From 2f7c57ed8650320ec25e981ff646820bf77e5793 Mon Sep 17 00:00:00 2001
From: Carl Hetherington <cth@carlh.net>
Date: Fri, 4 Aug 2017 01:29:48 +0100
Subject: [PATCH] Drop video frames if we running out of time.

---
 src/wx/film_viewer.cc | 21 ++++++++++++++++++---
 src/wx/film_viewer.h  |  9 +++++----
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/src/wx/film_viewer.cc b/src/wx/film_viewer.cc
index 2b7f73e68..50e357b54 100644
--- a/src/wx/film_viewer.cc
+++ b/src/wx/film_viewer.cc
@@ -281,6 +281,14 @@ FilmViewer::get ()
 		return;
 	}
 
+	if ((time() - video.second) > one_video_frame()) {
+		/* Too late; just drop this frame before we try to get its image (which will be the time-consuming
+		   part if this frame is J2K).
+		*/
+		_video_position = video.second;
+		return;
+	}
+
 	/* In an ideal world, what we would do here is:
 	 *
 	 * 1. convert to XYZ exactly as we do in the DCP creation path.
@@ -324,7 +332,7 @@ FilmViewer::timer ()
 	get ();
 	update_position_label ();
 	update_position_slider ();
-	DCPTime const next = _video_position + DCPTime::from_frames (1, _film->video_frame_rate ());
+	DCPTime const next = _video_position + one_video_frame();
 
 	if (next >= _film->length()) {
 		stop ();
@@ -382,10 +390,11 @@ FilmViewer::slider_moved (bool update_slider)
 		return;
 	}
 
+
 	DCPTime t (_slider->GetValue() * _film->length().get() / 4096);
 	/* Ensure that we hit the end of the film at the end of the slider */
 	if (t >= _film->length ()) {
-		t = _film->length() - DCPTime::from_frames (1, _film->video_frame_rate ());
+		t = _film->length() - one_video_frame();
 	}
 	seek (t, false);
 	update_position_label ();
@@ -529,7 +538,7 @@ FilmViewer::active_jobs_changed (optional<string> j)
 DCPTime
 FilmViewer::nudge_amount (wxMouseEvent& ev)
 {
-	DCPTime amount = DCPTime::from_frames (1, _film->video_frame_rate ());
+	DCPTime amount = one_video_frame ();
 
 	if (ev.ShiftDown() && !ev.ControlDown()) {
 		amount = DCPTime::from_seconds (1);
@@ -792,3 +801,9 @@ FilmViewer::set_dcp_decode_reduction (optional<int> reduction)
 {
 	_player->set_dcp_decode_reduction (reduction);
 }
+
+DCPTime
+FilmViewer::one_video_frame () const
+{
+	return DCPTime::from_frames (1, _film->video_frame_rate());
+}
diff --git a/src/wx/film_viewer.h b/src/wx/film_viewer.h
index 3f7a3be33..c08409529 100644
--- a/src/wx/film_viewer.h
+++ b/src/wx/film_viewer.h
@@ -94,6 +94,7 @@ private:
 	void start ();
 	bool stop ();
 	Frame average_latency () const;
+	DCPTime one_video_frame () const;
 
 	boost::shared_ptr<Film> _film;
 	boost::shared_ptr<Player> _player;
@@ -136,10 +137,10 @@ private:
 	bool _playing;
 	boost::shared_ptr<Butler> _butler;
 
-        std::list<Frame> _latency_history;
-        /** Mutex to protect _latency_history */
-        mutable boost::mutex _latency_history_mutex;
-        int _latency_history_count;
+	std::list<Frame> _latency_history;
+	/** Mutex to protect _latency_history */
+	mutable boost::mutex _latency_history_mutex;
+	int _latency_history_count;
 
 	boost::signals2::scoped_connection _config_changed_connection;
 };
-- 
2.30.2