JVET-R0367 Adjustment of shiftHor calculation in GPM [Y.-Z. Ma, Q.-H. Ran, R.-P. Qiu, M.-L. Zhang, J.-Y. Huo, F.-Z. Yang (Xidian Univ), S. Wan (NPU), Y.-F. Yu, Y. Liu (OPPO)]
In VVC8, a variable is derived to indicate the partitioning line shift direction (horizontal or vertical) in each CU using geometric partitioning mode (GPM). Given some GPM modes with specific angle being utilized for CUs with specific height/width ratio, the shift intervals between candidate partitioning lines are too narrow to be identified from each other. However, the interval can be increased by simply adjusting the shift direction in these cases. In this contribution, a quite simple modification is proposed in calculation method, with which the selected shift direction always lead to wider intervals between the partitioning lines.
The experimental results are as below:
For RA configuration: -0.04%, -0.04%, and -0.07%;
For LDB configuration: -0.04 %, -0.04%, and -0.01%.
It is claimed that the proposed method would be more consistent. However, there is nothing broken, and the benefit in compression is marginal. Stability of the design is more important at this moment.
No action was taken on this.