mpegts: Update the PSI/SI table only if the version change

If a PAT is finished while a PMT section filter is opened but
not yet finished, the PMT section filter is closed and all
the received data is discarded.

This is usually not an issue but some multiplexers (With very
quick PAT/PMT repetition settings) consistently emit a PMT
section start, then a PAT, and then the rest of the PMT,
causing the aforementioned behavior to result in no PMT being
finished.

In the most pathologic situation the stream information are lost
and the probe fallback miscategorizes subtitles as mp3 audio.

Avoid the issue through eliminating redundant PSI/SI table
updates by checking their version field, which is required by
the standard to be incremented on every change no matter how
minor.

CC: libav-stable@libav.org

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

1 files changed, 20 insertions, 0 deletions

diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index ae9d1f4e93..8f61f1727d 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -73,6 +73,7 @@ typedef void SetServiceCallback (void *opaque, int ret);
 typedef struct MpegTSSectionFilter {
     int section_index;
     int section_h_size;
+    int last_ver;
     uint8_t *section_buf;
     unsigned int check_crc : 1;
     unsigned int end_of_section_reached : 1;
@@ -372,6 +373,8 @@ static MpegTSFilter *mpegts_open_section_filter(MpegTSContext *ts,
     sec->opaque      = opaque;
     sec->section_buf = av_malloc(MAX_SECTION_SIZE);
     sec->check_crc   = check_crc;
+    sec->last_ver    = -1;
+
     if (!sec->section_buf) {
         av_free(filter);
         return NULL;
@@ -1255,6 +1258,7 @@ static void m4sl_cb(MpegTSFilter *filter, const uint8_t *section,
                     int section_len)
 {
     MpegTSContext *ts = filter->u.section_filter.opaque;
+    MpegTSSectionFilter *tssf = &filter->u.section_filter;
     SectionHeader h;
     const uint8_t *p, *p_end;
     AVIOContext pb;
@@ -1269,6 +1273,9 @@ static void m4sl_cb(MpegTSFilter *filter, const uint8_t *section,
         return;
     if (h.tid != M4OD_TID)
         return;
+    if (h.version == tssf->last_ver)
+        return;
+    tssf->last_ver = h.version;
 
     mp4_read_od(s, p, (unsigned) (p_end - p), mp4_descr, &mp4_descr_count,
                 MAX_MP4_DESCR_COUNT);
@@ -1507,6 +1514,7 @@ int ff_parse_mpeg2_descriptor(AVFormatContext *fc, AVStream *st, int stream_type
 static void pmt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len)
 {
     MpegTSContext *ts = filter->u.section_filter.opaque;
+    MpegTSSectionFilter *tssf = &filter->u.section_filter;
     SectionHeader h1, *h = &h1;
     PESContext *pes;
     AVStream *st;
@@ -1526,6 +1534,9 @@ static void pmt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
     p = section;
     if (parse_section_header(h, &p, p_end) < 0)
         return;
+    if (h->version == tssf->last_ver)
+        return;
+    tssf->last_ver = h->version;
 
     av_log(ts->stream, AV_LOG_TRACE, "sid=0x%x sec_num=%d/%d\n",
             h->id, h->sec_num, h->last_sec_num);
@@ -1657,6 +1668,7 @@ out:
 static void pat_cb(MpegTSFilter *filter, const uint8_t *section, int section_len)
 {
     MpegTSContext *ts = filter->u.section_filter.opaque;
+    MpegTSSectionFilter *tssf = &filter->u.section_filter;
     SectionHeader h1, *h = &h1;
     const uint8_t *p, *p_end;
     int sid, pmt_pid;
@@ -1670,6 +1682,9 @@ static void pat_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
         return;
     if (h->tid != PAT_TID)
         return;
+    if (h->version == tssf->last_ver)
+        return;
+    tssf->last_ver = h->version;
 
     clear_programs(ts);
     for (;;) {
@@ -1700,6 +1715,7 @@ static void pat_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
 static void sdt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len)
 {
     MpegTSContext *ts = filter->u.section_filter.opaque;
+    MpegTSSectionFilter *tssf = &filter->u.section_filter;
     SectionHeader h1, *h = &h1;
     const uint8_t *p, *p_end, *desc_list_end, *desc_end;
     int onid, val, sid, desc_list_len, desc_tag, desc_len, service_type;
@@ -1714,6 +1730,10 @@ static void sdt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
         return;
     if (h->tid != SDT_TID)
         return;
+    if (h->version == tssf->last_ver)
+        return;
+    tssf->last_ver = h->version;
+
     onid = get16(&p, p_end);
     if (onid < 0)
         return;