mirror of
https://github.com/f4exb/sdrangel.git
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287 lines
9.3 KiB
C++
287 lines
9.3 KiB
C++
/*
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Copyright (C) 2018 James C. Ahlstrom
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All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License version 2.1, as
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published by the Free Software Foundation. This program is
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distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include <stdlib.h>
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#include <string.h>
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#include <math.h>
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#include <complex.h>
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#include "freedv_filter.h"
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#include "freedv_filter_coef.h"
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#include "fdv_arm_math.h"
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#define cmplx(value) (COSF(value) + SINF(value) * std::complex<float>(0.0f, 1.0f))
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namespace FreeDV
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{
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/*
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* This is a library of filter functions. They were copied from Quisk and converted to single precision.
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*/
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/*---------------------------------------------------------------------------*\
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FUNCTIONS...: quisk_filt_cfInit
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AUTHOR......: Jim Ahlstrom
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DATE CREATED: 27 August 2015
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MODIFIED: 4 June 2018
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Initialize a FIR filter that has complex samples, and either real or complex coefficients.
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\*---------------------------------------------------------------------------*/
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void quisk_filt_cfInit(struct quisk_cfFilter * filter, float * coefs, int taps) {
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// Prepare a new filter using coefs and taps. Samples are complex. Coefficients can
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// be real or complex.
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filter->dCoefs = coefs;
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filter->cpxCoefs = NULL;
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filter->cSamples = (std::complex<float> *) malloc(taps * sizeof(std::complex<float>));
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memset(filter->cSamples, 0, taps * sizeof(std::complex<float>));
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filter->ptcSamp = filter->cSamples;
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filter->nTaps = taps;
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filter->cBuf = NULL;
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filter->nBuf = 0;
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filter->decim_index = 0;
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}
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/*---------------------------------------------------------------------------*\
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FUNCTIONS...: quisk_filt_destroy
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AUTHOR......: Jim Ahlstrom
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DATE CREATED: 27 August 2015
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MODIFIED: 4 June 2018
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Destroy the FIR filter and free all resources.
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\*---------------------------------------------------------------------------*/
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void quisk_filt_destroy(struct quisk_cfFilter * filter) {
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if (filter->cSamples) {
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free(filter->cSamples);
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filter->cSamples = NULL;
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}
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if (filter->cBuf) {
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free(filter->cBuf);
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filter->cBuf = NULL;
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}
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if (filter->cpxCoefs) {
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free(filter->cpxCoefs);
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filter->cpxCoefs = NULL;
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}
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}
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/*---------------------------------------------------------------------------*\
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FUNCTIONS...: quisk_cfInterpDecim
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AUTHOR......: Jim Ahlstrom
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DATE CREATED: 27 August 2015
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MODIFIED: 4 June 2018
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Take an array of samples cSamples of length count, multiply the sample rate
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by interp, and then divide the sample rate by decim. Return the new number
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of samples. Each specific interp and decim will require its own custom
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low pass FIR filter with real coefficients.
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\*---------------------------------------------------------------------------*/
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int quisk_cfInterpDecim(std::complex<float> * cSamples, int count, struct quisk_cfFilter * filter, int interp, int decim) {
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// Interpolate by interp, and then decimate by decim.
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// This uses the float coefficients of filter (not the complex). Samples are complex.
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int i, k, nOut;
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float * ptCoef;
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std::complex<float> *ptSample;
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std::complex<float> csample;
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if (count > filter->nBuf) { // increase size of sample buffer
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filter->nBuf = count * 2;
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if (filter->cBuf)
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free(filter->cBuf);
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filter->cBuf = (std::complex<float> *) malloc(filter->nBuf * sizeof(std::complex<float>));
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}
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memcpy(filter->cBuf, cSamples, count * sizeof(std::complex<float>));
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nOut = 0;
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for (i = 0; i < count; i++) {
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// Put samples into buffer left to right. Use samples right to left.
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*filter->ptcSamp = filter->cBuf[i];
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while (filter->decim_index < interp) {
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ptSample = filter->ptcSamp;
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ptCoef = filter->dCoefs + filter->decim_index;
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csample = 0;
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for (k = 0; k < filter->nTaps / interp; k++, ptCoef += interp) {
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csample += *ptSample * *ptCoef;
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if (--ptSample < filter->cSamples)
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ptSample = filter->cSamples + filter->nTaps - 1;
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}
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cSamples[nOut] = csample * (float) interp;
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nOut++;
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filter->decim_index += decim;
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}
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if (++filter->ptcSamp >= filter->cSamples + filter->nTaps)
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filter->ptcSamp = filter->cSamples;
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filter->decim_index = filter->decim_index - interp;
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}
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return nOut;
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}
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/*---------------------------------------------------------------------------*\
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FUNCTIONS...: quisk_ccfInterpDecim
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AUTHOR......: Jim Ahlstrom
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DATE CREATED: 7 June 2018
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Take an array of samples cSamples of length count, multiply the sample rate
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by interp, and then divide the sample rate by decim. Return the new number
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of samples. Each specific interp and decim will require its own custom
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low pass FIR filter with complex coefficients. This filter can be tuned.
