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Old 31st August 2011, 07:37   #13
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some more info from PMs and some other forums folks:

Originally Posted by MrSinatra
I'm not sure about multiple TPE1 or TPE2 frames. Can there be more than one?
There can be multiple artists inside the frame, but surely there can only be one frame, unless some buggy editor messes up....
here's what i know... a single TPE1 or TPE2, etc, frame CAN have multiple values in it, as you know. this is done using a "separator character." e.g. WMP uses ; i think. thats pretty straight forward.

however, what is ALSO true, is that you can have multiple values using "multiple frames." but exactly HOW that is done, i am not sure. so do you get two TPE1 frames, or is it a hack of the TPE1 frame that allows it to seem like two TPE1 frames? i don't know unfortunately, i wish i could better answer that for you.

the way you enter data to get "multiple frames" is not by using a separator character, but it depends on tag type. in mp3tag, you do like // or something for example. the squeezebox server supports this, and in its tag dump will show multiple frames. (its not recognizing a separator character, but rather the insertion of multiple frames somehow)

i however do NOT do this myself, so i have no example files and really can't speak to it. i just know the ability is out there and a lot of "serious" (anal) folks make use of it.
and then this:

Originally Posted by MrSinatra
so the first Q is, how does an app decide which frames it will support such characters?
I would guess necessity, customer demand, and a little common sense. A track can have two or more artists / or album artists, but not two track numbers, titles or album names.

the second Q is, does a standard for this exist anywhere, or is it just an ad-hoc invention?
Mostly ad-hoc. But standards do emerge from common usage, such as that for using TCMP, based on how iTunes uses it.

would a files tag actually have MORE than one frame called TPE1? so like this:

TPE1=Paul Simon
TPE1=Art Garfunkel

is it actually stored in the file that way? meaning, is TPE1 there twice, or is there only one TPE1 frame thats been hacked somehow?
how many multiple frames can there be?
No. There can be only one frame with a given name. Id3v2.4 frames use a null character separator. I believe that technically, it was only introduced in id3v2.4, but Mp3tag also does the same thing with id3v2.3 tags.



4.2. Text information frames

The text information frames are often the most important frames,
containing information like artist, album and more. There may only be
one text information frame of its kind in an tag. All text
information frames supports multiple strings, stored as a null
separated list, where null is reperesented by the termination code
for the charater encoding. All text frame identifiers begin with "T".
Only text frame identifiers begin with "T", with the exception of the
"TXXX" frame. All the text information frames have the following

<Header for 'Text information frame', ID: "T000" - "TZZZ",
excluding "TXXX" described in 4.2.6.>
Text encoding $xx
Information <text string(s) according to encoding>

and how do you do it in mp3tag? do you do two // characters to inject multiple frames, (where // acts as a separator?) how do you know if a file has multiple frames? can u tell in grid view? can any frame be made into multiple frames?
In Mp3tag it's \\. This is just a convention that Mp3tag uses. It appears in both the Tag Panel and in the grid view. In the Extended Tags dialog it always appears as separate fields when there are separate values (id3) or fields (Vorbis comments, APE tags).

It is possible to have \\ as a character sequence within a field, so it's far from a perfect user interface. If you have the character sequence \\ in a field then you save the file, Mp3tag will split the field (which means putting in the null byte separator). I played with it just now and it only does this when you save individual files, not when you save multiple files, so it's a little quirky.

BUG #1 = Winamp skips short tracks
Wish #1 = Multiple Column Sorting
Wish #2 = Add TCMP/Compilation editing
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