SDRPlusPlus/core/src/dsp/window.h

#pragma once
#include <dsp/block.h>
#include <dsp/types.h>
#include <dsp/utils/window_functions.h>
#include <fftw3.h>

namespace dsp {
    namespace filter_window {
        class generic_window {
        public:
            virtual int getTapCount() { return -1; }
            virtual void createTaps(float* taps, int tapCount, float factor = 1.0f) {}
        };

        class generic_complex_window {
        public:
            virtual int getTapCount() { return -1; }
            virtual void createTaps(dsp::complex_t* taps, int tapCount, float factor = 1.0f) {}
        };

        class BlackmanWindow : public filter_window::generic_window {
        public:
            BlackmanWindow() {}
            BlackmanWindow(float cutoff, float transWidth, float sampleRate) { init(cutoff, transWidth, sampleRate); }

            void init(float cutoff, float transWidth, float sampleRate) {
                _cutoff = cutoff;
                _transWidth = transWidth;
                _sampleRate = sampleRate;
            }

            void setSampleRate(float sampleRate) {
                _sampleRate = sampleRate;
            }

            void setCutoff(float cutoff) {
                _cutoff = cutoff;
            }
            
            void setTransWidth(float transWidth) {
                _transWidth = transWidth;
            }

            int getTapCount() {
                float fc = _cutoff / _sampleRate;
                if (fc > 1.0f) {
                    fc = 1.0f;
                }

                int _M = 4.0f / (_transWidth / _sampleRate);
                if (_M < 4) {
                    _M = 4;
                }

                if (_M % 2 == 0) { _M++; }

                return _M;
            }

            void createTaps(float* taps, int tapCount, float factor = 1.0f) {
                // Calculate cuttoff frequency
                float omega = 2.0f * FL_M_PI * (_cutoff / _sampleRate);
                if (omega > FL_M_PI) { omega = FL_M_PI; }

                // Generate taps
                float val;
                float sum = 0.0f;
                float tc = tapCount;
                for (int i = 0; i < tapCount; i++) {
                    val = math::sinc(omega, (float)i - (tc/2), FL_M_PI) * window_function::blackman(i, tc - 1);
                    taps[i] = val;
                    sum += val;
                }

                // Normalize taps and multiply by supplied factor
                for (int i = 0; i < tapCount; i++) {
                    taps[i] *= factor;
                    taps[i] /= sum;
                }
            }

        private:
            float _cutoff, _transWidth, _sampleRate;

        };

        class BandPassBlackmanWindow : public filter_window::generic_complex_window {
        public:
            BandPassBlackmanWindow() {}
            BandPassBlackmanWindow(float lowCutoff, float highCutoff, float transWidth, float sampleRate) { init(lowCutoff, highCutoff, transWidth, sampleRate); }

            void init(float lowCutoff, float highCutoff, float transWidth, float sampleRate) {
                assert(lowCutoff <= highCutoff);
                _lowCutoff = lowCutoff;
                _highCutoff = highCutoff;
                _transWidth = transWidth;
                _sampleRate = sampleRate;

                // Calculate other values
                _offset = (_lowCutoff + _highCutoff) / 2.0f;
                _cutoff = fabs((_highCutoff - _lowCutoff) / 2.0f);
            }

            void setSampleRate(float sampleRate) {
                _sampleRate = sampleRate;
            }

            void setCutoffs(float lowCutoff, float highCutoff) {
                assert(lowCutoff <= highCutoff);
                _lowCutoff = lowCutoff;
                _highCutoff = highCutoff;

                // Calculate other values
                _offset = (_lowCutoff + _highCutoff) / 2.0f;
                _cutoff = fabs((_highCutoff - _lowCutoff) / 2.0f);
            }

            void setLowCutoff(float lowCutoff) {
                assert(lowCutoff <= _highCutoff);
                _lowCutoff = lowCutoff;

                // Calculate other values
                _offset = (_lowCutoff + _highCutoff) / 2.0f;
                _cutoff = fabs((_highCutoff - _lowCutoff) / 2.0f);
            }

            void setHighCutoff(float highCutoff) {
                assert(_lowCutoff <= highCutoff);
                _highCutoff = highCutoff;

                // Calculate other values
                _offset = (_lowCutoff + _highCutoff) / 2.0f;
                _cutoff = fabs((_highCutoff - _lowCutoff) / 2.0f);
            }
            
            void setTransWidth(float transWidth) {
                _transWidth = transWidth;
            }

            int getTapCount() {
                float fc = _cutoff / _sampleRate;
                if (fc > 1.0f) {
                    fc = 1.0f;
                }

                int _M = 4.0f / (_transWidth / _sampleRate);
                if (_M < 4) {
                    _M = 4;
                }

                if (_M % 2 == 0) { _M++; }

                return _M;
            }

            void createTaps(dsp::complex_t* taps, int tapCount, float factor = 1.0f) {
                // Calculate cuttoff frequency
                float omega = 2.0f * FL_M_PI * (_cutoff / _sampleRate);
                if (omega > FL_M_PI) { omega = FL_M_PI; }

