jitterbuffer: estimate inter packet spacing

When we see two packets with consecutive seqnums and a different RTP time, use
the DTS difference as the inter packet spacing estimate.

diff --git a/gst/rtpmanager/gstrtpjitterbuffer.c b/gst/rtpmanager/gstrtpjitterbuffer.c
index 4b51d09..df06b67 100644 (file)
--- a/gst/rtpmanager/gstrtpjitterbuffer.c
+++ b/gst/rtpmanager/gstrtpjitterbuffer.c
@@ -150,6 +150,10 @@ struct _GstRtpJitterBufferPrivate
   GstClockTime last_out_time;
   GstClockTime last_out_dts;
   GstClockTime last_out_pts;
+  /* last valid input timestamp and rtptime pair */
+  GstClockTime last_in_dts;
+  GstClockTime last_in_rtptime;
+  GstClockTime packet_spacing;
   /* the next expected seqnum we receive */
   guint32 next_in_seqnum;
 
@@ -902,6 +906,9 @@ gst_rtp_jitter_buffer_flush_stop (GstRtpJitterBuffer * jitterbuffer)
   priv->last_out_dts = -1;
   priv->last_out_pts = -1;
   priv->next_seqnum = -1;
+  priv->last_in_rtptime = -1;
+  priv->last_in_dts = GST_CLOCK_TIME_NONE;
+  priv->packet_spacing = 0;
   priv->next_in_seqnum = -1;
   priv->clock_rate = -1;
   priv->eos = FALSE;
@@ -1278,6 +1285,7 @@ gst_rtp_jitter_buffer_chain (GstPad * pad, GstObject * parent,
   GstRtpJitterBuffer *jitterbuffer;
   GstRtpJitterBufferPrivate *priv;
   guint16 seqnum;
+  guint32 rtptime;
   GstFlowReturn ret = GST_FLOW_OK;
   GstClockTime dts, pts;
   guint64 latency_ts;
@@ -1295,6 +1303,7 @@ gst_rtp_jitter_buffer_chain (GstPad * pad, GstObject * parent,
 
   pt = gst_rtp_buffer_get_payload_type (&rtp);
   seqnum = gst_rtp_buffer_get_seq (&rtp);
+  rtptime = gst_rtp_buffer_get_timestamp (&rtp);
   gst_rtp_buffer_unmap (&rtp);
 
   /* make sure we have PTS and DTS set */
@@ -1382,6 +1391,23 @@ gst_rtp_jitter_buffer_chain (GstPad * pad, GstObject * parent,
         priv->last_popped_seqnum = -1;
         priv->next_seqnum = seqnum;
       }
+      /* reset spacing estimation when gap */
+      priv->last_in_rtptime = -1;
+      priv->last_in_dts = -1;
+    } else {
+      /* packet is expected, we need consecutive seqnums with a different
+       * rtptime to estimate the packet spacing. */
+      if (priv->last_in_rtptime != rtptime) {
+        /* rtptime changed, check dts diff */
+        if (priv->last_in_dts != -1 && dts != -1 && dts > priv->last_in_dts) {
+          priv->packet_spacing = dts - priv->last_in_dts;
+          GST_DEBUG_OBJECT (jitterbuffer,
+              "new packet spacing %" GST_TIME_FORMAT,
+              GST_TIME_ARGS (priv->packet_spacing));
+        }
+        priv->last_in_rtptime = rtptime;
+        priv->last_in_dts = dts;
+      }
     }
   }
   priv->next_in_seqnum = (seqnum + 1) & 0xffff;