bitRate not work

[bandy101]

IQAudioRecorderViewController *controller = [[IQAudioRecorderViewController alloc] init];
controller.delegate = self;
controller.title = @"Recorder";
controller.bitRate=128000;
controller.sampleRate=8000;
controller.maximumRecordDuration = 60*10;
controller.numberOfChannels=2;
controller.allowCropping = YES;

when I set bitRate,the recorder not work.