X-Git-Url: https://git.sesse.net/?p=c64tapwav;a=blobdiff_plain;f=decode.cpp;h=ec95faad5c960ad19fe5f137bded32c2faa2f7fb;hp=798a8729447ab143e51b3fd1bb9f1a11dad572be;hb=4146b98dc2a5bad67c67fe817cb2eb060eac19ea;hpb=35d290f19c02f0e884f4baec704851cfd1b86988

diff --git a/decode.cpp b/decode.cpp
index 798a872..ec95faa 100644
--- a/decode.cpp
+++ b/decode.cpp
@@ -1,71 +1,26 @@
 #include <stdio.h>
 #include <string.h>
 #include <math.h>
-#include <unistd.h>
 #include <assert.h>
+#include <limits.h>
 #include <vector>
 #include <algorithm>
 
-#define LANCZOS_RADIUS 30
+#include "audioreader.h"
+#include "interpolate.h"
+#include "tap.h"
+
 #define BUFSIZE 4096
 #define HYSTERESIS_LIMIT 3000
-#define SAMPLE_RATE 44100
 #define C64_FREQUENCY 985248
-#define TAP_RESOLUTION 8
 
 #define SYNC_PULSE_START 1000
-#define SYNC_PULSE_END 15000
-#define SYNC_PULSE_LENGTH 380.0
+#define SYNC_PULSE_END 20000
+#define SYNC_PULSE_LENGTH 378.0
 #define SYNC_TEST_TOLERANCE 1.10
 
-struct tap_header {
-	char identifier[12];
-	char version;
-	char reserved[3];
-	unsigned int data_len;
-};
-
-double sinc(double x)
-{
-	if (fabs(x) < 1e-6) {
-		return 1.0f - fabs(x);
-	} else {
-		return sin(x) / x;
-	}
-}
-
-#if 0
-double weight(double x)
-{
-	if (fabs(x) > LANCZOS_RADIUS) {
-		return 0.0f;
-	}
-	return sinc(M_PI * x) * sinc(M_PI * x / LANCZOS_RADIUS);
-}
-#else
-double weight(double x)
-{
-	if (fabs(x) > 1.0f) {
-		return 0.0f;
-	}
-	return 1.0f - fabs(x);
-}
-#endif
-
-double interpolate(const std::vector<short> &pcm, double i)
-{
-	int lower = std::max<int>(ceil(i - LANCZOS_RADIUS), 0);
-	int upper = std::min<int>(floor(i + LANCZOS_RADIUS), pcm.size() - 1);
-	double sum = 0.0f;
-
-	for (int x = lower; x <= upper; ++x) {
-		sum += pcm[x] * weight(i - x);
-	}
-	return sum;
-}
-	
 // between [x,x+1]
-double find_zerocrossing(const std::vector<short> &pcm, int x)
+double find_zerocrossing(const std::vector<float> &pcm, int x)
 {
 	if (pcm[x] == 0) {
 		return x;
@@ -74,14 +29,14 @@ double find_zerocrossing(const std::vector<short> &pcm, int x)
 		return x + 1;
 	}
 
-	assert(pcm[x + 1] > 0);
-	assert(pcm[x] < 0);
+	assert(pcm[x + 1] < 0);
+	assert(pcm[x] > 0);
 
-	double lower = x;
-	double upper = x + 1;
-	while (upper - lower > 1e-6) {
+	double upper = x;
+	double lower = x + 1;
+	while (lower - upper > 1e-3) {
 		double mid = 0.5f * (upper + lower);
-		if (interpolate(pcm, mid) > 0) {
+		if (lanczos_interpolate(pcm, mid) > 0) {
 			upper = mid;
 		} else {
 			lower = mid;
@@ -95,95 +50,68 @@ struct pulse {
 	double time;  // in seconds from start
 	double len;   // in seconds
 };
-	
-int main(int argc, char **argv)
-{
-	std::vector<short> pcm;
-
-	while (!feof(stdin)) {
-		short buf[BUFSIZE];
-		ssize_t ret = fread(buf, 2, BUFSIZE, stdin);
-		if (ret >= 0) {
-			pcm.insert(pcm.end(), buf, buf + ret);
-		}
-	}	
-
-#if 0
-	for (int i = 0; i < LEN; ++i) {
-		in[i] += rand() % 10000;
-	}
-#endif
 
