ref: f0d8dedb45838219f1e56debb2dd24cf2341d804
dir: /LEAF/Src/leaf-oversampler.c/
//
// leaf-oversampler.c
// LEAF
//
// Created by Matthew Wang and Joshua Becker on 2/28/19.
// Copyright © 2019 Princeton University. All rights reserved.
//
#if _WIN32 || _WIN64
#include "..\Inc\leaf-oversampler.h"
#include "..\Inc\leaf-tables.h"
#else
#include "../Inc/leaf-oversampler.h"
#include "../Inc/leaf-tables.h"
#endif
// Oversampler
// Latency is equal to the phase length (numTaps / ratio)
void tOversampler_init(tOversampler* const os, int ratio, oBool extraQuality)
{
uint8_t offset = 0;
if (extraQuality) offset = 6;
if (ratio == 2 || ratio == 4 ||
ratio == 8 || ratio == 16 ||
ratio == 32 || ratio == 64) {
os->ratio = ratio;
int idx = (int)(log2f(os->ratio))-1+offset;
os->numTaps = firNumTaps[idx];
os->phaseLength = os->numTaps / os->ratio;
os->pCoeffs = firCoeffs[idx];
os->upState = leaf_alloc(sizeof(float) * os->phaseLength);
os->downState = leaf_alloc(sizeof(float) * os->phaseLength);
}
}
float tOversampler_tick(tOversampler* const os, float input, float (*effectTick)(float))
{
float buf[os->ratio];
tOversampler_upsample(os, input, buf);
for (int i = 0; i < os->ratio; ++i) {
buf[i] = effectTick(buf[i]);
}
return tOversampler_downsample(os, buf);
}
// From CMSIS DSP Library
void tOversampler_upsample(tOversampler* const os, float input, float* output)
{
float *pState = os->upState; /* State pointer */
const float *pCoeffs = os->pCoeffs; /* Coefficient pointer */
float *pStateCur;
float *ptr1; /* Temporary pointer for state buffer */
const float *ptr2; /* Temporary pointer for coefficient buffer */
float sum0; /* Accumulators */
uint32_t i, tapCnt; /* Loop counters */
uint32_t phaseLen = os->phaseLength; /* Length of each polyphase filter component */
uint32_t j;
/* os->pState buffer contains previous frame (phaseLen - 1) samples */
/* pStateCur points to the location where the new input data should be written */
pStateCur = os->upState + (phaseLen - 1U);
/* Copy new input sample into the state buffer */
*pStateCur = input;
/* Address modifier index of coefficient buffer */
j = 1U;
/* Loop over the Interpolation factor. */
i = os->ratio;
while (i > 0U)
{
/* Set accumulator to zero */
sum0 = 0.0f;
/* Initialize state pointer */
ptr1 = pState;
/* Initialize coefficient pointer */
ptr2 = pCoeffs + (os->ratio - j);
/* Loop over the polyPhase length.
Repeat until we've computed numTaps-(4*os->L) coefficients. */
/* Initialize tapCnt with number of samples */
tapCnt = phaseLen;
while (tapCnt > 0U)
{
/* Perform the multiply-accumulate */
sum0 += *ptr1++ * *ptr2;
/* Upsampling is done by stuffing L-1 zeros between each sample.
* So instead of multiplying zeros with coefficients,
* Increment the coefficient pointer by interpolation factor times. */
ptr2 += os->ratio;
/* Decrement loop counter */
tapCnt--;
}
/* The result is in the accumulator, store in the destination buffer. */
*output++ = sum0 * os->ratio;
/* Increment the address modifier index of coefficient buffer */
j++;
/* Decrement the loop counter */
i--;
}
/* Advance the state pointer by 1
* to process the next group of interpolation factor number samples */
pState = pState + 1;
/* Processing is complete.
Now copy the last phaseLen - 1 samples to the satrt of the state buffer.
This prepares the state buffer for the next function call. */
/* Points to the start of the state buffer */
pStateCur = os->upState;
/* Initialize tapCnt with number of samples */
tapCnt = (phaseLen - 1U);
/* Copy data */
while (tapCnt > 0U)
{
*pStateCur++ = *pState++;
/* Decrement loop counter */
tapCnt--;
}
}
// From CMSIS DSP Library
float tOversampler_downsample(tOversampler *const os, float* input)
{
float *pState = os->downState; /* State pointer */
const float *pCoeffs = os->pCoeffs; /* Coefficient pointer */
float *pStateCur; /* Points to the current sample of the state */
float *px0; /* Temporary pointer for state buffer */
const float *pb; /* Temporary pointer for coefficient buffer */
float x0, c0; /* Temporary variables to hold state and coefficient values */
float acc0; /* Accumulator */
uint32_t numTaps = os->numTaps; /* Number of filter coefficients in the filter */
uint32_t i, tapCnt;
float output;
/* os->pState buffer contains previous frame (numTaps - 1) samples */
/* pStateCur points to the location where the new input data should be written */
pStateCur = os->downState + (numTaps - 1U);
/* Copy decimation factor number of new input samples into the state buffer */
i = os->ratio;
do
{
*pStateCur++ = *input++;
} while (--i);
/* Set accumulator to zero */
acc0 = 0.0f;
/* Initialize state pointer */
px0 = pState;
/* Initialize coeff pointer */
pb = pCoeffs;
/* Initialize tapCnt with number of taps */
tapCnt = numTaps;
while (tapCnt > 0U)
{
/* Read coefficients */
c0 = *pb++;
/* Fetch 1 state variable */
x0 = *px0++;
/* Perform the multiply-accumulate */
acc0 += x0 * c0;
/* Decrement loop counter */
tapCnt--;
}
/* Advance the state pointer by the decimation factor
* to process the next group of decimation factor number samples */
pState = pState + os->ratio;
/* The result is in the accumulator, store in the destination buffer. */
output = acc0;
/* Processing is complete.
Now copy the last numTaps - 1 samples to the satrt of the state buffer.
This prepares the state buffer for the next function call. */
/* Points to the start of the state buffer */
pStateCur = os->downState;
/* Initialize tapCnt with number of taps */
tapCnt = (numTaps - 1U);
/* Copy data */
while (tapCnt > 0U)
{
*pStateCur++ = *pState++;
/* Decrement loop counter */
tapCnt--;
}
return output;
}
int tOversampler_getLatency(tOversampler* const os)
{
return os->phaseLength;
}