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Latency when starting audio recording stack?
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Latency when starting audio recording stack?


  • Subject: Latency when starting audio recording stack?
  • From: Shaun Guth <email@hidden>
  • Date: Sun, 9 Jan 2011 19:13:28 -0800

Hello,

I'm writing an iPhone application wherein the user can click a button to start recording, and I would like recording to start near-immediately after button press; however,  I am having trouble with a consistent latency of 600-800ms on the first press of the button. (This is on an iPhone 3G, iOS 4.2),

Subsequent button presses result in only a ~20ms delay, which is great; however, if I let the phone idle for a minute or two, then press the button again, I get the same extended delay.

I narrowed it down to my call to AudioOutputUnitStart (when using audio units) or AudioQueueStart (using queue services).

To me, this feels like it could be related to the hardware powering up/down as needed -- is that the case?

If so, any suggestions on a workaround?  I was considering leaving the recording running continuously, but only rendering frames as needed; however, I don't know what the CPU/Battery implications of that are yet.

Thanks,
-- Shaun
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