音频处理（录音二）

录音设置

NSMutableDictionary *recordSetting = [[[NSMutableDictionary alloc]init] autorelease];

录音格式

[recordSetting setValue:[NSNumber numberWithInt:kAudioFormatMPEG4AAC] forKey:AVFormatIDKey];

录音采样率（影响音频质量）

[recordSetting setValue:[NSNumber numberWithFloat:44100] forKey:AVSampleRateKey];

录音通道数

[recordSetting setValue:[NSNumber numberWithInt:1] forKey:AVNumberOfChannelsKey];

线性采样数8、16、24、32

[recordSetting setValue:[NSNumber numberWithInt:16] forKey:AVLinearPCMBitDepthKey];

录音质量

[recordSetting setValue:[NSNumber numberWithInt:AVAudioQualityHigh] forKey:AVEncoderAudioQualityKey];

NSDictionary *recordSetting = [[NSDictionary alloc] initWithObjectsAndKeys:

[NSNumber numberWithFloat: 44100.0],AVSampleRateKey, //采样率

[NSNumber numberWithInt: kAudioFormatLinearPCM],AVFormatIDKey,

[NSNumber numberWithInt:16],AVLinearPCMBitDepthKey,//采样位数
默认 16

[NSNumber numberWithInt: 2], AVNumberOfChannelsKey,//通道的数目

[NSNumber numberWithBool:NO],AVLinearPCMIsBigEndianKey,//大端还是小端
是内存的组织方式

[NSNumber numberWithBool:NO],AVLinearPCMIsFloatKey,nil];//采样信号是整数还是浮点数

NSURL *recordedTmpFile = [NSURL fileURLWithPath:[NSTemporaryDirectory()stringByAppendingPathComponent: [NSString stringWithFormat: @"%.0f.%@",
[NSDatetimeIntervalSinceReferenceDate] * 1000.0, @"wav"]]]; //文件名的设置

//Setup the recorder to use this file and record to it.

AVAudioRecorder *recorder = [[ AVAudioRecorder alloc] initWithURL:recordedTmpFilesettings:recordSetting error:&error];

[recorder prepareToRecord];

[recorder record];

下面代码应该是当前.m文件加载时候就设置

AVAudioSession * audioSession = [AVAudioSession sharedInstance];

[audioSession setCategory:AVAudioSessionCategoryPlayAndRecord error: &error]; //设置音频类别，这里表示当应用启动，停掉后台其他音频

[audioSession setActive:YES error: &error];//设置当前应用音频活跃性