Problem with MPEG4AAC audio format

[gdg87]

Hi, if i record with audio format MPEG4AAC the encoding doesn't work. This is my recording settings dictionary

NSDictionary *recordSettings = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:kAudioFormatMPEG4AAC], AVFormatIDKey, [NSNumber numberWithInt:AVAudioQualityLow], AVEncoderAudioQualityKey, [NSNumber numberWithInt: 1], AVNumberOfChannelsKey, [NSNumber numberWithFloat:22050.0f], AVSampleRateKey, nil];

I need this settings because only this work with iPad Air.