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

[Michael Niedermayer]

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

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Democracy is the form of government in which you can choose your dictator
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