dashdemux: Find the current period in a live stream

Start from the correct period on a live stream

https://bugzilla.gnome.org/show_bug.cgi?id=737421

ext/dash/gstdashdemux.c

@@ -488,9 +488,37 @@ gst_dash_demux_setup_streams (GstAdaptiveDemux * demux)
 {
   GstDashDemux *dashdemux = GST_DASH_DEMUX_CAST (demux);
   gboolean ret = TRUE;
+  GstDateTime *now = NULL;
+  guint period_idx;
 
-  /* setup video, audio and subtitle streams, starting from first Period */
+  /* setup video, audio and subtitle streams, starting from first Period if
-  if (!gst_mpd_client_set_period_index (dashdemux->client, 0) ||
+   * non-live */
+  period_idx = 0;
+  if (gst_mpd_client_is_live (dashdemux->client)) {
+
+    /* get period index for period encompassing the current time */
+    now = gst_date_time_new_now_utc ();
+    if (dashdemux->client->mpd_node->suggestedPresentationDelay != -1) {
+      GstDateTime *target = gst_mpd_client_add_time_difference (now,
+          dashdemux->client->mpd_node->suggestedPresentationDelay * -1000);
+      gst_date_time_unref (now);
+      now = target;
+    }
+    period_idx =
+        gst_mpd_client_get_period_index_at_time (dashdemux->client, now);
+    if (period_idx == G_MAXUINT) {
+#ifndef GST_DISABLE_GST_DEBUG
+      gchar *date_str = gst_date_time_to_iso8601_string (now);
+      GST_DEBUG_OBJECT (demux, "Unable to find live period active at %s",
+          date_str);
+      g_free (date_str);
+#endif
+      ret = FALSE;
+      goto done;
+    }
+  }
+
+  if (!gst_mpd_client_set_period_index (dashdemux->client, period_idx) ||
       !gst_dash_demux_setup_all_streams (dashdemux)) {
     ret = FALSE;
     goto done;
@@ -500,16 +528,9 @@ gst_dash_demux_setup_streams (GstAdaptiveDemux * demux)
    * is closest to current time */
   if (gst_mpd_client_is_live (dashdemux->client)) {
     GList *iter;
-    GstDateTime *now = gst_date_time_new_now_utc ();
     gint seg_idx;
 
     GST_DEBUG_OBJECT (demux, "Seeking to current time of day for live stream ");
-    if (dashdemux->client->mpd_node->suggestedPresentationDelay != -1) {
-      GstDateTime *target = gst_mpd_client_add_time_difference (now,
-          dashdemux->client->mpd_node->suggestedPresentationDelay * -1000);
-      gst_date_time_unref (now);
-      now = target;
-    }
     for (iter = demux->streams; iter; iter = g_list_next (iter)) {
       GstDashDemuxStream *stream = iter->data;
       GstActiveStream *active_stream = stream->active_stream;
@@ -539,6 +560,8 @@ gst_dash_demux_setup_streams (GstAdaptiveDemux * demux)
   }
 
 done:
+  if (now != NULL)
+    gst_date_time_unref (now);
   return ret;
 }
 

ext/dash/gstmpdparser.c

@@ -2598,6 +2598,40 @@ gst_mpdparser_build_URL_from_template (const gchar * url_template,
   return ret;
 }
 
+guint
+gst_mpd_client_get_period_index_at_time (GstMpdClient * client,
+      GstDateTime * time)
+{
+  GList *iter;
+  guint period_idx = G_MAXUINT;
+  guint idx;
+  gint64 time_offset;
+  GstDateTime *avail_start =
+      gst_mpd_client_get_availability_start_time (client);
+  GstStreamPeriod *stream_period;
+
+  if (avail_start == NULL)
+    return 0;
+
+  time_offset = gst_mpd_client_calculate_time_difference (avail_start, time);
+  gst_date_time_unref (avail_start);
+
+  if (time_offset < 0)
+    return 0;
+
+  for (idx = 0, iter = client->periods; iter;
+       idx++, iter = g_list_next (iter)) {
+    stream_period = iter->data;
+    if (stream_period->start <= time_offset
+        && stream_period->start + stream_period->duration > time_offset) {
+      period_idx = idx;
+      break;
+    }
+  }
+
+  return period_idx;
+}
+
 static GstStreamPeriod *
 gst_mpdparser_get_stream_period (GstMpdClient * client)
 {

ext/dash/gstmpdparser.h

@@ -502,6 +502,7 @@ gint gst_mpd_client_get_segment_index_at_time (GstMpdClient *client, GstActiveSt
 gint gst_mpd_client_check_time_position (GstMpdClient * client, GstActiveStream * stream, GstClockTime ts, gint64 * diff);
 
 /* Period selection */
+guint gst_mpd_client_get_period_index_at_time (GstMpdClient * client, GstDateTime * time);
 gboolean gst_mpd_client_set_period_index (GstMpdClient *client, guint period_idx);
 gboolean gst_mpd_client_set_period_id (GstMpdClient *client, const gchar * period_id);
 guint gst_mpd_client_get_period_index (GstMpdClient *client);