Re: Audio Playback Latency
Re: Audio Playback Latency
- Subject: Re: Audio Playback Latency
- From: Brian Willoughby <email@hidden>
- Date: Wed, 14 Jan 2009 15:16:59 -0800
In order to get the predictability you want, I believe you need to be constantly providing audio buffers to an output device, even if you have to send silence when you don't want to hear anything. Once you get the pipe primed, the latency should be predictable. You don't say which API you're using for playback, so I assume that the variability is coming from startup times when you transition from playing nothing to playing your desired audio.
Brian Willoughby Sound Consulting
On Jan 14, 2009, at 15:04, Andrew Butcher wrote: I've searched the archives, and I've found information on computing latency and reducing latency, but I haven't found anything regarding the amount of variability in latency. I would take take as much as a 1 second delay, if it was constant, and always exactly 1 second.
On Tue, Jan 13, 2009 at 6:01 PM, Brian Willoughby <email@hidden> wrote: I'm not sure that this answers your question, but you can query the audio output device for its latency (be sure to add the multiple latency values for the device stream and channels) and any AudioUnits in your signal path. The sum total of all latencies along the way will tell you the difference between "now" and when the audio will be heard. Check the mailing list archives for more detailed discussion.
On Jan 13, 2009, at 14:26, Andrew Butcher wrote:
I need a way to accurately get a time stamp for when playback from a speaker begins. Any constant latency between the timestamp and playback is perfectly acceptable in my application, but variations between the timestamp and actual playback time are very problematic.
Can anyone suggest a highly accurate way of getting a timestamp for when playback begins? I've tried grabbing the time from the render callback, but it doesn't seem to be any more accurate. I've got a mean playback time that varies on the size of my buffer, but a standard deviation of about 4ms that I can't seem to reduce.
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