AVAudioRecorder文件太大

Question

我正在用AVAudioRecorder录制音频，文件太大了。比如20秒，结果是1.2mb？我怎么才能把它变小呢？谢谢。

Answer 1

这是我发现的最好的方法，你也可以使用它：

NSMutableDictionary *settings = [[NSMutableDictionary alloc] initWithCapacity:0];

[settings setValue :[NSNumber numberWithInt:kAudioFormatMPEG4AAC] forKey:AVFormatIDKey];//格式
[settings setValue:[NSNumber numberWithFloat:8000.0] forKey:AVSampleRateKey]; //采样8000次
[settings setValue:[NSNumber numberWithInt: 1] forKey:AVNumberOfChannelsKey];//声道
[settings setValue :[NSNumber numberWithInt:8] forKey:AVLinearPCMBitDepthKey];//位深度
[settings setValue :[NSNumber numberWithBool:NO] forKey:AVLinearPCMIsBigEndianKey];
[settings setValue :[NSNumber numberWithBool:NO] forKey:AVLinearPCMIsFloatKey];
//Encoder
[settings setValue :[NSNumber numberWithInt:12000] forKey:AVEncoderBitRateKey];//采样率
[settings setValue :[NSNumber numberWithInt:8] forKey:AVEncoderBitDepthHintKey];//位深度
[settings setValue :[NSNumber numberWithInt:8] forKey:AVEncoderBitRatePerChannelKey];//声道采样率
[settings setValue :AVAudioQualityMin           forKey:AVEncoderAudioQualityKey];//编码质量

Answer 2

尝试使用不同的格式和/或质量设置。下面的代码应该是一个非常小的文件：

NSDictionary *recordSettings =
    [[NSDictionary alloc] initWithObjectsAndKeys:
     [NSNumber numberWithFloat: 44100.0], AVSampleRateKey,
     [NSNumber numberWithInt: kAudioFormatAppleIMA4], AVFormatIDKey,
     [NSNumber numberWithInt: 1], AVNumberOfChannelsKey,
     [NSNumber numberWithInt: AVAudioQualityMedium],
     AVEncoderAudioQualityKey,
     nil];

    AVAudioRecorder *newRecorder =
    [[AVAudioRecorder alloc] initWithURL: myURL
                                settings: recordSettings
                                   error: nil];

Answer 3

录制的音频文件的大小取决于以下因素。还有其他因素。但下面的内容将值得注意。

1) 采样率

  A 22050Hz sample rate will produce a much smaller file than a 44000Hz sample rate

2) Channels

  Stereo output(2 channels) will produce twice the size of the file of that of a mono (1 channel)

3) 比特率

Bits used per sample.

你需要想出一个最适合你的设置，这样它就不会影响质量和大小。