                // Generate taps
                float val;
                float sum = 0.0f;
                float tc = tapCount;
                for (int i = 0; i < tapCount; i++) {
                    val = math::sinc(omega, (float)i - (tc/2), FL_M_PI) * window_function::blackman(i, tc - 1);
                    taps[i].re = val;
                    taps[i].im = 0;
                    sum += val;
                }

                // Normalize taps and multiply by supplied factor
                for (int i = 0; i < tapCount; i++) {
                    taps[i] = taps[i] * factor;
                    taps[i] = taps[i] / sum;
                }

                // Add offset
                lv_32fc_t phase = lv_cmake(1.0f, 0.0f);
                lv_32fc_t phaseDelta = lv_cmake(std::cos((-_offset / _sampleRate) * 2.0f * FL_M_PI), std::sin((-_offset / _sampleRate) * 2.0f * FL_M_PI));
                volk_32fc_s32fc_x2_rotator_32fc((lv_32fc_t*)taps, (lv_32fc_t*)taps, phaseDelta, &phase, tapCount);
            }

        private:
            float _lowCutoff, _highCutoff;
            float _cutoff, _transWidth, _sampleRate, _offset;
        };
    }

    class RRCTaps : public filter_window::generic_window {
    public:
        RRCTaps() {}
        RRCTaps(int tapCount, float sampleRate, float baudRate, float alpha) { init(tapCount, sampleRate, baudRate, alpha); }

        void init(int tapCount, float sampleRate, float baudRate, float alpha) {
            _tapCount = tapCount;
            _sampleRate = sampleRate;
            _baudRate = baudRate;
            _alpha = alpha;
        }

        int getTapCount() {
            return _tapCount;
        }

        void setSampleRate(float sampleRate) {
            _sampleRate = sampleRate;
        }

        void setBaudRate(float baudRate) {
            _baudRate = baudRate;
        }

        void setTapCount(int count) {
            _tapCount = count;
        }

        void setAlpha(float alpha) {
            _alpha = alpha;
        }

        void createTaps(float* taps, int tapCount, float factor = 1.0f) {
            // ======== CREDIT: GNU Radio =========
            tapCount |= 1; // ensure that tapCount is odd

            double spb = _sampleRate / _baudRate; // samples per bit/symbol
            double scale = 0;
            for (int i = 0; i < tapCount; i++)
            {
                double x1, x2, x3, num, den;
                double xindx = i - tapCount / 2;
                x1 = FL_M_PI * xindx / spb;
                x2 = 4 * _alpha * xindx / spb;
                x3 = x2 * x2 - 1;

                    // Avoid Rounding errors...
                if (fabs(x3) >= 0.000001) {
                    if (i != tapCount / 2)
                        num = cos((1 + _alpha) * x1) +
                            sin((1 - _alpha) * x1) / (4 * _alpha * xindx / spb);
                    else
                        num = cos((1 + _alpha) * x1) + (1 - _alpha) * FL_M_PI / (4 * _alpha);
                    den = x3 * FL_M_PI;
                }
                else {
                    if (_alpha == 1)
                    {
                        taps[i] = -1;
                        scale += taps[i];
                        continue;
                    }
                    x3 = (1 - _alpha) * x1;
                    x2 = (1 + _alpha) * x1;
                    num = (sin(x2) * (1 + _alpha) * FL_M_PI -
                        cos(x3) * ((1 - _alpha) * FL_M_PI * spb) / (4 * _alpha * xindx) +
                        sin(x3) * spb * spb / (4 * _alpha * xindx * xindx));
                    den = -32 * FL_M_PI * _alpha * _alpha * xindx / spb;
                }
                taps[i] = 4 * _alpha * num / den;
                scale += taps[i];
            }

            for (int i = 0; i < tapCount; i++) {
                taps[i] = taps[i] / scale;
            }
        }

    private:
        int _tapCount;
        float _sampleRate, _baudRate, _alpha;

    };

    // class NotchWindow : public filter_window::generic_complex_window {
    // public:
    //     NotchWindow() {}

    //     NotchWindow(float frequency, float width, float sampleRate, int tapCount) { init(frequency, width, sampleRate, tapCount); }

    //     ~NotchWindow() {
    //         if (fft_in) { fftwf_free(fft_in); }
    //         if (fft_out) { fftwf_free(fft_out); }
    //         fftwf_destroy_plan(fft_plan);
    //     }

    //     void init(float frequency, float width, float sampleRate, int tapCount) {
    //         _frequency = frequency;
    //         _width = width;
    //         _sampleRate = sampleRate;
    //         _tapCount = tapCount;

    //         // Ensure the number of taps is even
    //         if (_tapCount & 1) { _tapCount++; }    
        
    //         fft_in = (complex_t*)fftwf_malloc(_tapCount * sizeof(complex_t));
    //         fft_out = (complex_t*)fftwf_malloc(_tapCount * sizeof(complex_t));

    //         fft_plan = fftwf_plan_dft_1d(_tapCount, (fftwf_complex*)fft_in, (fftwf_complex*)fft_out, FFTW_BACKWARD, FFTW_ESTIMATE);
    //     }

    //     void setFrequency(float frequency) {
    //         _frequency = frequency;
    //     }

    //     void setWidth(float width) {
    //         _width = width;
    //     }

    //     void setSampleRate(float sampleRate) {
    //         _sampleRate = sampleRate;
    //     }

    //     void setTapCount(int count) {
    //         _tapCount = count;

    //         // Ensure the number of taps is even

    //         // Free buffers
    //         if (fft_in) { fftwf_free(fft_in); }
    //         if (fft_out) { fftwf_free(fft_out); }
    //         fftwf_destroy_plan(fft_plan);

    //         // Reallocate
    //         fft_in = (complex_t*)fftwf_malloc(_tapCount * sizeof(complex_t));
    //         fft_out = (complex_t*)fftwf_malloc(_tapCount * sizeof(complex_t));

    //         // Create new plan
    //         fft_plan = fftwf_plan_dft_1d(_tapCount, (fftwf_complex*)fft_in, (fftwf_complex*)fft_out, FFTW_BACKWARD, FFTW_ESTIMATE);
    //     }

    //     int getTapCount() {
    //         return _tapCount;
    //     }

    //     void createTaps(complex_t* taps, int tapCount, float factor = 1.0f) {
    //         float ratio = _sampleRate / (float)tapCount;
    //         int thalf = tapCount / 2;
    //         float start = _frequency - (_width / 2.0f);
    //         float stop = _frequency + (_width / 2.0f);
            
    //         // Fill taps
    //         float freq;
    //         float pratio = 2.0f * FL_M_PI / (float)tapCount;
    //         complex_t phaseDiff = {cosf(pratio), -sinf(pratio)};
    //         complex_t phasor = {1, 0};
    //         for (int i = 0; i < tapCount; i++) {
    //             freq = (i < thalf) ? ((float)i * ratio) : -((float)(tapCount - i) * ratio);
    //             if (freq >= start && freq <= stop) {
    //                 fft_in[i] = {0, 0};
    //             }
    //             else {
    //                 fft_in[i] = phasor;
    //             }
    //             phasor = phasor * phaseDiff;
    //         }

    //         // Run IFFT
    //         fftwf_execute(fft_plan);

    //         // Apply window and copy to output
    //         for (int i = 0; i < tapCount; i++) {
    //             taps[tapCount - i - 1] = fft_out[i] / (float)tapCount;
    //         }
    //     }

    // private:
    //     complex_t* fft_in = NULL;
    //     complex_t* fft_out = NULL;
    //     float _frequency, _width, _sampleRate;
    //     int _tapCount;

    //     fftwf_plan fft_plan;

    // };

    class NotchWindow : public filter_window::generic_complex_window {
    public:
        NotchWindow() {}

        NotchWindow(float frequency, float width, float sampleRate, int tapCount) { init(frequency, width, sampleRate, tapCount); }

        void init(float frequency, float width, float sampleRate, int tapCount) {
            _frequency = frequency;
            _sampleRate = sampleRate;
            _tapCount = tapCount;
        }

        void setFrequency(float frequency) {
            _frequency = frequency;
        }

        void setWidth(float width) {}

        void setSampleRate(float sampleRate) {
            _sampleRate = sampleRate;
        }

        void setTapCount(int count) {
            _tapCount = count;
        }

        int getTapCount() {
            return _tapCount;
        }

        void createTaps(complex_t* taps, int tapCount, float factor = 1.0f) {
            // Generate exponential decay
            float fact = 1.0f / (float)tapCount;
            for (int i = 0; i < tapCount; i++) {
                taps[tapCount - i - 1] = {expf(-fact*i) * (float)window_function::blackman(i, tapCount - 1), 0};
            }

            // Frequency translate it to the right place
            lv_32fc_t phase = lv_cmake(1.0f, 0.0f);
            lv_32fc_t phaseDelta = lv_cmake(std::cos((-_frequency / _sampleRate) * 2.0f * FL_M_PI), std::sin((-_frequency / _sampleRate) * 2.0f * FL_M_PI));
            volk_32fc_s32fc_x2_rotator_32fc((lv_32fc_t*)taps, (lv_32fc_t*)taps, phaseDelta, &phase, tapCount);
        }

    private:
        float _frequency, _sampleRate;
        int _tapCount;

    };
}