[FFmpeg-devel] [PATCH] nvenc: Compensate for hardware trying to mess with aspect ratio of DVD content.

Kieran Kunhya kierank at obe.tv
Sun Jan 18 15:13:00 CET 2015


On 18 January 2015 at 13:55, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Sun, Jan 18, 2015 at 01:28:36PM +0000, Kieran Kunhya wrote:
>> On 18 January 2015 at 12:22, Michael Niedermayer <michaelni at gmx.at> wrote:
>> > On Sun, Jan 18, 2015 at 02:52:59AM +0100, Hendrik Leppkes wrote:
>> >> On Sun, Jan 18, 2015 at 1:02 AM, Nicolas George <george at nsup.org> wrote:
>> >>
>> >> > L'octidi 28 nivôse, an CCXXIII, Kieran Kunhya a écrit :
>> >> > > Oops I misunderstood, you mean the software must comply with the users
>> >> > wishes.
>> >> >
>> >> > Yes.
>> >> >
>> >> > > Anyway my argument is that BT601 should be the default for the these
>> >> > > resolutions.
>> >> >
>> >> > If you want, but that must happen immediately when the contents enters into
>> >> > FFmpeg's data structure, not at a random point in the processing chain.
>> >> >
>> >> >
>> >> Without arguing for or against BT.601 behaviour...
>> >>
>> >> nvenc should behave the same as libx264, or any other video encoder, if
>> >> this patch makes it do that, then it should be applied.
>> >
>> > Yes, and AFAICS an earlier mail from philip indicates this is the case
>> > "
>> >     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
>> > "
>> >
>> > In above example the user asks for a NON BT.601 format 720x576 at
>> > SAR 64:45 and a DAR related to 720x576 NOT 702 or 704x576 of 16:9
>> > yet nvenc gives her something else
>>
>> Here's the point where I give up and start my own fork where things
>> are done properly.
>
> please elaborate about where you disagree
>
> I think theres a misunderstanding between people on what some of the
> aspect ratios mean and what they refer to

Read
https://web.archive.org/web/20130328121216/http://lipas.uwasa.fi/~f76998/video/conversion/

and ETSI TS 101 154 (specifically the section on h264 aspect_ratio_idc):
www.etsi.org/deliver/etsi_ts/101100_101199/101154/01.11.01_60/ts_101154v011101p.pdf

Kieran


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