Add support for decoding only parts of the sample.

diff --git a/decode.cpp b/decode.cpp
index 2a27371ac2db191c78c0119e812f8bad01834096..43d6766bfd38774c58f4b6fc4601f7c18f598bb0 100644 (file)
--- 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);
        }