[FFmpeg-user] prevent clean aperture value cropping

[Kieran O Leary]

Hi,


On Mon 12 May 2025 at 11:01, Christian Sievers via ffmpeg-user <
ffmpeg-user at ffmpeg.org> wrote:

> Hello,
>
> We would like to transcode v210 (uncompressed 8 bit 4:2:2 PAL) Quicktime
> mov video files to FFV1/MKV for archival purposes.
>
> ffmpeg crops these files, using Quicktime's CLAP atom (clean aperture
> value). We would like to preserve the full 720 pixel width. How can I do
> that?
>

As others have mentioned, this isn’t a true crop but a metadata value that
tells a player to perform a crop. From previous experience, QuickTime
Player was the only tool that obeyed this cropping and VLC ignored it but
that may have changed subsequently.



> I'm using this standard command:
> ffmpeg -i input_file -map 0 -dn -c:v ffv1 -level 3 -g 1 -slicecrc 1
> -slices 16 -c:a copy output_file.mkv


Out of curiosity, are you performing any listlessness checks? That would
also give you some comfort that a true cropping hasn’t been done.



>
> FYI
>  MediaInfo reports this about the original Quicktime file:
> Width                                    : 720 pixels
> Clean aperture width            : 703 pixels
> Height                                   : 576 pixels
> Clean aperture height          : 576 pixels
> Display aspect ratio             : 4:3
> Clean aperture display aspect ratio      : 4:3
>
> and this about the resulting MKV:
> Width                                    : 702 pixels
> Height                                   : 576 pixels
> Display aspect ratio              : 4:3


Does mediainfo not have additional values for width, perhaps
“Original_Width” or something? I’d be surprised if it also didn’t have a
value for 720 but you may need to add a more verbose flag for mediainfo to
display it.

Best,

Kieran