@@ -72,7 +72,7 @@
#define AM_MAX23 0.06 //smaller causes failure on synthetic signals
#define AM_MAX4 0.02
-#define FM_THRESHOLD .8 //TODO adjust
+#define FM_THRESHOLD 50 //TODO adjust
//Least squares fit at 1khz points of frequency response shown by Frank McClatchie, FM SYSTEMS, INC. 800-235-6960
static double emphasis75us(int f)
@@ -707,53 +707,61 @@ static int probe_fm(SDRContext *sdr)
int bandwidth_f = 180*1000;
int bandwidth_p2 = 38*1000; //phase 2 bandwidth
int half_bw_i = bandwidth_f * (int64_t)sdr->block_size / sdr->sdr_sample_rate;
- double avg[2] = {0}, tri = 0;
float last_score[3] = {FLT_MAX, FLT_MAX, FLT_MAX};
int border_i = (sdr->sdr_sample_rate - sdr->bandwidth) * sdr->block_size / sdr->sdr_sample_rate;
+ double noise_floor = FLT_MAX;
if (2*half_bw_i > 2*sdr->block_size)
return 0;
- for (i = 0; i<half_bw_i; i++) {
- avg[0] += sdr->len2block[i];
- tri += i*sdr->len2block[i];
- }
- for (; i<2*half_bw_i; i++) {
- avg[1] += sdr->len2block[i];
- tri += (2*half_bw_i-i)*sdr->len2block[i];
- }
+ for (int pass = 0; pass < 2; pass ++) {
+ double avg[2] = {0}, tri = 0;
+ for (i = 0; i<half_bw_i; i++) {
+ avg[0] += sdr->len2block[i];
+ tri += i*sdr->len2block[i];
+ }
+ for (; i<2*half_bw_i; i++) {
+ avg[1] += sdr->len2block[i];
+ tri += (2*half_bw_i-i)*sdr->len2block[i];
+ }
- for(i = half_bw_i; i<2*sdr->block_size - half_bw_i; i++) {
- double b = avg[0] + sdr->len2block[i];
- avg[0] += sdr->len2block[i] - sdr->len2block[i - half_bw_i];
- avg[1] -= sdr->len2block[i] - sdr->len2block[i + half_bw_i];
- b += avg[1];
- tri += avg[1] - avg[0];
+ for(i = half_bw_i; i<2*sdr->block_size - half_bw_i; i++) {
+ double b = avg[0] + sdr->len2block[i];
+ avg[0] += sdr->len2block[i] - sdr->len2block[i - half_bw_i];
+ avg[1] -= sdr->len2block[i] - sdr->len2block[i + half_bw_i];
+ b += avg[1];
+ tri += avg[1] - avg[0];
- last_score[2] = last_score[1];
- last_score[1] = last_score[0];
- last_score[0] = tri / (b * half_bw_i);
- if (i < border_i || i > 2*sdr->block_size - border_i)
- continue;
+ if (i < border_i || i > 2*sdr->block_size - border_i)
+ continue;
- if (last_score[1] >= last_score[0] &&
- last_score[1] > last_score[2] &&
- last_score[1] > FM_THRESHOLD) {
+ if (pass == 0) {
+ noise_floor = FFMIN(noise_floor, tri);
+ } else {
+ last_score[2] = last_score[1];
+ last_score[1] = last_score[0];
+ last_score[0] = tri / (noise_floor);
- float rmax = max_in_range(sdr, i-half_bw_i/4, i+half_bw_i/4);
- int lowcount = countbelow(sdr, i-half_bw_i/4, i+half_bw_i/4, rmax / 100);
- double peak_i;
+ if (last_score[1] >= last_score[0] &&
+ last_score[1] > last_score[2] &&
+ last_score[1] > FM_THRESHOLD) {
- if (lowcount / (half_bw_i*0.5) > 0.99)
- continue;
+ float rmax = max_in_range(sdr, i-half_bw_i/4, i+half_bw_i/4);
+ int lowcount = countbelow(sdr, i-half_bw_i/4, i+half_bw_i/4, rmax / 100);
+ double peak_i;
- // as secondary check, we could check that without the center 3 samples we are still having a strong signal FIXME
+ if (lowcount / (half_bw_i*0.5) > 0.99)
+ continue;
- peak_i = find_peak(sdr, last_score, 1, 3) + i - 1;
- if (peak_i < 0)
- continue;
- av_assert0(fabs(peak_i-i) < 2);
- create_candidate_station(sdr, FM, peak_i * 0.5 * sdr->sdr_sample_rate / sdr->block_size + sdr->block_center_freq - sdr->sdr_sample_rate/2, bandwidth_f, bandwidth_p2, last_score[1]);
+ // as secondary check, we could check that without the center 3 samples we are still having a strong signal FIXME
+
+ peak_i = find_peak(sdr, last_score, 1, 3) + i - 1;
+ if (peak_i < 0)
+ continue;
+ av_assert0(fabs(peak_i-i) < 2);
+ create_candidate_station(sdr, FM, peak_i * 0.5 * sdr->sdr_sample_rate / sdr->block_size + sdr->block_center_freq - sdr->sdr_sample_rate/2, bandwidth_f, bandwidth_p2, last_score[1]);
+ }
+ }
}
}
This way teh scores now resemble station vs noise floor while before they where "whatever" This results in somewhat cleaner results from probing as well Signed-off-by: Michael Niedermayer <michael@niedermayer.cc> --- libavradio/sdrdemux.c | 78 ++++++++++++++++++++++++------------------- 1 file changed, 43 insertions(+), 35 deletions(-)