chroma components, the performance may be degraded. Therefore, it is desirable develop Intra coding suited for non-square blocks.

[0005] From SILCOCK P ET AL, "AHG12: Extension of HM7 to Support Additional Chroma Formats", 10. JCT-VC MEETING; 101. MPEG MEETING; 11-7-2012 - 20-7-2012; STOCKHOLM; (JOINT COLLABORATIVE TEAM ON VIDEO CODING OF ISO/IEC JTC1/SC29/WG11 AND ITU-T SG.16); URL: HTTP://WFTP3.ITU.INT/AV-ARCH/JCTVC-SITE/, (20120702), no. JCTVC-J0191, a method for extending JCT-VC HM-7 to support chroma sampling formats YUV422 and YUV444 is known.

[0006] The following document falls under Article 54(3) EPC and is therefore not relevant for consideration of inventive step.

[0007] From WO 2013/160698 an Intra Prediction Mode-Dependent Coefficient Scanning (MDCS) for 4:2:2 Chroma Extended Format is known.

SUMMARY



[0008] The present invention is defined by the subject matter of the appended claims.

[0009] A method and apparatus for predictive Intra coding of a non-square block using modified mode-dependent coefficient scanning (MDCS) are disclosed. The modified MDCS is derived from the MDCS designed for a square block, where the Intra modes for the square block are divided into multiple groups comprising a first angular group and a second angular group. The square block is processed using first coefficient scanning if the Intra mode for the square block belongs to the first angular group and using second coefficient scanning if the Intra mode for the square block belongs to the second angular group. Examples modify the MDCS for the non-square block to improve the performance. The mapped Intra modes for the non-square block are derived by mapping the Intra modes for the square block to the mapped Intra modes for the non-square block. The mapped Intra modes are divided into multiple modified groups comprising a first modified angular group and a second modified angular group. The modified MDCS modifies the number of the mapped Intra modes in the first modified angular group or the second modified angular group by comparing an angle spanned by the mapped Intra modes in the first modified angular group or the second modified angular group with the angle spanned by the Intra modes in the first angular group or the second angular group respectively. A current non-square block is then processed according to the modified MDCS, where the current non-square block is Intra coded using the first coefficient scanning if the mapped Intra mode for the current non-square block belongs to the first modified angular group, and the current non-square block is Intra coded using the second coefficient scanning if the mapped Intra mode for the current non-square block belongs to the second modified angular group.

[0010] In one embodiment, the modified MDCS increases the number of the mapped Intra modes in the first modified angular group or the second modified angular group if the first angle is smaller than the second angle and the modified MDCS decreases the number of the mapped Intra modes in the first modified angular group or the second modified angular group if the first angle is larger than the second angle. The first coefficient scanning may correspond to horizontal coefficient scanning and the second coefficient scanning may correspond to vertical coefficient scanning. The modified MDCS can be applied to the Range Extension profile of the High Efficiency Video Coding (HEVC) standard. In HEVC, the Intra modes having mode 2 through mode 18 covers from -135 degree direction to -45 degree direction, mode 10 corresponds to -90 degree direction, and the first angular group consists of the Intra modes having mode 6 through mode 14. The first modified angular group according to one embodiment consists of the mapped Intra modes having mode from 8 through mode 12. In HEVC, the Intra modes having mode 18 through mode 34 covers from - 45 degree direction to +45 degree direction, mode 26 corresponds to 0 degree direction, and the second angular group consists of the Intra modes having mode 22 through mode 30. The second modified angular group according to another embodiment consists of the mapped Intra modes having mode from 18 through mode 34.

[0011] If the mapped Intra mode for the non-square block is in neither the first modified angular group nor the second modified angular group, the non-square block is Intra coded using diagonal coefficient scanning. The square block may correspond to a 2Nx2N luma block in a picture using 4:2:2 color sub-sampling, and the non-square block corresponds to an Nx2N or 2NxN chroma block, wherein N is a positive integer. For example, N may be 2 or 4.

