decklinkvideosink: Handle pipelines where the running time does not start around 0 properly

We were converting all times to our internal running times, that is the time
the sink itself spent in PLAYING already. But forgot to do that for the
running time calculated from the buffer timestamps. As such, all buffers were
scheduled much later if the pipeline's running time did not start at 0.

This happens for example if a base time is explicitly set on the pipeline.

https://bugzilla.gnome.org/show_bug.cgi?id=754528

1 files changed, 26 insertions, 4 deletions

diff --git a/sys/decklink/gstdecklinkvideosink.cpp b/sys/decklink/gstdecklinkvideosink.cpp
index 6a701a3b9..c72454ab0 100644
--- a/sys/decklink/gstdecklinkvideosink.cpp
+++ b/sys/decklink/gstdecklinkvideosink.cpp
@@ -354,12 +354,34 @@ convert_to_internal_clock (GstDecklinkVideoSink * self,
     gst_clock_get_calibration (self->output->clock, &internal, &external,
         &rate_n, &rate_d);
 
-    if (rate_n != rate_d && self->internal_base_time != GST_CLOCK_TIME_NONE) {
+    if (self->internal_base_time != GST_CLOCK_TIME_NONE) {
       GstClockTime external_timestamp = *timestamp;
+      GstClockTime base_time;
 
       // Convert to the running time corresponding to both clock times
-      internal -= self->internal_base_time;
-      external -= self->external_base_time;
+      if (internal < self->internal_base_time)
+        internal = 0;
+      else
+        internal -= self->internal_base_time;
+
+      if (external < self->external_base_time)
+        external = 0;
+      else
+        external -= self->external_base_time;
+
+      // Convert timestamp to the "running time" since we started scheduled
+      // playback, that is the difference between the pipeline's base time
+      // and our own base time.
+      base_time = gst_element_get_base_time (GST_ELEMENT_CAST (self));
+      if (base_time > self->external_base_time)
+        base_time = 0;
+      else
+        base_time = self->external_base_time - base_time;
+
+      if (external_timestamp < base_time)
+        external_timestamp = 0;
+      else
+        external_timestamp = external_timestamp - base_time;
 
       // Get the difference in the external time, note
       // that the running time is external time.
@@ -398,7 +420,7 @@ convert_to_internal_clock (GstDecklinkVideoSink * self,
             GST_TIME_ARGS (external), ((gdouble) rate_n) / ((gdouble) rate_d));
       }
     } else {
-      GST_LOG_OBJECT (self, "No clock conversion needed, relative rate is 1.0");
+      GST_LOG_OBJECT (self, "No clock conversion needed, not started yet");
     }
   } else {
     GST_LOG_OBJECT (self, "No clock conversion needed, same clocks");