From 63a03b167ad39f6d44ab941e7d871359f5bb88fe Mon Sep 17 00:00:00 2001
From: Edward Hervey <edward@centricular.com>
Date: Thu, 6 Feb 2025 09:11:14 +0100
Subject: [PATCH] mpegts: Take into account adaptation field discont

If the flag is set, there is an *expected* discontinuity:
* For CC, we ignore the fact it's not contiguous
* For PCR, we acknowledge the values aren't contiguous

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8420>
---
 .../gst/mpegtsdemux/mpegtspacketizer.c        | 22 +++++++++++++++++++
 .../gst-plugins-bad/gst/mpegtsdemux/tsdemux.c |  7 ++++++
 2 files changed, 29 insertions(+)

diff --git a/subprojects/gst-plugins-bad/gst/mpegtsdemux/mpegtspacketizer.c b/subprojects/gst-plugins-bad/gst/mpegtsdemux/mpegtspacketizer.c
index 2449d9814d..a6b66298b9 100644
--- a/subprojects/gst-plugins-bad/gst/mpegtsdemux/mpegtspacketizer.c
+++ b/subprojects/gst-plugins-bad/gst/mpegtsdemux/mpegtspacketizer.c
@@ -414,8 +414,24 @@ mpegts_packetizer_parse_adaptation_field_control (MpegTSPacketizer2 *
     if (packetizer->calculate_skew
         && GST_CLOCK_TIME_IS_VALID (packetizer->last_in_time)) {
       pcrtable = get_pcr_table (packetizer, packet->pid);
+      /* There is a signalled discontinuity. Reset observations */
+      if (afcflags & MPEGTS_AFC_DISCONTINUITY_FLAG) {
+        GST_DEBUG ("pcr 0x%04x Discontinuity signalled, resetting observations",
+            packet->pid);
+        pcrtable->base_time = GST_CLOCK_TIME_NONE;
+        pcrtable->base_pcrtime = GST_CLOCK_TIME_NONE;
+      }
       calculate_skew (packetizer, pcrtable, packet->pcr,
           packetizer->last_in_time);
+      if (afcflags & MPEGTS_AFC_DISCONTINUITY_FLAG) {
+        MpegTSPCR *ignore_pcr =
+            packetizer->observations[packetizer->pcrtablelut[0x1fff]];
+        if (ignore_pcr) {
+          GST_DEBUG ("Resetting fallback PCR table due to discontinuity");
+          /* If there is a discontinuity, we need to reset the fallback PCR in case of */
+          ignore_pcr->base_time = GST_CLOCK_TIME_NONE;
+        }
+      }
     }
     if (packetizer->calculate_offset) {
       if (!pcrtable)
@@ -990,6 +1006,12 @@ mpegts_packetizer_push_section (MpegTSPacketizer2 * packetizer,
     packetizer->streams[packet->pid] = stream;
   }
 
+  if (G_UNLIKELY (packet->afc_flags & MPEGTS_AFC_DISCONTINUITY_FLAG)) {
+    GST_DEBUG ("PID 0x%04x  discontinuity flag, resetting stream counter",
+        packet->pid);
+    stream->continuity_counter = CONTINUITY_UNSET;
+  }
+
   GST_MEMDUMP ("Full packet data", packet->data,
       packet->data_end - packet->data);
 
diff --git a/subprojects/gst-plugins-bad/gst/mpegtsdemux/tsdemux.c b/subprojects/gst-plugins-bad/gst/mpegtsdemux/tsdemux.c
index cdae23a823..a88f35efd4 100644
--- a/subprojects/gst-plugins-bad/gst/mpegtsdemux/tsdemux.c
+++ b/subprojects/gst-plugins-bad/gst/mpegtsdemux/tsdemux.c
@@ -2852,6 +2852,13 @@ gst_ts_demux_queue_data (GstTSDemux * demux, TSDemuxStream * stream,
   GST_LOG_OBJECT (demux, "pid: 0x%04x state:%d", stream->stream.pid,
       stream->state);
 
+  /* Handle expected discontinuity */
+  if (G_UNLIKELY (packet->afc_flags & MPEGTS_AFC_DISCONTINUITY_FLAG)) {
+    GST_LOG_OBJECT (demux, "pid: 0x%04x discontinuity flag, resetting counter",
+        stream->stream.pid);
+    stream->continuity_counter = CONTINUITY_UNSET;
+  }
+
   size = packet->data_end - packet->payload;
   data = packet->payload;