Re: Measuring Input/Output latencies
Re: Measuring Input/Output latencies
- Subject: Re: Measuring Input/Output latencies
- From: Ross Bencina <email@hidden>
- Date: Thu, 25 Aug 2011 12:58:44 +1000
Hi Stéphane
2) Measured latency differs from the driver reported latency, we were
assuming that:
Input latency = Input latency safety offset + Input latency + IO buffer
size
Output latency = IO buffer size + Output latency + Output latency
safety offset
So global IO latency would be : Input latency safety offset + Input
latency + 2 * IO buffer size + Output latency + Output latency safety
offset
As Brian said, defining "input latency" as the sum of
kAudioStreamPropertyLatency and kAudioDevicePropertyLatency the above
formula is what we're currently using in PortAudio.
We have noticed some discrepancies between actual and reported latency in
our own testing but the PA loopback test is still under development.
But we see this reported "extra loopback latency".
Does this value correspond to some additional ADC/DAC conversion latency?
I wonder if there are other system level audio processing/SRC in place, and
where the latency of these elements is reported.
Thanks
Ross.
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