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Potential serious bug in Apple Lossless codec in iTunes 10
Noble Tiger
post Oct 6 2010, 06:52
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Hi everyone,

I'm using iTunes 10.0.1.22 on Windows Vista Home Premium SP1 64-bit.

I noticed a potential bug in the Apple Lossless Codec in iTunes 10 where if you convert a WAV or AIFF file to Apple Lossless format in iTunes, then convert it back to it's original file type (WAV or AIFF respectively) in iTunes, the resulting files are not the same size in bytes or in time length as the original WAV or AIFF files. The files are usually 5KB or so smaller and can be about 1 second shorter than the original files. I did extensive testing with this using various WAV and AIFF files both generated by iTunes (e.g. ripping a CD track) and by other programs and every time the Apple Lossless codec in iTunes does not convert back to the original file's length or file size. Apple Lossless should convert back exactly, but it isn't. In previous versions of iTunes it did, but not in 10.0.1.22. This may also effect the accuracy Apple Lossess (ALAC) file playback in iTunes and conversion to other formats within iTunes as well.

I think it's a bug, but can anyone else reproduce this on their systems? or is it just on my system?

To test in iTunes:

Convert a WAV to Apple Lossess then back to WAV and compare the two WAV's
Convert an AIFF to Apple Lossless then back to AIFF and compare the two AIFF's
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Engelsstaub
post Oct 6 2010, 10:36
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This is what I got with F2K (and now I know how to do something new...so thanks for that, Robertina.)

CODE
Differences found in 1 out of 1 track pairs.

Comparing:
"...\Desktop\02 Cross My Heart And Hope To Die.wav"
"...\Desktop\original.wav"
Length mismatch : 4:06.503039 vs 4:06.573333, 10870784 vs 10873884 samples



(I modified the log to exclude the full directory and changed the file name of the original WAV ripped with iTunes so that I could differentiate between the two.)


EAC:





This post has been edited by Engelsstaub: Oct 6 2010, 10:48


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The Loudness War is over. Now it's a hopeless occupation.
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andy o
post Oct 6 2010, 14:29
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QUOTE (Engelsstaub @ Oct 6 2010, 02:36) *
This is what I got with F2K (and now I know how to do something new...so thanks for that, Robertina.)

So what about the first WAV conversion you made without iTunes? Seems to suggest the "problem" is in iTunes putting the audio in a wav container, not of the ALAC encoder.
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Engelsstaub
post Oct 7 2010, 05:50
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QUOTE (andy o @ Oct 6 2010, 08:29) *
QUOTE (Engelsstaub @ Oct 6 2010, 02:36) *
This is what I got with F2K (and now I know how to do something new...so thanks for that, Robertina.)

So what about the first WAV conversion you made without iTunes? Seems to suggest the "problem" is in iTunes putting the audio in a wav container, not of the ALAC encoder.


I would have to agree.

(...but my knowledge is limited on much of this and I guess I've been making a few assumptions until now. I would have never came across this "problem" had the OP not brought it up. That's the thing about not being a programmer or even working with a CLI once in a while: everything is GUI and I just trust the software I come to like. I always thought of iTunes (however "Apple" or bloated) as a decent ripper and such.

It would never occur to me to go testing the integrity of a dBpoweramp conversion. I hold Spoon's software in the highest esteem.)

...at this point I've become more a "follower" of the thread as you guys appear a bit more technically adept on its subject matter. smile.gif




