CSCore: playback float array from pure data

Question

I'm writing a program in C# which communicates with pure data using the libpd library (more information: http://libpd.cc/)

My pure data patch is simply creating a sine wave.

I wrote some test code to see if I get any data from my pure data patch. The LibPD.Process method writes samples into the outbuffer array and the contents are continuous values between -1 and 1:

// Initialise Pd with 0 input and 2 output channels and a samplerate of 44100. Project dependent.
int pdOpen = -1;
pdOpen = LibPD.OpenAudio(0, 2, 44100);

if (pdOpen != 0)
{
    Console.WriteLine("Error opening audio... exiting");
    return;
}

string patchFile = @"..\..\..\test.pd";
int patch = LibPD.OpenPatch(patchFile);
LibPD.ComputeAudio(true);

//Read from Process Function...
// The size of each buffer must be the product of the number of channels, the number of ticks, 
// and the number of samples per tick. (The number of samples per tick is the value 
// returned by libpd_blocksize(), i.e., 64.)

int ret;
float[] outbuffer = new float[2 * 1 * LibPD.BlockSize]; // Size = 128

for (int i = 0; i < 10; i++)
{
    ret = LibPD.Process(1, new float[0], outbuffer);
    Thread.Sleep(1000);
}

LibPD.ClosePatch(patch);
LibPD.Release();

So I am sure that I am getting processed data from my patch.

Now I would like to play back this float array using CSCore. I found the ISampleSource interface in the documentation and I think it's the right one to go for this task. I tried something like this in the Read method of my interface implementation:

...

public PureDataSource()
{
    _WaveFormat = new WaveFormat(44100, 16, 2);

    int pdOpen = -1;
    pdOpen = LibPD.OpenAudio(0, 2, 44100);

    if (pdOpen != 0)
    {
        Console.WriteLine("Error opening audio... exiting");
        return;
    }

    string patch = @"..\..\..\test.pd";
    _Patch = LibPD.OpenPatch(patch);
    LibPD.ComputeAudio(true);
}

...

public int Read(float[] buffer, int offset, int count)
{
    LibPD.Process(1, new float[0], buffer);

    return count;
}

But it doesn't work out - I only get crackling sounds (guess what). I know it has something to do with the buffer size of the Read method, but where can I configure this? The Process function of LibPd works like this:

The size of each buffer must be the product of the number of channels, the      number of ticks, 
and the number of samples per tick. (The number of samples per tick is the value 
returned by libpd_blocksize(), i.e., 64.)

in my case that's: 2 channels (output channels), 1 tick and number of samples per tick is 64 --> 128.

EDIT: I wrote a PureDataSource class which implements the ISampleSource interface using the information above:

class Program
{
    static void Main(string[] args)
    {
        PureDataSource pdSource = new PureDataSource();
        WasapiOut soundOut = new WasapiOut();

        soundOut.Initialize(pdSource.ToWaveSource());

        soundOut.Play();
        Thread.Sleep(5000);
        soundOut.Stop();
    }
}

class PureDataSource : ISampleSource
{
    public long Length
    {
        get
        {
            return 0;
        }
    }

    public long Position
    {
        get
        {
            return 0;
        }

        set
        {
            throw new NotImplementedException();
        }
    }
    private WaveFormat _WaveFormat;
    public WaveFormat WaveFormat
    {
        get
        {
            return _WaveFormat;
        }
    }

    private int _Patch;
    public int Patch
    {
        get { return _Patch; }
        //set { _Patch = value; }
    }

    public PureDataSource()
    {
        _WaveFormat = new WaveFormat(44100, 16, 2);

        // Initialise Pd with 2 ins and outs and a samplerate of 44100. Project dependent.
        int pdOpen = -1;
        pdOpen = LibPD.OpenAudio(0, 2, 44100);

        if (pdOpen != 0)
        {
            Console.WriteLine("Error opening audio... exiting");
            return;
        }

        string patch = @"..\..\..\test.pd";
        _Patch = LibPD.OpenPatch(patch);
        LibPD.ComputeAudio(true);
    }

    public void Dispose()
    {
        LibPD.ClosePatch(_Patch);
        LibPD.Release();
    }

    public int Read(float[] buffer, int offset, int count)
    {
        int ticks = 1;

        int pdBufferPos = 0;
        float[] pdBuffer = new float[2 * ticks * LibPD.BlockSize];
        LibPD.Process(ticks, new float[0], pdBuffer);

        for (int i = offset; i < count; i++)
        { 
            if (pdBufferPos >= pdBuffer.Length)
            {
                pdBufferPos = 0;
                LibPD.Process(ticks, new float[0], pdBuffer);
            }

            buffer[i] = pdBuffer[pdBufferPos];
            pdBufferPos++;
        }            

        return count;
    }
}

The Read method fills the whole buffer with the output provided by LibPD.Process (this is a float array with the size of 128 each time).

I can hear a sine wave now, but with a lot of crackling sound - it seems the samples are not processed continuously. Any ideas how to solve this?

Answer 1

But it doesn't work out - I only get crackling sounds (guess what). I know it has something to do with the buffer size of the Read method, but where can I configure this?

You can't "configure" it. If the WasapiOut requests a certain amount of data, it is in your hands, how much data you want to return. Fill the buffer, starting at the specified offset, with the data you want. Return the number of provided samples. That's how you "configure" it.