[FFmpeg-devel] [PATCH] mpegts: limit teletext timestamps to [pcr; pcr + 40.6ms] range.

[Reimar Döffinger]

The specification says they should not be buffered longer than
that, and this is also necessary since e.g. ORF HD sends teletext
with PES timestamps that are vastly off.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger at gmx.de>
---
 libavformat/mpegts.c |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index c39cf45..b8fa332 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -676,6 +676,16 @@ static void new_pes_packet(PESContext *pes, AVPacket *pkt)
         pkt->stream_index = pes->st->index;
     pkt->pts = pes->pts;
     pkt->dts = pes->dts;
+    if (pes->st->codec->codec_id == AV_CODEC_ID_DVB_TELETEXT) {
+        // teletext packets do not always have correct timestamps,
+        // the standard says they should be handled after 40.6 ms at most.
+        int64_t pcr = pes->ts->cur_pcr / 300;
+        if (pkt->dts == AV_NOPTS_VALUE || pkt->dts < pcr) {
+            pkt->pts = pkt->dts = pcr;
+        } else if (pes->dts > pcr + 3654) {
+            pkt->pts = pkt->dts = pcr + 4654;
+        }
+    }
     /* store position of first TS packet of this PES packet */
     pkt->pos = pes->ts_packet_pos;
     pkt->flags = pes->flags;
@@ -1668,6 +1678,9 @@ static void sdt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
     }
 }
 
+static int parse_pcr(int64_t *ppcr_high, int *ppcr_low,
+                     const uint8_t *packet);
+
 /* handle one TS packet */
 static int handle_packet(MpegTSContext *ts, const uint8_t *packet)
 {
@@ -1677,6 +1690,8 @@ static int handle_packet(MpegTSContext *ts, const uint8_t *packet)
         has_adaptation, has_payload;
     const uint8_t *p, *p_end;
     int64_t pos;
+    int64_t pcr_h;
+    int pcr_l;
 
     pid = AV_RB16(packet + 1) & 0x1fff;
     if(pid && discard_pid(ts, pid))
@@ -1733,6 +1748,9 @@ static int handle_packet(MpegTSContext *ts, const uint8_t *packet)
     pos = avio_tell(ts->stream->pb);
     ts->pos47= pos % ts->raw_packet_size;
 
+    if (parse_pcr(&pcr_h, &pcr_l, packet) == 0)
+        ts->cur_pcr = pcr_h * 300 + pcr_l;
+
     if (tss->type == MPEGTS_SECTION) {
         if (is_start) {
             /* pointer field present */
-- 
1.7.10.4