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Re: how to access HAL buffer timestamps when using AUHAL?
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Re: how to access HAL buffer timestamps when using AUHAL?

Thanks Jeff...

Is there any way to query CoreAudio for the hardware latency? e.g. the time
difference from when a sample enters the audio hardware at
inOutputTime->mHostTime to when it appears as a voltage or optical impulse
on the physical output?

The HAL provides the properties kAudioDevicePropertyLatency and kAudioStreamPropertyLatency. The latency for any particular channel on an audio device is the sum of the device latency and the latency of the stream the channel is in.

Sorry, just to check that I understand, for audio output, are these invariants correct?

inNow->mHostTime - scheduling jitter == scheduledIoProcTime

scheduled IoProcTime + [kAudioStreamPropertyLatency] == inOutputTime->mHostTime

scheduled IoProcTime + [kAudioStreamPropertyLatency] + [kAudioDevicePropertyLatency] == analog voltage output from DAC time


Note that AUHAL proxies most of the HAL's properties, so you can access them straight from AUHAL without dipping down to the HAL's API. 

Thanks

Ross. 

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References: 


 >how to access HAL buffer timestamps when using AUHAL? (From: "Ross Bencina" <email@hidden>)


 >Re: how to access HAL buffer timestamps when using AUHAL? (From: Jeff Moore <email@hidden>)


 >Re: how to access HAL buffer timestamps when using AUHAL? (From: "Ross Bencina" <email@hidden>)


 >Re: how to access HAL buffer timestamps when using AUHAL? (From: Jeff Moore <email@hidden>)























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