PICARD-3029: Incorrect mapping of case-variant tags in MP4 files

[jpmsousa03]

Summary

• This is a…

  • Bug fix
  • Feature addition
  • Refactoring
  • Minor/simple change (e.g., a typo)
  • Other

• Description (1-2 sentences):
  A change has been applied to mp4.py, ensuring that _casemap is checked before applying pre-mappings. This prevents duplicate tags from being saved in the file.

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Problem

Although _casemap correctly stores the capitalization of a tag when loading, an issue arises if a stored tag (e.g., ----:com.apple.iTunes:Label) shares the same internal Picard tag as one of the pre-mapped cases (e.g., label). In such cases, the internal tag would be converted to the pre-mapped format (e.g., ----:com.apple.iTunes:LABEL) when saving. This leads to duplicate tags in the saved file.

• JIRA ticket (optional): PICARD-3029

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Solution

The fix prioritizes maintaining the original tag capitalization. When saving or deleting a tag, _casemap is checked before applying the pre-mapped cases.

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Action

Additional actions required:

• Update Picard documentation
• Other (please specify below)

[phw]

Thanks for the bugfix. This looks sensible and should work.

But I'd like to test this some more and make sure the change does not have other side effects. Changing the order of tag processing could easily break some other case.

I'm currently low on time, hence it will take a couple of days until I get to testing this change fully.

[jpmsousa03]

Sure! Let me know if I can help with anything. I'll also keep testing to check if there are any case where the processing might break.

[phw]

Thanks a lot. I checked this, and I can't see that it would break anything. General change is good o go, I just have two minor stylistic comments.

And sorry for the longer delay, last two weeks didn't exactly turn out as expected for me.

[phw]

Looks good, thanks a lot. LGTM

As a side note I wonder whether we need something similar for ID3. I haven't checked the code yet, but it might have the same issue.

[jpmsousa03]

Thanks! I'm not sure if it happens in ID3 as well, I haven’t looked at the ID3 code yet, but I might take a look when I get some time.