Question

Write the code to generate a band limited 1000Hz sawtooth wave.

Accepted Answer

for(double time=0.; time < duration; time += 1. / sampleRate)

{

double s = 0;

for(int h=1; h<(sampleRate / (2 * 1000)); h++)

s += sin(2 * M_PI * h * 1000 * t) / h;

short sample = short(amplitude *s);

audio[0] = audio[1] = sample;

GenerateFrame(audio);

}

Answer

// Call to open the processing output

if(!ProcessBegin())

return;

short audio[2];

double t = 0;

for(int i=0; i<SampleFrames(); i++, t+= 1. / SampleRate())

{

ProcessReadFrame(audio);

double mix = 0.5 * audio[0] + 0.5 * audio[1];

double pongL = sin(2 * M_PI * 5 * t) * 0.5 + 0.5;

double pongR = 1 - pongL;

audio[0] = short(audio[0] * pongL);

audio[1] = short(audio[1] * pongR);

ProcessWriteFrame(audio);

// The progress control

if(!ProcessProgress(double(i) / SampleFrames()))

break;

}

// Call to close the generator output

ProcessEnd();

///////////////////////////////////////////////

Answer

double COscillator::GetSample()

{

double sample = amplitude * sin(radians);

radians += (2 * M_PI * m_freq1) / m_sampleRate;

return sample;

}

Answer

double radians = 0; // For the sine wave

double samplePeriod = 1. / sampleRate;

for(double time=0.; time < duration; time += samplePeriod)

{

double freq = 100 + (1000 - 100) * time / 10;

short sample = short(amplitude * sin(radians));

audio[0] = audio[1] = sample;

// Increment the phases

radians += (2 * M_PI * freq) / sampleRate;

GenerateFrame(audio);

}

/////////////////////////////////////////////////////////////////////////////

Audio signal generation code: sine, sawtooth, sweep

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