c# - 高效地将音频字节 - byte[] 转换为 Short[]

Question

我正在尝试使用 XNA 麦克风捕获音频并将其传递到我拥有的 API，该 API 可以分析数据以用于显示目的。但是，API 需要 16 位整数数组中的音频数据。所以我的问题相当简单；将字节数组转换为短数组的最有效方法是什么？

    private void _microphone_BufferReady(object sender, System.EventArgs e)
    {
        _microphone.GetData(_buffer);

        short[] shorts;

        //Convert and pass the 16 bit samples
        ProcessData(shorts);
    }

干杯，戴夫

编辑:这是我想出的并且似乎可行，但是可以做得更快吗？

    private short[] ConvertBytesToShorts(byte[] bytesBuffer)
    {
        //Shorts array should be half the size of the bytes buffer, as each short represents 2 bytes (16bits)
        short[] shorts = new short[bytesBuffer.Length / 2];

        int currentStartIndex = 0;

        for (int i = 0; i < shorts.Length - 1; i++)
        {
            //Convert the 2 bytes at the currentStartIndex to a short
            shorts[i] = BitConverter.ToInt16(bytesBuffer, currentStartIndex);

            //increment by 2, ready to combine the next 2 bytes in the buffer
            currentStartIndex += 2;
        }

        return shorts;

    }

Answer 1

阅读您的更新后，我可以看到您实际上需要将字节数组直接复制到短裤缓冲区中，合并字节。这是 documentation 中的相关部分:

The byte[] buffer format used as a parameter for the SoundEffect constructor, Microphone.GetData method, and DynamicSoundEffectInstance.SubmitBuffer method is PCM wave data. Additionally, the PCM format is interleaved and in little-endian.

现在，如果由于某种奇怪的原因你的系统有BitConverter.IsLittleEndian == false，那么你将需要循环遍历你的缓冲区，交换字节，从小端转换为大尾数。我将把代码留作练习 - 我有理由确信所有 XNA 系统都是小尾数法。

出于您的目的，您可以直接使用 Marshal.Copy 或 Buffer.BlockCopy 复制缓冲区。两者都将为您提供平台 native 内存复制操作的性能，这将非常快:

// Create this buffer once and reuse it! Don't recreate it each time!
short[] shorts = new short[_buffer.Length/2];

// Option one:
unsafe
{
    fixed(short* pShorts = shorts)
        Marshal.Copy(_buffer, 0, (IntPtr)pShorts, _buffer.Length);
}

// Option two:
Buffer.BlockCopy(_buffer, 0, shorts, 0, _buffer.Length);