Fix some compatibility issues in level.cpp, and possibly also a tiny accuracy improve...

[c64tapwav] / synth.cpp

diff --git a/synth.cpp b/synth.cpp
index f40a76b4837d61158582defe3c965f00305ddfed..90c16e05d956d055e2fead4f1d01b78d1626a470 100644 (file)
--- a/synth.cpp
+++ b/synth.cpp
@@ -4,17 +4,20 @@
 #include <vector>
 #include <assert.h>
 
 #include <vector>
 #include <assert.h>
 

+#include "common.h"
+

 using namespace std;
 
 #define LANCZOS_RADIUS 10
 #define RESOLUTION 256
 using namespace std;
 
 #define LANCZOS_RADIUS 10
 #define RESOLUTION 256

-#define WAVE_FREQ 44100
-#define C64_FREQ 985248

 
 // Cutoff frequency of low-pass filter (must be max. WAVE_FREQ / 2 or you
 // will get aliasing)
 #define LPFILTER_FREQ 22050
 
 
 // Cutoff frequency of low-pass filter (must be max. WAVE_FREQ / 2 or you
 // will get aliasing)
 #define LPFILTER_FREQ 22050
 

+// Cutoff frequency of high-pass filter
+#define HPFILTER_FREQ 40
+

 #define NORMALIZED_LPFILTER_FREQ (float(LPFILTER_FREQ) / float(WAVE_FREQ))
 #define LANCZOS_EFFECTIVE_RADIUS (LANCZOS_RADIUS / (NORMALIZED_LPFILTER_FREQ * 2.0))
 
 #define NORMALIZED_LPFILTER_FREQ (float(LPFILTER_FREQ) / float(WAVE_FREQ))
 #define LANCZOS_EFFECTIVE_RADIUS (LANCZOS_RADIUS / (NORMALIZED_LPFILTER_FREQ * 2.0))
 


@@ -80,45 +83,62 @@ struct pulse {
 };
 vector<pulse> pulses;
 
 };
 vector<pulse> pulses;
 

-int main(int argc, char **argv)
+static float a1, a2, b0, b1, b2;
+static float d0, d1;
+
+static void filter_init(float cutoff_radians)

 {
 {

-       make_table();
+       float resonance = 1.0f / sqrt(2.0f);
+       float sn, cs;
+       sincosf(cutoff_radians, &sn, &cs);
+
+       float alpha = float(sn / (2 * resonance));
+
+       // coefficients for highpass filter
+        float a0 = 1 + alpha;
+       b0 = (1 + cs) * 0.5f;
+       b1 = -(1 + cs);
+       b2 = b0;
+        a1 = -2 * cs;
+        a2 = 1 - alpha;
+
+       float invA0 = 1.0f / a0;
+       b0 *= invA0;
+       b1 *= invA0;
+       b2 *= invA0;
+       a1 *= invA0;
+       a2 *= invA0;
+
+       // reset filter delays
+       d0 = d1 = 0.0f;
+}

 
 

-       FILE *fp = fopen(argv[1], "rb");
-       fseek(fp, 14, SEEK_SET);
-
-       int x = 0;
-
-       while (!feof(fp)) {
-               int len = getc(fp);
-               int cycles;
-               if (len == 0) {
-                       int a = getc(fp);
-                       int b = getc(fp);
-                       int c = getc(fp);
-                       cycles = a | (b << 8) | (c << 16);
-               } else {
-                       cycles = len * 8;
-               }
-               pulse p;
-               p.start = float(x) * WAVE_FREQ / C64_FREQ;
-               p.end = (float(x) + cycles * 0.5) * WAVE_FREQ / C64_FREQ;
-               pulses.push_back(p);
-               x += cycles;
-       }
+static float filter_update(float in)
+{
+       float out = b0*in + d0;
+       d0 = b1 * in - a1 * out + d1;
+       d1 = b2 * in - a2 * out;
+       return out;
+}

 
 

-       int len_cycles = x;
-       int len_samples = int(ceil(float(len_cycles) * WAVE_FREQ / C64_FREQ));
+vector<float> synth(const vector<pulse> &pulses)
+{
+       make_table();
+
+       int len_samples = int(ceil(pulses.back().start + (pulses.back().end - pulses.back().start) * 2));

        
        

-       fprintf(stderr, "%d pulses, total %.2f seconds (%d samples)\n", pulses.size(), len_cycles / float(C64_FREQ), len_samples);
+       fprintf(stderr, "%d pulses, total %.2f seconds (%d samples)\n", int(pulses.size()), len_samples / float(WAVE_FREQ), len_samples);

 
        int pulse_begin = 0;
 
 
        int pulse_begin = 0;
 

+       vector<float> samples;
+       samples.reserve(len_samples);
+

        for (int i = 0; i < len_samples; ++i) {
 //     for (int i = 50000000; i < 51000000; ++i) {
 //             double t = i * 0.01;
                double t = i;
        for (int i = 0; i < len_samples; ++i) {
 //     for (int i = 50000000; i < 51000000; ++i) {
 //             double t = i * 0.01;
                double t = i;

-               double sample = 0.0;
+               double sample = -0.5;

                for (unsigned j = pulse_begin; j < pulses.size(); ++j) {
                        if (t - pulses[j].end > LANCZOS_EFFECTIVE_RADIUS) {
                                ++pulse_begin;
                for (unsigned j = pulse_begin; j < pulses.size(); ++j) {
                        if (t - pulses[j].end > LANCZOS_EFFECTIVE_RADIUS) {
                                ++pulse_begin;


@@ -130,8 +150,22 @@ int main(int argc, char **argv)
                        float contribution = window_integral(pulses[j].start - t, pulses[j].end - t);
                        sample += contribution;
                }
                        float contribution = window_integral(pulses[j].start - t, pulses[j].end - t);
                        sample += contribution;
                }

-               printf("%f\n", sample);
-//             short s = lrintf((sample - 0.5f) * 16384.0f);
-//             fwrite(&s, 2, 1, stdout);
+               samples.push_back(sample);

        }
        }

+
+       // filter forwards, then backwards (perfect phase filtering)
+       vector<float> filtered_samples, refiltered_samples;
+       filtered_samples.resize(len_samples);
+       refiltered_samples.resize(len_samples);
+
+       filter_init(M_PI * HPFILTER_FREQ / WAVE_FREQ);
+       for (int i = 0; i < len_samples; ++i) {
+               filtered_samples[i] = filter_update(samples[i]);
+       }
+       filter_init(M_PI * HPFILTER_FREQ / WAVE_FREQ);
+       for (int i = len_samples; i --> 0; ) {
+               refiltered_samples[i] = filter_update(filtered_samples[i]);
+       }
+
+       return refiltered_samples;

 }
 }