BRIEF DESCRIPTION OF DRAWINGS



[0012] 

Fig. 1 illustrates the 35 Intra prediction modes for High-Efficiency Video Coding (HEVC).

Fig. 2 illustrates examples of 8x8 coefficient scanning patterns for High-Efficiency Video Coding (HEVC).

Fig. 3 illustrates an example of mode-dependent coefficient scanning (MDCS) based on High-Efficiency Video Coding (HEVC).

Fig. 4 illustrates an example of mode-dependent coefficient scanning (MDCS) for an Nx2N non-square block based on High-Efficiency Video Coding (HEVC).

Fig. 5 illustrates an example of mode-dependent coefficient scanning (MDCS) for a 2NxN non-square block based on High-Efficiency Video Coding (HEVC).

Fig. 6 illustrates an example of modified mode-dependent coefficient scanning (MDCS) for an Nx2N non-square block.

Fig. 7 illustrates an example of modified mode-dependent coefficient scanning (MDCS) for a 2NxN non-square block.

Fig. 8 illustrates an exemplary flowchart for a system incorporating modified mode-dependent coefficient scanning (MDCS).


DETAILED DESCRIPTION



[0013] As mentioned before, the Intra prediction mode-dependent coefficient scanning (MDCS) for HEVC Range Extension profile is based on a square block. When the MDCS is applied to non-square blocks, the performance may be degraded. Examples adjust the range of angular Intra modes designed for a square block and use the result for a non-square block. The angle spanned by the adjusted range of Intra angular modes for the non-square block will be closer to the angle spanned by the range of Intra angular modes for the square block.

[0014] It is demonstrated for YCbCr 4:2:2 color sub-sampling. Each chroma block (Cr or Cb) associated with a 2Nx2N luma block has a size Nx2N. For the square luma block, vertical scan is applied to blocks having Intra modes 6-14. According to the conventional approach, vertical scan is also applied to mapped Intra modes 6-14 for the non-square chroma blocks. By comparing Fig. 1 with Fig. 4, the angle (410) spanned by mapped Intra modes 6-14 for the non-square chroma blocks is much wider than the angle (310) spanned by Intra modes 6-14 for the square luma blocks. On the other hand, the angle (420) spanned by mapped Intra modes 22-30 for the non-square chroma blocks is much narrower than the angle (320) spanned by Intra modes 22-30 for the square luma blocks. Intra mode 14 for the square luma block as shown in Fig. 1 has an angular direction closer to mapped Intra mode 12 for the non-square chroma block as shown in Fig. 4. Similarly, Intra mode 6 for the square luma block as shown in Fig. 1 has an angular direction closer to mapped Intra mode 8 for the non-square chroma block as shown in Fig. 4. Therefore, vertical coefficient scanning is applied to Nx2N chroma blocks having Intra modes 8-12. For horizontal coefficient scanning, angle spanned by Intra modes 22-30 for the square luma blocks is close to angle spanned by mapped Intra modes 18-34 for the non-square chroma blocks. Therefore, horizontal coefficient scanning is applied to mapped Intra modes 18-34 for the non-square Nx2N chroma blocks. Diagonal coefficient scanning is then applied to the rest mapped Intra modes for the non-square chroma blocks. The modified MDCS for the Nx2N non-square blocks is illustrated in Fig. 6. The angles (610 and 620) spanned by the mapped Intra modes for vertical and horizontal coefficient scanning are closer to the angles of the original MDCS for square blocks. The scanning patterns and corresponding mapped Intra modes for the Nx2N non-square blocks are summarized in Table 1.
Table 1.
DM modesCoefficient scanning
8-12 Vertical
18-34 Horizontal
All other modes Diagonal


