Re: ID3v2.4 Footer

Wed, 02 Jun 2010 10:58:31 -0700

Posted a 'reply on the MP3 programming forum.

: Hello
:
: 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 ?
:
: Thx, regards...
:

For prefixed tags (before the audio stream), you don't need to include either a footer or padding. So in this context they are considered OPTIONAL.

If you choose to include a footer there must be no padding. In other words they are mutually exclusive. You can have one or the other, but you MUST NOT include both.

However, a footer MUST be present when a tag is postfixed (after the audio stream). In this context it is REQUIRED. Since they are mutually exclusive, it therefore follows that padding MUST NOT be included in a postfixed tag.

PCForrest's Feed - Programmer's Heaven

Re: ID3v2.4 Footer