Stereo recording with AVAudioRecorder
Stereo recording with AVAudioRecorder
- Subject: Stereo recording with AVAudioRecorder
- From: patrick machielse <email@hidden>
- Date: Fri, 25 Jun 2010 15:44:33 +0200
I'm trying to record some audio on iOS 4 throug the built-in (or external) microphone using AVAudioRecorder. The problem I am having is that the recorded volume for the right channel is always reported as -120 dB (not -160 dB, the documented lowest value). And in fact no audio for the right channel is audible.
I tried this on two devices: an iPhone 3G and an iPod Touch 2G using a plug-in microphone.
When I run the same code in the simulator (finaly audio recording in the simulator, thanks!) the right channel is recorded properly.
Then I tried to find out the number of audio channels supported in hardware as follows:
UInt32 nChannels = 0;
UInt32 size = sizeof nChannels;
OSStatus err = AudioSessionGetProperty(kAudioSessionProperty_CurrentHardwareInputNumberChannels,
&size,
&nChannels);
if ( noErr != err ) {
unsigned int myerr = NSSwapBigIntToHost(err);
char *s = (char *)&myerr;
NSLog(@"AudioSessionGetProperty returned error: \'%c%c%c%c\'", s[0], s[1], s[2], s[3]);
} else {
NSLog(@"device has %d channels", nChannels);
}
Again, in the simulator it reports 2 channels, but on both devices the error code 'what' is returned. This code isn't in the Audio Session results code, but it seems to indicate that AudioSessionGetProperty() doesn't know the kAudioSessionProperty_CurrentHardwareInputNumberChannels property on the device.
I'm out of ideas. Am I'm overlooking something basic, or is audio recording (very) buggy?
patrick
--
Patrick Machielse
Hieper Software
http://www.hieper.nl
email@hidden
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