From: Steinar H. Gunderson <sgunderson@bigfoot.com>
Date: Wed, 11 Mar 2015 23:06:31 +0000 (+0100)
Subject: Add support for decoding only parts of the sample.
X-Git-Url: https://git.sesse.net/?p=c64tapwav;a=commitdiff_plain;h=7845bf4cd343d68c3314c7f30a10eada1bd714a7

Add support for decoding only parts of the sample.
---

diff --git a/decode.cpp b/decode.cpp
index 2a27371..43d6766 100644
--- a/decode.cpp
+++ b/decode.cpp
@@ -24,6 +24,8 @@ static float hysteresis_limit = 3000.0 / 32768.0;
 static bool do_calibrate = true;
 static bool output_cycles_plot = false;
 static bool use_filter = false;
+static bool do_crop = false;
+static float crop_start = 0.0f, crop_end = HUGE_VAL;
 static float filter_coeff[NUM_FILTER_COEFF] = { 1.0f };  // The rest is filled with 0.
 static bool output_filtered = false;
 static bool quiet = false;
@@ -154,6 +156,7 @@ static struct option long_options[] = {
 	{"hysteresis-limit", required_argument, 0, 'l' },
 	{"filter",           required_argument, 0, 'f' },
 	{"output-filtered",  0,                 0, 'F' },
+	{"crop",             required_argument, 0, 'c' },
 	{"quiet",            0,                 0, 'q' },
 	{"help",             0,                 0, 'h' },
 	{0,                  0,                 0, 0   }
@@ -168,6 +171,7 @@ void help()
 	fprintf(stderr, "  -l, --hysteresis-limit VAL   change amplitude threshold for ignoring pulses (0..32768)\n");
 	fprintf(stderr, "  -f, --filter C1:C2:C3:...    specify FIR filter (up to %d coefficients)\n", NUM_FILTER_COEFF);
 	fprintf(stderr, "  -F, --output-filtered        output filtered waveform to filtered.raw\n");
+	fprintf(stderr, "  -c, --crop START[:END]       use only the given part of the file\n");
 	fprintf(stderr, "  -q, --quiet                  suppress some informational messages\n");
 	fprintf(stderr, "  -h, --help                   display this help, then exit\n");
 	exit(1);
@@ -177,7 +181,7 @@ void parse_options(int argc, char **argv)
 {
 	for ( ;; ) {
 		int option_index = 0;
-		int c = getopt_long(argc, argv, "spl:f:Fqh", long_options, &option_index);
+		int c = getopt_long(argc, argv, "spl:f:Fc:qh", long_options, &option_index);
 		if (c == -1)
 			break;
 
@@ -209,6 +213,19 @@ void parse_options(int argc, char **argv)
 			output_filtered = true;
 			break;
 
+		case 'c': {
+			const char *cropstr = strtok(optarg, ":");
+			crop_start = atof(cropstr);
+			cropstr = strtok(NULL, ":");
+			if (cropstr == NULL) {
+				crop_end = HUGE_VAL;
+			} else {
+				crop_end = atof(cropstr);
+			}
+			do_crop = true;
+			break;
+		}
+
 		case 'q':
 			quiet = true;
 			break;
@@ -221,6 +238,18 @@ void parse_options(int argc, char **argv)
 	}
 }
 
+std::vector<float> crop(const std::vector<float>& pcm, float crop_start, float crop_end, int sample_rate)
+{
+	size_t start_sample, end_sample;
+	if (crop_start >= 0.0f) {
+		start_sample = std::min<size_t>(lrintf(crop_start * sample_rate), pcm.size());
+	}
+	if (crop_end >= 0.0f) {
+		end_sample = std::min<size_t>(lrintf(crop_end * sample_rate), pcm.size());
+	}
+	return std::vector<float>(pcm.begin() + start_sample, pcm.begin() + end_sample);
+}
+
 // TODO: Support AVX here.
 std::vector<float> do_filter(const std::vector<float>& pcm, const float* filter)
 {
@@ -276,7 +305,7 @@ std::vector<pulse> detect_pulses(const std::vector<float> &pcm, int sample_rate)
 			} 
 
 			// down-flank!
-			double t = find_zerocrossing(pcm, i - 1) * (1.0 / sample_rate);
+			double t = find_zerocrossing(pcm, i - 1) * (1.0 / sample_rate) + crop_start;
 			if (last_downflank > 0) {
 				pulse p;
 				p.time = t;
@@ -301,6 +330,10 @@ int main(int argc, char **argv)
 		exit(1);
 	}
 
+	if (do_crop) {
+		pcm = crop(pcm, crop_start, crop_end, sample_rate);
+	}
+
 	if (use_filter) {
 		pcm = do_filter(pcm, filter_coeff);
 	}