[0015] In another example, 2NxN non-square prediction blocks are derived from the 2Nx2N square coding blocks. For a square luma block, vertical scan is applied to blocks having Intra modes 6-14. According to the conventional approach, vertical coefficient scanning would be applied to mapped Intra modes 6-14 for the non-square blocks. By comparing Fig. 1 with Fig. 5, the angle (510) spanned by mapped Intra modes 6-14 for the non-square chroma blocks is much narrower than the angle (310) spanned by Intra modes 6-14 for the square luma blocks. On the other hand, the angle (520) spanned by mapped Intra modes 22-30 for the non-square chroma blocks is much wider than the angle (320) spanned by Intra modes 22-30 for the square luma blocks. Intra mode 14 for the square block as shown in Fig. 1 has an angular direction closer to mapped Intra mode 18 for the non-square block as shown in Fig. 5. Similarly, Intra mode 6 for the square block as shown in Fig. 1 has an angular direction closer to mapped Intra mode 2 for the non-square block as shown in Fig. 5. Therefore, vertical coefficient scanning is applied to 2NxN non-square blocks having Intra modes 2-18. For horizontal coefficient scanning, angle spanned by Intra modes 22-30 for the square blocks is close to angle spanned by mapped Intra modes 24-28 for the non-square blocks. Therefore, horizontal coefficient scanning is applied to mapped Intra modes 24-28 for the non-square blocks. Diagonal coefficient scanning is then applied to the rest mapped Intra modes for the non-square blocks. The modified MDCS for the 2NxN non-square blocks is illustrated in Fig. 7. The angles (710 and 720) spanned by the mapped Intra modes for vertical and horizontal coefficient scanning are closer to the angles of the original MDCS for square blocks. The scanning patterns and corresponding mapped Intra modes for the 2NxN non-square blocks are summarized in Table 2.
Table 2.
DM modesCoefficient scanning
2-18 Vertical
24-28 Horizontal
All other modes Diagonal


[0016] The modified MDCS can be applied to pictures having YCrCb422 or YUV422 color sub-sampling in the Range Extension profile of the HEVC. The chroma block corresponding to a 2Nx2N luma block is non-square with a size Nx2N. The modified MDCS for the Nx2N chroma block is shown in Table 1. Accordingly, if the mapped Intra mode for the Nx2N chroma block is from mode 8 to mode 12, vertical coefficient scanning is applied to the Nx2N chroma block. If the mapped Intra mode for the Nx2N chroma block is from mode 18 to mode 34, horizontal coefficient scanning is applied to the Nx2N chroma block. For other mapped Intra modes, diagonal coefficient scanning is applied to the Nx2N chroma block.

[0017] The performance for Intra coding using modified MDCS for non-square blocks is compared to that using conventional MDCS. The comparisons of bitrate performance for system configurations corresponding to All Intra Main-tier, All Intra High-tier and All Intra Super-High-tier based on various test video materials are shown in Table 3, where a negative number means improvement over the conventional MDCS based on HEVC. As shown in Table 3, an improvement of 0.1% has been achieved for All Intra Main-tier and All Intra High-tier. For Intra Super-High-tier, the performance is about the same.
Table 3.
 All Intra Main-tierAll Intra High-tierAll Intra Super-High-tier
UVUVUV
Traffic -0.20% -0.30% -0.10% -0.20% -0.10% -0.10%
Kimono 1 -0.10% -0.10% 0.00% -0.10% 0.00% 0.00%
EBUHorse -0.10% -0.20% 0.00% -0.10% 0.00% 0.00%
EBUGraphics -0.20% -0.20% -0.10% -0.10% -0.10% -0.10%
EBUWaterRocksClose 0.00% -0.10% 0.00% 0.00% 0.00% 0.00%
EBUKidsSoccer -0.10% -0.10% 0.00% 0.00% 0.00% 0.00%
Seeking -0.10% -0.10% -0.10% -0.10% 0.00% 0.00%
Overall -0.10% -0.20% -0.10% -0.10% 0.00% 0.00%


