[FFmpeg-devel] [PATCH] avformat/mpegts: Check the next sync byte to avoid incorrectt detected raw packet size

[lance.lmwang at gmail.com]

From: Limin Wang <lance.lmwang at gmail.com>

reanalyze() may misdetect the new packet size as 204, but it's 188 still actualy,
it'll cause many cc errors report and cannot be recovered. So it's better to check
the next sync byte before skip the extra unused bytes.

Also, it is best to change SIZE_STAT_THRESHOLD from 10 to 100? If the input stream has
a master/slave switch serveral times, the raw size can be easily detected by mistake.

Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
---
 libavformat/mpegts.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index 0833d62..049555c 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -2932,11 +2932,12 @@ static int read_packet(AVFormatContext *s, uint8_t *buf, int raw_packet_size,
     return 0;
 }
 
-static void finished_reading_packet(AVFormatContext *s, int raw_packet_size)
+static void finished_reading_packet(AVFormatContext *s, const uint8_t *data, int raw_packet_size)
 {
     AVIOContext *pb = s->pb;
     int skip = raw_packet_size - TS_PACKET_SIZE;
-    if (skip > 0)
+    /* Check the next sync byte to avoid incorrectt detected raw packet size */
+    if (skip > 0 && data[TS_PACKET_SIZE] != 0x47)
         avio_skip(pb, skip);
 }
 
@@ -2985,7 +2986,7 @@ static int handle_packets(MpegTSContext *ts, int64_t nb_packets)
         if (ret != 0)
             break;
         ret = handle_packet(ts, data, avio_tell(s->pb));
-        finished_reading_packet(s, ts->raw_packet_size);
+        finished_reading_packet(s, data, ts->raw_packet_size);
         if (ret != 0)
             break;
     }
@@ -3137,7 +3138,7 @@ static int mpegts_read_header(AVFormatContext *s)
             pid = AV_RB16(data + 1) & 0x1fff;
             if ((pcr_pid == -1 || pcr_pid == pid) &&
                 parse_pcr(&pcr_h, &pcr_l, data) == 0) {
-                finished_reading_packet(s, ts->raw_packet_size);
+                finished_reading_packet(s, data, ts->raw_packet_size);
                 pcr_pid = pid;
                 packet_count[nb_pcrs] = nb_packets;
                 pcrs[nb_pcrs] = pcr_h * 300 + pcr_l;
@@ -3154,7 +3155,7 @@ static int mpegts_read_header(AVFormatContext *s)
                     }
                 }
             } else {
-                finished_reading_packet(s, ts->raw_packet_size);
+                finished_reading_packet(s, data, ts->raw_packet_size);
             }
             nb_packets++;
         }
@@ -3194,7 +3195,7 @@ static int mpegts_raw_read_packet(AVFormatContext *s, AVPacket *pkt)
     }
     if (data != pkt->data)
         memcpy(pkt->data, data, ts->raw_packet_size);
-    finished_reading_packet(s, ts->raw_packet_size);
+    finished_reading_packet(s, data, ts->raw_packet_size);
     if (ts->mpeg2ts_compute_pcr) {
         /* compute exact PCR for each packet */
         if (parse_pcr(&pcr_h, &pcr_l, pkt->data) == 0) {
-- 
1.8.3.1