International organisation for standardisation
Yüklə 9,08 Mb.
|
6.15.2Intra mode coding6.15.2.1.1.1.1.1.1JCTVC-F062 Luma Intra Prediction Mode Coding [T.-D. Chuang, C.-Y. Chen, M. Guo, X. Guo, Y.-W. Huang, S. Lei (MediaTek)] In this contribution, a luma intra prediction mode coding method was proposed. As in HM-3.0, a current intra prediction mode was first checked to see if it is equal to a most probable mode (MPM) derived from its left block or upper block. When the current intra prediction mode was not equal to any MPM, at most three most probable remaining modes (MPRMs) according to the intra modes of neighboring blocks could be used. When the current intra prediction mode is not equal to any MPM or MPRM, one of the remaining modes was signaled to indicate the current intra prediction mode. Simulation results reportedly showed 0.4% bit rate reduction in the high efficiency all intra condition with 1% encoding time increase. Due to additional table mapping, complexity is increased Tables were trained with the test data. 6.15.2.1.1.1.1.1.2JCTVC-F108 Cross-verification results of MediaTek’s improved Intra Mode Coding (JCTVC-F062) by LG [J. Park, B. Jeon (LGE)]
This contribution proposes and intra mode coding method considering "Most Probable Mode" (MPM). At the last meeting held in Geneva, use of multiple MPMs was adopted in HM. So, it is suggested to study encoding method for remaining intra modes which depend on MPMs. The encoding method for remaining intra modes is proposed in this contribution. When multiple MPMs are used and prev_intra_luma_pred_flag is equal to ‘0’, rem_intra_luma_pred_mode may be determined without signalling the intra mode, since the number of remaining modes is only one and the mode can be expected. In this case, this contribution reduces the redundant bits for intra mode coding in HM with simple modification. However, this does not give a benefit in terms of bit rate reduction, and the determination at the decoder side is more complicated and also means that the derivation needs to be described in the text.
When parsing the syntax rem_intra_luma_pred_mode, if the syntax prev_intra_luma_pred_flag (mpm_flag) is equal to 0, the possible number of intra prediction modes is 3 (64x64), and the two MPM candidates have different intra prediction mode, the value of rem_intra_luma_pred_mode can be inferred without signalling since the possible number of intra prediction mode is three and the two MPM candidates have the two modes out of the three. However, the current HM always signals rem_intra_luma_pred_mode even though it can be inferred in that case. Therefore the current HM has a redundancy in signalling of the syntax rem_intra_luma_pred_mode. This contribution proposes to add a condition when parsing rem_intra_luma_pred_mode not to waste bits for the syntax element. Is similar to JCTVC-F416; no need to present according to contributor. 6.15.2.1.1.1.1.1.6JCTVC-F675 Cross Check of LGE’s proposal (JCTVC-F109) on Remaining mode redundancy removal [J. Zhao, A. Segall (Sharp)] [late reg. 07-07, upload 07-07] 6.15.2.1.1.1.1.1.7JCTVC-F378 Intra mode parsing without access neighbouring information [V. Seregin, T. Lee, J. Chen (Samsung)] In this document, making luma intra mode parsing independent from neighbours is investigated and tested. In the proposed method always two probable intra modes are used for coding luma intra directions. In order to do this, the following modifications were done on top of HM3.0: Planar mode was coded as one of angular intra directions and default most probable mode was added in case two most probable intra modes are same. Experimental results reportedly show 0.0%, −0.1%, −0.1% and 0.0%, 0.1%, 0.1% BD-rate differences for luma and chroma in high efficiency and low complexity intra-only test conditions respectively. The main intention is to decouple parsing and decoding and increase throughput. 6.15.2.1.1.1.1.1.8JCTVC-F212 Cross-check of intra mode parsing (JCTVC-F378) [J. Xu (Microsoft)] [late upload 07-12] 6.15.2.1.1.1.1.1.9JCTVC-F459 Parsing friendly intra mode coding [W.