[0018] The comparisons of bitrate performance for system configurations corresponding to Random Access Main-tier and Random Access High-tier based on various test video materials are shown in Table 4. As shown in Table 4, the improvement is between 0% and 0.1%.
Table 4.
 Random Access Main-tierRandom Access High-tier
UVUV
Traffic -0.10% -0.20% 0.00% -0.10%
Kimono 1 -0.10% 0.00% -0.10% -0.10%
EBUHorse 0.10% 0.00% 0.00% -0.10%
EBUGraphics -0.10% -0.10% 0.00% 0.00%
EBUWaterRocksClose 0.00% 0.00% 0.00% 0.00%
EBUKidsSoccer -0.10% -0.30% 0.00% -0.20%
Seeking -0.10% -0.10% -0.10% 0.00%
Overall -0.10% -0.10% 0.00% -0.10%


[0019] The comparisons of bitrate performance for system configurations corresponding to Low Delay Main-tier and Low Delay High-tier based on various test video materials are shown in Table 5. As shown in Table 5, the improvement is between 0% and 0.2%.
Table 5.
 Low delay B Main-tierLow delay B High-tier
UVUV
Traffic 0.00% 0.10% 0.00% 0.00%
Kimono 1 0.00% -0.20% 0.00% -0.10%
EBUHorse 0.00% -0.50% 0.00% -0.50%
EBUGraphics -0.20% 0.10% 0.00% 0.10%
EBUWaterRocksClose 0.00% -0.20% 0.00% 0.00%
EBUKidsSoccer -0.30% -0.20% -0.30% -0.20%
Seeking -0.10% 0.00% -0.10% -0.10%
Overall -0.10% -0.10% -0.10% -0.10%


[0020] Fig. 8 illustrates an exemplary flowchart for a coding system that uses the modified MDCS for Intra predictive coding of non-square blocks. As mentioned before, the modified MDCS is derived from the MDCS designed for square blocks. Intra modes for the square blocks are divided into multiple groups comprising a first angular group and a second angular group. The square blocks are processed using first coefficient scanning if the Intra mode for the square block belongs to the first angular group and using second coefficient scanning if the Intra mode for the square block belongs to the second angular group. After the MDCS is determined, the modified MDCS is derived by modifying the conventional MDCS as shown in step 810. The modification is performed as follows. First, mapped Intra modes for the non-square block are derived by mapping the Intra modes for the square block to the mapped Intra modes for the non-square block. The mapped Intra modes are then divided into multiple modified groups comprising a first modified angular group and a second modified angular group. The modified MDCS modifies the number of the mapped Intra modes in the first modified angular group or the second modified angular group by comparing the angle spanned by the mapped Intra modes in the first modified angular group or the second modified angular group with the angle spanned by the Intra modes in the first angular group or the second angular group respectively. After the modified MDCS is determined, the system can process the non-square blocks. As shown in step 820, input data associated with a current non-square block is received. For encoding, the input data associated the current non-square block corresponds to the non-square pixel data to be coded. For decoding, the input data associated with the current non-square block corresponds to the coded current non-square block to be decoded. The motion information of the current texture block may be retrieved from memory (e.g., computer memory, buffer (RAM or DRAM) or other media) or from a processor. The current non-square block is processed according to the modified MDCS as shown in step 830, where the current non-square block is Intra coded using the first coefficient scanning if the mapped Intra mode for the current non-square block belongs to the first modified angular group, and the current non-square block is Intra coded using the second coefficient scanning if the mapped Intra mode for the current non-square block belongs to the second modified angular group.

[0021] The flowchart shown in Fig. 8 is intended for serving as examples of using modified MDCS for Intra predictive coding of non-square blocks. Embodiment of 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 code integrated into video compression software to perform the processing described herein. An embodiment of the present invention may also be program code 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 code may be developed in different programming languages and different formats or styles. The software code may also be compiled for different target platforms, in different code formats, styles and languages of software codes and other means of configuring code to perform the tasks in accordance with the invention.