-#if 0
-	for (int i = 0; i < LEN; ++i) {
-		printf("%d\n", in[i]);
+// Calibrate on the first ~25k pulses (skip a few, just to be sure).
+double calibrate(const std::vector<pulse> &pulses) {
+	if (pulses.size() < SYNC_PULSE_END) {
+		fprintf(stderr, "Too few pulses, not calibrating!\n");
+		return 1.0;
 	}
-#endif
 
-	std::vector<pulse> pulses;  // in seconds
+	int sync_pulse_end = -1;
+	double sync_pulse_stddev = -1.0;
 
-	// Find the flanks.
-	int last_bit = -1;
-	double last_upflank = -1;
-	int last_max_level = 0;
-	for (unsigned i = 0; i < pcm.size(); ++i) {
-		int bit = (pcm[i] > 0) ? 1 : 0;
-		if (bit == 1 && last_bit == 0 && last_max_level > HYSTERESIS_LIMIT) {
-			// up-flank!
-			double t = find_zerocrossing(pcm, i - 1) * (1.0 / SAMPLE_RATE);
-			if (last_upflank > 0) {
-				pulse p;
-				p.time = t;
-				p.len = t - last_upflank;
-				pulses.push_back(p);
-			}
-			last_upflank = t;
-			last_max_level = 0;
+	// Compute the standard deviation (to check for uneven speeds).
+	// If it suddenly skyrockets, we assume that sync ended earlier
+	// than we thought (it should be 25000 cycles), and that we should
+	// calibrate on fewer cycles.
+	for (int try_end : { 2000, 4000, 5000, 7500, 10000, 15000, SYNC_PULSE_END }) {
+		double sum2 = 0.0;
+		for (int i = SYNC_PULSE_START; i < try_end; ++i) {
+			double cycles = pulses[i].len * C64_FREQUENCY;
+			sum2 += (cycles - SYNC_PULSE_LENGTH) * (cycles - SYNC_PULSE_LENGTH);
 		}
-		last_max_level = std::max(last_max_level, abs(pcm[i]));
-		last_bit = bit;
+		double stddev = sqrt(sum2 / (try_end - SYNC_PULSE_START - 1));
+		if (sync_pulse_end != -1 && stddev > 5.0 && stddev / sync_pulse_stddev > 1.3) {
+			fprintf(stderr, "Stopping at %d sync pulses because standard deviation would be too big (%.2f cycles); shorter-than-usual trailer?\n",
+				sync_pulse_end, stddev);
+			break;
+		}
+		sync_pulse_end = try_end;
+		sync_pulse_stddev = stddev;
 	}
+	fprintf(stderr, "Sync pulse length standard deviation: %.2f cycles\n",
+		sync_pulse_stddev);
 
-	// Calibrate on the first ~25k pulses (skip a few, just to be sure).
-	double calibration_factor = 1.0f;
-	if (pulses.size() < SYNC_PULSE_END) {
-		fprintf(stderr, "Too few pulses, not calibrating!\n");
-	} else {
-		double sum = 0.0;
-		for (int i = SYNC_PULSE_START; i < SYNC_PULSE_END; ++i) {
-			sum += pulses[i].len;
-		}
-		double mean_length = C64_FREQUENCY * sum / (SYNC_PULSE_END - SYNC_PULSE_START);
-		calibration_factor = SYNC_PULSE_LENGTH / mean_length;
-		fprintf(stderr, "Calibrated sync pulse length: %.2f -> 380.0 (change %+.2f%%)\n",
-			mean_length, 100.0 * (calibration_factor - 1.0));
-
-		// Check for pulses outside +/- 10% (sign of misdetection).
-		for (int i = SYNC_PULSE_START; i < SYNC_PULSE_END; ++i) {
-			double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
-			if (cycles < SYNC_PULSE_LENGTH / SYNC_TEST_TOLERANCE || cycles > SYNC_PULSE_LENGTH * SYNC_TEST_TOLERANCE) {
-				fprintf(stderr, "Sync cycle with upflank at %.6f was detected at %.0f cycles; misdetect?\n",
-					pulses[i].time, cycles);
-			}
-		}
+	double sum = 0.0;
+	for (int i = SYNC_PULSE_START; i < sync_pulse_end; ++i) {
+		sum += pulses[i].len;
+	}
+	double mean_length = C64_FREQUENCY * sum / (sync_pulse_end - SYNC_PULSE_START);
+	double calibration_factor = SYNC_PULSE_LENGTH / mean_length;
+	fprintf(stderr, "Calibrated sync pulse length: %.2f -> %.2f (change %+.2f%%)\n",
+		mean_length, SYNC_PULSE_LENGTH, 100.0 * (calibration_factor - 1.0));
 
