qtdemux: rework segment event pushing

Instead of always keeping a safe segment (start=0) event from the beginning,
delay the creation of this event to when we really know the timestamp of the
first sample. This is important to properly start fragmented streams that
we might join in the middle or to play isolated fragment files that might
have an advanced tfdt.

https://bugzilla.gnome.org/show_bug.cgi?id=752603

diff --git a/gst/isomp4/qtdemux.c b/gst/isomp4/qtdemux.c
index 4116f4c..5bbfadf 100644 (file)
--- a/gst/isomp4/qtdemux.c
+++ b/gst/isomp4/qtdemux.c
@@ -546,6 +546,9 @@ static void gst_qtdemux_stream_check_and_change_stsd_index (GstQTDemux * demux,
     QtDemuxStream * stream);
 static GstFlowReturn gst_qtdemux_process_adapter (GstQTDemux * demux,
     gboolean force);
+static GstClockTime gst_qtdemux_streams_get_first_sample_ts (GstQTDemux *
+    demux);
+static GstClockTime gst_qtdemux_streams_have_samples (GstQTDemux * demux);
 
 static gboolean qtdemux_parse_moov (GstQTDemux * qtdemux,
     const guint8 * buffer, guint length);
@@ -1034,9 +1037,27 @@ gst_qtdemux_push_event (GstQTDemux * qtdemux, GstEvent * event)
 static void
 gst_qtdemux_push_pending_newsegment (GstQTDemux * qtdemux)
 {
-  if (qtdemux->pending_newsegment) {
-    gst_qtdemux_push_event (qtdemux, qtdemux->pending_newsegment);
-    qtdemux->pending_newsegment = NULL;
+  if (G_UNLIKELY (qtdemux->need_segment)) {
+    GstClockTime min_ts;
+    GstEvent *newsegment;
+
+    if (!gst_qtdemux_streams_have_samples (qtdemux)) {
+      /* No samples yet, can't decide on segment.start */
+      GST_DEBUG_OBJECT (qtdemux, "No samples yet, postponing segment event");
+      return;
+    }
+
+    min_ts = gst_qtdemux_streams_get_first_sample_ts (qtdemux);
+
+    /* have_samples() above should guarantee we have a valid time */
+    g_assert (GST_CLOCK_TIME_IS_VALID (min_ts));
+
+    qtdemux->segment.start = min_ts;
+    newsegment = gst_event_new_segment (&qtdemux->segment);
+    if (qtdemux->segment_seqnum != GST_SEQNUM_INVALID)
+      gst_event_set_seqnum (newsegment, qtdemux->segment_seqnum);
+    qtdemux->need_segment = FALSE;
+    gst_qtdemux_push_event (qtdemux, newsegment);
   }
 }
 
@@ -2131,9 +2152,6 @@ gst_qtdemux_reset (GstQTDemux * qtdemux, gboolean hard)
     qtdemux->element_index = NULL;
 #endif
     qtdemux->major_brand = 0;
-    if (qtdemux->pending_newsegment)
-      gst_event_unref (qtdemux->pending_newsegment);
-    qtdemux->pending_newsegment = NULL;
     qtdemux->upstream_format_is_time = FALSE;
     qtdemux->upstream_seekable = FALSE;
     qtdemux->upstream_size = 0;
@@ -2154,6 +2172,7 @@ gst_qtdemux_reset (GstQTDemux * qtdemux, gboolean hard)
   gst_adapter_clear (qtdemux->adapter);
   gst_segment_init (&qtdemux->segment, GST_FORMAT_TIME);
   qtdemux->segment_seqnum = GST_SEQNUM_INVALID;
+  qtdemux->need_segment = TRUE;
 
   if (hard) {
     g_list_free_full (qtdemux->active_streams,
@@ -2199,12 +2218,6 @@ gst_qtdemux_reset (GstQTDemux * qtdemux, gboolean hard)
       stream->time_position = 0;
       stream->accumulated_base = 0;
     }
-    if (!qtdemux->pending_newsegment) {
-      qtdemux->pending_newsegment = gst_event_new_segment (&qtdemux->segment);
-      if (qtdemux->segment_seqnum != GST_SEQNUM_INVALID)
-        gst_event_set_seqnum (qtdemux->pending_newsegment,
-            qtdemux->segment_seqnum);
-    }
   }
 }
 
