Lists

Open Menu Close Menu

Terms and Conditions
Lists hosted on this site
Email the Postmaster
Tips for posting to public mailing lists

Re: latency of MusicDeviceMIDIEvent and sampler device on iOS

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: latency of MusicDeviceMIDIEvent and sampler device on iOS

Subject: Re: latency of MusicDeviceMIDIEvent and sampler device on iOS
From: Paul Davis <email@hidden>
Date: Mon, 17 Mar 2014 08:38:24 -0400

On Mon, Mar 17, 2014 at 4:01 AM, Hamish Moffatt <email@hidden> wrote:

Hi,

I'm playing MIDI out through the AUSampler device. I've got a few samplers, a mixer and a RemoteIO output in an AUGraph, and I'm sending note on and note off (etc) events to it at the right time with MusicDeviceMIDIEvent. Because we're using the same code on OSX as well as Windows we're doing our own timing, MIDI sequencing etc rather than using higher level audio frameworks to do it.

Now this works except I'm getting some variable latency from when I call MusicDeviceMIDIEvent until I actually hear the sound. For example we're just playing a metronome, with a regular note on event every 120ms, but sometimes the actual audio is 30ms late. The next event is back on time though.

I'm sure we're calling MusicDeviceMIDIEvent accurately, timing it using mach_wait_until() and mach_absolute_time().

I don't hear any issues at all running the same code on the Mac.

So is there some other way I should be timing this? I'm guessing yes given the sample number parameter on the MusicDeviceMIDIEvent call, but I'm not sure.

If you are trying to sync to audio, you should *always* use the audio clock as the reference, not the system clock, nor any other clock. Some systems will provide you will a DLL or PLL to link the system and audio clocks, but in general if you're already handling audio (i.e. have registered an IO callback with the HAL), then you can just do the timing directly yourself.

As someone who also has to avoid all higher level apple APIs in order to facilitate cross platform portability, welcome to the club :)

 _______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list      (email@hidden)
Help/Unsubscribe/Update your Subscription:

This email sent to email@hidden

Follow-Ups:
- Re: latency of MusicDeviceMIDIEvent and sampler device on iOS
  - From: Hamish Moffatt <email@hidden>

References:
	>latency of MusicDeviceMIDIEvent and sampler device on iOS (From: Hamish Moffatt <email@hidden>)

Prev by Date: latency of MusicDeviceMIDIEvent and sampler device on iOS
Next by Date: AUGraph remove NodeInputCallback
Previous by thread: latency of MusicDeviceMIDIEvent and sampler device on iOS
Next by thread: Re: latency of MusicDeviceMIDIEvent and sampler device on iOS
Index(es):
- Date
- Thread