view data/fft/FFTapi.h @ 1196:c7b9c902642f spectrogram-minor-refactor

Fix threshold in spectrogram -- it wasn't working in the last release.
There is a new protocol for this. Formerly the threshold parameter had a
range from -50dB to 0 with the default at -50, and -50 treated internally
as "no threshold". However, there was a hardcoded, hidden internal threshold
for spectrogram colour mapping at -80dB with anything below this being rounded
to zero. Now the threshold parameter has range -81 to -1 with the default
at -80, -81 is treated internally as "no threshold", and there is no hidden
internal threshold. So the default behaviour is the same as before, an
effective -80dB threshold, but it is now possible to change this in both
directions. Sessions reloaded from prior versions may look slightly different
because, if the session says there should be no threshold, there will now
actually be no threshold instead of having the hidden internal one.

Still need to do something in the UI to make it apparent that the -81dB
setting removes the threshold entirely. This is at least no worse than the
previous, also obscured, magic -50dB setting.

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2006 Chris Cannam and QMUL.
    
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
    published by the Free Software Foundation; either version 2 of the
    License, or (at your option) any later version.  See the file
    COPYING included with this distribution for more information.
*/

#ifndef _FFT_API_H_
#define _FFT_API_H_

#ifdef HAVE_FFTW3F

#include <fftw3.h>

#define fftf_complex fftwf_complex
#define fftf_malloc fftwf_malloc
#define fftf_free fftwf_free
#define fftf_plan fftwf_plan
#define fftf_plan_dft_r2c_1d fftwf_plan_dft_r2c_1d
#define fftf_plan_dft_c2r_1d fftwf_plan_dft_c2r_1d
#define fftf_execute fftwf_execute
#define fftf_destroy_plan fftwf_destroy_plan

#else

// Provide a fallback FFT implementation if FFTW3f is not available.

typedef float fftf_complex[2];
#define fftf_malloc malloc
#define fftf_free free

struct fftf_plan_;
typedef fftf_plan_ *fftf_plan;

fftf_plan fftf_plan_dft_r2c_1d(int n, float *in, fftf_complex *out, unsigned);
fftf_plan fftf_plan_dft_c2r_1d(int n, fftf_complex *in, float *out, unsigned);
void fftf_execute(const fftf_plan p);
void fftf_destroy_plan(fftf_plan p);

#define FFTW_ESTIMATE 0
#define FFTW_MEASURE 0

#endif

#include <vector>
#include <complex>
#include <mutex>

class FFTForward // with fft shift but not window
{
    static std::mutex m_mutex;
    
public:
    FFTForward(int size) :
        m_size(size)
    {
        std::lock_guard<std::mutex> lock(m_mutex);
        m_input = (float *)fftf_malloc(size * sizeof(float));
        m_output = (fftf_complex *)fftf_malloc((size/2 + 1) * sizeof(fftf_complex));
        m_plan = fftf_plan_dft_r2c_1d(size, m_input, m_output, FFTW_ESTIMATE);
    }

    ~FFTForward() {
        std::lock_guard<std::mutex> lock(m_mutex);
        fftf_destroy_plan(m_plan);
        fftf_free(m_input);
        fftf_free(m_output);
    }

    std::vector<std::complex<float> > process(const std::vector<float> &in) const {
        const int hs = m_size/2;
        for (int i = 0; i < hs; ++i) {
            m_input[i] = in[i + hs];
        }
        for (int i = 0; i < hs; ++i) {
            m_input[i + hs] = in[i];
        }
        fftf_execute(m_plan);
        std::vector<std::complex<float> > result;
        result.reserve(hs + 1);
        for (int i = 0; i <= hs; ++i) {
            result.push_back({ m_output[i][0], m_output[i][1] });
        }
        return result;
    }

private:
    int m_size;
    float *m_input;
    fftf_complex *m_output;
    fftf_plan m_plan;
};

#endif