Claims

1. A method for predictive Intra coding of a non-square chroma block, referred to as a non-square block, wherein the non-square block is collocated with a square luma block, referred to as a corresponding square block, wherein the corresponding square block is Intra coded using mode-dependent coefficient scanning, MDCS, wherein the square block is a 2Nx2N block, and N is a positive integer, wherein Intra modes for the corresponding square block are divided into multiple groups comprising a first angular group and a second angular group, and wherein the corresponding square block is processed using first coefficient scanning if an Intra mode for the corresponding square block belongs to the first angular group and using second coefficient scanning if the Intra mode for the corresponding square block belongs to the second angular group,
the method comprising:

receiving (820) input data associated with a current non-square block; and

processing (830) the current non-square block according to a modified MDCS, wherein the current non-square block is Intra coded using the first coefficient scanning if an Intra mode for the current non-square block belongs to a first modified angular group, and the current non-square block is Intra coded using the second coefficient scanning if the Intra mode for the current non-square block belongs to a second modified angular group,

wherein vertical coefficient scanning is applied in the first coefficient scanning, horizontal coefficient scanning is applied in the second coefficient scanning, and the non-square block is Intra coded using diagonal coefficient scanning if the mapped Intra mode for the non-square block is neither in the first modified angular group nor in the second modified angular group,

characterized in that

for the non-square block being an Nx2N block, the Intra modes having mode 2 though mode 18 cover from -135 degree direction to -45 degree direction, mode 10 corresponds to -90 degree direction, the first angular group consists of the HEVC Intra modes 6 through 14, and the first modified angular group consists of the HEVC Intra modes 8 through 12,

the second angular group consists of the HEVC Intra modes 22 through 30, and the second modified angular group consists of HEVC Intra modes 18 through 34.


 
2. The method of Claim 1, wherein the non-square block is a Nx2N chroma block in a picture using 4:2:2 color sub-sampling.
 
3. The method of Claim 2, wherein N is 2 or 4.
 
4. An apparatus for predictive Intra coding of a non-square chroma block, referred to as a non-square block, wherein the non-square block is collocated with a square luma block, referred to as a corresponding square block, wherein the corresponding square block is Intra coded using mode-dependent coefficient scanning, MDCS, wherein the square block is a 2Nx2N block, and N is a positive integer, wherein Intra modes for the corresponding square block are divided into multiple groups comprising a first angular group and a second angular group, and wherein the corresponding square block is processed using first coefficient scanning if an Intra mode for the corresponding square block belongs to the first angular group and using second coefficient scanning if the Intra mode for the corresponding square block belongs to the second angular group, the apparatus comprising one or more electronic circuits, wherein said one or more electronic circuits are configured to:

receive (820) input data associated with a current non-square block; and process (830) the current non-square block according to a modified MDCS, wherein the current non-square block is Intra coded using the first coefficient scanning if an Intra mode for the current non-square block belongs to a first modified angular group, and the current non-square block is Intra coded using the second coefficient scanning if the Intra mode for the current non-square block belongs to a second modified angular group,

wherein vertical coefficient scanning is applied in the first coefficient scanning, horizontal coefficient scanning is applied in the second coefficient scanning, and the non-square block is Intra coded using diagonal coefficient scanning if the mapped Intra mode for the non-square block is neither in the first modified angular group nor in the second modified angular group,

characterized in that for the non-square block being an Nx2N block, the Intra modes having mode 2 through mode 18 cover from -135 degree direction to -45 degree direction, mode 10 corresponds to -90 degree direction, the first angular group consists of the HEVC Intra modes 6 through 14, and the first modified angular group consists of the HEVC Intra modes 8 through 12, the second angular group consists of the HEVC Intra modes 22 through 30, and the second modified angular group consists of HEVC Intra modes 18 through 34.


