[vlc-devel] [PATCH] mp3: id3: support id3v2.4 tag for id3 chapter markers

[Wang Gary]

Rémi Denis-Courmont <remi at remlab.net> 于2021年2月19日周五 上午2:18写道：
> Sorry about the delay but the original patch could really use more
> explanations of the changes...

I'm sorry for that, it's my first time sending an email-based patch, in fact,
I'm still not sure about how to use it correctly, please let me know if I did
something wrong.

> > Previously VLC4 cannot load chapter markers from MP3 files that contain the
> > ID3v2.4 tag, which caused by ID3TAG_ReadSize will always read the chunk
> > size in an ID3v2.3 fashion. The syncsafe bit is also not used to determining
> > how we read the chunk size here.
>
> May well be so, but this would have belonged in the original patch
> description.

Do I need to send a v2 patch with those as the commit description? If needed,
is there any other place that needs to be changed so I can send the v2 patch
with the changed code? Thanks!

Francois Cartegnie <fcvlcdev at free.fr> 于2021年2月19日周五 上午2:37写道：
> I spent few hours with hex editor trying to understand that mess and
> libid3's code did not help me on this.
>
> Finally found by comparing all the specs(using the latest and the v2.0
> does not reveal the inconsistencies). The v3 spec does not mention
> syncsafe... so I guess that's the reason.

Thanks for your time! The ID3 spec is pretty confused to me too.
Reading the v2.3 [1] and v2.4 [2] spec could help a little, and I also
read taglib's implementation to help me understand these. Hope that
helps!

[1]: https://id3.org/id3v2.3.0
[2]: https://id3.org/id3v2.4.0-structure