Rebuilding an MP3 stream...

[*BTK*]

I posted this on a music forum but no one replied so hopefully someone here can shed some light because i have come across a lot of mp3's that wont play on my ipod classic or my ipod 5.5gen w/rockbox.


Original Post:

Hope I can find someone that has ran tests or researched this, because I can't find too much detailed information.

I want to use the "Rebuild MP3 Stream" feature that is in foobar. Supposedly this, along with the "Fix VBR Header" utility will solve all problems related to mp3 files displaying wrong info or not playing on portable devices. What I would like to know is, what is it that changes when the stream is rebuilt and how does it do it? Is the file decoded then re-encoded or can the program work with the file itself with no extra encoding? If it does de/re-encode, does that mean that there is even more quality loss on top of what was lost in the original CD to mp3 conversion?

I tried this method on a couple files and one stuck out in particular. it was a 4 minute-ish song in high VBR that originally was a little over 7MB. after rebuilding the stream/fixing header the size went down to about 6.5 MB. i can not tell a sound quality difference, and would run wave analysis on the files if i knew how, lol.

Does it sound like there was quality loss since the file size went down half - or even 3/4 of a MB, or could the extra stuff cut out actually been "junk" in the file that was not needed at all to begin with. Has anyone ever analyzed the file afterwards like some do to check if mp3s have been re-encoded from webrips or whatever?


Thanks for any help, I have a lot of files in VBR and I would hate to have to re-rip or re-download because they will not play on my ipod

I would really like to learn more about what causes problems and what actually fixes and how those problems are fixed. Thanks a bunch for anyone that can explain this

[Febs]

This is really not a Rockbox-related question.  I suggest that you post your question on http://www.hydrogenaudio.org.

[*BTK*]

Sorry, I thought I would ask here since I have been coming across the problem of mp3 files not playing when I use Rockbox to see if rebuilding VBR headers or streams would be helpful in Rockbox playing problem files, or if it would possibly make things worse.

I guess my next stop is hydrogenaudio, thanks.

[Febs]

I'll leave your thread open just in case anyone more knowledgeable than I can provide any guidance to you, but the folks at Hydrogen Audio are the real experts when it comes to this sort of thing.  Good luck.