On Dec 22, 2005, at 3:22 AM, Ruedi Heimlicher wrote:
Hi
Experimenting with WHackedTV, I get a strange behaviour:
Normally, recording works fine. But from time to time, the input is
instable and produces loud noise itself. restarting the app solves
the problem until next time.
I use the app to let my kids at school record their reading to
control themselves.
The main change I made is to let the level meter show the input
level while recording.
I tried to programmatically set the input gain to zero at startup
and then set it to the normal level. But this did not help.
What could that be? Is that a hardware damage?
I've not heard any reports of loud noise while recording. What's
probably happening is that you're doing too much processing on the
real-time audio IOProc thread, and that's causing enough of a
slowdown that it overloads the cpu and the hal misses IO cycles,
resulting in glitches, or loud noises. You can verify this for
yourself by building HALLab (it's in the CoreAudio section in /
Developer/Examples/CoreAudio/HAL, and running it while your modified
WhackedTV is running. You can monitor notifications coming from the
record or playback devices, and it will soon become apparent if
you're causing overloads.
Another essential tool to use when tracking down such issues is
Shark. It comes with Apple's CHUD tools. It lets you see where your
app is spending all of its CPU time.
Finally, what device are you recording from and previewing to?
-Brad Ford
QuickTime Engineering
Thanks for every response
Ruedi_______________________________________________
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