tsdemux: send initial GAP event on sparse streams for faster startup with playbin

Signal sparse streams properly in stream-start event and force sending
of pending sticky events which have been stored on the pad already and
which otherwise would only be sent on the first buffer or serialized
event (which means very late in case of subtitle streams). Playsink in
playbin waits for stream-start or another serialized event, and if we
don't do this it will wait for the multiqueue to run full before
starting playback, which might take a couple of seconds.

https://bugzilla.gnome.org/show_bug.cgi?id=734040

1 files changed, 19 insertions, 0 deletions

diff --git a/gst/mpegtsdemux/tsdemux.c b/gst/mpegtsdemux/tsdemux.c
index aba2c5a43..3cfa13d64 100644
--- a/gst/mpegtsdemux/tsdemux.c
+++ b/gst/mpegtsdemux/tsdemux.c
@@ -144,6 +144,9 @@ struct _TSDemuxStream
   /* Whether the pad was added or not */
   gboolean active;
 
+  /* Whether this is a sparse stream (subtitles or metadata) */
+  gboolean sparse;
+
   /* TRUE if we are waiting for a valid timestamp */
   gboolean pending_ts;
 
@@ -1024,6 +1027,7 @@ create_pad_for_stream (MpegTSBase * base, MpegTSBaseStream * bstream,
   GstPadTemplate *template = NULL;
   const GstMpegtsDescriptor *desc = NULL;
   GstPad *pad = NULL;
+  gboolean sparse = FALSE;
 
   gst_ts_demux_create_tags (stream);
 
@@ -1075,6 +1079,7 @@ create_pad_for_stream (MpegTSBase * base, MpegTSBaseStream * bstream,
         template = gst_static_pad_template_get (&subpicture_template);
         name = g_strdup_printf ("subpicture_%04x", bstream->pid);
         caps = gst_caps_new_empty_simple ("subpicture/x-pgs");
+        sparse = TRUE;
         break;
       case ST_BD_AUDIO_DTS_HD:
       case ST_BD_AUDIO_DTS_HD_MASTER_AUDIO:
@@ -1152,6 +1157,7 @@ create_pad_for_stream (MpegTSBase * base, MpegTSBaseStream * bstream,
         template = gst_static_pad_template_get (&private_template);
         name = g_strdup_printf ("private_%04x", bstream->pid);
         caps = gst_caps_new_empty_simple ("application/x-teletext");
+        sparse = TRUE;
         break;
       }
       desc =
@@ -1162,6 +1168,7 @@ create_pad_for_stream (MpegTSBase * base, MpegTSBaseStream * bstream,
         template = gst_static_pad_template_get (&private_template);
         name = g_strdup_printf ("private_%04x", bstream->pid);
         caps = gst_caps_new_empty_simple ("subpicture/x-dvb");
+        sparse = TRUE;
         break;
       }
 
@@ -1324,6 +1331,7 @@ create_pad_for_stream (MpegTSBase * base, MpegTSBaseStream * bstream,
       template = gst_static_pad_template_get (&subpicture_template);
       name = g_strdup_printf ("subpicture_%04x", bstream->pid);
       caps = gst_caps_new_empty_simple ("subpicture/x-dvd");
+      sparse = TRUE;
       break;
     default:
       GST_WARNING ("Non-media stream (stream_type:0x%x). Not creating pad",
@@ -1359,6 +1367,9 @@ done:
     event = gst_event_new_stream_start (stream_id);
     if (demux->have_group_id)
       gst_event_set_group_id (event, demux->group_id);
+    if (sparse)
+      gst_event_set_stream_flags (event, GST_STREAM_FLAG_SPARSE);
+    stream->sparse = sparse;
 
     gst_pad_push_event (pad, event);
     g_free (stream_id);
@@ -1476,6 +1487,14 @@ activate_pad_for_stream (GstTSDemux * tsdemux, TSDemuxStream * stream)
     gst_element_add_pad ((GstElement *) tsdemux, stream->pad);
     stream->active = TRUE;
     GST_DEBUG_OBJECT (stream->pad, "done adding pad");
+    /* force sending of pending sticky events which have been stored on the
+     * pad already and which otherwise would only be sent on the first buffer
+     * or serialized event (which means very late in case of subtitle streams),
+     * and playsink waits for stream-start or another serialized event */
+    if (stream->sparse) {
+      GST_DEBUG_OBJECT (stream->pad, "sparse stream, pushing GAP event");
+      gst_pad_push_event (stream->pad, gst_event_new_gap (0, 0));
+    }
   } else {
     GST_WARNING_OBJECT (tsdemux,
         "stream %p (pid 0x%04x, type:0x%03x) has no pad", stream,