Recording artifact issue when recording with RemoteIO
Recording artifact issue when recording with RemoteIO
- Subject: Recording artifact issue when recording with RemoteIO
- From: John Nastos <email@hidden>
- Date: Thu, 29 Nov 2012 15:46:35 -0800
I'm running into a problem that has me stumped -- I'm wondering if anyone here has experienced a similar issue.
I'm recording audio in my iOS app with a RemoteIO audio unit. At first, it works fine, and records clean audio.
Eventually in the life of the app, I start hearing weird artifacts in the recording. A little static followed by what seems like almost an odd echo of sorts.
I've confirmed that doesn't have to do with how I'm writing the audio to disk -- I've drawn the waveforms on the screen while recording and can see the artifacts in the waveform as well.
I'd post code, but there's a relatively large amount of it -- I'm hoping that someone might be able to recognize the issue from the sound of the recordings.
One important factor may be that I'm playing output via one audio unit and recording through another. I'd use the normal design pattern of one unit to handle both, but I need to synchronize the input/output and I haven't found a good way to do that with just one audio unit. The echoing, however does not come from it picking up the output. I've confirmed by turning the volume off and speaking or clapping instead -- still get the artifacts.
Here's what the recording sounds like when it's clean (just a recording of a metronome):
Here's what it sounds like with the artifacts:
And an example of what the waveform with artifacts looks like:
Reinitializing the audio unit between record sessions doesn't seem to solve the issue. Killing the app and restarting it does. Sound familiar to anyone?
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