[Bug]: Covers not loading for m4b audiobooks

[sandreas]

What happened?

I have a library of many m4b's and after upgrading audiobookshelf to a newer version, the covers of newly added m4b files don't show up, although I ensured that the files contain a valid cover.

What did you expect to happen?

I would have expected the covers to show up as normal.

Steps to reproduce the issue

Add the attached file to your audio book folder and wait for it to be scanned.
input.zip

This problem might be related to #1063 and #2885 - but is very specific to m4b files with embedded cover. I found out that the problem is possibly a wrong ffmpeg extraction command in:

audiobookshelf/server/utils/ffmpegHelpers.js

Line 56 in 190a100

/** @type {import('../libs/fluentFfmpeg/index').FfmpegCommand} */

    var ffmpeg = Ffmpeg(filepath)
    ffmpeg.addOption(['-map 0:v:0', '-frames:v 1'])
    ffmpeg.output(outputpath)

which results in

ffmpeg -i input.m4b -map 0:v:0 -frames:v 1 cover.jpg

This command extracts a FULLY BLACK cover for m4b files.

Possible solution
The corrected command that works and extracts the cover as expected would be:

ffmpeg -i input.m4b -map 0:v -map -0:V -c copy -frames:v 1 cover.jpg

or in code

    var ffmpeg = Ffmpeg(filepath)
    ffmpeg.addOption(['-map 0:v', '-map 0:V', '-c copy', '-frames:v 1'])
    ffmpeg.output(outputpath)

but I'm not sure, that this is the place the problem occurs.

Audiobookshelf version

2.17.4

How are you running audiobookshelf?

Docker

What OS is your Audiobookshelf server hosted from?

Linux

If the issue is being seen in the UI, what browsers are you seeing the problem on?

Chrome

Logs

No errors in log files

Additional Notes

Suggested solution should fix the problem.

[sandreas]

Reproduced and fixed the problem on my system - the fix can be used as described above (use other ffmpeg params). I try to submit a PR in the next days.

[advplyr]

Did this PR break it for you? #3529

That update was needed in my testing for multiple embedded covers

[sandreas]

Did this PR break it for you? #3529

I'm going to check this in the next days.

That update was needed in my testing for multiple embedded covers

Yeah, I know that this might cause a regression for other formats not extracting the covers any more. I try to find a generic solution that works for all formats, otherwise I think we must provide a format paramter to switch the parameters depending on the format.

[sandreas]

@advplyr

Did this PR break it for you? #3529

Yes, before this change it worked. Re-checked this also manually via:

# works, cover is extracted as expected
ffmpeg -i input.m4b -map 0:v -frames:v 1 cover.jpg

vs

# creates all black cover
ffmpeg -i input.m4b -map 0:v -frames:v 1 cover.jpg

What does this mean? I think that my version also might work with multi cover files:

ffmpeg -i input.m4b -map 0:v -map -0:V -c copy -frames:v 1 cover.jpg

EDIT: but to be sure I would at least setup some regression tests...