X-Git-Url: https://git.sesse.net/?p=c64tapwav;a=blobdiff_plain;f=decode.cpp;h=49be647ea2cc67442718f2765e66ff508cd91064;hp=ca0c675e411fbddfca3037cddbbd7fc1e69083e7;hb=8df851a0c512f869ef6b928cff20dd84a258e959;hpb=52dc441eb7db99f2231478474f228a62d642eacf

diff --git a/decode.cpp b/decode.cpp
index ca0c675..49be647 100644
--- a/decode.cpp
+++ b/decode.cpp
@@ -1,31 +1,24 @@
 #include <stdio.h>
 #include <string.h>
 #include <math.h>
-#include <unistd.h>
 #include <assert.h>
+#include <limits.h>
 #include <vector>
 #include <algorithm>
 
 #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 378.0
 #define SYNC_TEST_TOLERANCE 1.10
 
-struct tap_header {
-	char identifier[12];
-	char version;
-	char reserved[3];
-	unsigned int data_len;
-};
-
 // between [x,x+1]
 double find_zerocrossing(const std::vector<short> &pcm, int x)
 {
@@ -36,12 +29,12 @@ 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 (lanczos_interpolate(pcm, mid) > 0) {
 			upper = mid;
@@ -60,6 +53,7 @@ struct pulse {
 	
 int main(int argc, char **argv)
 {
+	make_lanczos_weight_table();
 	std::vector<short> pcm;
 
 	while (!feof(stdin)) {
@@ -86,18 +80,18 @@ int main(int argc, char **argv)
 
 	// Find the flanks.
 	int last_bit = -1;
-	double last_upflank = -1;
+	double last_downflank = -1;
 	for (unsigned i = 0; i < pcm.size(); ++i) {
 		int bit = (pcm[i] > 0) ? 1 : 0;
-		if (bit == 1 && last_bit == 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 max_level_after = -32768;
+			int min_level_after = 32767;
 			for (j = i; j < pcm.size(); ++j) {
-				max_level_after = std::max<int>(max_level_after, pcm[j]);
-				if (pcm[j] < 0) break;
-				if (pcm[j] > HYSTERESIS_LIMIT) {
+				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;
 				}
@@ -105,22 +99,22 @@ int main(int argc, char **argv)
 
 			if (!true_pulse) {
 #if 0
-				fprintf(stderr, "Ignored up-flank at %.6f seconds due to hysteresis (%d < %d).\n",
-					double(i) / SAMPLE_RATE, max_level_after, HYSTERESIS_LIMIT);
+				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;
 			} 
 
-			// up-flank!
+			// down-flank!
 			double t = find_zerocrossing(pcm, i - 1) * (1.0 / SAMPLE_RATE);
-			if (last_upflank > 0) {
+			if (last_downflank > 0) {
 				pulse p;
 				p.time = t;
-				p.len = t - last_upflank;
+				p.len = t - last_downflank;
 				pulses.push_back(p);
 			}
-			last_upflank = t;
+			last_downflank = t;
 		}
 		last_bit = bit;
 	}
@@ -143,7 +137,7 @@ int main(int argc, char **argv)
 		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",
+				fprintf(stderr, "Sync cycle with downflank at %.6f was detected at %.0f cycles; misdetect?\n",
 					pulses[i].time, cycles);
 			}
 		}
@@ -166,7 +160,7 @@ int main(int argc, char **argv)
 		fprintf(fp, "%f %f\n", pulses[i].time, cycles);
 		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) {
@@ -189,4 +183,20 @@ int main(int argc, char **argv)
 
 	fwrite(&hdr, sizeof(hdr), 1, stdout);
 	fwrite(tap_data.data(), tap_data.size(), 1, stdout);
+
+	// Output a debug raw file with pulse detection points.
+	fp = fopen("debug.raw", "wb");
+	short one = 32767;
+	short zero = 0;
+	unsigned pulsenum = 0;
+	for (unsigned i = 0; i < pcm.size(); ++i) {
+		unsigned next_pulse = (pulsenum >= pulses.size()) ? INT_MAX : int(pulses[pulsenum].time * SAMPLE_RATE);
+		if (i >= next_pulse) {
+			fwrite(&one, sizeof(one), 1, fp);
+			++pulsenum;
+		} else {
+			fwrite(&zero, sizeof(zero), 1, fp);
+		}
+	}
+	fclose(fp);
 }