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Posts in this topic
- Noble Tiger   Potential serious bug in Apple Lossless codec in iTunes 10   Oct 6 2010, 06:52
- - Engelsstaub   I just tried this and the file sizes are exactly t...   Oct 6 2010, 07:44
|- - greynol   QUOTE (Engelsstaub @ Oct 5 2010, 23:44) T...   Oct 6 2010, 08:45
- - greynol   QUOTE (Noble Tiger @ Oct 5 2010, 22:52) T...   Oct 6 2010, 08:36
- - Engelsstaub   I didn't know that. I just assumed that the fi...   Oct 6 2010, 09:15
|- - Robertina   QUOTE (Engelsstaub @ Oct 5 2010, 21:15) I...   Oct 6 2010, 09:19
- - Engelsstaub   This is what I got with F2K (and now I know how to...   Oct 6 2010, 10:36
|- - andy o   QUOTE (Engelsstaub @ Oct 6 2010, 02:36) T...   Oct 6 2010, 14:29
|- - Engelsstaub   QUOTE (andy o @ Oct 6 2010, 08:29) QUOTE ...   Oct 7 2010, 05:50
- - mixminus1   Confirmed under Windows XP SP3: a 52 second WAV co...   Oct 6 2010, 15:18
- - twostar   Same thing here using iTunes version 10.0.0.68 and...   Oct 6 2010, 15:36
- - mixminus1   It's also interesting that there doesn't s...   Oct 6 2010, 15:58
|- - C.R.Helmrich   QUOTE (mixminus1 @ Oct 6 2010, 16:58) Jus...   Oct 6 2010, 20:09
- - tuffy   It's worth noting that the default block size ...   Oct 6 2010, 16:05
|- - mixminus1   QUOTE (tuffy @ Oct 6 2010, 08:05) It...   Oct 6 2010, 16:39
- - twostar   I wonder if other pre-iTunes 10 versions are affec...   Oct 6 2010, 16:14
- - Corby   Same on Mac version of iTunes. Foobar (running on ...   Oct 6 2010, 17:14
- - Noble Tiger   It looks like it is a bug in iTunes 10. I didn...   Oct 6 2010, 19:19
- - mixminus1   Et viola: CODEDifferences found in 1 out of 1 tra...   Oct 6 2010, 20:28
- - greynol   The problem with 3rd party encoders/decoders is th...   Oct 7 2010, 05:54
|- - Engelsstaub   QUOTE (greynol @ Oct 6 2010, 23:54) The p...   Oct 7 2010, 06:34
- - greynol   Well, no, I'm not ruling out the possibility t...   Oct 7 2010, 06:42
- - Corby   QUOTE (greynol @ Oct 7 2010, 06:54) The p...   Oct 7 2010, 06:46
- - Engelsstaub   If I didn't currently have an iPod I'd lik...   Oct 7 2010, 06:52
- - greynol   I'm part of the camp that thinks lossless on p...   Oct 7 2010, 06:57
- - Engelsstaub   Yeah, I'm sorry too, Corby. (I think I was typ...   Oct 7 2010, 07:26
- - greynol   Briefly and not to belabor the point or change the...   Oct 7 2010, 07:46
- - vitos   I reported this bug to Apple.   Oct 8 2010, 15:02
- - higherlove   I tried ALAC -> AAC(iTunes Plus). Sample omiss...   Oct 8 2010, 21:27
- - dv1989   Noble Tiger, I donít suppose this bug has been fix...   Oct 30 2010, 10:40
|- - Noble Tiger   No, unfortunately Apple hasn't released a new ...   Nov 2 2010, 05:46
- - Noble Tiger   BUG FIXED! It seems this bug has been fixed w...   Nov 13 2010, 22:32
- - mixminus1   Fix confirmed under OS X 10.6.5, iTunes 10.1.54 - ...   Nov 14 2010, 03:37
- - Engelsstaub   I'm glad they fixed this issue. It was making ...   Nov 14 2010, 04:30
- - kawaiigardiner   One of the very reasons I just use iTunes as a med...   Dec 1 2010, 15:46
- - RandyOsbourne   The problem I see in iTunes is a 96khz-24 bit wav ...   Jan 15 2011, 02:43
|- - Engelsstaub   QUOTE (RandyOsbourne @ Jan 14 2011, 19:43...   Jan 15 2011, 06:49
- - mixminus1   Not reproducible using iTunes 10.1.1 under OS X 10...   Jan 15 2011, 03:13


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