Odd heights

[rakslice]

I don't know how much this really matters, since maybe everyone just avoids this case already for now by just not calling with height values that obviously don't work, but for posterity:

When the height of the video is an odd number, we get some lines of chroma error at the top, and a single line of it at the bottom.

Also for some odd heights but not others it seems like the bottom line is truncated in the pre-scaling video (this is easier to see at lower resolutions with something like this caption with a gap underneath at the bottom):

I suspect playing back videos where the resolution is not a multiple of the subsampling is probably a bad time generally because of all the instances in the code of stuff like:
height >> p[i].ss.y
and
((width * height) >> (p[i].ss.x + p[i].ss.y))
i.e. right shifting by the subsampling bits, in other words dividing by the subsampling multiple rounding down, when you need to round up -- the actual plane obviously has to have another line to cover the last less-than-a-full-subsample's-worth lines of the overall image.

But just fixing instances of those that I could find isn't enough on its own. There's something that needs the extra full subsample worth of lines in the output image, I guess. The hack of just doing e.g.:

    height = ROUND_UP(height, 2);

at the top of nvCreateSurface2() and

    picture_height = ROUND_UP(picture_height, 2);

at the top of nvCreateContext() does make all the problems go away, at least testing from mpv.

[elFarto]

I think that would be fine to add those ROUND_UPs in. It has no effect on 'normal' evenly sized videos so it shouldn't be an issue.

[thesword53]

The issue is in CUVIDDECODECREATEINFO where ulTargetWidth and ulTargetHeight should be multiple of 2. In ffmpeg ulTargetWidth and ulTargetHeight are rounded up to 2.

cuviddec.c:167 FFmpeg n7.1

    // target width/height need to be multiples of two
    cuinfo.ulTargetWidth = avctx->width = (avctx->width + 1) & ~1;
    cuinfo.ulTargetHeight = avctx->height = (avctx->height + 1) & ~1;