 


Ansprüche

1. Verfahren zur prädiktiven Intra-Codierung eines nicht-quadratischen Chroma-Blocks, der als nicht-quadratischer Block bezeichnet wird, wobei der nicht-quadratische Block mit einem quadratischen Luma-Block, der als entsprechender quadratischer Block bezeichnet wird, kollokiert wird, wobei der entsprechende quadratische Block unter Verwendung der modusabhängigen Koeffizientenabtastung, MDCS, Intra-codiert wird, wobei der quadratische Block ein 2Nx2N-Block ist und N eine positive ganze Zahl ist, wobei die Intra-Modi für den entsprechenden quadratischen Block in mehrere Gruppen unterteilt sind, die eine erste Winkelgruppe und eine zweite Winkelgruppe umfassen, und wobei der entsprechende quadratische Block unter Verwendung einer ersten Koeffizientenabtastung, wenn ein Intra-Modus für den entsprechenden quadratischen Block zu der ersten Winkelgruppe gehört, und unter Verwendung einer zweiten Koeffizientenabtastung verarbeitet wird, wenn der Intra-Modus für den entsprechenden quadratischen Block zu der zweiten Winkelgruppe gehört,
wobei das Verfahren aufweist:

Empfangen (820) von Eingangsdaten, die mit einem aktuellen nicht-quadratischen Block verbunden sind; und

Verarbeiten (830) des aktuellen nicht-quadratischen Blocks gemäß einer modifizierten MDCS, wobei der aktuelle nicht-quadratische Block unter Verwendung der ersten Koeffizientenabtastung Intra-codiert wird, wenn ein Intra-Modus für den aktuellen nicht-quadratischen Block zu einer ersten modifizierten Winkelgruppe gehört, und der aktuelle nicht-quadratische Block unter Verwendung der zweiten Koeffizientenabtastung Intra-codiert wird, wenn der Intra-Modus für den aktuellen nicht-quadratischen Block zu einer zweiten modifizierten Winkelgruppe gehört,

wobei eine vertikale Koeffizientenabtastung bei der ersten Koeffizientenabtastung angewendet wird, eine horizontale Koeffizientenabtastung bei der zweiten Koeffizientenabtastung angewendet wird und der nicht-quadratische Block unter Verwendung einer diagonalen Koeffizientenabtastung Intra-codiert wird, wenn der abgebildete Intra-Modus für den nicht-quadratischen Block weder in der ersten modifizierten Winkelgruppe noch in der zweiten modifizierten Winkelgruppe liegt,

dadurch gekennzeichnet, dass

für den nicht-quadratischen Block, der ein Nx2N-Block ist, die Intra-Modi mit Modus 2 bis Modus 18 eine -135 Grad-Richtung bis -45 Grad-Richtung abdecken, wobei Modus 10 einer -90 Grad-Richtung entspricht,
wobei die erste Winkelgruppe aus den HEVC-Intra-Modi 6 bis 14 besteht, und die erste modifizierte Winkelgruppe aus den HEVC-Intra-Modi 8 bis 12 besteht,

wobei die zweite Winkelgruppe aus den HEVC-Intra-Modi 22 bis 30 besteht, und die zweite modifizierte Winkelgruppe aus den HEVC-Intra-Modi 18 bis 34 besteht.


 
2. Verfahren nach Anspruch 1, bei dem der nicht-quadratische Block ein Nx2N-Chroma-Block in einem Bild mit 4:2:2-Farbunterabtastung ist.
 
