I'm actually developping a class system to read/write into MP3's ID3v2.4 tags. I've found this description about footers on the site www.id3.org:
3.4. ID3v2.4 footer
To speed up the process of locating an ID3v2.4 tag when searching from the end of a file, a footer can be added to the tag. It is REQUIRED to add a footer to an appended tag, i.e. a tag located after all audio data. The footer is a copy of the header, but with a different identifier.
ID3v2 identifier "3DI"
ID3v2 version $04 00
ID3v2 flags %abcd0000
ID3v2 size 4 * %0xxxxxxx
The ID3v2.4 footer is marked as optional, but here it's seems that into some cases, this footer is required. So, this description is not easy to understand. My questions are :
- Is ID3v2.4 footers are optional or required ?
- If optionals, in whitch cases there are required ?