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Posted by Nalin on Feb-05-2003 07:10:

mp3 question

Why are some mp3s displayed when first opened as being longer in length (be it much longer or just a bit longer) then they really are? Also is there a way to fix this?

For example, I open up an Astral Proj. set using winamp and the set length is displayed as 230 mins yet when I click it to play it, the correct time of of 170something mins is displayed and stays like that untill I create a new list and add that file to my winamp list again. I've noticed this is other occasional sets or tracks. And most importantly, how do I fix it?

Posted by Sonata Arctica on Feb-05-2003 10:51:

Well this requires some basic knowledge of mp3:

An mp3 file has no superblock in any part of the file. This means a program cannot read part of the mp3file to know its size, bitrate, etc.

These values are calculated during playing. For instance if first part of the file takes 30MB in space and contains 30min of music, you can calculate how long the music will be if the complete file is 60MB. But when the last 30MB (due to higher bitrate) only contain 20min of music, the calculation is 10min off. But you will only know when you analyze the whole file!

This ofcourse takes way to much time if an mp3player would do that with every file. So at loading the mp3player loads the first few seconds and then calculates the length of the mp3file. If the bitrate is the same in the whole file (which is normally when you ripped the mp3file yourself) then the calculation will be pretty good. But if you for instance downloaded the file from different sources (different bitrates, broken frames due to broken downloads) the calculation can be way of!

One thing you can do: decode the mp3 to wav and code back to mp3 again, this reduces the quality though . Or try getting the mp3file from one source next time (rip yourself, ftp, whatever )

Posted by Nalin on Feb-05-2003 21:26:

Thank you very much for the explanation.

I can thus conclude that their is no way to fix any such file to be initially displayed by its proper time length?

Posted by Sonata Arctica on Feb-06-2003 00:09:

No, and it shouldn't keep you occupied either

Posted by noikeee on Feb-09-2003 15:48:

I also noticed that winamp counts the bytes needed for the ID3 Tag as part of the track length.. I put an extensive comment with a tracklist on a liveset tag and winamp adds around one minute to the correct length.

Posted by KilldaDJ on Feb-10-2003 22:24:

wow, ive never been in this forum
for a dumb-ass explanation
the mp3 is a vbr, with a fucked header