3. Verfahren nach Anspruch 2, bei dem N 2 oder 4 ist.
 
4. Vorrichtung zur prädiktiven Intra-Codierung eines nicht-quadratischen Chroma-Blocks, der als nicht-quadratischer Block bezeichnet wird, wobei der nicht-quadratische Block mit einem quadratischen Luma-Block, der als entsprechender quadratischer Block bezeichnet wird, kollokiert wird, wobei der entsprechende quadratische Block unter Verwendung der modusabhängigen Koeffizientenabtastung, MDCS, Intra-codiert wird, wobei der quadratische Block ein 2Nx2N-Block ist und N eine positive ganze Zahl ist, wobei die Intra-Modi für den entsprechenden quadratischen Block in mehrere Gruppen unterteilt werden, die eine erste Winkelgruppe und eine zweite Winkelgruppe umfassen, und wobei der entsprechende quadratische Block unter Verwendung einer ersten Koeffizientenabtastung, wenn ein Intra-Modus für den entsprechenden quadratischen Block zu der ersten Winkelgruppe gehört, und unter Verwendung einer zweiten Koeffizientenabtastung verarbeitet wird, wenn der Intra-Modus für den entsprechenden quadratischen Block zu der zweiten Winkelgruppe gehört, wobei die Vorrichtung eine oder mehrere elektronische Schaltungen aufweist, wobei die eine oder die mehreren elektronischen Schaltungen so konfiguriert sind, dass sie
Eingangsdaten empfangen (820), die einem aktuellen nicht-quadratischen Block zugeordnet sind; und den aktuellen nicht-quadratischen Block gemäß einer modifizierten MDCS verarbeiten (830), wobei der aktuelle nicht-quadratische Block unter Verwendung der ersten Koeffizientenabtastung Intra-codiert wird, wenn ein Intra-Modus für den aktuellen nicht-quadratischen Block zu einer ersten modifizierten Winkelgruppe gehört, und der aktuelle nicht-quadratische Block unter Verwendung der zweiten Koeffizientenabtastung Intra-codiert wird, wenn der Intra-Modus für den aktuellen nicht-quadratischen Block zu einer zweiten modifizierten Winkelgruppe gehört,
wobei eine vertikale Koeffizientenabtastung bei der ersten Koeffizientenabtastung angewendet wird, eine horizontale Koeffizientenabtastung bei der zweiten Koeffizientenabtastung angewendet wird und der nicht-quadratische Block unter Verwendung einer diagonalen Koeffizientenabtastung Intra-codiert wird, wenn der abgebildete Intra-Modus für den nicht-quadratischen Block weder in der ersten modifizierten Winkelgruppe noch in der zweiten modifizierten Winkelgruppe liegt,
dadurch gekennzeichnet, dass für den nicht-quadratischen Block, der ein Nx2N-Block ist, die Intra-Modi mit Modus 2 bis Modus 18 eine -135 Grad-Richtung bis -45 Grad-Richtung abdecken, wobei Modus 10 einer -90 Grad-Richtung entspricht, wobei die erste Winkelgruppe aus den HEVC-Intra-Modi 6 bis 14 besteht und die erste modifizierte Winkelgruppe aus den HEVC-Intra-Modi 8 bis 12 besteht, wobei die zweite Winkelgruppe aus den HEVC-Intra-Modi 22 bis 30 besteht und die zweite modifizierte Winkelgruppe aus den HEVC-Intra-Modi 18 bis 34 besteht.
 


Revendications

1. Méthode de codage intra-prédictif d'un bloc de chrominance non carré, appelé bloc non carré, dans laquelle le bloc non carré est colocalisé avec un bloc de luminance carré, appelé bloc carré correspondant, dans laquelle le bloc carré correspondant est intra-codé en utilisant un balayage à coefficient dépendant du mode, MDCS, dans laquelle le bloc carré est un bloc 2Nx2N, et N est un entier positif, dans laquelle des modes Intra pour le bloc carré correspondant sont divisés en de multiples groupes comprenant un premier groupe angulaire et un second groupe angulaire, et dans laquelle le bloc carré correspondant est traité en utilisant un premier balayage à coefficient si un mode Intra pour le bloc carré correspondant appartient au premier groupe angulaire et en utilisant un second balayage à coefficient si le mode Intra pour le bloc carré correspondant appartient au second groupe angulaire,
la méthode comprenant les étapes consistant à :

recevoir (820) des données d'entrée associées à un bloc non carré actuel ; et

traiter (830) le bloc non carré actuel selon un MDCS modifié, dans laquelle le bloc non carré actuel est intra-codé en utilisant le premier balayage à coefficient si un mode Intra pour le bloc non carré actuel appartient à un premier groupe angulaire modifié, et le bloc non carré actuel est intra-codé en utilisant le second balayage à coefficient si le mode Intra pour le bloc non carré actuel appartient à un second groupe angulaire modifié,

