播放未知时间的正弦波

Question

Whole day I was looking for some tutorial or piece of code, "just" to play simple sin wave for "infinity" time. I know it sounds a little crazy.

But I want to be able to change frequency of tone in time, for instance - increase it. Imagine that I want to play tone A, and increase it to C in "+5" frequency steps each 3ms (it's really just example), don't want to have free places, stop the tone.

Is it possible? Or can you help me?

Answer 1

Use NAudio library for audio output.

Make notes wave provider:

class NotesWaveProvider : WaveProvider32
{
    public NotesWaveProvider(Queue<Note> notes)
    {
        this.Notes = notes;
    }
    public readonly Queue<Note> Notes;
    int sample = 0;

    Note NextNote()
    {
        for (; ; )
        {
            if (Notes.Count == 0)
                return null;
            var note = Notes.Peek();
            if (sample < note.Duration.TotalSeconds * WaveFormat.SampleRate)
                return note;

            Notes.Dequeue();
            sample = 0;
        }

    }
    public override int Read(float[] buffer, int offset, int sampleCount)
    {
        int sampleRate = WaveFormat.SampleRate;
        for (int n = 0; n < sampleCount; n++)
        {
            var note = NextNote();
            if (note == null)
                buffer[n + offset] = 0;
            else
                buffer[n + offset] = (float)(note.Amplitude * Math.Sin((2 * Math.PI * sample * note.Frequency) / sampleRate));
            sample++;
        }
        return sampleCount;
    }
}
class Note
{
    public float Frequency;
    public float Amplitude = 1.0f;
    public TimeSpan Duration = TimeSpan.FromMilliseconds(50);

}

start play:

WaveOut waveOut;
this.Notes = new Queue<Note>(new[] { new Note { Frequency = 1000 }, new Note { Frequency = 1100 } });
var waveProvider = new NotesWaveProvider(Notes);
waveProvider.SetWaveFormat(16000, 1); // 16kHz mono    

waveOut = new WaveOut();
waveOut.Init(waveProvider);
waveOut.Play();

add new notes:

void Timer_Tick(...)
{
 if (Notes.Count < 10)
   Notes.Add(new Note{Frecuency = 900});
}

ps this code is idea only. for real using add mt-locking etc

Answer 2

use NAudio and SineWaveProvider32: http://mark-dot-net.blogspot.com/2009/10/playback-of-sine-wave-in-naudio.html

private WaveOut waveOut;

private void button1_Click(object sender, EventArgs e)
{
  StartStopSineWave();
}

private void StartStopSineWave()
{
  if (waveOut == null)
  {
    var sineWaveProvider = new SineWaveProvider32();
    sineWaveProvider.SetWaveFormat(16000, 1); // 16kHz mono
    sineWaveProvider.Frequency = 1000;
    sineWaveProvider.Amplitude = 0.25f;
    waveOut = new WaveOut();
    waveOut.Init(sineWaveProvider);
    waveOut.Play();
  }
  else
  {
    waveOut.Stop();
    waveOut.Dispose();
    waveOut = null;
  }
}