From 4273093d4021f7de8b8a5c769200091ba03240b4 Mon Sep 17 00:00:00 2001
From: Carl Hetherington <carl@carlh.net>
Date: Tue, 4 Jan 2011 03:35:10 +0000
Subject: [PATCH] Send full MTC messages every 1/4 of a second when
 quarter-frame messages are suspended (due to out-of-range transport speed)

git-svn-id: svn://localhost/ardour2/branches/3.0@8429 d708f5d6-7413-0410-9779-e7cbd77b26cf
---
 libs/ardour/ardour/session.h   |  4 ++++
 libs/ardour/session_midi.cc    |  1 +
 libs/ardour/session_process.cc | 32 ++++++++++++++++++++++----------
 libs/ardour/session_state.cc   |  1 +
 4 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index 38ee8688f0..a056c7a2f2 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -960,6 +960,10 @@ class Session : public PBD::StatefulDestructible, public PBD::ScopedConnectionLi
 	std::string             _name;
 	bool                    _is_new;
 	bool                    _send_qf_mtc;
+	/** Number of process frames since the last MTC output (when sending MTC); used to
+	 *  know when to send full MTC messages every so often.
+	 */
+	pframes_t               _pframes_since_last_mtc;
 	bool                     session_midi_feedback;
 	bool                     play_loop;
 	bool                     loop_changing;
diff --git a/libs/ardour/session_midi.cc b/libs/ardour/session_midi.cc
index f09722f31c..f4aef76adc 100644
--- a/libs/ardour/session_midi.cc
+++ b/libs/ardour/session_midi.cc
@@ -400,6 +400,7 @@ Session::send_full_time_code (framepos_t const t)
 		return -1;
 	}
 
+	_pframes_since_last_mtc = 0;
 	return 0;
 }
 
diff --git a/libs/ardour/session_process.cc b/libs/ardour/session_process.cc
index d67744dbe7..9902e5a1e3 100644
--- a/libs/ardour/session_process.cc
+++ b/libs/ardour/session_process.cc
@@ -270,17 +270,29 @@ Session::process_with_events (pframes_t nframes)
 	bool const was_sending_qf_mtc = _send_qf_mtc;
 	double const tolerance = Config->get_mtc_qf_speed_tolerance() / 100.0;
 
-	_send_qf_mtc = (
-		Config->get_send_mtc () &&
-		_transport_speed >= (1 - tolerance) &&
-		_transport_speed <= (1 + tolerance)
-		);
-
-	if (_send_qf_mtc && !was_sending_qf_mtc) {
-		/* we will re-start quarter-frame MTC this cycle, so send a full update to set things up */
-		_send_timecode_update = true;
+	if (_transport_speed != 0) {
+		_send_qf_mtc = (
+			Config->get_send_mtc () &&
+			_transport_speed >= (1 - tolerance) &&
+			_transport_speed <= (1 + tolerance)
+			);
+		
+		if (_send_qf_mtc && !was_sending_qf_mtc) {
+			/* we will re-start quarter-frame MTC this cycle, so send a full update to set things up */
+			_send_timecode_update = true;
+		}
+		
+		if (Config->get_send_mtc() && !_send_qf_mtc && _pframes_since_last_mtc > (frame_rate () / 4)) {
+			/* we're sending MTC, but we're not sending QF MTC at the moment, and it's been
+			   a quarter of a second since we sent anything at all, so send a full MTC update
+			   this cycle.
+			*/
+			_send_timecode_update = true;
+		}
+		
+		_pframes_since_last_mtc += nframes;
 	}
-	
+		
 	/* Events caused a transport change (or we re-started sending
 	 * MTC), so send an MTC Full Frame (Timecode) message.  This
 	 * is sent whether rolling or not, to give slaves an idea of
diff --git a/libs/ardour/session_state.cc b/libs/ardour/session_state.cc
index ed94e20c2a..cd9cb7b9b2 100644
--- a/libs/ardour/session_state.cc
+++ b/libs/ardour/session_state.cc
@@ -207,6 +207,7 @@ Session::first_stage_init (string fullpath, string snapshot_name)
 	_was_seamless = Config->get_seamless_loop ();
 	_slave = 0;
 	_send_qf_mtc = false;
+	_pframes_since_last_mtc = 0;
 	g_atomic_int_set (&_playback_load, 100);
 	g_atomic_int_set (&_capture_load, 100);
 	_play_range = false;