AVAudioRecorder相关参数

<!-- lang: cpp -->
    NSMutableDictionary *setting = [NSMutableDictionary dictionary];  
[setting setValue:[NSNumber numberWithInt:kAudioFormatMPEG4AAC] forKey:AVFormatIDKey];//音乐格式  
[setting setValue:[NSNumber numberWithFloat:8000.0] forKey:AVSampleRateKey];//音乐采样率  
[setting setValue:[NSNumber numberWithInt:1] forKey:AVNumberOfChannelsKey];//音乐通道数  
[setting setValue:[NSNumber numberWithInt:1] forKey:AVEncoderBitRateKey];//音频比特率  
[setting setValue:[NSNumber numberWithInt:1] forKey:AVEncoderBitRatePerChannelKey];//标识每通道的音频比特率  

self.recorder = [[[AVAudioRecorder alloc]initWithURL:recordedFile settings:setting error:nil]autorelease];