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16th Meeting: Geneva, October 2019 2019-10-04 09:23
AHG18: Residual coding method for lossless mode
Authors: Mohammed Golam Sarwer Alibaba R. L. Liao Alibaba J. Luo Alibaba Y. Ye Alibaba
Abstract
This contribution first reports and fixes a BDPCM-related software bug in the AHG18 lossless software. The bug fix achieves {-2.80%, -1.63%} rate reduction for {class F, TGM} in AI and {-1.18%, -0.55%} for {class F, TGM} in RA.
Meeting Notes
JVET-P0463 AHG18: Residual coding method for lossless mode [M. G. Sarwer, R. L. Liao, J. Luo, Y. Ye (Alibaba)]

This contribution first reports and fixes a BDPCM-related software bug in the AHG18 lossless software. The bug fix achieves {-2.80%, -1.63%} rate reduction for {class F, TGM} in AI and {-1.18%, -0.55%} for {class F, TGM} in RA.

In VVC draft 6 and in the lossless software, when BDPCM mode is selected, transform-skip (TS) residual coding is used. This contribution allows BDPCM mode to select the residual coding method based on the value of cu_transquant_bypass_flag. In the proposed method, if cu_transquant_bypass_flag = 1, BDPCM mode selects transform residual coding, otherwise BDPCM mode selects TS residual coding. This contribution also proposes to remove signalling the position of last coefficient from the transform residual coding if cu_transquant_bypass_flag = 1.

Following results are reported (Anchor is the VTM-6.0 lossless + Bug fix):

  • Test 1: remove signalling the position of last significant coefficient
    • -0.51% (AI) and -0.44% (RA) BD-rate saving in CTC test conditions in lossless coding
  • Test 2: select transform residual coding for BDPCM mode
    • -1.28% (AI) and -0.26% (RA) BD-rate saving in lossless coding
  • Test 3: combine test 1 and test 2
    • –1.71% (AI) and -0.70% (RA) BD-rate saving in lossless coding

As an alternative, this contribution also proposes a SPS level flag to signal residual coding method of the BDPCM mode.

In version2 of the contribution, TS residual coding of VTM-6.0 lossless software is replaced by CE7-1.3.b alternative method proposed in JVET-P0072. Following results are reported (Anchor is the VTM-6.0 lossless + Bug fix):

  • Test 4: TS residual coding of VTM-6.0 is replaced by CE7-1.3.b-alt
    • -0.96% (AI) and -x.xx% (RA) BD-rate saving in lossless coding
  • Test 5: Test 1 + test 4
    • -1.33% (AI) and -x.xx% (RA) BD-rate saving in lossless coding

Note: x.xx = values not provided in contribution.

One method identical as JVET-P0148, another method identical to JVET-P0258. See further notes there.

References:
JVET-P0072
Cited:
JVET-P0018 JVET-P0072 JVET-P0466 JVET-P0914 X JVET-P2023 JVET-Q0023 X JVET-Q0137 JVET-Q0139
PATENTS:
EP4668752A2 0.34 2025-12-24 US12335470B2 0.32 2025-06-17 JP2025026466A 0.30 2025-02-21 JP2025178260A 0.28 2025-12-05 JP2025184883A 0.26 2025-12-18 US20250337888A1 0.24 2025-10-30 WO2021133510A1 0.22 2021-07-01 JP2025169949A 0.20 2025-11-14
ARCHIVE v3 :
JVET-P0463-v2-clean.docx JVET-P0463-v2.docx JVET-P0463-v3.docx JVET-P0463.pptx JVET-P0463_Table 10.xlsm JVET-P0463_Table 4- Bug FIx.xlsm JVET-P0463_Table 5.xlsm JVET-P0463_Table 6.xlsm JVET-P0463_Table 7.xlsm JVET-P0463_Table 8.xlsm JVET-P0463_Table 9.xlsm
Decisions
One method identical as JVET-P0148, another method identical to JVET-P0258. See further notes there.
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