v4l2src: add frame loss detection

In case of v4l2 driver filled offset/sequence values add frame
loss detection (and write a warning message).

Move offset meta data setting and frame loss checking after the
timestamp adjustment code to get proper timestamps for the
warning message.

https://bugzilla.gnome.org/show_bug.cgi?id=745441

1 files changed, 23 insertions, 7 deletions

diff --git a/sys/v4l2/gstv4l2src.c b/sys/v4l2/gstv4l2src.c
index e4b068702..ab36a5820 100644
--- a/sys/v4l2/gstv4l2src.c
+++ b/sys/v4l2/gstv4l2src.c
@@ -675,6 +675,7 @@ gst_v4l2src_create (GstPushSrc * src, GstBuffer ** buf)
   GstClock *clock;
   GstClockTime abs_time, base_time, timestamp, duration;
   GstClockTime delay;
+  GstMessage *qos_msg;
 
   do {
     ret = GST_BASE_SRC_CLASS (parent_class)->alloc (GST_BASE_SRC (src), 0,
@@ -779,13 +780,6 @@ retry:
 
   /* set buffer metadata */
 
-  /* use generated offset values only if there are not already valid ones
-   * set by the v4l2 device */
-  if (!GST_BUFFER_OFFSET_IS_VALID (*buf) || !GST_BUFFER_OFFSET_END_IS_VALID (*buf)) {
-    GST_BUFFER_OFFSET (*buf) = v4l2src->offset++;
-    GST_BUFFER_OFFSET_END (*buf) = v4l2src->offset;
-  }
-
   if (G_LIKELY (abs_time != GST_CLOCK_TIME_NONE)) {
     /* the time now is the time of the clock minus the base time */
     timestamp = abs_time - base_time;
@@ -813,6 +807,28 @@ retry:
   GST_INFO_OBJECT (src, "sync to %" GST_TIME_FORMAT " out ts %" GST_TIME_FORMAT,
       GST_TIME_ARGS (v4l2src->ctrl_time), GST_TIME_ARGS (timestamp));
 
+  /* use generated offset values only if there are not already valid ones
+   * set by the v4l2 device */
+  if (!GST_BUFFER_OFFSET_IS_VALID (*buf) || !GST_BUFFER_OFFSET_END_IS_VALID (*buf)) {
+    GST_BUFFER_OFFSET (*buf) = v4l2src->offset++;
+    GST_BUFFER_OFFSET_END (*buf) = v4l2src->offset;
+  } else {
+    /* check for frame loss with given (from v4l2 device) buffer offset */
+    if ((v4l2src->offset != 0) && (GST_BUFFER_OFFSET (*buf) != (v4l2src->offset + 1))) {
+      guint64 lost_frame_count = GST_BUFFER_OFFSET (*buf) - v4l2src->offset - 1;
+      GST_WARNING_OBJECT (v4l2src,
+          "lost frames detected: count = %" G_GUINT64_FORMAT " - ts: %" GST_TIME_FORMAT,
+              lost_frame_count, GST_TIME_ARGS (timestamp));
+
+      qos_msg = gst_message_new_qos (GST_OBJECT_CAST (v4l2src), TRUE,
+          GST_CLOCK_TIME_NONE, GST_CLOCK_TIME_NONE, timestamp,
+          GST_CLOCK_TIME_IS_VALID (duration) ? lost_frame_count * duration : GST_CLOCK_TIME_NONE);
+      gst_element_post_message (GST_ELEMENT_CAST (v4l2src), qos_msg);
+
+    }
+    v4l2src->offset = GST_BUFFER_OFFSET (*buf);
+  }
+
   GST_BUFFER_TIMESTAMP (*buf) = timestamp;
   GST_BUFFER_DURATION (*buf) = duration;