| JCTVC-O0091 AhG 5 and 18: Sample Adaptive Offset on High Bit-depth [W.-S. Kim, J. Sole, M. Karczewicz (Qualcomm)]
(Reviewed Thu 24th evening GJS)
(This was an information document.)
In this document it is reported that the sample adaptive offset (SAO) does not work properly when bit-depth is high. It is reported that in the case of 16 bit video coding SAO is used in 0% of LCUs in a picture, thus providing 0% coding gain. As HEVC Range Extension covers high bit-depth video coding, it is encouraged to perform further study to resolve the issue.
It was remarked that the way the design currently interacts with bit depth is to scale up the SAO offsets as bit depth increases, which may make them so large at high bit depths as to be useless.
Also, the edge classifiers are not scaled up, and become extremely sensitive to noise.
The contributor noted that there were previous relevant contributions, e.g. N0201 and N0246.
Some approaches were suggested as being promising.
Further work in AHG was encouraged.
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