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

Nicolas George george at nsup.org
Mon Jan 19 14:42:31 CET 2015

Le nonidi 29 nivôse, an CCXXIII, Philip Langdale a écrit :
> Right. And it's obviously wrong if you consider that trying to encode
> any square pixel content at this size results in non-square output.
> I'd also argue that bt.601 semantics come into play when you're
> authoring the DVD, and any transcoding you do after that should
> preserve the input characteristics - and that means the encoded SAR is
> based on a 720 pixel width. Why on earth my transcoded file should have
> a different SAR from the original when doing a digital->digital
> conversion is beyond me.

I believe part of Kieran's point is: you do not encode to anamorphic 720×576
unless you are actually authoring a DVD, and in that case it should conform
to BT.601.

This makes sense: if you are starting with nice square pixels from HD
contents, why on Earth would you stretch them to an absurd resolution?

On the other hand, if you are authoring a DVD, you are encoding to MPEG-2,
not H.264, and therefore you are not using nvenc, so this is still absurd.

And of course, the fact that is behaves differently than every single other
encoder makes it a braindead design, even if the result is, in some regards,
considered correct.


  Nicolas George
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