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-Brading Software Message Board
+--Forum: Mp3/Tag Studio Support and Bug Reports
+---Topic: Mass set flags on whole file messes up CRCs started by iamnoone


Posted by: iamnoone on Feb. 14 2003,02:57

Recently I upgraded my OS and hadn't gotten around to installing good ol' Winamp, and was using Windows Media Player (WMP).  I was surprised to find known working mp3's not working in WMP.  The seek slider would move along as well as the time, but there would be no sound.  With all the changes to my system, it took a while to find the cause.  I used v2.16 when that was the current version on a large set of files.  Among other tools, I used the set Mass flags options to clear out the flags throughout the whole files.  In files with CRCs, this caused the CRCs calculated at playback to differ from the stored CRCs.  The reason it took so long to discover is because Winamp will still output the sound even if the CRC fails.  It seems Media Player skips bad frames.

I downloaded the most recent version 3.05 to see if the problem has been fixed; it has not.  However, there is now a pop-up dialog when selecting "whole file", but the warning it gives is vague.

I can only guess that the problem arises because:
1) The flags are included in the CRC calculation, and the CRC doesn't get updated.  So maybe a "fix CRC's" tool could be added in the future.
OR
2) The flags AREN'T in the CRC calculation, but some other part of the data frame is being altered that shouldn't be.

Like I said, there is a warning now, but it would it be desirable
to have the problem fixed.  Hope this helps.
Posted by: Magnus Brading on Feb. 14 2003,12:29

Yes, such a "CRC correction" tool is already on the todo list for a future version.
And you are correct, the flags are included in the crc'd data, nothing else is altered.

Sorry for any trouble, I will try to make that warning message a bit more clear about the CRC issue too.
Posted by: Gary Hammer on Mar. 06 2003,00:48

You can use mp3Trim to fix the CRCs in those files. The tool is free for basic functions like that.

< http://www.logiccell.com/~mp3trim/ >
Posted by: Magnus Brading on Mar. 06 2003,02:09

Thanks for the tip Gary.
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