iTunes AAC bad quality encodes
2006-02-09 00:03:36
After reading about the listening test here on HA praising 128kpbs iTunes AAC and such I decided to do my own listening test with real music I listen to. I'm not very experienced with this, so I started at 64kbps to spot problem regions under the assumption that these will remain problem regions with similar artefacts at higher bitrates. Besides lots of other things I noticed that the stereo image was not correct, but thought this was normal for 64kbps (maybe its using is, or whatever). However, to my surprise the stereo image problems remained up to 128kbps "VBR" (I was going in steps) and even at 192kpbs "VBR". I can't imagine no one noticed this untill now. Even 192kpbs is a piece of cake to ABX cause of this. To make sure it's not the decoder I also decoded using iTunes with the same results. Original sample can be downloaded here . (Since I'm new to this: should I have uploaded the encoded version, too?) The thunder right at the beginning is not correctly positioned. Also the second, higher frequency synth sound (the one that is percusion-like used and to the right, first used after the main synth "melody" begins) sounded strange at 128kpbs (and is also not correctly positioned) -- didn't bother to check at 192kbps. Granted, the problem is not an anoying one -- I probably couldn't tell which is which without direct comparison, but anyways I'm less than impressed by iTune's performance. I wouldn't have thought that AAC is so easy to ABX even at 192kbps VBR:foo_abx v1.2 report foobar2000 v0.8.3 2006/02/09 00:02:12 File A: file://H:\test\thunder.wav File B: file://H:\test\_\_\_ 00 - _.m4a 00:02:13 : Test started. 00:02:42 : 01/01 50.0% 00:02:49 : 02/02 25.0% 00:02:55 : 03/03 12.5% 00:02:59 : 04/04 6.3% 00:03:13 : 05/05 3.1% 00:03:20 : 06/06 1.6% 00:03:26 : 07/07 0.8% 00:03:30 : 08/08 0.4% 00:03:45 : 09/09 0.2% 00:03:50 : 10/10 0.1% 00:03:54 : Test finished. ---------- Total: 10/10 (0.1%) iTunes version used: 6.0.1.3 Can anyone confirm my findings? Is this a known problem? Edit: wording, last sentence
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