|
Rockbox mail archiveSubject: Re: Corrupt recorded fileRe: Corrupt recorded file
From: Michael Hentschel <michael.hentschel_at_gmx.at>
Date: Mon, 09 Feb 2009 10:05:32 +0100 > This is a bug in the chip doing all the MP3 encoding and > decoding in the Archos Recorders and Ondio FM. When recording, > it may happen that a few bits from the encoded bitstream get > lost, so that the mp3 frames are no longer byte aligned, and > most media players become confused. > > All that said, there's a chance to salvage your recording. By > careful checking with a hex editor, you need to find at which > position(s) the bit alignment is shifted. Using this information > it is possible to correct the bitshift, with a simple custom > tool. > Hi Jens, Indeed I figured this out myself by seeking and following the frame headers. The VBR didn't make this task easy, I had a lot of 160kbps and occasionally 192kbps frames. But I found the place where the error occured. I analyzed the next (corrupted) frame header and found out, that indeed I had to shift it by 2 bits to the left(!). This was before your reply, so I was really lucky to spot this fact. After I knew what the problem was, I searched again in the mail archives and found a post about exactly this bug in the MAS. I wrote a small tool to do the bit-shifting, and I had to do this correction a few times (about 5 times in a 2.5 hrs file). The only supprising thing is, that I always had to remove bits from the stream (or did I miss a padding flag?). Anyway, finally the file played well on winamp, however not on Media-Player and neither in my audio editing software (still something wrong with Xing-header, CRCs or bit-reservoir???). But I did an analog rerecording and now I can use it. After all I'm glad I could rescue my recording. Next time I'll go down with recording quality... Thanx for your help and I hope this discussion might help others in similar cases. regards, Mike ------------------------------------------------------------------- List admin: http://cool.haxx.se/cgi-bin/mailman/listinfo/rockbox FAQ: http://www.rockbox.org/twiki/bin/view/Main/GeneralFAQ Etiquette: http://www.rockbox.org/mail/etiquette.html Received on 2009-02-09 Page template was last modified "Tue Sep 7 00:00:02 2021" The Rockbox Crew -- Privacy Policy |