iOS - AVAudioRecorder - recording with ADPCM or IMA

Question

USing these recording settings, I am able to get the AVAudioRecorder to work:

    recordSetting = [NSDictionary dictionaryWithObjectsAndKeys:
//                     [NSNumber numberWithFloat:2048.0f],AVSampleRateKey,
//                     [NSNumber numberWithInt:1],AVNumberOfChannelsKey,
//                     [NSNumber numberWithInt:8],AVLinearPCMBitDepthKey,
                     [NSNumber numberWithInt:kAudioFormatLinearPCM],AVFormatIDKey,
//                     [NSNumber numberWithBool:NO], AVLinearPCMIsFloatKey,
//                     [NSNumber numberWithBool:0], AVLinearPCMIsBigEndianKey,
//                     [NSNumber numberWithBool:NO], AVLinearPCMIsNonInterleaved,
//                     [NSNumber numberWithInt:256], AVEncoderBitRateKey,
                     [NSData data], AVChannelLayoutKey, nil];


recorder = [[ AVAudioRecorder alloc] initWithURL:url settings:recordSetting error:&err];


if(!recorder){
    NSLog(@"recorder: %@ %d %@", [err domain], [err code], [[err userInfo] description]);
    UIAlertView *alert =
    [[UIAlertView alloc] initWithTitle: @"Warning"
                               message: [err localizedDescription]
                              delegate: nil
                     cancelButtonTitle:@"OK"
                     otherButtonTitles:nil];
    [alert show];

    return;
}

As soon as I change this:

[NSNumber numberWithInt:kAudioFormatLinearPCM],AVFormatIDKey,

to this:

[NSNumber numberWithInt:kAudioFormatAppleIMA4],AVFormatIDKey,

I get the following error:

recorder: NSOSStatusErrorDomain 1718449215 {
}

Which is to say, the audio format is not supported. kAudioFormatUnsupportedDataFormatError

What do I need to do to get ADPCM or IMA to work with AVAudioRecorder?

Answer 1

1) Please ensure that you set the session correctly for either Recording (or) Playback (or) Both (ie VOIP) as follows:

[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryRecord error:nil];

2) Use the following code, as this works fine for me (I compress to low quality as I have a messaging app):

NSDictionary *AudioSettings = [[NSDictionary alloc] initWithObjectsAndKeys:
                               [NSNumber numberWithInt:kAudioFormatAppleIMA4], AVFormatIDKey
                               , [NSNumber numberWithFloat:11025.00], AVSampleRateKey
                               , [NSNumber numberWithInt:1], AVNumberOfChannelsKey
                               , [NSNumber numberWithInt:11025], AVEncoderBitRateKey
                               , [NSNumber numberWithInt:8], AVLinearPCMBitDepthKey
                               , [NSNumber numberWithInt:AVAudioQualityMin], AVEncoderAudioQualityKey
                               , [NSNumber numberWithInt:1], AVNumberOfChannelsKey
                               , nil
                               ];

Regards Heider Sati