1) I don't agree with the fact that small blocks matter more. The ETS lab ran tests with the HM and demonstrated that as the QP increases, smaller blocks are neglected at the profit of bigger ones. At QP 37, more than 50% of the blocks are 64x64. This is true for the HEVC test sequences of classes B (1920x1080), C (832x480) and E (1280x720). This ratio is less for the sequences in class D (416x240) where no more than 40% of the blocks are 64x64.
The blocks that did get split may have consumed the majority of the bits, though. Not splitting them may cause the residual to grow very large. We'll see in practice.
2) More experiments need to be carried out to make sure replacing context bins by a fixed value of 50% isn't a false good idea. Observations were carried out at QP 30. Do they hold at QP 20 and QP 40?
Yes. But I expect that if it works for QP 30, then it's going to keep working at least for one QP direction (up or down, I don't know which).
3) I would probably also look at the intra 16x16 modes selected prior to doing any processing at the 32x32 level. We should look for a common direction/mode. My gut feeling tells me that if all modes are very different, intra 32x32 will rarely win. I think that this will be especially useful to skip intra 32x32 at borders where intra 16x16 are better suited to capture the signal characteristics.
Yes, that's the correlation test I was referring to.
4) Did you mean 32x16 and 16x32 searches in "then the 32x32 search is performed, and possibly 16x8 and 8x16 too, following the same logic as the 16x16 CB.” ? AFAIK, inter 16x8 and 8x16 would have been carried out by the time we get to the 32x32 level. In fact, AMP look to be triggered when 16x8 or 8x16 are competitive.
Yes, typo. Thanks for the review. Laurent -- To unsubscribe visit http://f265.org or send a mail to [email protected].
