iTunes 8.1.1.10 PC Problem
On our previous article “CAS 5 – CD Ripping”, we have proven that iTunes is a good audio file player. Personally, it is the best GUI program and more importantly, the playback output is bit transparent for CD ripping and playback. However, recently we heard more Weiss user reports that the iTunes doesn’t sound good for high resolution file, and Daniel also shared some measurements with us. This is an update article about our findings on iTunes version 8.1.1.10
We test iTunes version 8.1.1.10 on both PC & MAC.
When you use iTunes (PC & MAC). The first thing you should do is uncheck those DSP processing like Crossfade, Sound Enhancer, Sound Check etc. These are under the Preference setting.
Turn OFF the Equalizer (uncheck the on box), even all the settings are 0dB but ON, your music playback quality will be highly affected. on MAC iTunes ( Under top menu bar – “Windows Tab” apple key + option key + 2) / PC iTunes (Under top menu bar – “View”)
We did some loop test. What is a loop test? We playback the file from iTunes and capture the output back to computer to compare. Since digital is binary number, if the playback output and record input is transparent, the I/O loop should carry the bit transparent identical data. For more details regarding the loop test, please read our CAS 5 – CD Ripping article.
iTunes MAC with our Audiophile Jazz Prologue III various resolution formats.
Mac iTunes => 16/44.1 & 24/96 & 24/192 => Weiss AFI1 => PC Lynx => Wavelab
We lined up the captured file in sync with the original file. Flip the priority (L&R) on one file and playback both file together. If they carry identical data, their waveform will cancel out each other, and the result is no output level down to 24bit limit (-144dBFS).
In ALL resolution, the Wavelab captured file is bit identical with the source file. The result proves Mac iTunes 8.1.1.10 is bit transparent on playback.
PC iTunes 8.1.1.10
We did the same thing with PC iTunes
PC iTunes => 16/44.1 & 24/96 & 24/192 => Weiss AFI1 => PC Lynx => Wavelab
The PC iTunes playback CD resolution file (16bit/44.1kHz) perfectly, our CAS 5 – CD Ripping article is still remain valid. However playback 24bit/96kHz & 24bit/192kHz files are not bit transparent to the source file. This is a shocking bad thing! ***(UPDATE: you can get bit transparent playback on iTUNES PC by setting up the correct QuickTime Preference setting. More info please read CAS8 : http://www.designwsound.com/dwsblog/?page_id=1720)***
More testings:
We did another tests by using SARACON to convert one of our 24bit/96kHz file to 24bit/44.1kHz file. We playback this 24bit/44.1kHz by PC iTunes and recapture with Wavelab. The test result shown there is a truncation on -96.33dBFS (@16bit).
Conclusion:
Mac iTunes 8.1.1.10 produces bit transparent results on all our tests: 16/44.1 & 24/96 & 24/192
PC iTunes 8.1.1.10 produces bit transparent result on CD format (16bit/44.1kHz). The digital data higher than 16bit (20bit-24bit) or sampling rate (96kHz & 192kHz) are changed by PC iTunes playback engine. ***(UPDATE: you can get bit transparent playback on iTUNES PC by setting up the correct QuickTime Preference setting. More info please read CAS8 : http://www.designwsound.com/dwsblog/?page_id=1720)***
The following test is using Wavelab as playback and record engine on 24bit/192kHz with bit transparent result.
On the PC, is it Vista or XP? Could it be Kmixer artifacts?
Hi glt, this is not kmixer articfacts. We also use Wavelab WDM driver which is bit transparent.
hi ,WDM驱动好像会改变数据，以前用RME的digital check测过，用wmp播放16bit会升到24bit，估计是开了dither，但用MME就没问题。
这个测试是基于WDM的吗？itune可以用MME测试一下吗？可能问题出在微软WDM身上？
This is not about WDM or MME problem. Play 16 bit is okay, but playback 24bit, the last 8 bits are not transparent.
Well, iTunes 8.2 is out…
The problem remains with iTunes 8.2………..
When playing 24bits 96Khz/192kHz does the audio preferences of the QuickTime Player were changed to reflect the bit depth/bit rate of the track played ?
Hello Greg, Do you mean on PC or Mac? If it is MAC, the QT movie inspector does provide the bit / sample rate of the audio. However under Audio Midi, you will need to choice the correct sampling rate.
Except your audio interface is using ASIO or Amarra.
I mean on a PC. When on a PC you open the Qt player and goes to Edit/Preference/Quicktime Preferences (may not be exactly that as my OS is French) and then go to the audio tab, you can set the sample rate and the bit depth of the output sound device. So I was wondering if this was not for iTunes some kind of Windows Equivalent of the Mac Audio Midi App and if these values were not used by iTunes to up-sample or down-sample the tracks it plays.
Hello Greg, I checked your QT preference, it has nothing to do with iTunes setting, at least not like the Mac Audio Midi setup.
Hello Greg, thanks for your writing, I have further look at the QT preference and found out that my older blog regarding PC iTunes is not bit transparent above 16/44.1kHz was due to the QT setting reason. I will write up an update later this week. Thanks.
Hello, it’s nice to read that. I suspected something (based on listening) but had no way to check if bit transparent playback could be achieved by adjusting QT preferences. Thanks for doing the formal testing and also for the very interesting articles on your blog.