Pitch Scaler
A pitch shifter implementation that scales the harmonics appropriately with the base frequencies. It is an implementation of Stephen M. Sprengler's pitch scaler design. It gives reasonable, general purpose results for small changes, but won't give Antares or Eventide anything to worry about.
The FFT block size and oversampling has been kept at a minimum to keep the CPU usage low.
pitch_scale(buffers, mult, FRAME_LENGTH, OVER_SAMP, sample_count, sample_rate, input, output, RUN_ADDING, run_adding_gain);
*(plugin_data->latency) = FRAME_LENGTH - (FRAME_LENGTH /
OVER_SAMP);
int i;
float arg;
buffers = malloc(sizeof(sbuffers));
sample_rate = s_rate;
buffers->gInFIFO = malloc(FRAME_LENGTH * sizeof(float));
buffers->gOutFIFO = malloc(FRAME_LENGTH * sizeof(float));
buffers->gLastPhase = malloc(FRAME_LENGTH * sizeof(float));
buffers->gSumPhase = malloc(FRAME_LENGTH * sizeof(float));
buffers->gOutputAccum = malloc(2*FRAME_LENGTH * sizeof(float));
buffers->gAnaFreq = malloc(FRAME_LENGTH * sizeof(float));
buffers->gAnaMagn = malloc(FRAME_LENGTH * sizeof(float));
buffers->gSynFreq = malloc(FRAME_LENGTH * sizeof(float));
buffers->gSynMagn = malloc(FRAME_LENGTH * sizeof(float));
buffers->gWindow = malloc(FRAME_LENGTH * sizeof(float));
/*
if (aplan == NULL) {
#ifdef FFTW3
aplan = fftwf_plan_r2r_1d(FRAME_LENGTH, ps_in, ps_out, FFTW_R2HC, FFTW_MEASURE);
splan = fftwf_plan_r2r_1d(FRAME_LENGTH, ps_in, ps_out, FFTW_HC2R, FFTW_MEASURE);
#else
aplan = rfftw_create_plan(FRAME_LENGTH, FFTW_REAL_TO_COMPLEX, FFTW_ESTIMATE);
splan = rfftw_create_plan(FRAME_LENGTH, FFTW_COMPLEX_TO_REAL, FFTW_ESTIMATE);
#endif
}
*/
arg = 2.0f * M_PI / (float)(FRAME_LENGTH-1);
for (i=0; i < FRAME_LENGTH; i++) {
// Blackman-Harris
buffers->gWindow[i] = 0.35875f - 0.48829f * cos(arg * (float)i) + 0.14128f * cos(2.0f * arg * (float)i) - 0.01168f * cos(3.0f * arg * (float)i);
// Gain correction
buffers->gWindow[i] *= 0.761f;
}
memset(buffers->gInFIFO, 0, FRAME_LENGTH*sizeof(float));
memset(buffers->gOutFIFO, 0, FRAME_LENGTH*sizeof(float));
memset(buffers->gLastPhase, 0, FRAME_LENGTH*sizeof(float)/2);
memset(buffers->gSumPhase, 0, FRAME_LENGTH*sizeof(float)/2);
memset(buffers->gOutputAccum, 0, 2*FRAME_LENGTH*sizeof(float));
memset(buffers->gAnaFreq, 0, FRAME_LENGTH*sizeof(float));
memset(buffers->gAnaMagn, 0, FRAME_LENGTH*sizeof(float));
buffers->gRover = 0;
sample_rate = sample_rate;
/* do one run to make sure the plans are set up */
pitch_scale(buffers, 1.0, FRAME_LENGTH, 4, FRAME_LENGTH, sample_rate, buffers->gInFIFO, buffers->gOutFIFO, 0, 0.0f);
buffers->gInFIFO);
free (plugin_data->buffers->gOutFIFO);
free (plugin_data->buffers->gLastPhase);
free (plugin_data->buffers->gSumPhase);
free (plugin_data->buffers->gOutputAccum);
free (plugin_data->buffers->gAnaFreq);
free (plugin_data->buffers->gAnaMagn);
free (plugin_data->buffers->gSynFreq);
free (plugin_data->buffers->gSynMagn);
free (plugin_data->buffers->gWindow);
free (plugin_data->buffers);
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Pitch co-efficient
Input
Output
latency