So I noticed that a track I was playing sounded really distorted in iTunes, even though I know the file itself should be of high quality. I tried the track in Quicktime and, sure enough, it sounded perfect and distortion free. Decoding it to Wav using QT and iTunes resulted in different files, where the iTunes Wav was distorted whereas the QT one was OK (in both players), which leads me to believe something's up with the decoder in iTunes..

A snippet of the AAC in question (it should be really noticeable towards the end):

http://www.hydrogenaudio.org/forums/index....ost&id=5405

Is anyone else able to reproduce or is there just something on my end??

well, I successfully played it back in Safari with no apparent sound quality issues, but I was unable to find a way to download it and play it back in iTunes... any suggestions?

(on a side note, who is the artist/group in question? it's quite different from my usual musical tastes, but I think I'd still find it an interesting listen)

Right-click the link and 'save link as' .m4a type MP4 on your HDD..FWIW, it does sound distorted when playing with iTunes..Not so via quicktime..Playing on lappy with Vista..

Confirmed on WinXP SP3 w/iTunes 9.0.1 and Quicktime 7.6.4.

iTunes playback causes distortion on the stereo synth hits, while playback via Quicktime (both the standalone player and the Firefox plugin) is perfectly clean. I did a quick encode of a file using Nero @ q 0.5 and it was fine in iTunes.

Interestingly, foobar2000 won't play the file (or even display properties) - here's the error from the console:



yet iTunes will properly display all the tags and file info (which shows that it was encoded with Quicktime 7.6.3 via XLD, which has never caused problems for me).

The track is 'Morpheus' by french electronica producer Etienne de Crécy.. Good stuff!



Hmm that's strange. I trimmed the file with QT X, though, which I guess could be the reason for that error.

It'd be interesting to see if the distortion is there with previous versions of iTunes too, I'm pretty sure I would have noticed it earlier but you never know..

iTunes 9.0.0.7 has the exact same distortion, but iTunes 7.6.1.9 is clean, as is VLC 0.9.6 and 1.0.1 (reads the tags just fine, too).

Would it be possible for you to upload less than 30 seconds of that track (but still retaining that segment) with the beginning uncut, i.e. either rip to WAV/AIFF, trim out that section and encode with XLD, or use Quicktime Player X to cut 30 seconds in?

Further edit: Actually, if you could do both, that would be ideal.

It's a bug in TNS decoding introduced in iTunes 9. I found it about 15 minutes ago. Will be fixed in the next release.

I find this issue curious. I was under the impression that iTunes used the QuickTime libraries for decoding. Where in in the chain is the bug, exactly?

iTunes uses its own decoder for AAC and MP3, its own encoder for MP3, and the CoreAudio encoder for AAC.

I'm definitely having distortion playing back MP3 files as well, not just AAC.
Also the problem for me seemed to actually start in a late version of iTunes 8.
For some reason it seems to be even worse while sending audio over AirTunes.

QUOTE (Busemann @ Sep 23 2009, 17:06)
So I noticed that a track I was playing sounded really distorted in iTunes, even though I know the file itself should be of high quality. I tried the track in Quicktime and, sure enough, it sounded perfect and distortion free. Decoding it to Wav using QT and iTunes resulted in different files, where the iTunes Wav was distorted whereas the QT one was OK (in both players), which leads me to believe something's up with the decoder in iTunes..

A snippet of the AAC in question (it should be really noticeable towards the end):

http://www.hydrogenaudio.org/forums/index....ost&id=5405

Is anyone else able to reproduce or is there just something on my end??

I am having a very similar problem, all my songs in Itunes when played have distorted sounds, audio clipping or freeze up and this happened all of sudden for no reason with ITunes 9.01 which was working for a few days perfectly until yesterday. I played itunes files in QT with no problem and I been searching forums for help with this issue. So far I tried updated sound drivers, directx drivers, I changed options on QT in control panel to 16 bit, even put it in wavsound safe mode from the default direct sound, turn off eq in itunes adjusted preamp & turned off sound enhancer too. I even updated my windows vista to SP2 for the heck of it hoping it would fix the problem. I have a sound blaster X-FI and I changed various options with sound card settings with no results. I know it is not my system or sound card: Current Specs 3.2 ghz intel processor, 3gig ram, sb blaster x-fi and so on. Also, played music with wmp player and dvds no clipping. I dont know if this makes difference in identifying the problem, but the windows startup sound clips and distorts too for some reason. I hope someone has the magical solution to fix this issue short of reinstalling windows in hope of fixing the issue.

I forgot to mention that already reinstalled itunes and tried older ver 8.2 to see if that would work and did full virus scan & spyware scan too. Still no luck

Can anybody confirm that this is actually the case in the new 9.0.2?

It seems to be fixed!

iTunes 9.0.2 seems to fix the decoding problem with this sample.