-J. Chien, X. Wang, M. Karczewicz (Qualcomm)] This contribution presents a coding method for intra prediction mode. In the current HEVC Test Model, different codeword binarizations are defined based on the intra prediction modes of neighboring partitions for the luma intra prediction mode coding. It also uses different codeword binarization for chroma intra prediction mode based on the luma intra prediction mode of the current partition. This method reportedly unifies different binarizations by utilizing constant number of candidate modes. The simulation results reportedly show average performance gain of 0.3% and 0.2% in Intra only configurations. It is suggested to use a fixed number of most probable modes, but additional MPMs are suggested which are systematically derived. This is where the gain comes from. 6.15.2.1.1.1.1.1.10JCTVC-F721 Cross-verification of Qualcomm’s JCTVC-F459 on parsing friendly intra mode coding [V. Seregin, J. Chen (Samsung)] [late reg. 07-12, upload 07-12] 6.15.2.1.1.1.1.1.11JCTVC-F340 Fixing the number of MPM candidates [T. Kumakura, S. Fukushima, M. Ueda (JVC Kenwood)] In the 5th JCT-VC meeting, a most probable mode (MPM) signalling was adopted. However, the parsing process for deriving intra prediction mode becomes more complex since the number of MPM is variable with the combination of decoded intra prediction modes. In this contribution, it is proposed to change the parsing process by fixing the number or MPM candidates to two for all prediction units. This is done by adding the predetermined mode as MPM candidates in case that the intra prediction mode of left prediction unit and the intra prediction mode of above prediction unit are identical. The simulation results reportedly show that the proposed technique provides no BD-rate loss for intra high efficiency settings and average 0.1% loss for intra low complexity settings. Fixing to number of 2 is suggested (like JCTVC-F378) Furthermore, it is suggested to add a mode 17 for 4x4 and mode 3 for 64x64 (not related to MPM). However, this increases encoder runtime, with no gain. 6.15.2.1.1.1.1.1.12JCTVC-F350 Cross-check report on JCTVC-F340 [K. Chono, H. Aoki (NEC)] a) Targets of (JCTVC-F378, JCTVC-F459, JCTVC-F340): Simplification of HM/WD parsing by using a fixed number of MPMs (should be 2). b) Targets of (JCTVC-F062, JCTVC-F459): Increasing compression by adding more MPMs A breakout group was asked to work on a harmonized solution on a) and b) if possible, and this was done. See conclusions from BoG discussion and planned CE6. 6.15.2.1.1.1.1.1.13JCTVC-F190 Planar Mode Binarization for Intra Mode Coding [F. Zou, O. C. Au, C. Pang, J. Dai, X. Wen (HKUST)] This contribution proposes a codeword mapping scheme for the planar mode with CABAC. In HM3.0, when the syntax prev_intra_luma_pred_flag (MPM_flag) is 0 and the two MPM candidates are different, there is always one redundant codeword in the remaining mode coding. The proposed scheme removes the codeword redundancy by mapping the planar mode to the mode that corresponds to the redundant codeword. In this case, the DCPlanar flag is also saved. In particular, the proposed scheme allows the planar mode to be mapped to Mode 2 first, and then decides whether the most probable modes can predict it correctly. If most probable modes cannot predict the current mode correctly (prev_intra_luma_pred_flag=0), and the two most probable modes are different, the Planar mode is remapped to the mode who corresponds to the max allowable codeword used in remaining mode coding. Therefore there is no need to transmit the DCPlanar flag in this case. Otherwise, the original HM3.0 scheme is applied. Doing so saves DCPlanar flag and is asserted to remove codeword design redundancy in HM3.0. The proposed scheme is implemented in HM3.0, achieving a reported average 0.1% bit rate reduction for intra HE with no effect on encoding and decoding time. The results are verified by Motorola Mobility in JCTVC-F572. Note: Redundant bin removal is also suggested in JCTVC-F378. 6.15.2.1.1.1.1.1.14JCTVC-F572 Cross-check report for HKUST's test JCTVC-F190 by Motorola Mobility [J. Lou, L. Wang (Motorola Mobility)] 6.15.2.1.1.1.1.1.15JCTVC-F426 Fixed probability coding for Intra mode [H. Sasai, T. Nishi (Panasonic)] This proposal presents a technique for complexity reduction for intra-mode parameter parsing process. In this contribution, it is proposed that 1) redundant bit saving for binarization for CABAC, 2) bypass coding and 3) no context updates are used for intra mode coding. In current HM3.0, the additional bin to indicate whether 32 or 33 is specified even it is always less than 33 in case that number of MPM equal to 2 and one context index is used and updated for all bins of intra mode coding. The proposed solution was implemented in HMv3 and their coding efficiencies were evaluated. The result reportedly shows 0.1% performance gain with fixed probability and less than 0.1% performance change with redundant bit reduction and bypass coding for All-Intra high efficiency configuration. Redundant bin removal (as JCTVC-F190). Bypass mode frequently used (equal probabilities). An interpretation for no performance loss in case of fixed probability coding of intra modes may be the local variation of statistics. Also related to the delayed context update – further study. 6.15.2.1.1.1.1.1.16JCTVC-F678 Cross-verification results of Panasonic’s intra mode coding (JCTVC-F426) [LG J. Park, B. Jeon (LGE)] [late reg. 07-07, upload 07-11]
