[FFmpeg-devel] [PATCH 1/3] libavfilter/scale2ref: Add constants for the non-ref input

Kevin Mark kmark937 at gmail.com
Tue May 30 12:57:09 EEST 2017

On Sun, May 28, 2017 at 12:14 PM, Gyan <gyandoshi at gmail.com> wrote:
> If you do, I suggest 'mdar' for main_dar which is the only one that ought
> to be required.
> The scale filter adjusts the SAR of the result so that the DAR is preserved
> i.e. when a 100x100 canvas w/ SAR of 2.0 is scaled to 50x100, the result
> will have SAR 4.0. In the scale2ref filter, this adjustment is made so that
> the ref's DAR is effected onto the scaled result. I don't believe your
> patch changes this behaviour. Now, the overlay filter does not respect the
> overlay input's SAR - a 100x100 canvas of SAR 2 is overlaid as a square -
> so having a shorthand for the main DAR and promoting its use will silently
> enforce a visually correct-looking input for overlays and other compositing
> uses.

Sounds good. If my understanding is correct, you would recommend changing the
scale2ref=iw/6:iw/(6*main_a) [main][ref]
example to
scale2ref=iw/6:iw/(6*mdar) [main][ref]


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