%_length% and %length%

The first one %_length% is a file attribute and is the running time of the song in minutes and seconds (mm:ss). All tracks have this field.

The second one %length% is a tag and is the running time of the song in milliseconds. I have some tracks that have this tag and some that don't.

Does anyone know how this tag is created? I've tried several different media players (WMP, Musicmatch and Quintessential) and none of them create this tag. I'm wondering why some of my tracks have it and some don't and how it got there.

I think I'm just going to delete that tag off all my tracks since is seems redundant when you have the other field. Has anyone found a use for this tag?

File Attribute?

The length in granulation of milliseconds may be the accurate length of the music part.

Mp3tag's %_length% or %_length_seconds% info fields give a value rounded per second, which may not to be the accurate length of the music part.

Your LENGTH tagfield may have been inserted by some encoding software.

DD.20100225.1939.CET

Thanks for the reply DetlevD.

By file attribute I mean a field that's calculated by the system and a field that can't be edited.

The LENGTH tag isn't consistent. I have a song that's 2:00 min. (_length) 120 (_length_seconds) and the LENGTH is 120000, that's ok. But then I have a song that's 2:01 min. (_length) 121 (_length_seconds) and the LENGTH is 120000, not ok.

If I did want to calculate that tag accurately what software would I use?

To me inaccurate and inconsistent data is useless data, so unless I can find a way to make it accurate I'm going to delete it. Besides, knowing the length of a song to the nearest second is fine with me, I really don't need it more accurate than that.

I've found this thread, which possibly is related to your problem ...
http://www.un4seen.com/forum/?action=printpage;topic=10390.0

Foobar 2000 can do it. In the Properties dialog you can add new Metadata tagfield, e. g. LENGTH_SAMPLES.
Use context menu option "Format from other fields ..." and take as the format string "%length_samples%". After applying the change, the file has a new Tagfield LENGTH_SAMPLES containing the accurate number of samples.

DD.20100225.2312.CET
Edit.
DD.20100225.2324.CET

And CDex also adds a length field.
And creates a corrupt header so that the length field is particularly pointless as the corrupt header hinders the proper seeking.

I did a little more testing and yes I did see that CDex does create the TLEN tag. I tried Exact Audio Copy and it doesn't create the tag, so that explains why some of my tracks don't have the tag because I've used both programs in the past.

I'm going to try out Foobar to see what that does. Thanks for the infornation.