JVET-AK0169 AHG13: Film grain synthesis improvement using frequency shaping [P. de Lagrange (InterDigital)] [late]

This contribution reports about the implementation of a soft frequency window instead of a rectangular frequency cutoff, when using film grain synthesis based on the FGC SEI message in frequency-filtering mode. This is reported to visually improve the synthetic grain.

example of soft frequency window (natural and squared)

example of 2D soft frequency window (compared to rectangular window):
natural (top) and squared (bottom)

Only the generation of grain patterns is changed, such that typical hardware implementations could still be used.

The rectangular window approach is described as an example in the SEI message, but not mandatory to use it.

Decision: It was agreed to include this in the draft for v2 of the FGS report JVET-AK2020.

It is noted that software used in recent investigations on film grain are in a git repository of AHG13. It should be investigated to potentially attach relevant parts of it to the TR version 2, and/or add them to VTM.