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Old 2005-07-11, 04:29 PM
4candles 4candles is offline
Join Date: Nov 2004
Re: SBE fix gives different result with shntool & flac front-end?

Originally Posted by Five
I was fixing a similar set recently where it just needed padding on the last track. I was thinking that I could add the padding manually in CEP, so I decided to try it with FLAC frontend first and really zoom in and look at what it does. The last few samples aren't zero samples, they have values like 12, which is very very very close to zero. I remember something about how cd players don't like it when the final sample is a zero, it has to be a little different. So I'm thinking that maybe both FLAC frontend and SHNtool pad the last track with "almost zero" samples at the tail end, perhaps these samples are slightly different. I've also taken a track which was padded by FLAC frontend and mixpased the inverted original over it and came up with a perfect flat line, so the difference should be in the padding by my theory. I can't recall if I did this, but another test to do would be to pad the track, then open it with a wav editor and only remove the padding (remember to turn smoothing off!), resave then generate a SHNtool md5 and see if there is any variance.

Hopefully we can get to the bottom of this when I find a couple hours to test all these variations. I can't get to it tonight, if somebody wants to beat me to it I won't be offended.
I don't think it's a case of FLAC doing something clever - it's clear from looking at the source code that it's a bug.

If you use a hex editor to look at the WAV file "fixed" by shntool, you will see that it contains the correct number of zero-valued bytes at the end.

If you look at the WAV version of the last track "fixed" by FLAC, then you will see that the first half of the padding is zero, but the second half isn't. This is easier to see if the last track you are fixing doesn't already have silence at the end.
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