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Subject: Re: junk in idv2 tags
From: Bill Napier (napier_at_pobox.com)
Date: 2002-09-16


On Mon, 16 Sep 2002 12:45:02 +0200, "Danijel Ilisin" <d.ilisin_at_wtnet.de> said:
> Hi again, i just tried a different id3 tag editor (named ID3 Edit)
> and guess what: After the ID3V2 data there is plenty of zero
> bytes. Mp3check says this:

> E:\ftp\linus>mp3check -e *.mp3 [01] Roger Sanchez - Another
> Chance.mp3: 419 bytes of junk before first frame header valid id3
> tag trailer v1.1 found

> I mean, that's better than Winamp's version:

> E:\ftp\linus>mp3check -e *.mp3 [01] Roger Sanchez - Another
> Chance.mp3: 626 bytes of junk before first frame header valid id3
> tag trailer v1.1 found

> So it seems there are many tools out there that work that way.

I did some further investigation of my own and found out that mp3check
(at least version 0.7.3) doesn't seem to know about id3v2 headers.
2 examples:

Examples 1:
C:\Documents and Settings\bnapier\Desktop\id3>mp3check -e "Guns N' Roses - Appetite For Destruction - 01 - Welcome To The Jungle.mp3"
Guns N' Roses - Appetite For Destruction - 01 - Welcome To The Jungle.mp3:
355 bytes of junk before first frame header
valid id3 tag trailer v1.0 found

napier_at_billspc:~/rockbox/id3$ ./id3 Guns\ N\'\ Roses\ -\ Appetite\ For\ Destruction\ -\ 01\ -\ Welcome\ To\ The\ Jungle.mp3
version: 3
headerlen: 355
title : Welcome To The Jungle
artist: Guns N' Roses
album : Appetite For Destruction
track#: 1

Example 2:
C:\Documents and Settings\bnapier\Desktop\id3>mp3check -e "04 I Dreamed a Dream.
mp3"
04 I Dreamed a Dream.mp3:
2174 bytes of junk before first frame header

napier_at_billspc:~/rockbox/id3$ ./id3 04\ I\ Dreamed\ a\ Dream.mp3
version: 2
headerlen: 2174
title : I Dreamed a Dream
artist: Exaltshow Ltd.
album : (null)
track#: 0

So what mp3check is reporting as "junk" is really the id3v2 header at
the beginning. And yes, there is a large area of zero's at the
beginning (to simplify changes, as another poster has already pointed
out). But in both of the files I looked at, that area of zero's was
included as part of the id3v2 header (the length of the id3v2 header
was *CORRECT*). If you are going to chop of the id3v2 header from the
beginning, check the length field and trust it. I even used winamp
which did pad out some extra space, but did also adjust the length tag
to get it right.

Long story short: trust the id3v2 length tag, it seems to usually be
correct.

BTW - Linus, I would be interested to see (at least the beginning) of
the mp3 file that had the padding where the length tag was wrong. I
was unable to produce any files like that (even using the blasted
winamp that you seem to dislike so much).

b

-- 
If it happens once, it's a bug.
If it happens twice, it's a feature.
If it happens more than twice, it's a design philosophy.



Page was last modified "Jan 10 2012" The Rockbox Crew
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