created ascii art dft plotter in uhd

1 files changed, 320 insertions, 0 deletions

diff --git a/host/examples/ascii_art_dft.hpp b/host/examples/ascii_art_dft.hpp
new file mode 100644
index 000000000..ee2267c2d
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+++ b/host/examples/ascii_art_dft.hpp
@@ -0,0 +1,320 @@
+//
+// ASCII Art DFT Plotter - Josh Blum
+//
+
+#ifndef ASCII_ART_DFT_HPP
+#define ASCII_ART_DFT_HPP
+
+#include <string>
+#include <cstddef>
+#include <vector>
+#include <complex>
+#include <stdexcept>
+
+namespace acsii_art_dft{
+
+    //! Type produced by the log power DFT function
+    typedef std::vector<float> log_pwr_dft_type;
+
+    /*!
+     * Get a logarithmic power DFT of the input samples.
+     * Samples are expected to be in the range [-1.0, 1.0].
+     * \param samps a pointer to an array of complex samples
+     * \param nsamps the number of samples in the array
+     * \return a real range of DFT bins in units of dB
+     */
+    template <typename T> log_pwr_dft_type log_pwr_dft(
+        const std::complex<T> *samps, size_t nsamps
+    );
+
+    /*!
+     * Convert a DFT to a piroundable ascii plot.
+     * \param dft the log power dft bins
+     * \param width the frame width in characters
+     * \param height the frame height in characters
+     * \param samp_rate the sample rate in Sps
+     * \param dc_freq the DC frequency in Hz
+     * \param dyn_rng the dynamic range in dB
+     * \param ref_lvl the reference level in dB
+     * \return the plot as an ascii string
+     */
+    std::string dft_to_plot(
+        const log_pwr_dft_type &dft,
+        size_t width,
+        size_t height,
+        double samp_rate,
+        double dc_freq,
+        float dyn_rng,
+        float ref_lvl
+    );
+
+} //namespace ascii_dft
+
+/***********************************************************************
+ * Implementation includes
+ **********************************************************************/
+#include <cmath>
+#include <sstream>
+#include <algorithm>
+
+/***********************************************************************
+ * Helper functions
+ **********************************************************************/
+namespace {/*anon*/
+
+    static const double pi = double(std::acos(-1.0));
+
+    //! Round a floating-point value to the nearest integer
+    template <typename T> int iround(T val){
+        return (val > 0)? int(val + 0.5) : int(val - 0.5);
+    }
+
+    //! Pick the closest number that is nice to display
+    template <typename T> T to_clean_num(const T num){
+        if (num == 0) return 0;
+        const T pow10 = std::pow(T(10), int(std::floor(std::log10(std::abs(num)))));
+        const T norm = std::abs(num)/pow10;
+        static const int cleans[] = {1, 2, 5, 10};
+        int clean = cleans[0];
+        for (size_t i = 1; i < sizeof(cleans)/sizeof(cleans[0]); i++){
+            if (std::abs(norm - cleans[i]) < std::abs(norm - clean))
+                clean = cleans[i];
+        }
+        return ((num < 0)? -1 : 1)*clean*pow10;
+    }
+
+    //! Compute an FFT with pre-computed factors using Cooley-Tukey
+    template <typename T> std::complex<T> ct_fft_f(
+        const std::complex<T> *samps, size_t nsamps,
+        const std::complex<T> *factors,
+        size_t start = 0, size_t step = 1
+    ){
+        if (nsamps == 1) return samps[start];
+        std::complex<T> E_k = ct_fft_f(samps, nsamps/2, factors+1, start,      step*2);
+        std::complex<T> O_k = ct_fft_f(samps, nsamps/2, factors+1, start+step, step*2);
+        return E_k + factors[0]*O_k;
+    }
+
+    //! Compute an FFT for a particular bin k using Cooley-Tukey
+    template <typename T> std::complex<T> ct_fft_k(
+        const std::complex<T> *samps, size_t nsamps, size_t k
+    ){
+        //pre-compute the factors to use in Cooley-Tukey
+        std::vector<std::complex<T> > factors;
