JVET-AL0207 AHG10/AHG17: On matching target bitrate for subjective quality evaluation [K. Andersson, P. Wennersten (Ericsson)]

The current approach for matching target bitrate for subjective evaluation is to increase the base QP by one at a given frame. This may give an abrupt change in quality after the QP change. In this document it is proposed to start from the base QP closest to the target bitrate and adjust the lambda to correspond to a fractional QP in-between the two closest QPs.

It is proposed to add this functionality to the VTM reference software and is suggested to use it for matching a target bitrate in the context of subjective quality evaluation.

v2 also contains results for low-delay configuration and also some fixes to the results.

It was asked if results for ECM are also available? Not yet.

Results in terms of adjusting to the target rate are slightly less accurate than for the current QP+1 method.

It was commented that VTM has already different approaches for estimating the best adjustment point.

To be further studied in the context of preparing anchors for CfE.

It was asked if the current “QP+1” method was designed to match the target rate +/- 2% (as usually required in past Calls)? Not known, might have been designed 10-15 years ago.

Proponents are requested to prepare rate-matched bitstreams following the conditions defined in JVET-AL2026 in the context of the AHG17 activities.

Decision (SW/non-CTC): Adopt JVET-AL0207, to be included in VTM23.9

AHG13: Film grain synthesis (1+4)

Contributions in this area were discussed during 0725–0920 on Tuesday 1 April 2025 (chaired by JRO).

JVET-AL0207 AHG10/AHG17: On matching target bitrate for subjective quality evaluation [K. Andersson, P. Wennersten (Ericsson)]

See section 4.10.