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Created attachment 4712 [details]
Unit test case for this issue
When using AudioUnit instance to record PCM audio from IOS device microphone, all audio bytes returned in callback method are zeros. On IOS simulator audio data is returned as expected.
Attached unit test case to reproduce this issue. Unit test passes on IOS simulator running on Mac but fails when running on IOS device.
Tested with following software and hardware versions:
Xamarin.iOS version 126.96.36.199
iOS Simulator version 6.0 and SDK version 6.1
iPhone 4S device having iOS version 6.1.3
I'm happy to provide any help or additional information which helps you solving this issue.
It seems you're mixing Input and Output incorrectly in your test case. The microphone is an input device, while you're setting stuff for output (playback code?).
The test case works for me with the following change:
diff --git a/Users/poupou/Downloads/AudioUnitTest/MicrophoneTests.cs b/Users/poupou/Downloads/AudioUnitTest2/MicrophoneTests.cs
index 2bd75b6..2dfcb24 100644
@@ -43,7 +43,7 @@ namespace AudioUnitTest
//Configure audio unit to record PCM audio
AudioStreamBasicDescription desc = AudioStreamBasicDescription.CreateLinearPCM (8000, 1, 16, false);
- audioUnit.SetAudioFormat(desc, AudioUnitScopeType.Output, 1);
+ audioUnit.SetAudioFormat(desc, AudioUnitScopeType.Input, 0);
//Set AudioUnit render callback method
status = audioUnit.SetRenderCallback( (actionFlags, timeStamp, busNumber, numberFrames, data) =>