Chainik wrote:historically MVTools
since then there're no real evidences that 32px block is somehow better than 16px
and now you want 64 and 128 px
we just don't want to do useless job
But I gave you the evidence you want in the OP. I used a GIF in the OP to show that reducing the frame size(in effect emulating larger block sizes) dramatically reduces the artifacts of animated footage, while preserving camera motion interpolation.
Even the "animation guide" on the SVP website recommends 32px block size, albeit with overlap. I don't recommend the overlap as it doesn't improve camera motion and only increases artifacts, but this and my GIF proves the trend that increasing block size reduces object artifacts while preserving camera motion.
The reason few if any anime/cartoon watchers use SVP is because animation is impossible to motion interpolate without introducing awful artifacts everywhere.
It doesn't matter if you argue that "the algorithm does a pretty good job", because one bad frame is enough to turn off most interested people, and you are guaranteed to get a few bad frames in any animated video.
Increasing the block size allows for camera interpolation in the place of object motion interpolation, which delivers only the benefits of SVP with none of the drawbacks.
64 and say 128px block size would in effect create an option where those who like the idea of camera interpolation, but hate the idea of object interpolation, can still enjoy some benefits to SVP.
Plus as you mentioned, the benefits are also present outside of animated footage, as 4K footage is essentially double the frame size of 1080p footage, so it would make sense to have at least double the block size available, and 8K video is obviously going to happen in the distant future, but could be brought into consideration now.
As a stopgap, I suppose it could be possible to analyse a downsampled 1080/720p-540/360p video but then apply the interpolation to the original footage? I'm not sure if this would reduce performance, though I imagine it could be implemented easily.