[FFmpeg-user] Quicktime DV MOVs - 2 different SAR informations

[Christian Ebert]

* Christoph Gerstbauer on Thursday, May 15, 2014 at 16:56:29 +0200
> I was a little bit wrong:
> 
> Fileprobe 1 has a CORRECT SAR value: SAR 59:54 -> DAR 295:216
> Because Digital PAL SD sources do have a SAR of 59:54 -> SAR 1.09:1 ->
> DAR 295:216 (in common it is also named as 4:3, but technical it is
> not 4:3)
> Analog SD sources have a SAR of 1.07:1 and THAT is the real 4:3 Aspect
> Ratio.
> Info to this facts: http://www.mikeafford.com/blog/2009/03/pal-d1-dv-widescreen-square-pixel-settings-in-after-effects-cs4-vs-cs3/
> So the b.) values is correct.

But applications like QuickTime will play them slightly
distorted. For example "4:3" will be display the entire picture
at SPAL 768x576.

> Fileprobe 1:
> a.) 720x576 [SAR 16:15 DAR 4:3]
> b.) SAR 59:54 DAR 295:216
> 
> Therfore: only Fileprobe 2 has a wrong SAR 178:163 -> SAR 1.09:1 ->
> DAR 1958:1467 (close to 4:3, but the video is 16:9)
> 
> Fileprobe 2:
> a.) 720x576 [SAR 64:45 DAR 16:9]
> b.) SAR 178:163 DAR 1958:1467

You are not saying what your practical purpose is, but one way to
show/transcode a "4:3" DV PAL (almost) undistorted for a computer
screen would be (also according to the reference you gave) by
cropping 9px off left and right:

ffmpeg -i in.mov -vf crop=iw-18:ih,scale=768:576 -f null /dev/null 2>&1 | grep 'Video: rawvideo'
    Stream #0:0(eng): Video: rawvideo (I420 / 0x30323449), yuv420p, 768x576 [SAR 767:768 DAR 767:576], q=2-31, 200 kb/s, 90k tbn, 25 tbc (default)

The minimal inaccuracy can then be "corrected" with setsar:

ffmpeg -i in.mov -vf crop=iw-18:ih,scale=768:576,setsar=1/1 -f null /dev/null 2>&1 | grep 'Video: rawvideo'
    Stream #0:0(eng): Video: rawvideo (I420 / 0x30323449), yuv420p, 768x576 [SAR 1:1 DAR 4:3], q=2-31, 200 kb/s, 90k tbn, 25 tbc (default)

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