Re: USB Audio - Strange Behavior of Explicit Feedback calcul
Posted: Thu Jan 02, 2014 3:40 am
Apple's tech note certainly pushes the implicit feedback method.
I went ahead and implemented it as a definable. Here's my results:
1 - Windows and Theyscon driver. Theyscon uses implicit feedback not matter if set for explicit or implicit on the device. Works well. Input and output track each other +-1 sample max.
2 - iOS. Implicit feedback has issues with an iPhone at least. Tracking wonders around, and can cause a buffer "sync" (my code is +-24 samples). 48K sample rate is much better, but still not perfect. Explicit feedback is required in my testing. +-2 samples were achieved with stability.
3 - OSX. Not tested yet.
4 - Linux. Didn't work with Ubuntu V12, either implicit or explicit. Didn't explore yet.
I went ahead and implemented it as a definable. Here's my results:
1 - Windows and Theyscon driver. Theyscon uses implicit feedback not matter if set for explicit or implicit on the device. Works well. Input and output track each other +-1 sample max.
2 - iOS. Implicit feedback has issues with an iPhone at least. Tracking wonders around, and can cause a buffer "sync" (my code is +-24 samples). 48K sample rate is much better, but still not perfect. Explicit feedback is required in my testing. +-2 samples were achieved with stability.
3 - OSX. Not tested yet.
4 - Linux. Didn't work with Ubuntu V12, either implicit or explicit. Didn't explore yet.