[MOVED FROM GST-P-FARSIGHT] liveadder : Handle jitter in incoming buffers

Incoming buffers (especially those from an RTP connection) might have slight timestamp jitter. This is normally handled by audiosink (accepting up to 500ms of jitter).
Here we accept a maximum jitter of 10ms. If a buffer is within 10ms of the expected time, we correct its timestamp.

diff --git a/gst/liveadder/liveadder.c b/gst/liveadder/liveadder.c
index dd6ffe7..637dbae 100644 (file)
--- a/gst/liveadder/liveadder.c
+++ b/gst/liveadder/liveadder.c
@@ -897,11 +897,16 @@ gst_live_live_adder_chain (GstPad *pad, GstBuffer *buffer)
   GstFlowReturn ret = GST_FLOW_OK;
   GList *item = NULL;
   GstClockTime skip = 0;
+  gint64 drift = 0; /* Positive if new buffer after old buffer */
 
   GST_OBJECT_LOCK (adder);
 
   ret = adder->srcresult;
 
+  GST_DEBUG ("Incoming buffer time:%"GST_TIME_FORMAT" duration:%"GST_TIME_FORMAT,
+            GST_TIME_ARGS(GST_BUFFER_TIMESTAMP(buffer)),
+            GST_TIME_ARGS(GST_BUFFER_DURATION(buffer)));
+
   if (ret != GST_FLOW_OK)
   {
     GST_DEBUG_OBJECT (adder, "Passing non-ok result from src: %s",
@@ -942,17 +947,28 @@ gst_live_live_adder_chain (GstPad *pad, GstBuffer *buffer)
   if (padprivate->segment.format != GST_FORMAT_TIME)
     goto invalid_segment;
 
+  buffer = gst_buffer_make_metadata_writable (buffer);
+
+  drift = GST_BUFFER_TIMESTAMP (buffer) - padprivate->expected_timestamp;
+
   /* Just see if we receive invalid timestamp/durations */
   if (GST_CLOCK_TIME_IS_VALID (padprivate->expected_timestamp) &&
       !GST_BUFFER_FLAG_IS_SET(buffer, GST_BUFFER_FLAG_DISCONT) &&
-      GST_BUFFER_TIMESTAMP(buffer) != padprivate->expected_timestamp)
+      (drift != 0)) {
     GST_LOG_OBJECT (adder,
         "Timestamp discontinuity without the DISCONT flag set"
-        " (expected %" GST_TIME_FORMAT ", got %" GST_TIME_FORMAT")",
+        " (expected %" GST_TIME_FORMAT ", got %" GST_TIME_FORMAT" drift:%ldms)",
         GST_TIME_ARGS (padprivate->expected_timestamp),
-        GST_TIME_ARGS (GST_BUFFER_TIMESTAMP (buffer)));
+                   GST_TIME_ARGS (GST_BUFFER_TIMESTAMP (buffer)),
+                   drift / GST_MSECOND);
+
+    /* We accept drifts of 10ms*/
+    if (ABS(drift) < (10 * GST_MSECOND)) {
+      GST_DEBUG ("Correcting minor drift");
+      GST_BUFFER_TIMESTAMP (buffer) = padprivate->expected_timestamp;
+    }
+  }
 
-  buffer = gst_buffer_make_metadata_writable (buffer);
 
   /* If there is no duration, lets set one */
   if (!GST_BUFFER_DURATION_IS_VALID (buffer)) {
@@ -976,8 +992,10 @@ gst_live_live_adder_chain (GstPad *pad, GstBuffer *buffer)
       adder->bps);
 
   /* buffer can be NULL if it's completely outside of the segment */
-  if (!buffer)
+  if (!buffer) {
+    GST_DEBUG ("Buffer completely outside of configured segment, dropping it");
     goto out;
+  }
 
   /*
    * Make sure all incoming buffers share the same timestamping
@@ -1297,6 +1315,10 @@ gst_live_adder_loop (gpointer data)
   if (newseg_event)
     gst_pad_push_event (adder->srcpad, newseg_event);
 
+  GST_DEBUG ("About to push buffer time:%"GST_TIME_FORMAT" duration:%"GST_TIME_FORMAT,
+            GST_TIME_ARGS(GST_BUFFER_TIMESTAMP(buffer)),
+            GST_TIME_ARGS(GST_BUFFER_DURATION(buffer)));
+
   result = gst_pad_push (adder->srcpad, buffer);
   if (result != GST_FLOW_OK)
     goto pause;