AlternatingWaveProvider.cs

namespace ToneGenerator
{
	/// <summary>
	/// Alternates between two sides, each having 3 soundtracks (in the current implementation).
	/// </summary>
	public class AlternatingWaveProvider : SineWaveProvider
	{
		public AlternatingWaveProvider(double period)
		{
			Period = period;
		}

		public double Period { get; set; }
		// Tone duration in seconds.
		public double ToneDuration { get { return Period; } }
		public int ToneSamples { get { return (int)(SAMPLE_RATE * ToneDuration); } }

		// 0 if left side is being played, 1 if right side.
		public int CurrentSoundtrackIndex { get; set; }
		public double DutyCycle { get; set; } = 0.5;

		public override int Read(float[] buffer, int offset, int sampleCount)
		{
			if (IsPlaying)
			{
				for (int i = 0; i < sampleCount; i += 2)
				{
					float left = 0, right = 0;
					for (int j = CurrentSoundtrackIndex; j < Soundtracks.Count; j += 2)
					{
						var track = Soundtracks[j];
						track.CurrentPhase += 2 * Math.PI * track.Frequency / WaveFormat.SampleRate;

						float val = (float)(Math.Sin(track.CurrentPhase));
						if (track.Left)
							left += LeftCalibration.GetCalibratedAmplitude(track, UseLoudnessInCalibration) * val;
						if (track.Right)
							right += RightCalibration.GetCalibratedAmplitude(track, UseLoudnessInCalibration) * val;
					}
					buffer[i + offset] = left;
					buffer[i + offset + 1] = right;

					++Sample;
					if (Sample % ToneSamples == 0 && DutyCycle != 1)
						SetSoundtrackIndex(0);
					else if (Sample % ToneSamples == (int)((1 - DutyCycle) * ToneSamples))
						SetSoundtrackIndex(1);
				}
			}
			else
			{
				for (int i = 0; i < sampleCount; i++)
				{
					buffer[i + offset] = 0;
				}
			}

			return sampleCount;
		}

		private void SetSoundtrackIndex(int index)
		{
			int d = index == 0 ? 1 : -1;
			for (int i = index; Math.Max(i, i + d) < Soundtracks.Count; i += 2)
			{
				// Move current phase into phase of soundtrack on other side
				Soundtracks[i].CurrentPhase = Soundtracks[i + d].CurrentPhase;
			}
			CurrentSoundtrackIndex = index;
		}
	}
}