iTunes, Audio MIDI Setup, and all that
by, 10-31-2011 at 10:31 PM (2871 Views)
One of the first things I learned when I first visited this site about a year and a half ago was the following:
iTunes (on OS 10.6.X at the time) will only play a track bit-perfectly if Audio MIDI Setup's sample frequency matches that of the track in iTunes. Otherwise it (or core audio?) up/down samples. I was told that in order to play a 96kHz track without resampling directly after playing a 44.1 kHz track, it was not enough simply to reset Audio MIDI Setup, but one had to first reset Audio MIDI Setup to 96kHz, then quit iTunes, then restart iTunes, and then play the 96kHz track.
Most of my quest with third-party software has been to make that transition more seamless. The differences in sound quality, to my ear, through my equipment (which upsamples everything), is not particularly striking.
Anyway, today Paul mentioned in another thread that more current versions of iTunes no longer necessitate the quit/restart cycle. If there was a way to automatically read the native sampling frequency of the track about to be played, match it to that of Audio MIDI, and if necessary pause the track and change it, then resume playing, you could get bit-perfect playback with iTunes with no further heroics.
I have no reason not to believe this, but I am suspicious, because it sounds almost too good to be true. Moreover, Bob Stern and I cobbled together a shell-script and iTunes plug-in to do this. I've now got versions for 10.6 and 10.7.
If someone could verify that iTunes indeed now behaves as Paul says, I would be happy to make these freely available to the community. Please let me know...