+        for (size_t N = nsamps; N != 0; N /= 2){
+            factors.push_back(std::exp(std::complex<T>(0, T(-2*pi*k/N))));
+        }
+        return ct_fft_f(samps, nsamps, &factors.front());
+    }
+
+    //! Helper class to build a DFT plot frame
+    class frame_type{
+    public:
+        frame_type(size_t width, size_t height):
+            _frame(width-1, std::vector<char>(height, ' '))
+        {
+            /* NOP */
+        }
+
+        //accessors to parts of the frame
+        char &get_plot(size_t b, size_t z){return _frame.at(b+albl_w).at(z+flbl_h);}
+        char &get_albl(size_t b, size_t z){return _frame.at(b)       .at(z+flbl_h);}
+        char &get_ulbl(size_t b)          {return _frame.at(b)       .at(flbl_h-1);}
+        char &get_flbl(size_t b)          {return _frame.at(b+albl_w).at(flbl_h-1);}
+
+        //dimension accessors
+        size_t get_plot_h(void) const{return _frame.front().size() - flbl_h;}
+        size_t get_plot_w(void) const{return _frame.size() - albl_w;}
+        size_t get_albl_w(void) const{return albl_w;}
+
+        std::string to_string(void){
+            std::stringstream frame_ss;
+            for (size_t z = 0; z < _frame.front().size(); z++){
+                for (size_t b = 0; b < _frame.size(); b++){
+                    frame_ss << _frame[b][_frame[b].size()-z-1];
+                }
+                frame_ss << std::endl;
+            }
+            return frame_ss.str();
+        }
+
+    private:
+        static const size_t albl_w = 6, flbl_h = 1;
+        std::vector<std::vector<char> > _frame;
+    };
+
+} //namespace /*anon*/
+
+/***********************************************************************
+ * Implementation code
+ **********************************************************************/
+namespace acsii_art_dft{
+
+    //! skip constants for amplitude and frequency labels
+    static const size_t albl_skip = 5, flbl_skip = 20;
+
+    template <typename T> log_pwr_dft_type log_pwr_dft(
+        const std::complex<T> *samps, size_t nsamps
+    ){
+        if (nsamps & (nsamps - 1))
+            throw std::runtime_error("num samps is not a power of 2");
+
+        //compute the window
+        double win_pwr = 0;
+        std::vector<std::complex<T> > win_samps;
+        for(size_t n = 0; n < nsamps; n++){
+            //double w_n = 1;
+            //double w_n = 0.54 //hamming window
+            //    -0.46*std::cos(2*pi*n/(nsamps-1))
+            //;
+            double w_n = 0.35875 //blackman-harris window
+                -0.48829*std::cos(2*pi*n/(nsamps-1))
+                +0.14128*std::cos(4*pi*n/(nsamps-1))
+                -0.01168*std::cos(6*pi*n/(nsamps-1))
+            ;
+            //double w_n = 1 // flat top window
+            //    -1.930*std::cos(2*pi*n/(nsamps-1))
+            //    +1.290*std::cos(4*pi*n/(nsamps-1))
+            //    -0.388*std::cos(6*pi*n/(nsamps-1))
+            //    +0.032*std::cos(8*pi*n/(nsamps-1))
+            //;
+            win_samps.push_back(T(w_n)*samps[n]);
+            win_pwr += w_n*w_n;
+        }
+
+        //compute the log-power dft
+        log_pwr_dft_type log_pwr_dft;
+        for(size_t k = 0; k < nsamps; k++){
+            std::complex<T> dft_k = ct_fft_k(&win_samps.front(), nsamps, k);
+            log_pwr_dft.push_back(float(
+                + 20*std::log10(std::abs(dft_k))
+                - 20*std::log10(T(nsamps))
+                - 10*std::log10(win_pwr/nsamps)
+                + 3
+            ));
+        }
+
+        return log_pwr_dft;
+    }
+
+    std::string dft_to_plot(
+        const log_pwr_dft_type &dft_,
+        size_t width,
+        size_t height,
+        double samp_rate,
+        double dc_freq,
+        float dyn_rng,
+        float ref_lvl
+    ){
+        frame_type frame(width, height); //fill this frame
+
+        //re-order the dft so dc in in the center
