basesrc: preserve seqnum on segments after seeks

The seqnum of the segment after a seek should be the same of
the seek event. Downstream elements might rely on seqnums to
identify events related to a seek.

This is particularly important when a demuxer maps a TIME seek
into a BYTES seek for upstream and it needs to identify the
corresponding segment event and map it back into TIME to push
downstream, possibly using the values from the original seek
event.

https://bugzilla.gnome.org/show_bug.cgi?id=707530

diff --git a/libs/gst/base/gstbasesrc.c b/libs/gst/base/gstbasesrc.c
index ccc5b0b..e35824f 100644 (file)
--- a/libs/gst/base/gstbasesrc.c
+++ b/libs/gst/base/gstbasesrc.c
@@ -224,8 +224,10 @@ struct _GstBaseSrcPrivate
   /* if a stream-start event should be sent */
   gboolean stream_start_pending;
 
-  /* if segment should be sent */
+  /* if segment should be sent and a
+   * seqnum if it was originated by a seek */
   gboolean segment_pending;
+  guint32 segment_seqnum;
 
   /* if EOS is pending (atomic) */
   gint pending_eos;
@@ -818,6 +820,7 @@ gst_base_src_new_seamless_segment (GstBaseSrc * src, gint64 start, gint64 stop,
 
   /* Mark pending segment. Will be sent before next data */
   src->priv->segment_pending = TRUE;
+  src->priv->segment_seqnum = gst_util_seqnum_next ();
 
   GST_DEBUG_OBJECT (src,
       "Starting new seamless segment. Start %" GST_TIME_FORMAT " stop %"
@@ -1667,6 +1670,7 @@ gst_base_src_perform_seek (GstBaseSrc * src, GstEvent * event, gboolean unlock)
       stop = seeksegment.duration;
 
     src->priv->segment_pending = TRUE;
+    src->priv->segment_seqnum = seqnum;
   }
 
   src->priv->discont = TRUE;
@@ -2671,7 +2675,11 @@ gst_base_src_loop (GstPad * pad)
 
   /* push events to close/start our segment before we push the buffer. */
   if (G_UNLIKELY (src->priv->segment_pending)) {
-    gst_pad_push_event (pad, gst_event_new_segment (&src->segment));
+    GstEvent *seg_event = gst_event_new_segment (&src->segment);
+
+    gst_event_set_seqnum (seg_event, src->priv->segment_seqnum);
+    src->priv->segment_seqnum = gst_util_seqnum_next ();
+    gst_pad_push_event (pad, seg_event);
     src->priv->segment_pending = FALSE;
   }
 
@@ -3182,6 +3190,7 @@ gst_base_src_start (GstBaseSrc * basesrc)
   basesrc->num_buffers_left = basesrc->num_buffers;
   basesrc->running = FALSE;
   basesrc->priv->segment_pending = FALSE;
+  basesrc->priv->segment_seqnum = gst_util_seqnum_next ();
   GST_LIVE_UNLOCK (basesrc);
 
   bclass = GST_BASE_SRC_GET_CLASS (basesrc);