[FFmpeg-user] prevent clean aperture value cropping

[Tobias Rapp]

On 16/05/2025 09:48, Kieran O Leary wrote:

> Hi
>
> I do think this is a bug, as FFmpeg did not previously behave this
> way. I made an ffv1/mkv from the test video provided, then reversed
> that back to v210/mov. I got matching md5 values when decoding the
> video streams, but the width values appear to be hardcoded to the clap
> value. I used mediatrace within mediainfo as well and could not find
> any trace of '720' in the FFv1 or 'reversed' v210. For example, from
> the original source video:
>
> 3548AF8    Track width:                         720.000
>
> 3548C3E        Width:                           720 (0x02D0)
>
> 3548CA8         apertureWidth_N:                703 (0x000002BF)
>
> 3548CAC         apertureWidth_D:                1 (0x00000001)
>
> 3548DFC     cleanApertureWidth:                 787.000
>
> 3548E10     productionApertureWidth:            787.000
>
> 3548E24     encodedApertureWidth:               720.000
>
>
> and from the reversed mov (source video -> ffv1.mkv -> back to v210.mov)
>
> 4C3EE8    Track width:                         702.000
>
> 34C402E        Width:                           702 (0x02BE)
>
> 34C4098         apertureWidth_N:                702 (0x000002BE)
>
> 34C409C         apertureWidth_D:                1 (0x00000001)
>
> 34C41EC     cleanApertureWidth:                 767.000
>
> 34C4200     productionApertureWidth:            767.000
>
> 34C4214     encodedApertureWidth:               702.000
>
> Best,
>
> Kieran

Hi Kieran,

apparently, by an unexpected coincidence, Andreas has just posted a 
patch that adds a test for this scenario in 
https://ffmpeg.org/pipermail/ffmpeg-devel/2025-May/343619.html.

Since v7.1 there seems to be a new command-line option "-apply_cropping" 
which defaults to on. See 
https://git.ffmpeg.org/gitweb/ffmpeg.git/commit/bf87688a9fb8afdd9fd9150fb6c7d2b4ca10f48c.

Regards, Tobias