Add support for filtering the waveform before detection.
authorSteinar H. Gunderson <sgunderson@bigfoot.com>
Wed, 11 Mar 2015 22:20:06 +0000 (23:20 +0100)
committerSteinar H. Gunderson <sgunderson@bigfoot.com>
Wed, 11 Mar 2015 22:21:45 +0000 (23:21 +0100)
decode.cpp

index 80921b2..94bc1dd 100644 (file)
 #define SYNC_PULSE_LENGTH 378.0
 #define SYNC_TEST_TOLERANCE 1.10
 
+#define NUM_FILTER_COEFF 32
+
 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 float filter_coeff[NUM_FILTER_COEFF] = { 1.0f };  // The rest is filled with 0.
+static bool output_filtered = false;
 
 // between [x,x+1]
 double find_zerocrossing(const std::vector<float> &pcm, int x)
@@ -142,6 +147,8 @@ static struct option long_options[] = {
        {"no-calibrate",     0,                 0, 's' },
        {"plot-cycles",      0,                 0, 'p' },
        {"hysteresis-limit", required_argument, 0, 'l' },
+       {"filter",           required_argument, 0, 'f' },
+       {"output-filtered",  0,                 0, 'F' },
        {"help",             0,                 0, 'h' },
        {0,                  0,                 0, 0   }
 };
@@ -153,6 +160,8 @@ void help()
        fprintf(stderr, "  -s, --no-calibrate           do not try to calibrate on sync pulse length\n");
        fprintf(stderr, "  -p, --plot-cycles            output debugging info to cycles.plot\n");
        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, "  -h, --help                   display this help, then exit\n");
        exit(1);
 }
@@ -161,7 +170,7 @@ void parse_options(int argc, char **argv)
 {
        for ( ;; ) {
                int option_index = 0;
-               int c = getopt_long(argc, argv, "spl:h", long_options, &option_index);
+               int c = getopt_long(argc, argv, "spl:f:Fh", long_options, &option_index);
                if (c == -1)
                        break;
 
@@ -177,6 +186,21 @@ void parse_options(int argc, char **argv)
                        hysteresis_limit = atof(optarg) / 32768.0;
                        break;
 
+               case 'f': {
+                       const char *coeffstr = strtok(optarg, ":");
+                       int coeff_index = 0;
+                       while (coeff_index < NUM_FILTER_COEFF && coeffstr != NULL) {
+                               filter_coeff[coeff_index++] = atof(coeffstr);
+                               coeffstr = strtok(NULL, ":");
+                       }
+                       use_filter = true;
+                       break;
+               }
+
+               case 'F':
+                       output_filtered = true;
+                       break;
+
                case 'h':
                default:
                        help();
@@ -185,6 +209,28 @@ void parse_options(int argc, char **argv)
        }
 }
 
+// TODO: Support AVX here.
+std::vector<float> do_filter(const std::vector<float>& pcm, const float* filter)
+{
+       std::vector<float> filtered_pcm;
+       filtered_pcm.reserve(pcm.size());
+       for (unsigned i = NUM_FILTER_COEFF; i < pcm.size(); ++i) {
+               float s = 0.0f;
+               for (int j = 0; j < NUM_FILTER_COEFF; ++j) {
+                       s += filter[j] * pcm[i - j];
+               }
+               filtered_pcm.push_back(s);
+       }
+
+       if (output_filtered) {
+               FILE *fp = fopen("filtered.raw", "wb");
+               fwrite(filtered_pcm.data(), filtered_pcm.size() * sizeof(filtered_pcm[0]), 1, fp);
+               fclose(fp);
+       }
+
+       return filtered_pcm;
+}
+
 int main(int argc, char **argv)
 {
        parse_options(argc, argv);
@@ -196,6 +242,10 @@ int main(int argc, char **argv)
                exit(1);
        }
 
+       if (use_filter) {
+               pcm = do_filter(pcm, filter_coeff);
+       }
+
 #if 0
        for (int i = 0; i < LEN; ++i) {
                in[i] += rand() % 10000;