[FFmpeg-devel] [PATCH] FATE: Add test for libavfilter/scale2ref

[Kevin Mark]

On Sun, Jun 4, 2017 at 4:19 AM, Gyan <gyandoshi at gmail.com> wrote:
>  Now that this feature has been applied, it may be helpful to check if one
> of the W/H arguments is of the form '-n' and log a warning that this will
> force the ref's display aspect ratio. The warning should also convey the
> expression to use: 'oh*mdar' or 'ow/mdar' , as the case may be.
>
> Additionally, since the output SAR will be adjusted to force the ref's DAR,
> it would be helpful to add a warning for that (tell users to append
> setsar=1 after the scale)  --or--  (ideally) patch the filter so that the
> main's DAR is preserved.

I was thinking about this as well. The next step for improving the
scale2ref filter is probably patching it to preserve main's DAR, as
you mentioned. It's definitely easy enough to correct with the setsar
filter but given scale2ref's purpose the current behavior still feels
dramatically unintuitive. Perhaps I'm just being unimaginative when it
comes to use-cases but it certainly seems like the vast majority of
uses would involve keeping main's DAR. This would be a breaking
change, unlike the previous patches.

The warning for the "-n" stuff sounds helpful. I'll take a look at this.