avformat/mpegts: Fix probing of mpegts with invalid ASC

Fixes Ticket5566
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mpegts.c

@@ -542,8 +542,10 @@ static int analyze(const uint8_t *buf, int size, int packet_size,
     memset(stat, 0, packet_size * sizeof(*stat));
 
     for (i = 0; i < size - 3; i++) {
-        if (buf[i] == 0x47 &&
-            (!probe || (buf[i + 3] & 0x30))) {
+        if (buf[i] == 0x47) {
+            int pid = AV_RB16(buf+1) & 0x1FFF;
+            int asc = buf[i + 3] & 0x30;
+            if (!probe || pid == 0x1FFF || asc) {
                 int x = i % packet_size;
                 stat[x]++;
                 stat_all++;
@@ -552,6 +554,7 @@ static int analyze(const uint8_t *buf, int size, int packet_size,
                 }
             }
         }
+    }
 
     return best_score - FFMAX(stat_all - 10*best_score, 0)/10;
 }