創建三角形音頻波形

Question

我使用NAudio創建具有兩個通道的不同音頻波形。對於正弦波我有下一個代碼：

 int sampleRate = WaveFormat.SampleRate; 
     for (int n = 0; n < sampleCount; n += 2) 
     { 
      buffer[n + offset] = (float)(AmplitudeLeft * Math.Sin((2 * Math.PI * sample * FrequencyLeft)/sampleRate)); 
      buffer[n + offset + 1] = (float)(AmplitudeRight * Math.Sin((2 * Math.PI * sample * FrequencyRight)/sampleRate)); 
      sample++; 
      if (sample >= sampleRate) 
       sample = 0; 
     } 
     return sampleCount; 

我需要一個簡單的公式來創建一個三角形的音頻波。

Answer 1

分工，使其更容易：

void makesamples_mono(float[] buffer, int offset, int sampleCount, int rate, double amp, double freq) 
{ 
    double one_over_half_per = freq * 2.0/rate; 
    for (int i = 0; i < sampleCount; i++) 
    { 
     double div = i * one_over_half_per; 
     buffer[offset + 2 * i] = (float)(((((int)div) % 2 == 0) ? -amp : amp) * (1.0 - 2.0 * (div - (int)div))); 
    } 
} 

void writesamples_stereo(float[] buffer, int offset, int sampleCount, int rate, double l_amp, double r_amp, double l_freq, double r_freq) 
{ 
    makesamples_mono(buffer, offset, sampleCount, rate, l_amp, l_freq);  // left channel 
    makesamples_mono(buffer, offset+1, sampleCount, rate, r_amp, r_freq); // right channel 
}