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This filter is not currently used.
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\*---------------------------------------------------------------------------*/
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#if 0
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int quisk_ccfInterpDecim(complex float * cSamples, int count, struct quisk_cfFilter * filter, int interp, int decim) {
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// Interpolate by interp, and then decimate by decim.
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// This uses the complex coefficients of filter (not the real). Samples are complex.
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int i, k, nOut;
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complex float * ptCoef;
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complex float * ptSample;
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complex float csample;
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if (count > filter->nBuf) { // increase size of sample buffer
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filter->nBuf = count * 2;
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if (filter->cBuf)
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FREE(filter->cBuf);
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filter->cBuf = (complex float *)MALLOC(filter->nBuf * sizeof(complex float));
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}
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memcpy(filter->cBuf, cSamples, count * sizeof(complex float));
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nOut = 0;
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for (i = 0; i < count; i++) {
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// Put samples into buffer left to right. Use samples right to left.
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*filter->ptcSamp = filter->cBuf[i];
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while (filter->decim_index < interp) {
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ptSample = filter->ptcSamp;
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ptCoef = filter->cpxCoefs + filter->decim_index;
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csample = 0;
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for (k = 0; k < filter->nTaps / interp; k++, ptCoef += interp) {
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csample += *ptSample * *ptCoef;
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if (--ptSample < filter->cSamples)
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ptSample = filter->cSamples + filter->nTaps - 1;
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}
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cSamples[nOut] = csample * interp;
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nOut++;
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filter->decim_index += decim;
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}
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if (++filter->ptcSamp >= filter->cSamples + filter->nTaps)
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filter->ptcSamp = filter->cSamples;
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filter->decim_index = filter->decim_index - interp;
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}
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return nOut;
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}
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#endif
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/*---------------------------------------------------------------------------*\
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FUNCTIONS...: quisk_cfTune
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AUTHOR......: Jim Ahlstrom
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DATE CREATED: 4 June 2018
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Tune a low pass filter with float coefficients into an analytic I/Q bandpass filter
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with complex coefficients. The "freq" is the center frequency / sample rate.
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If the float coefs represent a low pass filter with bandwidth 1 kHz, the new bandpass
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filter has width 2 kHz. The filter can be re-tuned repeatedly.
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\*---------------------------------------------------------------------------*/
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void quisk_cfTune(struct quisk_cfFilter * filter, float freq) {
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float D, tune;
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int i;
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if ( ! filter->cpxCoefs)
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filter->cpxCoefs = (std::complex<float> *) malloc(filter->nTaps * sizeof(std::complex<float>));
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tune = 2.0 * M_PI * freq;
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D = (filter->nTaps - 1.0) / 2.0;
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for (i = 0; i < filter->nTaps; i++) {
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float tval = tune * (i - D);
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filter->cpxCoefs[i] = cmplx(tval) * filter->dCoefs[i];
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}
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}
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/*---------------------------------------------------------------------------*\
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FUNCTIONS...: quisk_ccfFilter
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AUTHOR......: Jim Ahlstrom
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DATE CREATED: 4 June 2018
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Filter complex samples using complex coefficients. The inSamples and outSamples may be
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the same array. The loop runs forward over coefficients but backwards over samples.
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Therefore, the coefficients must be reversed unless they are created by quisk_cfTune.
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Low pass filter coefficients are symmetrical, so this does not usually matter.
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\*---------------------------------------------------------------------------*/
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void quisk_ccfFilter(std::complex<float> *inSamples, std::complex<float> *outSamples, int count, struct quisk_cfFilter * filter) {
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int i, k;
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std::complex<float> *ptSample;
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std::complex<float> *ptCoef;
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std::complex<float> accum;
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for (i = 0; i < count; i++) {
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*filter->ptcSamp = inSamples[i];
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accum = 0;
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ptSample = filter->ptcSamp;
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ptCoef = filter->cpxCoefs;
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for (k = 0; k < filter->nTaps; k++, ptCoef++) {
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accum += *ptSample * *ptCoef;
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if (--ptSample < filter->cSamples)
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ptSample = filter->cSamples + filter->nTaps - 1;
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}
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outSamples[i] = accum;
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if (++filter->ptcSamp >= filter->cSamples + filter->nTaps)
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filter->ptcSamp = filter->cSamples;
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}
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}
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} // freeDV
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