dans laquelle un balayage à coefficient vertical est appliqué dans le premier balayage à coefficient, un balayage à coefficient horizontal est appliqué dans le second balayage à coefficient, et le bloc non carré est intra-codé en utilisant un balayage à coefficient diagonal si le mode intra-mappé pour le bloc non carré n'est ni dans le premier groupe angulaire modifié ni dans le second groupe angulaire modifié,

caractérisée en ce que

pour le bloc non carré étant un bloc Nx2N, les modes Intra ayant du mode 2 au mode 18 couvrent d'une direction de -135 degrés à une direction de -45 degrés, le mode 10 correspond à une direction de -90 degrés, le premier groupe angulaire se compose des modes HEVC Intra 6 à 14, et le premier groupe angulaire modifié se compose des modes HEVC Intra 8 à 12,

le second groupe angulaire se compose des modes HEVC Intra 22 à 30, et le second groupe angulaire modifié se compose des modes HEVC Intra 18 à 34.


 
2. Méthode selon la revendication 1, dans laquelle le bloc non carré est un bloc de chrominance Nx2N dans une image utilisant un sous-échantillonnage de couleurs 4 : 2 : 2.
 
3. Méthode selon la revendication 2, dans laquelle N est 2 ou 4.
 
4. Appareil de codage intra prédictif d'un bloc de chrominance non carré, appelé bloc non carré, dans lequel le bloc non carré est colocalisé avec un bloc de luminance carré, appelé bloc carré correspondant, dans lequel le bloc carré correspondant est intra-codé en utilisant un balayage à coefficient dépendant du mode, MDCS, dans lequel le bloc carré est un bloc 2Nx2N, et N est un entier positif, dans lequel des modes Intra pour le bloc carré correspondant sont divisés en de multiples groupes comprenant un premier groupe angulaire et un second groupe angulaire, et dans lequel le bloc carré correspondant est traité en utilisant un premier balayage à coefficient si un mode Intra pour le bloc carré correspondant appartient au premier groupe angulaire et en utilisant un second balayage à coefficient si le mode Intra pour le bloc carré correspondant appartient au second groupe angulaire, l'appareil comprenant un ou plusieurs circuits électroniques, dans lequel lesdits un ou plusieurs circuits électroniques sont configurés pour
recevoir (820) des données d'entrée associées à un bloc non carré actuel ; et traiter (830) le bloc non carré actuel selon un MDCS modifié, dans lequel le bloc non carré actuel est intra-codé en utilisant le premier balayage à coefficient si un mode Intra pour le bloc non carré actuel appartient à un premier groupe angulaire modifié, et le bloc non carré actuel est intra-codé en utilisant le second balayage à coefficient si le mode Intra pour le bloc non carré actuel appartient à un second groupe angulaire modifié,
dans lequel un balayage à coefficient vertical est appliqué dans le premier balayage à coefficient, un balayage à coefficient horizontal est appliqué dans le second balayage à coefficient, et le bloc non carré est intra-codé en utilisant un balayage à coefficient diagonal si le mode intra-mappé pour le bloc non carré n'est ni dans le premier groupe angulaire modifié ni dans le second groupe angulaire modifié,
caractérisée en ce que pour le bloc non carré étant un bloc Nx2N, les modes Intra ayant du mode 2 au mode 18 couvrent d'une direction de 135 degrés à une direction de -45 degrés, le mode 10 correspond à une direction de -90 degrés, le premier groupe angulaire se compose des modes HEVC Intra 6 à 14, et le premier groupe angulaire modifié se compose des modes HEVC Intra 8 à 12, le second groupe angulaire se compose des modes HEVC Intra 22 à 30, et le second groupe angulaire modifié se compose des modes HEVC Intra 18 à 34.
 




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