In this document CABAC equal probability coding (bypass) mode utilization in addition to current context modelling for luma and chroma intra modes coding is studied and tested. In the proposed method a majority bins of intra mode are coded with bypass mode without context modelling with the exception of the first bin of chroma intra mode, and luma intra mode for 8x8, 16x16 and 32x32 prediction units. Experimental results reportedly show 70% bins bypass coded with 0.0%, 0.0% and 0.0% BD-rate gain in high efficiency intra-only, random access and low-delay test conditions respectively. Question: Why code first bin context-based in chroma, and bypass in luma? It could potentially be done more consistently, including first bin of the remaining mode. (Does not apply to MPM.) Further study – may have implications that are not fully understood yet, and it can easily be done later. In general, it is agreed that this is a reasonable thing to do. 6.15.2.1.1.1.1.1.18JCTVC-F514 Crosscheck of Samsung’s proposal JCTVC-F376 by Huawei [Q. Shen, H. Yang, H. Yu (Huawei)]
This document proposes a method for binarization and coding of Intra prediction modes. Unlike the current Intra mode coding technique, the proposed approach uses the same binarization and adaptation in Low Complexity (LC) and High Efficiency (HE) and does not use a VLC or initialization tables. Using this approach 400 bytes of VLC tables are removed and, on average, a compression gain of 0.3% and 0.1% were reported in the HE and LC settings, respectively. Gain in HE most probably comes mainly due to the fact that similar swapping is used as in LC, and number of contexts is increased. 6.15.2.1.1.1.1.1.20JCTVC-F603 Cross-check of Sony proposed JCTVC-F091 on Unifying binarizations of Intra modes in HE and LC [W.-J. Chien, M. Karczewicz (Qualcomm)] 6.15.2.1.1.1.1.1.21JCTVC-F154 Cross-check of JCTVC-F091 on Intra prediction mode coding [T. Davies (Cisco)] [late upload 07-07] 6.15.2.1.1.1.1.1.22JCTVC-F269 Modified Intra Mode Coding [E. François, S. Pautet, C. Gisquet (Canon)] This contribution proposes a modification of the Intra Mode Coding process. The current HM design does not take (in CABAC configuration) or partially takes (in CAVLC configuration) into account the intra mode statistics. In this proposal, intra mode statistics are updated on the fly and further used to decode the intra mode when the mode is not equal to one of the neighboring Most Probable Modes (MPMs). In the CABAC case, counters and related mode ranking tables are used and updated each time an intra mode is decoded. This updating is done when the intra mode is signaled as an MPM or not. Ranking tables are further used to adaptively binarize the mode value before arithmetic coding. In the CAVLC case, the number of modes-codewords mapping tables is reduced from 4 (2 for 4x4 CUs, 2 for 8x8 to 32x32 CUs) to 2 (1 for 4x4 CUs, 1 for 8x8 to 32x32 CUs). The swapping process is done based on the real mode value (not the decoded codeword value) when the intra mode is signaled as an MPM or not. The tool was tested in HM3.1. The overall average luma BD-rate improvement is reportedly 0.3% for the High Efficiency All Intra configuration, 0.1% for the Low Complexity All Intra and High Efficiency Random Access configurations. No impact is reported for the other configurations. Higher gains are reported on high resolution than on low resolution sequences. The proposal has also reportedly been evaluated on the HM3.0_SDIP branch. Consistent results are reportedly obtained, showing that SDIP and the proposal give additive gains. Very similar to JCTVC-F091, but exactly same swapping (counter based) is used for CABAC as in CAVLC. 6.15.2.1.1.1.1.1.23JCTVC-F540 Crosscheck report for Canon's Modified Intra Mode Coding (JCTVC-F269) [C. Lai, L. Liu, J. Zheng (HiSilicon), H. Yu (Huawei)] [late upload 07-07]
