[FFmpeg-devel] [PATCH 2/3] avcodec/nvenc: Handle non-square pixel aspect ratios

[wm4]

On Sat, 17 Jan 2015 13:37:30 +0100
Michael Niedermayer <michaelni at gmx.at> wrote:

> On Fri, Jan 16, 2015 at 08:48:59PM -0800, Philip Langdale wrote:
> > On Fri, 16 Jan 2015 22:17:56 +0100
> > Nicolas George <george at nsup.org> wrote:
> > 
> > > Le septidi 27 nivôse, an CCXXIII, Philip Langdale a écrit :
> > > > Right. It is display aspect ratio, not sample aspect ratio. And then
> > > > you have the 45/44 problem, unless that's somehow just affecting me.
> > > 
> > > IIRC, the tests you ran were not accurate enough to know for sure. I
> > > suggest the following test case:
> > > 
> > > - start with a 832 × 448 input (testsrc=s=832x448 should do the
> > > trick);
> > > 
> > > - force darWidth / darHeight = 19 / 17 (patching the source directly
> > > seems like the simplest way of doing it for this kind of tests);
> > > 
> > > - encode to H.265 elementary stream;
> > > 
> > > - check the output file with the ffmpeg summary AND ffprobe
> > > -show_stream AND ffmpeg -vf showinfo -f null -.
> > > 
> > > The numbers are selected with unambiguous prime factors.
> > > 
> > > I do not have access to nvidia hardware, so I can not run the tests.
> > 
> > Ok. I did this test and it produces correct results - SAR 133:221 which
> > yields the correct final aspect ratio, but if I try and do a real world
> > case, like my PAL DVD, it goes wrong - and Timo's patch goes wrong too,
> > with this same weird 1.02 (45/44) scale factor.
> > 
> > It's making my head hurt.
> > 
> > So I feed in this input:
> > 
> > Stream #0:0: Video: rawvideo (RGB[24] / 0x18424752), rgb24, 720x576
> > [SAR 64:45 DAR 16:9], 25 tbr, 25 tbn, 25 tbc
> > 
> > With libx264, I get the same SAR and DAR out.
> > 
> > With nvenc, I get:
> > 
> > sample_aspect_ratio=16:11
> > display_aspect_ratio=20:11
> > 
> > which is everything off by ~1.02.
> 
> this leaves the explanation that "nvidias stuff is buggy" as the
> obvious explanation

Leave it to them to fix their shit? The user gets what nvidia intends.