JVET-AM0068 AHG12: On Shifting Quantization Center [Y. Yu, H. Yu, J. Gan, L. Xu, H. Huang, F. Wang, Z. Xie, D. Wang (OPPO)]

A method of shifting quantization centers was adopted in the ECM software where the shifting amount is inversely proportional to the quantization indices of DQ. This contribution first proposes to apply the quantization center shifting to both RRC and TSRC when DQ is not enabled (i.e., in a non-CTC setting). In addition, when DQ is enabled, this contribution further proposes for both RRC and TSRC the amount of quantization center shifting is inversely proportional to the quantization level of individual quantizer instead of the quantization indices of DQ. On top of ECM-17.0, the simulation results are reported as follows.

Non-CTC (DQ off, and as a result, sign prediction is also off)

AI: Natural content: { -0.22%, -0.45%, -0.57%, 101.0%, 100.8%}

Class F: {-0.21%, -0.30%, -0.13%, 98.6%, 100.1%}

Class TGM: {-0.16%, -0.13%, -0.13%, 98.8%, 100.1%}

RA: Natural content: { -0.13%, -0.51%, -0.50%, 100.3%, 100.8%}

Class F: {-0.13%, -0.08%, 0.10%, 100.3%, 99.3%}

Class TGM: {0.03%, -0.13%, -0.07%, 99.7%, 99.5%}

LDB: Natural content { -0.09%, 0.27%, -0.25%, 99.8%, 100.9%}

Class F: {-0.26%, 0.30%, 0.72%, 99.3%, 100.1%}

Class TGM: {-0.15%, -0.08%, -0.13%, 99.8%, 96.4% }

CTC

AI: Natural content: { -0.02%, -0.09%, -0.05%, 100.2%, 99.6%}

Class F: {-0.07%, -0.04%, -0.11%, 99.4%, 100.6%}

Class TGM: {-0.11%, -0.04%, -0.10%, 98.4%, 99.7%}

RA: Natural content: { 0.00%, -0.08%, -0.05%, 99.8%, 100.3%}

Class F: {-0.05%, -0.03%, 0.21%, 99.9%, 100.6%}

Class TGM: {0.02%, -0.01%, -0.12%, 99.8%, 99.6%}

LDB: Natural content { -0.05%, 0.30%, 0.50%,}

Class F: {0.06%, 0.75%, 1.94%}

Class TGM: {-0.18%, -0.33%, -0.21%}

It was reported by the proponent that some encoder related operations of two previously adopted JVET-AE0102 (coding of LFNST and NSPT transform coefficients) and JVET-AG0100 (adding greater than flags in RRC) were not at all implemented in the ECM-17.0 when dependent quantization is off. This implementation has been added by the proponent.

Proponent of JVET-AE0102 and JVET-AG0100 (also one of the cross checkers of this proposal) confirmed the implementation was correct.

Decision (SW): Add the missing implementation of JVET-AE0102 and JVET-AG0100 encoder operations to the next version of ECM.

Regarding the normative algorithm for both non-CTC and CTC, cross checkers confirmed the results.

It was commented that JVET-AM0311 is a related contribution, but JVET-AM0311 modifies quantization center shift for a different non-CTC conditions, DQ off and RDOQ off, whereas this proposal focuses on quantization center shift modification for RDOQ on.

• For the proposed modifications under CTC, there are two main components: Apply quantization center shift to TSRC (which is currently not applied in ECM)
• Modify the quantization center shift table for RRC

For the CTC case, investigate this in an EE the two proposed modifications separately and in combination.

For the non-CTC case with DQ off and RDOQ on, investigate this in an EE the proposed method, report results for RRC and TSRC separately and in combination.

For the non-CTC case with both DQ off and RDOQ off, see notes under JVET-AM0311.