+        const size_t num_bins = dft_.size() - 1 + dft_.size()%2; //make it odd
+        log_pwr_dft_type dft(num_bins);
+        for (size_t n = 0; n < num_bins; n++){
+            dft[n] = dft_[(n + num_bins/2)%num_bins];
+        }
+
+        //fill the plot with dft bins
+        for (size_t b = 0; b < frame.get_plot_w(); b++){
+            //indexes from the dft to grab for the plot
+            const size_t n_start = std::max(iround(double(b-0.5)*(num_bins-1)/(frame.get_plot_w()-1)), 0);
+            const size_t n_stop  = std::min(iround(double(b+0.5)*(num_bins-1)/(frame.get_plot_w()-1)), int(num_bins));
+
+            //calculate val as the max across points
+            float val = dft.at(n_start);
+            for (size_t n = n_start; n < n_stop; n++) val = std::max(val, dft.at(n));
+
+            const float scaled = (val - (ref_lvl - dyn_rng))*(frame.get_plot_h()-1)/dyn_rng;
+            for (size_t z = 0; z < frame.get_plot_h(); z++){
+                static const std::string syms(".:!|");
+                if      (scaled-z > 1) frame.get_plot(b, z) = syms.at(syms.size()-1);
+                else if (scaled-z > 0) frame.get_plot(b, z) = syms.at(size_t((scaled-z)*syms.size()));
+            }
+        }
+
+        //create vertical amplitude labels
+        const float db_step = to_clean_num(dyn_rng/(frame.get_plot_h()-1)*albl_skip);
+        for (
+            float db = db_step*(int((ref_lvl - dyn_rng)/db_step));
+            db      <=  db_step*(int(ref_lvl/db_step));
+            db      +=  db_step
+        ){
+            const int z = iround((db - (ref_lvl - dyn_rng))*(frame.get_plot_h()-1)/dyn_rng);
+            if (z < 0 or size_t(z) >= frame.get_plot_h()) continue;
+            std::stringstream ss; ss << db; std::string lbl = ss.str();
+            for (size_t i = 0; i < lbl.size() and i < frame.get_albl_w(); i++){
+                frame.get_albl(i, z) = lbl[i];
+            }
+        }
+
+        //create vertical units label
+        std::string ulbl = "dBfs";
+        for (size_t i = 0; i < ulbl.size(); i++){
+            frame.get_ulbl(i+1) = ulbl[i];
+        }
+
+        //create horizontal frequency labels
+        const double f_step = to_clean_num(samp_rate/frame.get_plot_w()*flbl_skip);
+        for (
+            double freq = f_step*int((-samp_rate/2/f_step));
+            freq       <= f_step*int((+samp_rate/2/f_step));
+            freq       += f_step
+        ){
+            const int b = iround((freq + samp_rate/2)*(frame.get_plot_w()-1)/samp_rate);
+            std::stringstream ss; ss << (freq+dc_freq)/1e6 << "MHz"; std::string lbl = ss.str();
+            if (b < int(lbl.size()/2) or b + lbl.size() - lbl.size()/2 >= frame.get_plot_w()) continue;
+            for (size_t i = 0; i < lbl.size(); i++){
+                frame.get_flbl(b + i - lbl.size()/2) = lbl[i];
+            }
+        }
+
+        return frame.to_string();
+    }
+} //namespace ascii_dft
+
+#endif /*ASCII_ART_DFT_HPP*/
+
+/*
+
+//example main function to test the dft
+
+#include <iostream>
+#include <cstdlib>
+#include <curses.h>
+
+int main(void){
+    initscr();
+
+    while (true){
+        clear();
+
+        std::vector<std::complex<float> > samples;
+        for(size_t i = 0; i < 512; i++){
+            samples.push_back(std::complex<float>(
+                float(std::rand() - RAND_MAX/2)/(RAND_MAX)/4,
+                float(std::rand() - RAND_MAX/2)/(RAND_MAX)/4
+            ));
+            samples[i] += 0.5*std::sin(i*3.14/2) + 0.7;
+        }
+
+        acsii_art_dft::log_pwr_dft_type dft;
+        dft = acsii_art_dft::log_pwr_dft(&samples.front(), samples.size());
+
+        printw("%s", acsii_art_dft::dft_to_plot(
+            dft, COLS, LINES,
+            12.5e4, 2.45e9,
+            60, 0
+        ).c_str());
+
+        sleep(1);
+    }
+
+
+    endwin();
+    std::cout << "here\n";
+    return 0;
+}
+
+*/
+