[ID3 Dev] Why is footer not included in total size?

[Andy]

I am pretty sure that footers are only to be written to a file when the tag
is appended, not pre-pended.


On 14/11/06, Jim <jmartin92 at comcast.net> wrote:
>
>  Hi.
>
> I am wondering what the reasoning was behind the size stored in ID3v2.4tags not including the size of the footer (if present).
>
> I've been looking through the source code for some utilities for MP3 files
> and some other audio file types.  Many of these utilities use a simple
> method for skipping over the ID3v2 tag if it is there.  They read the first
> 10 bytes of the file, do some simple checking (look for 'ID3', check that
> version bytes are less than $FF and in some cases check that size bytes are
> syncsafe, i.e. < $80) and if it looks like a tag, convert the size and
> skip that many bytes ahead (+ 10 bytes for header).  Most of these utilities
> would be broken if the tag has a footer.  They don't do any specific version
> checking or checking of the flags byte.
>
> If the size stored in ID3v2.4 tags included the footer size (if it is
> present), it would make these tags much more backwards compatible.  (I know
> it is a pretty easy change to add checking for the footer flag but wouldn't
> it have been better to make it compatible with older apps that don't really
> need to read the tag, just skip it?)   Were there reasons that came up
> during development why it was done the way it is?  If so, I'd appreciate if
> someone could share them with me.  Or if there is somewhere I can read about
> this (like some archive of the mailing list) I would appreciate someone
> pointing me in the right direction.
>
> Thanks.
>
> Jim Martin
>
>



-- 
Andy.
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