Re: Core Audio playback precision on iOS devices (and simulator)
Re: Core Audio playback precision on iOS devices (and simulator)
- Subject: Re: Core Audio playback precision on iOS devices (and simulator)
- From: Kyle Sluder <email@hidden>
- Date: Fri, 16 Jul 2010 08:37:23 -0700
On Fri, Jul 16, 2010 at 7:53 AM, Antonio Nunes <email@hidden> wrote:
> To the best of my knowledge, the technique I use here is sample precise, and should achieve near absolute precision (well, sub-microsecond precision anyway). However, when I play this back, and record the sound in a sound editor, I do not see the precision I was expecting. Playback is very good, but there is a small, accumulating lag on each subsequent tick. I first thought I had my math wrong somewhere, or had setup the audiounit incorrectly, but upon double checking all the parameters look correct. In addition, since I was getting these results in the simulator, I decided to measure performance on the actual iPad too. Not to my surprise, there was a small accumulating lag, but much to my surprise, the lag was significantly smaller than in the simulator.
"Precision" and "usleep()" don't mix. It looks like your -driver
method is trying to play catch-up with your realtime audio thread? If
you wind up sleeping for long enough in the call to usleep() to
exhaust the stack of samples, you're going to start lagging.
--Kyle Sluder
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