basedepay: Handle initial gaps and no clock-base

When generating segment, we can't assume the first buffer is actually
the first expected one. If it's not, we need to adjust the segment to
start a bit before.

Additionally, we if don't know when the stream is suppose to have
started (no clock-base in caps), it means we need to keep everything in
running time and only rely on jitterbuffer to synchronize.

https://bugzilla.gnome.org/show_bug.cgi?id=635701

gst-libs/gst/rtp/gstrtpbasedepayload.c

@@ -39,6 +39,7 @@ struct _GstRTPBaseDepayloadPrivate
   GstClockTime npt_stop;
   gdouble play_speed;
   gdouble play_scale;
+  guint clock_base;
 
   gboolean discont;
   GstClockTime pts;
@@ -52,6 +53,7 @@ struct _GstRTPBaseDepayloadPrivate
   gboolean negotiated;
 
   GstCaps *last_caps;
+  GstEvent *segment_event;
 };
 
 /* Filter signals and args */
@@ -92,6 +94,8 @@ static void gst_rtp_base_depayload_class_init (GstRTPBaseDepayloadClass *
     klass);
 static void gst_rtp_base_depayload_init (GstRTPBaseDepayload * rtpbasepayload,
     GstRTPBaseDepayloadClass * klass);
+static GstEvent *create_segment_event (GstRTPBaseDepayload * filter,
+    guint rtptime, GstClockTime position);
 
 GType
 gst_rtp_base_depayload_get_type (void)
@@ -238,6 +242,7 @@ gst_rtp_base_depayload_init (GstRTPBaseDepayload * filter,
   priv->npt_stop = -1;
   priv->play_speed = 1.0;
   priv->play_scale = 1.0;
+  priv->clock_base = -1;
   priv->dts = -1;
   priv->pts = -1;
   priv->duration = -1;
@@ -306,6 +311,12 @@ gst_rtp_base_depayload_setcaps (GstRTPBaseDepayload * filter, GstCaps * caps)
   else
     priv->play_scale = 1.0;
 
+  value = gst_structure_get_value (caps_struct, "clock-base");
+  if (value && G_VALUE_HOLDS_UINT (value))
+    priv->clock_base = g_value_get_uint (value);
+  else
+    priv->clock_base = -1;
+
   if (bclass->set_caps) {
     res = bclass->set_caps (filter, caps);
     if (!res) {
@@ -422,6 +433,13 @@ gst_rtp_base_depayload_chain (GstPad * pad, GstObject * parent, GstBuffer * in)
     }
   }
 
+  /* prepare segment event if needed */
+  if (filter->need_newsegment) {
+    priv->segment_event = create_segment_event (filter, rtptime,
+        GST_BUFFER_PTS (in));
+    filter->need_newsegment = FALSE;
+  }
+
   bclass = GST_RTP_BASE_DEPAYLOAD_GET_CLASS (filter);
 
   if (G_UNLIKELY (bclass->process == NULL))
@@ -487,6 +505,7 @@ gst_rtp_base_depayload_handle_event (GstRTPBaseDepayload * filter,
       gst_segment_init (&filter->segment, GST_FORMAT_UNDEFINED);
       filter->need_newsegment = TRUE;
       filter->priv->next_seqnum = -1;
+      gst_event_replace (&filter->priv->segment_event, NULL);
       break;
     case GST_EVENT_CAPS:
     {
@@ -560,30 +579,46 @@ gst_rtp_base_depayload_handle_sink_event (GstPad * pad, GstObject * parent,
 }
 
 static GstEvent *
-create_segment_event (GstRTPBaseDepayload * filter, GstClockTime position)
+create_segment_event (GstRTPBaseDepayload * filter, guint rtptime,
+    GstClockTime position)
 {
   GstEvent *event;
-  GstClockTime stop, running_time;
+  GstClockTime start, stop, running_time;
   GstRTPBaseDepayloadPrivate *priv;
   GstSegment segment;
 
   priv = filter->priv;
 
