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

Nicolas George george at nsup.org
Sun Jan 18 00:52:45 CET 2015

L'octidi 28 nivôse, an CCXXIII, Kieran Kunhya a écrit :
> > There is a very simple way of flagging content that is supposed to comply
> > with BT601: the SAR is 512/351. If SAR is 64/45, that means someone before
> > nvenc decided that the video is not expected to conform with BT601, and
> > nvenc has no right to decide otherwise.
> You fail to realise this but SARs are not necessarily arithmetic for
> historical reasons.

Care to explain how historical reasons can change the laws of geometry?

If a visible surface with a physical aspect ratio of 16/9 is cut into
702×576 identical rectangular pixels, then the aspect ratio of each pixel is
(16/9) / (702/576) = 512/351. Can you give one good reason for FFmpeg to
use, internally, any other value?


  Nicolas George
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