@@ -2275,12 +2288,7 @@ gst_qtdemux_handle_sink_event (GstPad * sinkpad, GstObject * parent,
       GST_DEBUG_OBJECT (demux, "received newsegment %" GST_SEGMENT_FORMAT,
           &segment);
 
-      /* erase any previously set segment */
-      gst_event_replace (&demux->pending_newsegment, NULL);
-
       if (segment.format == GST_FORMAT_TIME) {
-        GST_DEBUG_OBJECT (demux, "new pending_newsegment");
-        gst_event_replace (&demux->pending_newsegment, event);
         demux->upstream_format_is_time = TRUE;
       } else {
         GST_DEBUG_OBJECT (demux, "Not storing upstream newsegment, "
@@ -2359,13 +2367,15 @@ gst_qtdemux_handle_sink_event (GstPad * sinkpad, GstObject * parent,
         if (demux->fragmented) {
           GstEvent *segment_event = gst_event_new_segment (&segment);
 
-          gst_event_replace (&demux->pending_newsegment, NULL);
           gst_event_set_seqnum (segment_event, demux->segment_seqnum);
           gst_qtdemux_push_event (demux, segment_event);
         } else {
-          gst_event_replace (&demux->pending_newsegment, NULL);
           gst_qtdemux_map_and_push_segments (demux, &segment);
         }
+        /* keep need-segment as is in case this is the segment before
+         * fragmented data, we might not have pads yet to push it */
+        if (demux->exposed)
+          demux->need_segment = FALSE;
       }
 
       /* clear leftover in current segment, if any */
@@ -4516,6 +4526,11 @@ gst_qtdemux_loop_state_header (GstQTDemux * qtdemux)
       gst_buffer_unmap (moov, &map);
       gst_buffer_unref (moov);
       qtdemux->got_moov = TRUE;
+      if (!qtdemux->fragmented && !qtdemux->upstream_format_is_time) {
+        /* in this case, parsing the edts entries will give us segments
+           already */
+        qtdemux->need_segment = FALSE;
+      }
 
       break;
     }
@@ -6527,7 +6542,7 @@ gst_qtdemux_drop_data (GstQTDemux * demux, gint bytes)
 static void
 gst_qtdemux_check_send_pending_segment (GstQTDemux * demux)
 {
-  if (G_UNLIKELY (demux->pending_newsegment)) {
+  if (G_UNLIKELY (demux->need_segment)) {
     gint i;
     GList *iter;
 
@@ -6572,6 +6587,35 @@ gst_qtdemux_send_gap_for_segment (GstQTDemux * demux,
   }
 }
 
+static GstClockTime
+gst_qtdemux_streams_get_first_sample_ts (GstQTDemux * demux)
+{
+  GstClockTime res = GST_CLOCK_TIME_NONE;
+  GList *iter;
+
+  for (iter = demux->active_streams; iter; iter = g_list_next (iter)) {
+    QtDemuxStream *stream = QTDEMUX_STREAM (iter->data);
+    if (stream->n_samples) {
+      res = MIN (QTSAMPLE_PTS (stream, &stream->samples[0]), res);
+      res = MIN (QTSAMPLE_DTS (stream, &stream->samples[0]), res);
+    }
+  }
+  return res;
+}
+
+static GstClockTime
+gst_qtdemux_streams_have_samples (GstQTDemux * demux)
+{
+  GList *iter;
+
+  for (iter = demux->active_streams; iter; iter = g_list_next (iter)) {
+    QtDemuxStream *stream = QTDEMUX_STREAM (iter->data);
+    if (stream->n_samples)
+      return TRUE;
+  }
+  return FALSE;
+}
+
 static GstFlowReturn
 gst_qtdemux_chain (GstPad * sinkpad, GstObject * parent, GstBuffer * inbuf)
 {
@@ -6831,15 +6875,6 @@ gst_qtdemux_process_adapter (GstQTDemux * demux, gboolean force)
               if (demux->moov_node)
                 g_node_destroy (demux->moov_node);
               demux->moov_node = NULL;
-            } else {
-              /* prepare newsegment to send when streaming actually starts */
-              if (!demux->pending_newsegment) {
-                demux->pending_newsegment =
-                    gst_event_new_segment (&demux->segment);
-                if (demux->segment_seqnum != GST_SEQNUM_INVALID)
-                  gst_event_set_seqnum (demux->pending_newsegment,
-                      demux->segment_seqnum);
-              }
             }
 
