audio - CSCore - 将立体声转换为环绕声

Question

我必须解码立体声 mp4 文件并将 L 和 R 声道映射到 5.1 or 7.1 surround .另外我必须提供一个特定的输出格式:16bit pcm 44.1kHz .
将音频源转换为44100Hz 16bit 没有问题.唯一的问题是 channel 混合。
我有以下编码:

const string filename = @"stereo.mp3";
IWaveSource waveSource = CodecFactory.Instance.GetCodec(filename)
    .AppendSource(x => new CSCore.Streams.CachedSoundSource(x))
    .ChangeSampleRate(44100) //44.1kHz
    .ToSampleSource()
    .ToWaveSource(16); //16bit

官方项目页面在这里: http://cscore.codeplex.com/告诉我 channel 混合是可能的。我找到了 CSCore.DSP.ChannelMatrix类，但很难弄清楚如何使用它。
也许有人可以帮助我？

Answer 1

你是绝对正确的，你必须使用 CSCore.DSP.ChannelMatrix类(class)。
我为您创建了一个小示例并添加了一些评论。它应该是自我解释的:

static void Main(string[] args)
{
    const string filename = @"stereo.mp3";

    /*
     * First of all you need a channel matrix that fits your needs.
     * There are many ways to get one...:
     */

    //Simply use one of the predefined...
    ChannelMatrix channelMatrix = ChannelMatrix.StereoToSevenDotOneSurround;

    //or

    //use some kind of factory to get one
    channelMatrix = ChannelMatrix.GetMatrix(
        ChannelMasks.StereoMask,
        ChannelMasks.SevenDotOneMask);

    //or

    //or create your own one (the matrix below equals the two above but of course you can use custom values)
    //the rows represent your input channels (the stereo signal) and the columns your output channels.
    //specify with a value from 0-1 how much percentage of the L (row index 0) or the R (row index 1) channel
    //you want to apply to the specific column (the columns are getting mapped to the output channel mask
    // -> the SevenDotOneMask ordered by the values of the certain flags inside of the channel mask).
    channelMatrix = new ChannelMatrix(
        ChannelMasks.StereoMask,
        ChannelMasks.SevenDotOneMask);
    channelMatrix.SetMatrix(
        new[,]
        {
            {0.222f, 0f, 0.157f, 0.022f, 0.189f, 0.116f, 0.203f, 0.090f},
            {0f, 0.222f, 0.157f, 0.022f, 0.116f, 0.189f, 0.090f, 0.203f}
        });

    IWaveSource waveSource = CodecFactory.Instance.GetCodec(filename)
        .AppendSource(x => new CSCore.Streams.CachedSoundSource(x))
        .ChangeSampleRate(44100) //44.1kHz
        .AppendSource(x => new DmoChannelResampler(x, channelMatrix)) //append a channelresampler with the channelmatrix
        .ToSampleSource()
        .ToWaveSource(16); //16bit

    ...
}

我强烈建议您使用预定义的 channel 矩阵。
当然，如果您需要一些自定义值，请在上面的示例中定义您自己的值。

顺便提一句。您还可以实时更改 channel 矩阵:
只需对 channelMatrix 进行更改即可之后调用 CommitChannelMatrixChanges (当然，您必须存储 DmoChannelResampler 实例 -> 使用 out parameter 方法的 AppendSource 来做到这一点)。