-		// Compute the standard deviation (to check for uneven speeds).
-		double sum2 = 0.0;
-		for (int i = SYNC_PULSE_START; i < SYNC_PULSE_END; ++i) {
-			double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
-			sum2 += (cycles - SYNC_PULSE_LENGTH) * (cycles - SYNC_PULSE_LENGTH);
+	// Check for pulses outside +/- 10% (sign of misdetection).
+	for (int i = SYNC_PULSE_START; i < sync_pulse_end; ++i) {
+		double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
+		if (cycles < SYNC_PULSE_LENGTH / SYNC_TEST_TOLERANCE || cycles > SYNC_PULSE_LENGTH * SYNC_TEST_TOLERANCE) {
+			fprintf(stderr, "Sync cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n",
+				pulses[i].time, cycles);
 		}
-		double stddev = sqrt(sum2 / (SYNC_PULSE_END - SYNC_PULSE_START - 1));
-		fprintf(stderr, "Sync pulse length standard deviation: %.2f cycles\n",
-			stddev);
 	}
 
+	return calibration_factor;
+}
+
+void output_tap(const std::vector<pulse>& pulses, double calibration_factor)
+{
 	std::vector<char> tap_data;
 	for (unsigned i = 0; i < pulses.size(); ++i) {
 		double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
 		int len = lrintf(cycles / TAP_RESOLUTION);
 		if (i > SYNC_PULSE_END && (cycles < 100 || cycles > 800)) {
-			fprintf(stderr, "Cycle with upflank at %.6f was detected at %.0f cycles; misdetect?\n",
+			fprintf(stderr, "Cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n",
 					pulses[i].time, cycles);
 		}
 		if (len <= 255) {
@@ -206,3 +134,80 @@ int main(int argc, char **argv)
 	fwrite(&hdr, sizeof(hdr), 1, stdout);
 	fwrite(tap_data.data(), tap_data.size(), 1, stdout);
 }
+	
+int main(int argc, char **argv)
+{
+	make_lanczos_weight_table();
+	std::vector<float> pcm;
+	int sample_rate;
+	if (!read_audio_file(argv[1], &pcm, &sample_rate)) {
+		exit(1);
+	}
+
+#if 0
+	for (int i = 0; i < LEN; ++i) {
+		in[i] += rand() % 10000;
+	}
+#endif
+
+#if 0
+	for (int i = 0; i < LEN; ++i) {
+		printf("%d\n", in[i]);
+	}
+#endif
+
+	std::vector<pulse> pulses;  // in seconds
+
+	// Find the flanks.
+	int last_bit = -1;
+	double last_downflank = -1;
+	for (unsigned i = 0; i < pcm.size(); ++i) {
+		int bit = (pcm[i] > 0) ? 1 : 0;
+		if (bit == 0 && last_bit == 1) {
+			// Check if we ever go up above HYSTERESIS_LIMIT before we dip down again.
+			bool true_pulse = false;
+			unsigned j;
+			int min_level_after = 32767;
+			for (j = i; j < pcm.size(); ++j) {
+				min_level_after = std::min<int>(min_level_after, pcm[j]);
+				if (pcm[j] > 0) break;
+				if (pcm[j] < -HYSTERESIS_LIMIT) {
+					true_pulse = true;
+					break;
+				}
+			}
+
+			if (!true_pulse) {
+#if 0
+				fprintf(stderr, "Ignored down-flank at %.6f seconds due to hysteresis (%d < %d).\n",
+					double(i) / sample_rate, -min_level_after, HYSTERESIS_LIMIT);
+#endif
+				i = j;
+				continue;
+			} 
+
+			// down-flank!
+			double t = find_zerocrossing(pcm, i - 1) * (1.0 / sample_rate);
+			if (last_downflank > 0) {
+				pulse p;
+				p.time = t;
+				p.len = t - last_downflank;
+				pulses.push_back(p);
+			}
+			last_downflank = t;
+		}
+		last_bit = bit;
+	}
+
+	double calibration_factor = calibrate(pulses);
+
+	FILE *fp = fopen("cycles.plot", "w");
+	std::vector<char> tap_data;
+	for (unsigned i = 0; i < pulses.size(); ++i) {
+		double cycles = pulses[i].len * calibration_factor * C64_FREQUENCY;
+		fprintf(fp, "%f %f\n", pulses[i].time, cycles);
+	}
+	fclose(fp);
+
+	output_tap(pulses, calibration_factor);
+}