[ID3 Dev] Tag location

[Jim]

Sorry...I realized after I sent it that the explanation in my previous
message was rather long.

A quick summary would be:  I suggest that you do not write a footer as part
of a prepended 2.4 tag even if it doesn't have any padding.


----- Original Message ----- 
From: "Michal Vician" <id3v2 at audiott.com>
To: <id3v2 at id3.org>
Sent: Friday, January 12, 2007 1:40 PM
Subject: Re: [ID3 Dev] Tag location


> Thanks for quick reply.
>
>  > So far I haven't encountered any software that writes appended
> ID3v2.4 tags.
> That's why I'm asking. Because I want to create one. I have already
> written one library which I use in my application "AudioTT". I found
> this library quite easy to modify and have some free time now. Therefore
> I decided to modify it, so it will be able to read and write all
> versions of ID3v2 and also make conversions between the versions.
>
> > However, in the parsing software I've written, when searching for
appended
> > tags, I look for the 2.4 tag both before and after APEv2 tag.
> Sure. In the spec there is written that you should do it like that.
>
>      1. Look for a prepended tag using the pattern found in section 3.1.
>      2. If a SEEK frame was found, use its values to guide further
> searching.
>      3. Look for a tag footer, scanning from the back of the file.
>
> > And I would still like to see it clarified in the spec that 2.4 tags at
the
> > beginning of a file cannot have a footer.  I think the current wording
is
> > ambiguous.  (To me it means that a prepended tag can have either a
footer or
> > padding but not both.)
>
> Wow. What? I understand it exactly like that ("tag can have either a
> footer or padding but not both"). My implementation currently allows to
> write a footer in prepended tag.
> So, your are saying that prepended tag MUST NOT have footer?? If yes, I
> would logically expect to have in specification something like this:
> 1. "Footer is intended for tag (or part of the tag) located at the end
> of the file. Prepended tag MUST NOT have footer, because footer brings
> no benefit to prepended tag."
> 2. "Padding is intended only for prepended tag. Appended tag MUST NOT
> have padding, because it would be useful, while there are no audio data
> under the tag."
>
>
> Jim wrote:
> > That's the way I've understood it as well.
> >
> > audio data
> > -----------
> > ID3v2.4
> > -----------
> > APEv2
> > -----------
> > Lyrics3v2
> > -----------
> > ID3v1
> >
> > So far I haven't encountered any software that writes appended ID3v2.4
tags.
> > However, in the parsing software I've written, when searching for
appended
> > tags, I look for the 2.4 tag both before and after APEv2 tag.  (Just
because
> > I expect some confusion in early implementations of this.)
> >
> > And I would still like to see it clarified in the spec that 2.4 tags at
the
> > beginning of a file cannot have a footer.  I think the current wording
is
> > ambiguous.  (To me it means that a prepended tag can have either a
footer or
> > padding but not both.)
> > ----- Original Message ----- 
> > From: "Jud White" <jwhite at cdtag.com>
> > To: <id3v2 at id3.org>
> > Sent: Friday, January 12, 2007 11:36 AM
> > Subject: Re: [ID3 Dev] Tag location
> >
> >
> > Michal,
> > That's my understanding (don't forget APE tags).  I think the idea is
that
> > anything aware of ID3v2 tags at the end of the file should be able to
handle
> > its position among other tags, whereas something that only reads ID3v1
> > (+Lyrics3, or +APE) at the end of the file should not be disrupted.
> >
> > Jud
>
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