[FFmpeg-user] Crop, Scale, Pad without distortion

[William Caulfield]

On Sun, Jan 26, 2020 at 7:28 PM Hans Carlson <forbyta at gmx.com> wrote:

> On Mon, 27 Jan 2020, Carl Eugen Hoyos wrote:
>
> > Am Mo., 27. Jan. 2020 um 03:27 Uhr schrieb Hans Carlson <forbyta at gmx.com
> >:
> >
> >> Is 16/9 the correct value for setdar since that's what I want it to end
> >> up to be?
> >
> > Apparently not but it is what you told us you'd like. (I did not
> > calculate myself)
>
> OK... perhaps I don't know WHAT dar I want.  I plan to concat this video
> to some others (using concat protocol or demuxer) and the other videos
> have a DAR of 16:9, eg:
>
>    Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, top first),
> 720x480 [SAR 32:27 DAR 16:9], Closed Captions, 29.97 fps, 29.97 tbr, 90k
> tbn, 59.94 tbc
>
> So, based on that, I assumed it would be a good idea to match the aspect
> ration (720x480) and the DAR.
>
> If the DAR value doesn't matter when concat'ing multiple files, then I
> just
> want the video to LOOK correct.
>
> How do I calculate the correct dar (and/or sar) values to use?
> _______________________________________________
>
>
Your larger issues are all coming from the anamorphic aspects of PAL and
NTSC. They are not "right" to begin with, but will play back at the correct
resolution using DAR. You need to take the original PAL 720x576 4:3, trim
it  to 704x416, then resize it to 720x480 with 16/9 DAR. Then you can
combine the two with the 16/9 DAR and they will play back correctly. (This
is highly over-simplified without doing the math).

This, of course does not address the framerates. Either the 25fps PAL or
the 29.97fps NTSC will need to be converted to the other.


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