From ad240b0ae37877966a8272ec4ade67a7797feaae Mon Sep 17 00:00:00 2001
From: "Joshua M. Doe" <oss@nvl.army.mil>
Date: Fri, 29 Jun 2012 07:35:26 -0400
Subject: [PATCH] niimaq: try to improve accuracy of timestamping

By reducing instructions in callback, and adjusting for base time. This last
part needs testing however.
---
 sys/niimaq/gstniimaq.c | 79 ++++++++++++++++++++++--------------------
 sys/niimaq/gstniimaq.h | 12 ++++---
 2 files changed, 48 insertions(+), 43 deletions(-)

diff --git a/sys/niimaq/gstniimaq.c b/sys/niimaq/gstniimaq.c
index 8160d4e..fda2018 100644
--- a/sys/niimaq/gstniimaq.c
+++ b/sys/niimaq/gstniimaq.c
@@ -123,30 +123,39 @@ gst_niimaqsrc_frame_start_callback (SESSION_ID sid, IMG_ERR err,
 {
   GstNiImaqSrc *niimaqsrc = GST_NIIMAQSRC (userdata);
   GstClock *clock;
-  GstNiImaqSrcFrameTime *frametime = g_new (GstNiImaqSrcFrameTime, 1);
-  uInt32 val;
+  GstNiImaqSrcFrameTime *frametime;
+  guint32 bufnum;
+  GstClockTime abstime;
+
+  if (!niimaqsrc->session_started)
+    return 1;
 
   if (G_UNLIKELY (niimaqsrc->start_time == NULL))
     niimaqsrc->start_time = gst_date_time_new_now_utc ();
 
-  /* get clock time and set to frametime struct */
+  /* get clock time */
   clock = gst_element_get_clock (GST_ELEMENT (niimaqsrc));
-  if (G_LIKELY (clock)) {
-    frametime->time = gst_clock_get_time (clock);
-    gst_object_unref (clock);
-  } else {
-    frametime->time = GST_CLOCK_TIME_NONE;
-  }
+  g_assert (clock != NULL);
+  abstime = gst_clock_get_time (clock);
 
   /* get current frame number */
-  imgGetAttribute (sid, IMG_ATTR_FRAME_COUNT, &val);
-  frametime->number = val;
+  imgGetAttribute (sid, IMG_ATTR_FRAME_COUNT, &bufnum);
+
+  /* first frame, use as element base time */
+  if (niimaqsrc->base_time == GST_CLOCK_TIME_NONE)
+    niimaqsrc->base_time = abstime;
+
+  frametime = g_new (GstNiImaqSrcFrameTime, 1);
+  frametime->number = bufnum;
+  frametime->time = abstime;
 
   /* append frame number and clock time to list */
   g_mutex_lock (niimaqsrc->frametime_mutex);
   niimaqsrc->timelist = g_slist_append (niimaqsrc->timelist, frametime);
   g_mutex_unlock (niimaqsrc->frametime_mutex);
 
+  gst_object_unref (clock);
+
   /* return 1 to rearm the callback */
   return 1;
 }
@@ -654,6 +663,7 @@ gst_niimaqsrc_reset (GstNiImaqSrc * niimaqsrc)
   niimaqsrc->timelist = NULL;
   niimaqsrc->start_time = NULL;
   niimaqsrc->start_time_sent = FALSE;
+  niimaqsrc->base_time = GST_CLOCK_TIME_NONE;
 }
 
 static gboolean
@@ -692,36 +702,36 @@ static GstClockTime
 gst_niimaqsrc_get_timestamp_from_buffer_number (GstNiImaqSrc * niimaqsrc,
     guint32 buffer_number)
 {
-  GstClockTime timestamp = GST_CLOCK_TIME_NONE;
+  GstClockTime abstime = GST_CLOCK_TIME_NONE;
   GstNiImaqSrcFrameTime *frametime;
 
