I have not heard of any issues at the hardware level or HAL level with
hardware running at 192K, other than potentially bandwidth issues on
constrained busses (e.g. USB). Depending on the bit depth and number
of channels involved, it's quite possible to run out of isoch bandwidth.
One thing you might run into though is that to maintain an ~11.5ms IO
cycle, the buffer size would increase from the default of 512 frames
to 2048 frames. If this is the case, you probably need to update each
AU's kAudioUnitProperty_MaximumFramesPerSlice property to be large
enough.
On Mar 29, 2007, at 8:10 AM, Evan Olcott wrote:
I've finally gotten my hands on a small interface that does 192kHz
sample rate, and we're testing the apps with them, because some
users have reported that they won't playback at that sample rate.
Well, I can confirm this, but what seems to be happening is the HAL
Output Unit is not calling AudioUnitRender at all!
I have *extreme* error checking at every level (wrapped in Cocoa),
and *nothing* is reporting any errors.
Yet when I call AUGraphStart, nothing happens when the sample rate
is 192kHz. All other sample rates with the same hardware device work
fine.
Is this the fault of the driver? Of the HAL Output Unit? Something
I'm not configuring properly? I wished there was an error that would
point me in the right direction, but everything seems happy in the
setup calls...
Thanks in advance for any pointers!
--
Jeff Moore
Core Audio
Apple
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