When processing a video with fpcm audio, ffmpeg always produces an error

[Dave Branagh-Miscampbell]

Summary of the bug:

When processing a video with an audio track with fpcm encoding (produced via QuickTime), ffmpeg always produces the following error

[mov,mp4,m4a,3gp,3g2,mj2 @ 0x123104280] Unsupported 'chnl' box with version 1, flags: 0error reading header
[in#0 @ 0x6000018e4000] Error opening input: Invalid data found when processing input
Error opening input file AssetVideo_original.mov.
Error opening input files: Invalid data found when processing input

How to reproduce:

1. Open a video with an audio track in QuickTime
2. Trim the video using the built-in QuickTime tools
3. Save the video
4. The resultant video has an fpcm Audio codec
5. Attempt to load the video using ffmpeg -i [PATH TO VIDEO]
6. FFMPEG produces the error message described above

[Dave Branagh-Miscampbell]

A mov file produced in QuickTime using the Trim feature which exhibits the bug in question

[Gyan]

This is a regression since d7e864366be2c4807d6d0796177051ad32c6378d
Use 6.0 or older versions for such files.

This is a QT branded file with a chnl box instead of a chan box as expected by ffmpeg.
May be better to fall back on default layout assignment in these cases rather than aborting.

[James]

Fixed in cd92ef77c95d3483b29089d09142bc1eb0b1df2b, and backported to release/8.1, release/8.0, release/7.1, and release/7.0 branches.