On Wed, Jul 18, 2018 at 12:22:21AM +0200, Hendrik Leppkes wrote: > On Wed, Jul 18, 2018 at 12:13 AM Carl Eugen Hoyos <ceffm...@gmail.com> wrote: > > > > 2018-07-17 23:58 GMT+02:00, Hendrik Leppkes <h.lepp...@gmail.com>: > > > On Tue, Jul 17, 2018 at 11:54 PM Carl Eugen Hoyos <ceffm...@gmail.com> > > > wrote: > > >> > > >> 2018-07-17 21:39 GMT+02:00, Vittorio Giovara > > >> <vittorio.giov...@gmail.com>: > > >> > YUV410P requires that sizes are divisible by 4. > > >> > > >> Do you mean that AV_PIX_FMT_YUV410P requires it? > > >> Where is this documented? > > > > > > Its a consequence of the subsampling factor. 4:1:0 is one-fourth the > > > horizontal resolution and half the vertical resolution, as such the > > > width has to be a multiple of 4 for that to result in a valid chroma > > > dimension. > > > > (Apart from the fact that it appears to work here and is needed to > > archive some multimedia files.) > > Why wouldn't the chroma dimension be rounded up? > > >
> Where is it ever specified that this would be the case? > If I'm an API user, and I get an odd image size with such a > subsampling factor, what guarantees do I have that the chroma plane is > big enough to be rounded up, and I don't overread the buffer, or > process garbage information? This is a good question. I would argue that logic gurantees this, because without the chroma plane being large enough you would have vissible areas with luma samples but no chroma samples. But besides logic, i think all of our code works this way, FFmpeg itself would overead if this wasnt true > > Its the same with 4:2:0 images, non-mod2 images using 4:2:0 are just > flat out invalid, or non-mod4 if they are interlaced even. But this is not really true. There are many files that have mod2 != 0 with 420. For example this is common in jpegs. gimp for example will happily create such files you just crop or scale and you have a 50% chance to get that on export [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB Its not that you shouldnt use gotos but rather that you should write readable code and code with gotos often but not always is less readable
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