[FFmpeg-devel] [PATCH 03/12] avradio/rds: Keep track of program_id

[Michael Niedermayer <michael@niedermayer.cc>]

This allows detecting more damaged blocks

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavradio/rds.c | 16 ++++++++++++++++
 libavradio/sdr.h |  1 +
 2 files changed, 17 insertions(+)

diff --git a/libavradio/rds.c b/libavradio/rds.c
index 2cb7942bbd..dc7124cab3 100644
--- a/libavradio/rds.c
+++ b/libavradio/rds.c
@@ -85,7 +85,13 @@ static int check_rds_block(Station *station, uint16_t group[4], const float diff
             int ret = burst_len(syndrom);
             group[block] ^= (syndrom << i) >> 10;
 
+            if (block == 0 && station->program_id[0]) {
+                if (group[0] == station->program_id[0]) {
                     return ret;
+                } else if (group[0] == station->program_id[1]) {
+                    return ret;
+                } else if (ret) {
+                    return 20; //PI change is uncommon, so dont accept this in a damaged block, PI is repeated alot so we can wait for a clean block
                 }
             }
 
@@ -108,6 +114,16 @@ static int decode_rds_group(SDRContext *sdr, SDRStream *sst, uint16_t group[4])
     int tp = group[1] & 0x400;
     int pty= (group[1] >> 5) & 0x1F;
 
+    if (station->program_id[0] && station->program_id[0] != pi)
+        av_log(sdr->avfmt, AV_LOG_INFO, "PI changed to %X\n", pi);
+
+    if (station->program_id[1] == pi) {
+        FFSWAP(int, station->program_id[1], station->program_id[0]);
+    } else if (station->program_id[0] != pi) {
+        station->program_id[1] = pi;
+        return 0; // skip first packet with new PI, likely its just damaged
+    }
+
     switch(a) {
     case 0:
         AV_WB16(station->name + 2*(group[1]&3), group[3]);
diff --git a/libavradio/sdr.h b/libavradio/sdr.h
index 212358fad9..b83264ae0d 100644
--- a/libavradio/sdr.h
+++ b/libavradio/sdr.h
@@ -74,6 +74,7 @@ typedef struct Station {
     char name[9];
     char radiotext[65];
     char programm_type_name[9];
+    int program_id[2];
     enum Modulation modulation;
     double frequency;
     int nb_frequency;       ///< number of detections which are used to compute the frequency
-- 
2.31.1

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