On Sat, 17 Jan 2015 19:27:17 +0000 Kieran Kunhya <kier...@obe.tv> wrote:
> On 17 January 2015 at 18:14, Nicolas George <geo...@nsup.org> wrote: > > Le septidi 27 nivôse, an CCXXIII, Philip Langdale a écrit : > >> On Fri, 16 Jan 2015 22:17:56 +0100 > >> Nicolas George <geo...@nsup.org> wrote: > >> Ok. I did this test and it produces correct results - SAR 133:221 > >> which yields the correct final aspect ratio, > > > > This is a good start. > > > >> 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. > > > > The 45/44 value looks like 704/720: the sign that some people long > > time ago in committees in the broadcast industry could not agree > > whether the aspect ratio applies to the whole image or only the > > part that is displayed on screen. > > The active picture width is 702 pixels. I would read the following > thread and ETSI TS 101 154 for more information about SAR/DAR etc > https://lists.libav.org/pipermail/ffmpeg-user/2010-March/024551.html > > I haven't quite followed what's going on to decide whether Nvidia or > FFmpeg is correct. For me, the problem is that the encoder is silently doing this aspect ratio fiddling, whether I want it or not. If I want to transcode material at the original size and aspect ratio, I should be able to. If I, for whatever reason, want to adjust for active picture constraints at encode time, I can set the SAR appropriately. So, ffmpeg applies what you tell it to, the hardware adjusts what you tell it by 44/45 - I'd call that wrong. --phil _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel