#ifndef INCLUDE_HIGHPASS_H #define INCLUDE_HIGHPASS_H #define _USE_MATH_DEFINES #include #include "dsp/dsptypes.h" template class Highpass { public: Highpass() { } void create(int nTaps, double sampleRate, double cutoff) { double wc = 2.0 * M_PI * cutoff; double Wc = wc / sampleRate; int i; // check constraints if(!(nTaps & 1)) { qDebug("Highpass filter has to have an odd number of taps"); nTaps++; } // make room m_samples.resize(nTaps); for(int i = 0; i < nTaps; i++) m_samples[i] = 0; m_ptr = 0; m_taps.resize(nTaps / 2 + 1); // generate Sinc filter core for lowpass but inverting every other tap for highpass keeping center tap for(i = 0; i < nTaps / 2 + 1; i++) { if(i == (nTaps - 1) / 2) m_taps[i] = -(Wc / M_PI); else m_taps[i] = -sin(((double)i - ((double)nTaps - 1.0) / 2.0) * Wc) / (((double)i - ((double)nTaps - 1.0) / 2.0) * M_PI); } m_taps[(nTaps - 1) / 2] += 1; // apply Hamming window for(i = 0; i < nTaps / 2 + 1; i++) m_taps[i] *= 0.54 + 0.46 * cos((2.0 * M_PI * ((double)i - ((double)nTaps - 1.0) / 2.0)) / (double)nTaps); // normalize Real sum = 0; for(i = 0; i < (int)m_taps.size() - 1; i++) sum += m_taps[i] * 2; sum += m_taps[i]; for(i = 0; i < (int)m_taps.size(); i++) m_taps[i] /= sum; } Type filter(Type sample) { Type acc = 0; int a = m_ptr; int b = a - 1; int i, n_taps, size; m_samples[m_ptr] = sample; size = m_samples.size(); // Valgrind optim (2) while(b < 0) { b += size; } n_taps = m_taps.size() - 1; // Valgrind optim for (i = 0; i < n_taps; i++) { acc += (m_samples[a] + m_samples[b]) * m_taps[i]; a++; while (a >= size) { a -= size; } b--; while (b < 0) { b += size; } } acc += m_samples[a] * m_taps[i]; m_ptr++; while (m_ptr >= size) { m_ptr -= size; } return acc; } private: std::vector m_taps; std::vector m_samples; int m_ptr; }; #endif // INCLUDE_HIGHPASS_H