+  /* determin the start of the segment */
+  start = 0;
+  if (priv->clock_base != -1 && position != -1) {
+    GstClockTime exttime, gap;
+
+    exttime = priv->clock_base;
+    gst_rtp_buffer_ext_timestamp (&exttime, rtptime);
+    gap = gst_util_uint64_scale_int (exttime - priv->clock_base,
+        filter->clock_rate, GST_SECOND);
+
+    /* account for lost packets */
+    if (position > gap)
+      start = position - gap;
+  }
+
+  /* determin the stop of the segment */
+  stop = -1;
   if (priv->npt_stop != -1)
-    stop = position + priv->npt_stop - priv->npt_start;
+    stop = start + (priv->npt_stop - priv->npt_start);
-  else
-    stop = -1;
 
   if (position == -1)
     position = 0;
 
   running_time = gst_segment_to_running_time (&filter->segment,
-      GST_FORMAT_TIME, position);
+      GST_FORMAT_TIME, start);
 
   gst_segment_init (&segment, GST_FORMAT_TIME);
   segment.rate = priv->play_speed;
   segment.applied_rate = priv->play_scale;
-  segment.start = position;
+  segment.start = start;
   segment.stop = stop;
   segment.time = priv->npt_start;
   segment.position = position;
@@ -654,25 +689,9 @@ gst_rtp_base_depayload_prepare_push (GstRTPBaseDepayload * filter,
   }
 
   /* if this is the first buffer send a NEWSEGMENT */
-  if (G_UNLIKELY (filter->need_newsegment)) {
+  if (G_UNLIKELY (filter->priv->segment_event)) {
-    GstEvent *event;
+    gst_pad_push_event (filter->srcpad, filter->priv->segment_event);
-    GstClockTime pts;
+    filter->priv->segment_event = NULL;
-
-    if (is_list) {
-      GstBufferList **blist = obj;
-      GstBuffer *buf = gst_buffer_list_get (*blist, 0);
-      pts = GST_BUFFER_PTS (buf);
-    } else {
-      GstBuffer **buf = obj;
-      set_headers (buf, 0, &data);
-      pts = GST_BUFFER_PTS (*buf);
-    }
-
-    event = create_segment_event (filter, pts);
-
-    gst_pad_push_event (filter->srcpad, event);
-
-    filter->need_newsegment = FALSE;
     GST_DEBUG_OBJECT (filter, "Pushed newsegment event on this first buffer");
   }
 
@@ -778,9 +797,11 @@ gst_rtp_base_depayload_change_state (GstElement * element,
       priv->npt_stop = -1;
       priv->play_speed = 1.0;
       priv->play_scale = 1.0;
+      priv->clock_base = -1;
       priv->next_seqnum = -1;
       priv->negotiated = FALSE;
       priv->discont = FALSE;
+      gst_event_replace (&filter->priv->segment_event, NULL);
       break;
     case GST_STATE_CHANGE_PAUSED_TO_PLAYING:
       break;

tests/check/libs/rtpbasedepayload.c

@@ -253,6 +253,11 @@ validate_event (guint index, const gchar * name, const gchar * field, ...)
       const GstSegment *segment;
       gst_event_parse_segment (event, &segment);
       fail_unless_equals_uint64 (segment->rate, expected);
+    } else if (!g_strcmp0 (field, "base")) {
+      GstClockTime expected = va_arg (var_args, GstClockTime);
+      const GstSegment *segment;
+      gst_event_parse_segment (event, &segment);
+      fail_unless_equals_uint64 (segment->base, expected);
     } else if (!g_strcmp0 (field, "media-type")) {
       const gchar *expected = va_arg (var_args, const gchar *);
       GstCaps *caps;
@@ -292,6 +297,15 @@ validate_event (guint index, const gchar * name, const gchar * field, ...)
       fail_unless (gst_structure_get_double (gst_caps_get_structure (caps, 0),
               "play-scale", &scale));
       fail_unless (scale == expected);
+    } else if (!g_strcmp0 (field, "clock-base")) {
+      guint expected = va_arg (var_args, guint);
+      GstCaps *caps;
+      guint clock_base;
+      gst_event_parse_caps (event, &caps);
+      fail_unless (gst_structure_get_uint (gst_caps_get_structure (caps, 0),
+              "clock-base", &clock_base));
+      fail_unless (clock_base == expected);
+
     } else {
       fail ("test cannot validate unknown event field '%s'", field);
     }
@@ -933,8 +947,8 @@ GST_START_TEST (rtp_base_depayload_npt_test)
 
