From bf9ecd65cf43bb87dada09bc0d3d172a0631eacf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Dr=C3=B6ge?= <sebastian@centricular.com>
Date: Mon, 15 Jul 2019 12:06:25 +0300
Subject: [PATCH] decklinkvideosrc: Don't report that we have signal until we
 know for sure

Previously we would've reported that there is signal unless we know for
sure that we don't have signal. For example signal would've been
reported before the device is even opened.

Now keep track whether the signal state is unknown or not and report no
signal if we don't know yet. As before, only send an INFO message about
signal recovery if we actually had a signal loss before.
---
 sys/decklink/gstdecklinkvideosrc.cpp | 28 +++++++++++++++++-----------
 sys/decklink/gstdecklinkvideosrc.h   |  8 +++++++-
 2 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/sys/decklink/gstdecklinkvideosrc.cpp b/sys/decklink/gstdecklinkvideosrc.cpp
index dc4578d51f..cdde7d7a16 100644
--- a/sys/decklink/gstdecklinkvideosrc.cpp
+++ b/sys/decklink/gstdecklinkvideosrc.cpp
@@ -391,7 +391,7 @@ gst_decklink_video_src_init (GstDecklinkVideoSrc * self)
   self->video_format = GST_DECKLINK_VIDEO_FORMAT_AUTO;
   self->duplex_mode = bmdDuplexModeHalf;
   self->timecode_format = bmdTimecodeRP188Any;
-  self->no_signal = FALSE;
+  self->signal_state = SIGNAL_STATE_UNKNOWN;
   self->output_stream_time = DEFAULT_OUTPUT_STREAM_TIME;
   self->skip_first_time = DEFAULT_SKIP_FIRST_TIME;
   self->drop_no_signal_frames = DEFAULT_DROP_NO_SIGNAL_FRAMES;
@@ -530,7 +530,7 @@ gst_decklink_video_src_get_property (GObject * object, guint property_id,
       g_value_set_boolean (value, self->drop_no_signal_frames);
       break;
     case PROP_SIGNAL:
-      g_value_set_boolean (value, !self->no_signal);
+      g_value_set_boolean (value, self->signal_state == SIGNAL_STATE_AVAILABLE);
       break;
     case PROP_HW_SERIAL_NUMBER:
       if (self->input)
@@ -1224,10 +1224,10 @@ retry:
   // We will have no frame if frames without signal are dropped immediately
   // but we still have to signal that it's lost here.
   if (f.no_signal || !f.frame) {
-    if (!self->no_signal) {
-      self->no_signal = TRUE;
+    if (self->signal_state != SIGNAL_STATE_LOST) {
+      self->signal_state = SIGNAL_STATE_LOST;
       g_object_notify (G_OBJECT (self), "signal");
-      GST_ELEMENT_WARNING (GST_ELEMENT (self), RESOURCE, READ, ("No signal"),
+      GST_ELEMENT_WARNING (GST_ELEMENT (self), RESOURCE, READ, ("Signal lost"),
           ("No input source was detected - video frames invalid"));
     }
     // If we have no frame here, simply retry until we got one
@@ -1236,11 +1236,16 @@ retry:
       goto retry;
     }
   } else {
-    if (self->no_signal) {
-      self->no_signal = FALSE;
+    GstDecklinkSignalState previous_signal_state = self->signal_state;
+
+    if (previous_signal_state != SIGNAL_STATE_AVAILABLE) {
+      self->signal_state = SIGNAL_STATE_AVAILABLE;
       g_object_notify (G_OBJECT (self), "signal");
-      GST_ELEMENT_INFO (GST_ELEMENT (self), RESOURCE, READ, ("Signal found"),
-          ("Input source detected"));
+    }
+
+    if (previous_signal_state == SIGNAL_STATE_LOST) {
+      GST_ELEMENT_INFO (GST_ELEMENT (self), RESOURCE, READ,
+          ("Signal recovered"), ("Input source detected"));
     }
   }
 
@@ -1341,7 +1346,8 @@ retry:
 
   // If we have a format that supports VANC and we are asked to extract CC,
   // then do it here.
-  if ((self->output_cc || self->output_afd_bar) && !self->no_signal)
+  if ((self->output_cc || self->output_afd_bar)
+      && self->signal_state != SIGNAL_STATE_LOST)
     extract_vbi (self, buffer, vf, mode);
 
   if (f.no_signal)
@@ -1594,7 +1600,7 @@ gst_decklink_video_src_change_state (GstElement * element,
 
   switch (transition) {
     case GST_STATE_CHANGE_PAUSED_TO_READY:
-      self->no_signal = FALSE;
+      self->signal_state = SIGNAL_STATE_UNKNOWN;
 
       gst_decklink_video_src_stop (self);
       break;
diff --git a/sys/decklink/gstdecklinkvideosrc.h b/sys/decklink/gstdecklinkvideosrc.h
index eb3b548036..7b2c711540 100644
--- a/sys/decklink/gstdecklinkvideosrc.h
+++ b/sys/decklink/gstdecklinkvideosrc.h
@@ -46,6 +46,12 @@ G_BEGIN_DECLS
 typedef struct _GstDecklinkVideoSrc GstDecklinkVideoSrc;
 typedef struct _GstDecklinkVideoSrcClass GstDecklinkVideoSrcClass;
 
+typedef enum {
+  SIGNAL_STATE_UNKNOWN,
+  SIGNAL_STATE_LOST,
+  SIGNAL_STATE_AVAILABLE,
+} GstDecklinkSignalState;
+
 struct _GstDecklinkVideoSrc
 {
   GstPushSrc parent;
@@ -74,7 +80,7 @@ struct _GstDecklinkVideoSrc
   GMutex lock;
   gboolean flushing;
   GstQueueArray *current_frames;
-  gboolean no_signal;
+  GstDecklinkSignalState signal_state;
 
   guint buffer_size;