By analyzing the behavior of the detectability of stations with different SDR settings we can separate some SDR artifacts from weak stations.
Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> --- libavradio/sdr.h | 5 +++++ libavradio/sdrdemux.c | 36 +++++++++++++++++++++++++++++++++++- 2 files changed, 40 insertions(+), 1 deletion(-) diff --git a/libavradio/sdr.h b/libavradio/sdr.h index 838fb1cef7..1053e45efe 100644 --- a/libavradio/sdr.h +++ b/libavradio/sdr.h @@ -66,6 +66,8 @@ typedef enum Modulation { //QAM, PSK, ... } Modulation; +#define HISTOGRAMM_SIZE 9 + typedef struct Station { char *name; enum Modulation modulation; @@ -78,6 +80,9 @@ typedef struct Station { int timeout; //since how many blocks was this detectable but not detected int multiplex_index; //DAB can have multiple stations on one frequency + int detection_per_mix_frequency[HISTOGRAMM_SIZE]; + int non_detection_per_mix_frequency[HISTOGRAMM_SIZE]; + struct SDRStream *stream; } Station; diff --git a/libavradio/sdrdemux.c b/libavradio/sdrdemux.c index 6cb9d3b70a..1fc528317c 100644 --- a/libavradio/sdrdemux.c +++ b/libavradio/sdrdemux.c @@ -111,6 +111,23 @@ static void free_station(Station *station) av_free(station); } +static inline int histogram_index(SDRContext *sdr, double f) +{ + f = HISTOGRAMM_SIZE*((f - sdr->block_center_freq) / sdr->sdr_sample_rate + 0.5); + return av_clip((int)f, 0, HISTOGRAMM_SIZE-1); +} + +static int histogram_score(Station *s) +{ + int score = 0; + for(int i = 0; i<HISTOGRAMM_SIZE; i++) { + score += + (5*s->detection_per_mix_frequency[i] > s->non_detection_per_mix_frequency[i]) + -(5*s->detection_per_mix_frequency[i] < s->non_detection_per_mix_frequency[i]); + } + return score; +} + typedef struct FindStationContext { double freq; double range; @@ -184,6 +201,10 @@ static int create_station(SDRContext *sdr, Station *candidate_station) { if (candidate_station->in_station_list) return 0; + // suspect looking histogram + if (histogram_score(candidate_station) <= 0) + return 0; + Station *station_list[1000]; int nb_stations = find_stations(sdr, sdr->block_center_freq, sdr->sdr_sample_rate*0.5, station_list, FF_ARRAY_ELEMS(station_list)); for (i=0; i<nb_stations; i++) { @@ -328,8 +349,20 @@ static void decay_stations(SDRContext *sdr) station->frequency + station->bandwidth/2 > sdr->block_center_freq + sdr->bandwidth/2) continue; + if (station->timeout) + station->non_detection_per_mix_frequency[histogram_index(sdr, station->frequency)] ++; + if (station->in_station_list) { - if (station->timeout++ > STATION_TIMEOUT) { + int station_timeout = STATION_TIMEOUT; + int hs = histogram_score(station); + + if (hs == 0) { + station_timeout = 5; //give the station a moment to be properly detected and then discard it + } else if(hs < 0) { + station_timeout = 0; //probably not a station + } + + if (station->timeout++ > station_timeout) { if (!station->stream) station->in_station_list = 0; } @@ -376,6 +409,7 @@ static int create_candidate_station(SDRContext *sdr, enum Modulation modulation, } station->frequency /= ++station->nb_frequency; + station->detection_per_mix_frequency[histogram_index(sdr, freq)] ++; station->modulation = modulation; station->bandwidth = bandwidth; station->bandwidth_p2 = bandwidth_p2; -- 2.31.1 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".