gistfile1.m

    AudioChannelLayout channelLayout;
    memset(&channelLayout, 0, sizeof(AudioChannelLayout));
    channelLayout.mChannelLayoutTag = kAudioChannelLayoutTag_Stereo;
    NSDictionary *outputSettings =
    [NSDictionary dictionaryWithObjectsAndKeys:
     [NSNumber numberWithInt:kAudioFormatLinearPCM], AVFormatIDKey,
     [NSNumber numberWithFloat:44100.0], AVSampleRateKey,
     [NSNumber numberWithInt:2], AVNumberOfChannelsKey,
     [NSData dataWithBytes:&channelLayout length:sizeof(AudioChannelLayout)],
     AVChannelLayoutKey,
     [NSNumber numberWithInt:16], AVLinearPCMBitDepthKey,
     [NSNumber numberWithBool:NO], AVLinearPCMIsNonInterleaved,
     [NSNumber numberWithBool:NO],AVLinearPCMIsFloatKey,
     [NSNumber numberWithBool:NO], AVLinearPCMIsBigEndianKey,
     nil];