   /* search linked list for frame time */
   g_mutex_lock (niimaqsrc->frametime_mutex);
-  if (G_LIKELY (niimaqsrc->timelist)
-      && g_slist_length (niimaqsrc->timelist) > 0) {
-    /* remove all old frametimes from the list */
+
+  g_assert (niimaqsrc->timelist != NULL);
+
+  /* remove all old frametimes from the list */
+  frametime = (GstNiImaqSrcFrameTime *) niimaqsrc->timelist->data;
+  while (frametime->number < buffer_number) {
+    niimaqsrc->timelist =
+        g_slist_delete_link (niimaqsrc->timelist, niimaqsrc->timelist);
     frametime = (GstNiImaqSrcFrameTime *) niimaqsrc->timelist->data;
-    while (frametime->number < buffer_number) {
-      niimaqsrc->timelist =
-          g_slist_delete_link (niimaqsrc->timelist, niimaqsrc->timelist);
-      frametime = (GstNiImaqSrcFrameTime *) niimaqsrc->timelist->data;
-    }
+  }
 
-    if (frametime->number == buffer_number) {
-      timestamp = frametime->time;
+  if (frametime->number == buffer_number) {
+    abstime = frametime->time;
 
-      /* remove frame time as we no longer need it */
-      niimaqsrc->timelist =
-          g_slist_delete_link (niimaqsrc->timelist, niimaqsrc->timelist);
-    } else {
-      GST_WARNING_OBJECT (niimaqsrc,
-          "Did NOT find buffer date-timestamp in list generated by callback");
-    }
+    /* remove frame time as we no longer need it */
+    niimaqsrc->timelist =
+        g_slist_delete_link (niimaqsrc->timelist, niimaqsrc->timelist);
+  } else {
+    GST_WARNING_OBJECT (niimaqsrc,
+        "Did NOT find buffer date-timestamp in list generated by callback");
   }
 
   g_mutex_unlock (niimaqsrc->frametime_mutex);
 
-  return timestamp;
+  return GST_CLOCK_DIFF (niimaqsrc->base_time, abstime);
 }
 
 static GstFlowReturn
@@ -780,14 +790,7 @@ gst_niimaqsrc_create (GstPushSrc * psrc, GstBuffer ** buffer)
   /* set timestamp */
   timestamp =
       gst_niimaqsrc_get_timestamp_from_buffer_number (niimaqsrc, copied_number);
-  if (timestamp == GST_CLOCK_TIME_NONE) {
-    GST_WARNING_OBJECT (niimaqsrc, "No timestamp found; callback failed?");
-    /* FIXME: the clock isn't valid before the first FVAL callback? */
-  } else {
-    timestamp =
-        GST_CLOCK_DIFF (gst_element_get_base_time (GST_ELEMENT (niimaqsrc)),
-        timestamp);
-  }
+  g_assert (timestamp != GST_CLOCK_TIME_NONE);
 
   /* make guess of duration from timestamp and cumulative buffer number */
   if (GST_CLOCK_TIME_IS_VALID (timestamp)) {
diff --git a/sys/niimaq/gstniimaq.h b/sys/niimaq/gstniimaq.h
index f20f603..742dbd9 100644
--- a/sys/niimaq/gstniimaq.h
+++ b/sys/niimaq/gstniimaq.h
@@ -49,26 +49,28 @@ typedef struct _GstNiImaqSrcClass GstNiImaqSrcClass;
 struct _GstNiImaqSrc {
   GstPushSrc element;
 
+  /* properties */
+  gchar *interface_name;
+  gint bufsize;
+
+  /* image info */
   GstVideoFormat format;
   int width;
   int height;
   gint framesize;
   int rowpixels;
 
-  /* private */
-  GstClockTime running_time;    /* total running time */
   gint64 n_frames;      /* total frames sent */
   uInt32 cumbufnum;
   gint64 n_dropped_frames;
-  gboolean segment;
-  gint bufsize; 
+  
   guint32** buflist;
 
-  gchar *interface_name;
   INTERFACE_ID iid;
   SESSION_ID sid;
 
   gboolean session_started;
+  GstClockTime base_time;
 
   GSList *timelist;
   GMutex *frametime_mutex;