This contribution recommends that next WD description corresponds to HM implementation in terms of coding of intra prediction mode because WD3 description is different from HM3.0 implementation. In addition, this contribution recommends that the chroma intra prediction mode is coded after the luma intra prediction mode located at the same position in the same prediction unit, so coding order of luma and chroma intra prediction modes is changed. Alignment between WD text and SW implementation – Apparently the text must be corrected. AVC does it the same way as the software currently does it. Regarding other chroma formats than 4:2:0 – needs further discussion. 6.15.2.1.1.1.1.1.26JCTVC-F465 Item 2 (Chroma codeword switch) of Experiments on tools in Working Daft (WD) and HEVC Test Mode (HM-3.0) [I.-K. Kim, E. Alshina, J. Chen, T. Lee, W.-J. Han, J. H. Park (Samsung), V. Sze, M. Budagavi, M. Zhou (TI)] Item 2: Chroma codeword switch Not clean design. Not in the text. Decision: Remove the switch from the software. (If evidence of usefulness arrives later, …) 6.15.2.1.1.1.1.1.27JCTVC-F098 Cross-check for JVC Kenwood's proposal on intra coding (JCTVC-F094) [M. Matsumura, S. Matsuo, Y. Bandoh, S. Takamura, H. Jozawa (NTT)] 6.15.2.1.1.1.1.1.28JCTVC-F106 CAVLC coding for intra prediction mode [J. Park, B. Jeon (LGE)] This contribution proposes a mode coding with CAVLC for luma intra prediction. In HM 3.0, the index mapping tables for intra remaining modes represent the accumulated distribution of intra remaining modes. However, those tables do not consider the dependency of remaining modes on the values of MPM candidates. In the proposed method, the orders of index mapping process and remaining mode calculation process are switched. By switching them, the tables can allegedly represent the distribution of prediction modes instead of the distribution of remaining modes. The proposed change reportedly brings 0.2% BD-rate reduction for intra low complexity configurations. Concept same as JCTVC-F269, other VLC table – does not need to be presented. 6.15.2.1.1.1.1.1.29JCTVC-F066 Crosscheck for LGE's Luma Intra Prediction Mode Coding in JCTVC-F106 [T.-D Chuang, Y.-W. Huang (MediaTek)] 6.15.2.1.1.1.1.1.30JCTVC-F111 Intra prediction mode coding with LCEC on SDIP [J. Lim, B. Jeon (LGE)] This contribution proposes a CAVLC joint coding scheme for intra prediction mode on SDIP. When SDIP is enabled, split mode and four kinds of partitioning type exist for intra prediction. Similar CAVLC joint coding scheme and counters as used for inter mode coding was also applied to intra mode coding. The simulation result reportedly shows that the proposed method achieves 0.1% bit rate reduction for INLC configuration without any encoder and decoder complexity changes. Applies to split flag used in SDIP partitioning. Results are relative to 3.0 SDIP branch, not harmonized version. 6.15.2.1.1.1.1.1.31JCTVC-F660 Cross Check of LGE’s proposal (JCTVC-F111) on Intra prediction mode coding with LCEC on SDIP [Jane Zhao, Andrew Segall] [late reg. 07-06, upload 07-06]
In HM3.0, DC and Planar modes are coded using a dependent manner, which shares the same codeword in the codeword tables of CAVLC. After the codeword, one flag is then transmitted to signal whether DC or Planar is used. This contribution proposes to update the CAVLC codeword tables in HM3.0 with separate codewords for DC and Planar modes. It is reported that an average BD-Rate reduction of 0.2% is achieved for low complexity all intra (LC-AI) configuration using the proposed method. It is also reported that the running time is almost the same with that of anchor. Conclusion: Establish CE on Intra Mode coding to establish a unified and (hopefully) simplified solution for the whole package (expected gain: 0.5%?)
6.15.2.1.1.1.1.1.33JCTVC-F490 Cross-checking of results of JCTVC-F123 from MediaTek [E. François (Canon)] 6.15.2.1.1.1.1.1.34JCTVC-F339 Intra prediction mode coding based on direction difference [T. Kumakura, S. Fukushima (JVC Kenwood)] MPM for Intra prediction mode is applied in the HM3.0 and is asserted to reduce the entropy of intra prediction mode. The technique is based on a uniform probabilistic model. It is estimated that the current intra prediction mode correlates with the combination of intra prediction modes of the decoded prediction units. And it is estimated that the suitable probabilistic model is switched by each prediction unit. In this proposed method, MPM sets are switched by using direction difference of two intra prediction modes in adjacent blocks. The contribution reports that the proposed technique provides average 0.2% BD-rate gain for intra high efficiency settings and average 0.1% gain for intra low complexity settings. Comment: A fixed number of MPM would be desirable. 6.15.2.1.1.1.1.1.35JCTVC-F432 Crosscheck for JVC's proposal JCTVC-F339 [M. Guo, X. Guo (MediaTek)] [late upload 07-09]
Yüklə 9,08 Mb. Dostları ilə paylaş:
|