Strange Error when using AVAudioRecorder with MPEG4AAC
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I have tested this on two different iPad3s and on one I can record and playback both .m4a and .caf files on the other I can only playback .caf files. 
 
What I do is record a .m4a-file using the setting

    AVFormatIDKey set to kAudioFormatMPEG4AAC

On the one iPad it works fine. If I test it on the other iPad I get the error "OSStatus error 1685348671" when I try to play the file recorded.

However if I comment out that setting and record as a .caf-file it works flawlessly.


Here the relevant code snippets:

    NSDictionary *recorderSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                          //[NSNumber numberWithInt:kAudioFormatMPEG4AAC], AVFormatIDKey,
                                          [NSNumber numberWithInt:AVAudioQualityMin], AVEncoderAudioQualityKey,
                                          [NSNumber numberWithInt:16], AVEncoderBitRateKey,
                                          [NSNumber numberWithInt:1], AVNumberOfChannelsKey,
                                          [NSNumber numberWithFloat:16000.0], AVSampleRateKey, nil];

I then go and call a simple

    AudioRecorder *audioRecorder = [[AVAudioRecorder alloc] initWithURL:soundFileURL settings:recorderSettings error:&error];

To play back I call

    AudioPlayer *audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:soundFileURL error:&error];
    [audioPlayer play];

Thanks