             demux->last_moov_offset = demux->offset;
@@ -6858,8 +6893,7 @@ gst_qtdemux_process_adapter (GstQTDemux * demux, gboolean force)
             QTDEMUX_EXPOSE_UNLOCK (demux);
 
             demux->got_moov = TRUE;
-
-            gst_event_replace (&demux->pending_newsegment, NULL);
+            demux->need_segment = TRUE;
             gst_qtdemux_map_and_push_segments (demux, &demux->segment);
 
             if (demux->moov_node_compressed) {
@@ -6943,20 +6977,15 @@ gst_qtdemux_process_adapter (GstQTDemux * demux, gboolean force)
               ret = GST_FLOW_ERROR;
               goto done;
             }
+
             /* in MSS we need to expose the pads after the first moof as we won't get a moov */
             if (demux->mss_mode && !demux->exposed) {
-              if (!demux->pending_newsegment) {
-                GST_DEBUG_OBJECT (demux, "new pending_newsegment");
-                demux->pending_newsegment =
-                    gst_event_new_segment (&demux->segment);
-                if (demux->segment_seqnum != GST_SEQNUM_INVALID)
-                  gst_event_set_seqnum (demux->pending_newsegment,
-                      demux->segment_seqnum);
-              }
               QTDEMUX_EXPOSE_LOCK (demux);
               qtdemux_expose_streams (demux);
               QTDEMUX_EXPOSE_UNLOCK (demux);
             }
+
+            gst_qtdemux_check_send_pending_segment (demux);
           } else {
             GST_DEBUG_OBJECT (demux, "Discarding [moof]");
           }
@@ -12376,14 +12405,6 @@ qtdemux_update_streams (GstQTDemux * qtdemux)
       stream->stream_tags = NULL;
       if (!gst_qtdemux_add_stream (qtdemux, stream, list))
         return FALSE;
-
-      /* New segment will be exposed at _update_segment in case of pull mode */
-      if (!qtdemux->pending_newsegment && !qtdemux->pullbased) {
-        qtdemux->pending_newsegment = gst_event_new_segment (&qtdemux->segment);
-        if (qtdemux->segment_seqnum)
-          gst_event_set_seqnum (qtdemux->pending_newsegment,
-              qtdemux->segment_seqnum);
-      }
     }
   }
 
@@ -12430,13 +12451,6 @@ qtdemux_expose_streams (GstQTDemux * qtdemux)
       if (!gst_qtdemux_add_stream (qtdemux, stream, list))
         return GST_FLOW_ERROR;
 
-      /* New segment will be exposed at _update_segment in case of pull mode */
-      if (!qtdemux->pending_newsegment && !qtdemux->pullbased) {
-        qtdemux->pending_newsegment = gst_event_new_segment (&qtdemux->segment);
-        if (qtdemux->segment_seqnum)
-          gst_event_set_seqnum (qtdemux->pending_newsegment,
-              qtdemux->segment_seqnum);
-      }
     }
   }
 

diff --git a/gst/isomp4/qtdemux.h b/gst/isomp4/qtdemux.h
index dde6abc..056d287 100644 (file)
--- a/gst/isomp4/qtdemux.h
+++ b/gst/isomp4/qtdemux.h
@@ -119,8 +119,8 @@ struct _GstQTDemux {
   /* configured playback region */
   GstSegment segment;
 
-  /* The SEGMENT_EVENT from upstream *OR* generated from segment (above) */
-  GstEvent *pending_newsegment;
+  /* If a segment event needs to be pushed */
+  gboolean need_segment;
 
   guint32 segment_seqnum;