   validate_event (6, "segment",
       "time", G_GUINT64_CONSTANT (1234),
-      "start", GST_SECOND,
+      "start", G_GUINT64_CONSTANT (0),
-      "stop", GST_SECOND + G_GUINT64_CONSTANT (4321 - 1234), NULL);
+      "stop", G_GUINT64_CONSTANT (4321 - 1234), NULL);
 
   destroy_depayloader (state);
 }
@@ -994,7 +1008,7 @@ GST_START_TEST (rtp_base_depayload_play_scale_test)
 
   validate_event (6, "segment",
       "time", G_GUINT64_CONSTANT (0),
-      "start", GST_SECOND,
+      "start", G_GUINT64_CONSTANT (0),
       "stop", G_MAXUINT64, "rate", 1.0, "applied-rate", 2.0, NULL);
 
   destroy_depayloader (state);
@@ -1055,12 +1069,78 @@ GST_START_TEST (rtp_base_depayload_play_speed_test)
 
   validate_event (6, "segment",
       "time", G_GUINT64_CONSTANT (0),
-      "start", GST_SECOND,
+      "start", G_GUINT64_CONSTANT (0),
       "stop", G_MAXUINT64, "rate", 2.0, "applied-rate", 1.0, NULL);
 
   destroy_depayloader (state);
 }
 
+GST_END_TEST
+/* when a depayloader receives new caps events with npt-start, npt-stop and
+ * clock-base it should save these timestamps as they should affect the next
+ * segment event being pushed by the depayloader. the produce segment should
+ * make the positon of the stream reflect the postion form clock-base instead
+ * of reflecting the running time (for RTSP).
+ */
+GST_START_TEST (rtp_base_depayload_clock_base_test)
+{
+  State *state;
+
+  state = create_depayloader ("application/x-rtp", NULL);
+
+  set_state (state, GST_STATE_PLAYING);
+
+  push_rtp_buffer (state,
+      "pts", 0 * GST_SECOND,
+      "rtptime", G_GUINT64_CONSTANT (1234), "seq", 0x4242, NULL);
+
+  reconfigure_caps (state,
+      "application/x-rtp, npt-start=(guint64)1234, npt-stop=(guint64)4321, clock-base=(guint)1234");
+
+  flush_pipeline (state);
+
+  push_rtp_buffer (state,
+      "pts", 1 * GST_SECOND,
+      "rtptime", 1234 + DEFAULT_CLOCK_RATE,
+      "seq", 0x4242 + 1, NULL);
+
+  set_state (state, GST_STATE_NULL);
+
+  validate_buffers_received (2);
+
+  validate_buffer (0, "pts", 0 * GST_SECOND, "discont", FALSE, NULL);
+
+  validate_buffer (1, "pts", 1 * GST_SECOND, "discont", FALSE, NULL);
+
+  validate_events_received (7);
+
+  validate_event (0, "stream-start", NULL);
+
+  validate_event (1, "caps", "media-type", "application/x-rtp", NULL);
+
+  validate_event (2, "segment",
+      "time", G_GUINT64_CONSTANT (0),
+      "start", G_GUINT64_CONSTANT (0), "stop", G_MAXUINT64, NULL);
+
+  validate_event (3, "caps",
+      "media-type", "application/x-rtp",
+      "npt-start", G_GUINT64_CONSTANT (1234),
+      "npt-stop", G_GUINT64_CONSTANT (4321),
+      "clock-base", 1234, NULL);
+
+  validate_event (4, "flush-start", NULL);
+
+  validate_event (5, "flush-stop", NULL);
+
+  validate_event (6, "segment",
+      "time", G_GUINT64_CONSTANT (1234),
+      "start", GST_SECOND,
+      "stop", GST_SECOND + G_GUINT64_CONSTANT (4321 - 1234),
+      "base", GST_SECOND, NULL);
+
+  destroy_depayloader (state);
+}
+
 GST_END_TEST static Suite *
 rtp_basepayloading_suite (void)
 {
@@ -1085,6 +1165,7 @@ rtp_basepayloading_suite (void)
   tcase_add_test (tc_chain, rtp_base_depayload_npt_test);
   tcase_add_test (tc_chain, rtp_base_depayload_play_scale_test);
   tcase_add_test (tc_chain, rtp_base_depayload_play_speed_test);
+  tcase_add_test (tc_chain, rtp_base_depayload_clock_base_test);
 
   return s;
 }