On Jun 3, 2014, at 12:18 PM, Laurent Birtz <[email protected]> wrote:
> >> 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. The tests simply observed the percentage of CTBs of each size. They didn’t observed the differences between the cost of using a 2Nx2N CU against four NxN CUs. I do agree with your logic that not merging blocks that should have been merge will have less of an impact than not splitting a CU that should clearly have been. The latter case would result in either a steep increase in bit-rate, or very poor quality because of aggressive quantization. We want neither of these options. > > >> 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). > Just for the sake of science, we should test it before. A couple of videos 3 ~ 4 should be enough. > >> 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 NP François > -- > To unsubscribe visit http://f265.org > or send a mail to [email protected]. > -- To unsubscribe visit http://f265.org or send a mail to [email protected].
