unity录音获取真实音频大小并获取字节流保存录音文件

unity录音长度时提前设置的并且结束录音后大文件大小也是预设大小，保存文件的话就会有许多无效字节，这里提供一种方法截取真正的AudioClip大小。需要注意的是先调用获取真实大小录音的方法再调用 Microphone.End(null);结束录音。

public AudioClip RecordedClip;
void 开始录音(){
  RecordedClip = Microphone.Start(null, false, 60, 16000);
}
void 停止录音(){
     byte[] data = 获取真实大小录音(ref RecordedClip);
     Microphone.End(null);
     string path = Application.persistentDataPath + "/录音.wav";
     Debug.Log("保存录音文件:" + path);
     using (FileStream fs = CreateEmpty(path))
      {
          fs.Write(data, 0, data.Length);
          WriteHeader(fs, RecordedClip); //wav文件头
      }
}
public static byte[] 获取真实大小录音(ref AudioClip recordedClip)
    {
        int position = Microphone.GetPosition(null);
        if (position<=0 || position> recordedClip.samples)
        {
            position = recordedClip.samples;
        }
        float[] soundata = new float[position * recordedClip.channels];
        recordedClip.GetData(soundata, 0);
        recordedClip = AudioClip.Create(recordedClip.name, position,         
        recordedClip.channels, recordedClip.frequency, false);
        recordedClip.SetData(soundata, 0);
        int rescaleFactor = 32767;
        byte[] outData = new byte[soundata.Length * 2];
        for (int i = 0; i < soundata.Length; i++)
        {
            short temshort = (short)(soundata[i] * rescaleFactor);
            byte[] temdata = BitConverter.GetBytes(temshort);
            outData[i * 2] = temdata[0];
            outData[i * 2 + 1] = temdata[1];
        }
        Debug.Log("position=" + position + "outData.leng=" + outData.Length);
        return outData;
    }
public static void WriteHeader(FileStream stream, AudioClip clip)
    {
        int hz = clip.frequency;
        int channels = clip.channels;
        int samples = clip.samples;

        stream.Seek(0, SeekOrigin.Begin);

        Byte[] riff = System.Text.Encoding.UTF8.GetBytes("RIFF");
        stream.Write(riff, 0, 4);

        Byte[] chunkSize = BitConverter.GetBytes(stream.Length - 8);
        stream.Write(chunkSize, 0, 4);

        Byte[] wave = System.Text.Encoding.UTF8.GetBytes("WAVE");
        stream.Write(wave, 0, 4);

        Byte[] fmt = System.Text.Encoding.UTF8.GetBytes("fmt ");
        stream.Write(fmt, 0, 4);

        Byte[] subChunk1 = BitConverter.GetBytes(16);
        stream.Write(subChunk1, 0, 4);

        UInt16 one = 1;

        Byte[] audioFormat = BitConverter.GetBytes(one);
        stream.Write(audioFormat, 0, 2);

        Byte[] numChannels = BitConverter.GetBytes(channels);
        stream.Write(numChannels, 0, 2);

        Byte[] sampleRate = BitConverter.GetBytes(hz);
        stream.Write(sampleRate, 0, 4);

        Byte[] byteRate = BitConverter.GetBytes(hz * channels * 2); 
        stream.Write(byteRate, 0, 4);

        UInt16 blockAlign = (ushort)(channels * 2);
        stream.Write(BitConverter.GetBytes(blockAlign), 0, 2);

        UInt16 bps = 16;
        Byte[] bitsPerSample = BitConverter.GetBytes(bps);
        stream.Write(bitsPerSample, 0, 2);

        Byte[] datastring = System.Text.Encoding.UTF8.GetBytes("data");
        stream.Write(datastring, 0, 4);

        Byte[] subChunk2 = BitConverter.GetBytes(samples * channels * 2);
        stream.Write(subChunk2, 0, 4);
    }
    private FileStream CreateEmpty(string filepath)
    {
        FileStream fileStream = new FileStream(filepath, FileMode.Create);
        byte emptyByte = new byte();

        for (int i = 0; i < 44; i++) //为wav文件头留出空间
        {
            fileStream.WriteByte(emptyByte);
        }

        return fileStream;
    }