ios - 将来自麦克风的音频录制为 .wav 格式并使用 Xamarin.ios 中的 AudioUnit 进行播放

Question

我正在尝试将来自麦克风的音频数据记录到 .wav 文件中并进行播放。我还需要实际数据(振幅)来绘制图形，所以我使用的是 AudioUnit。我为 AudioUnit 对象设置了 inputCallBack 和 renderCallBack 但我不知道如何从 render_CallBack 方法将 AudioBuffers 写入 .wav 文件。我附上了我到目前为止尝试过的代码。

请帮帮我...

步骤 - 1

AudioStreamBasicDescription audioStreamBasicDesc;
AudioUnit.AudioUnit audioUnit;
string m_recordingFilePath;
ExtAudioFile extAudioFileObj;

public override void ViewDidLoad()
{
    base.ViewDidLoad();        

    audioStreamBasicDesc.SampleRate = 16000;
    audioStreamBasicDesc.Format = AudioFormatType.LinearPCM;
    audioStreamBasicDesc.FramesPerPacket = 1;
    audioStreamBasicDesc.ChannelsPerFrame = 1;
    audioStreamBasicDesc.BytesPerFrame = 
                                audioStreamBasicDesc.ChannelsPerFrame * sizeof(short);
    audioStreamBasicDesc.BytesPerPacket = 
                                audioStreamBasicDesc.ChannelsPerFrame * sizeof(short);
    audioStreamBasicDesc.BitsPerChannel = 16;
    audioStreamBasicDesc.Reserved = 0;
    audioStreamBasicDesc.FormatFlags = AudioFormatFlags.IsSignedInteger | 
                                       AudioFormatFlags.IsPacked;

    var documents = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
    var tmp = Path.Combine(documents, "..", "tmp");
    m_recordingFilePath = Path.Combine(tmp, 
        String.Format("{0}.wav", 
            "MyFile" + DateTime.Now.ToString("MM-dd-yyyy HH-mm-ss",
                                             CultureInfo.InvariantCulture)));       
    extAudioFileObj = ExtAudioFile.CreateWithUrl(CFUrl.FromFile(m_recordingFilePath), 
                                                 AudioFileType.WAVE, 
                                                 audioStreamBasicDesc, 
                                                 AudioFileFlags.EraseFlags);
    prepareAudioUnit();
}

步骤 - 2

public void prepareAudioUnit()
{                            
    var _audioComponent =   AudioComponent.FindComponent(AudioTypeOutput.Remote);

    audioUnit = _audioComponent.CreateAudioUnit();

    audioUnit = new AudioUnit.AudioUnit(_audioComponent);

    audioUnit.SetEnableIO(true,
        AudioUnitScopeType.Input,
        1 // Remote Input
    );

    // setting audio format
    audioUnit.SetAudioFormat(audioStreamBasicDesc,
        AudioUnitScopeType.Output,
        1
    );                                    

    audioUnit.SetInputCallback(input_CallBack, AudioUnitScopeType.Input, 1);

    audioUnit.SetRenderCallback(render_CallBack, AudioUnitScopeType.Global, 0);          

    audioUnit.Initialize();
    audioUnit.Start();
}

步骤 - 3

AudioUnitStatus input_CallBack(AudioUnitRenderActionFlags actionFlags, 
                               AudioTimeStamp timeStamp, 
                               uint busNumber,
                               uint numberFrames, 
                               AudioUnit.AudioUnit audioUnit)
{
    return AudioUnitStatus.NoError;
}

步骤 - 4

AudioUnitStatus render_CallBack(AudioUnitRenderActionFlags actionFlags, 
                                AudioTimeStamp timeStamp, 
                                uint busNumber, 
                                uint numberFrames, 
                                AudioBuffers data)
{
    // getting microphone input signal
    var status = audioUnit.Render(ref actionFlags,
                                 timeStamp,
                                 1, // Remote input
                                 numberFrames,
                                 data);
    if (status != AudioUnitStatus.OK)
    {
        return status;
    }

    //get pointer to buffer
    var outP = data[0].Data;
    unsafe
    {
        var outPtr = (int*)outP.ToPointer();
        for (int i = 0; i < numberFrames; i++)
        {
            var val = *outPtr;
            outPtr++;
            //lastestPickVal = val; //This is for ploting graph
            Console.WriteLine(val);
        }
    }
    extAudioFileObj.ClientDataFormat = audioStreamBasicDesc;
    //Here i am trying to write data into .wav file and file is generated also 
    //but corrupted file without actual data (create file size is approx 4kb or 100 kb )
    var err = extAudioFileObj.Write(numberFrames, data); 
    Console.WriteLine("OUTPUT" + busNumber);
    return AudioUnitStatus.NoError;
}

Answer 1

前段时间我为 Xamarin 写了一个 IAudioStream 抽象，它可能对你没什么帮助。它从 AudioQueueBuffer 获取字节缓冲区，您可能正在寻找的是将缓冲区编码为字节:

https://github.com/XLabs/Xamarin-Forms-Labs/blob/master/src/Platform/XLabs.Platform.iOS/Services/Media/Microphone.cs#L125-L132

还有一个 WAV 录音器类，它连接到源并将其写入 WAV，但这是在提取原始信号之后:

https://github.com/XLabs/Xamarin-Forms-Labs/blob/master/src/Platform/XLabs.Platform/Services/Media/WaveRecorder.cs

我希望这些至少能给你一些帮助。