diff --git a/libs/appleutility/wscript b/libs/appleutility/wscript
index 27dc1b9d26..87b713a0dc 100644
--- a/libs/appleutility/wscript
+++ b/libs/appleutility/wscript
@@ -28,7 +28,7 @@ def configure(conf):
 	
 def build(bld):
 	obj              = bld.new_task_gen('cxx', 'shlib',
-										uselib = 'COREAUDIO CORESERVICES COREFOUNDATION AUDIOTOOLBOX AUDIOUNITS OSX GTKOSX')
+                                            uselib = 'COREAUDIO CORESERVICES COREFOUNDATION AUDIOTOOLBOX AUDIOUNITS OSX GTKOSX')
 	obj.source       = libappleutility_sources
 	obj.export_incdirs = ['.']
 	obj.includes     = ['.']
@@ -41,4 +41,4 @@ def shutdown():
 	autowaf.shutdown()
 
 def i18n(bld):
-	pass
\ No newline at end of file
+	pass
diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index a3505ec587..4f0acc9381 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -986,6 +986,13 @@ class Session : public PBD::StatefulDestructible, public boost::noncopyable
 		PostTransportClearSubstate      = 0x80000
 	};
 
+	enum SlaveState {
+		Stopped,
+		Waiting,
+		Running
+	};
+	
+	SlaveState slave_state() const { return _slave_state; }
 
   protected:
 	friend class AudioEngine;
@@ -1088,20 +1095,13 @@ class Session : public PBD::StatefulDestructible, public boost::noncopyable
 	int  average_dir;
 	bool have_first_delta_accumulator;
 
-	enum SlaveState {
-		Stopped,
-		Waiting,
-		Running
-	};
-
-	SlaveState slave_state;
+	SlaveState _slave_state;
 	nframes_t slave_wait_end;
 
 	void reset_slave_state ();
 	bool follow_slave (nframes_t);
 	void calculate_moving_average_of_slave_delta(int dir, nframes_t this_delta);
-	void track_slave_state(float slave_speed, nframes_t slave_transport_frame,
-	                       nframes_t this_delta, bool starting);
+	void track_slave_state(float slave_speed, nframes_t slave_transport_frame, nframes_t this_delta);
 	void follow_slave_silently(nframes_t nframes, float slave_speed);
 
         void use_sync_source (SyncSource);
diff --git a/libs/ardour/ardour/slave.h b/libs/ardour/ardour/slave.h
index 16e11097ea..dae0d80d10 100644
--- a/libs/ardour/ardour/slave.h
+++ b/libs/ardour/ardour/slave.h
@@ -29,6 +29,8 @@
 #include "midi++/parser.h"
 #include "midi++/types.h"
 
+class PIController;
+
 namespace MIDI {
 	class Port;
 }
@@ -140,11 +142,18 @@ class Slave {
 	virtual nframes_t resolution() const = 0;
 
 	/**
-	 * @return - when returning true, ARDOUR will wait for one second before transport
+	 * @return - when returning true, ARDOUR will wait for seekahead_distance() before transport
 	 * starts rolling
 	 */
 	virtual bool requires_seekahead () const = 0;
 
+	/**
+	 * @return the number of frames that this slave wants to seek ahead. Relevant
+	 * only if @func requires_seekahead() returns true.
+	 */
+
+	virtual nframes64_t seekahead_distance() const { return 0; }
+
 	/**
 	 * @return - when returning true, ARDOUR will use transport speed 1.0 no matter what
 	 *           the slave returns
@@ -222,35 +231,40 @@ class MTC_Slave : public Slave, public sigc::trackable {
 
 	nframes_t resolution() const;
 	bool requires_seekahead () const { return true; }
+	nframes64_t seekahead_distance() const;
+	bool give_slave_full_control_over_transport_speed() const;
 
   private:
 	Session&    session;
 	MIDI::Port* port;
 	std::vector<sigc::connection> connections;
 	bool        can_notify_on_unknown_rate;
-	
+	PIController* pic;
+
 	SafeTime    current;
-	double      instantaneous_speed;
 	nframes_t   mtc_frame;               /* current time */
 	nframes_t   last_inbound_frame;      /* when we got it; audio clocked */
 	MIDI::byte  last_mtc_fps_byte;
-	bool        qtr_frame_messages_valid_for_time;
-
+	nframes64_t window_begin;
+	nframes64_t window_end;
+	nframes64_t    last_mtc_timestamp;
+	nframes64_t    last_mtc_frame;
 	bool           did_reset_tc_format;
 	TimecodeFormat saved_tc_format;
-
-	static const int32_t accumulator_size = 128;
-	double   accumulator[accumulator_size];
-	int32_t accumulator_index;
-	bool    have_first_accumulated_speed;
+	size_t         speed_accumulator_size;
+	double*        speed_accumulator;
+	size_t         speed_accumulator_cnt;
+	bool           have_first_speed_accumulator;
+	double         average_speed;
 
 	void reset ();
 	void update_mtc_qtr (MIDI::Parser&, int, nframes_t);
 	void update_mtc_time (const MIDI::byte *, bool, nframes_t);
-	void update_mtc_status (MIDI::Parser::MTC_Status);
+	void update_mtc_status (MIDI::MTC_Status);
 	void read_current (SafeTime *) const;
-	double compute_apparent_speed (nframes64_t);
-
+	void reset_window (nframes64_t);
+	bool outside_window (nframes64_t) const;
+	void process_apparent_speed (double);
 };
 
 class MIDIClock_Slave : public Slave, public sigc::trackable {
@@ -337,24 +351,6 @@ class MIDIClock_Slave : public Slave, public sigc::trackable {
 	bool _starting;
 };
 
-class ADAT_Slave : public Slave
-{
-  public:
-	ADAT_Slave () {}
-	~ADAT_Slave () {}
-
-	bool speed_and_position (double& speed, nframes64_t& pos) {
-		speed = 0;
-		pos = 0;
-		return false;
-	}
-
-	bool locked() const { return false; }
-	bool ok() const { return false; }
-	nframes_t resolution() const { return 1; }
-	bool requires_seekahead () const { return true; }
-};
-
 class JACK_Slave : public Slave
 {
   public:
diff --git a/libs/ardour/audioengine.cc b/libs/ardour/audioengine.cc
index 2e5aea9047..2f344eb8ba 100644
--- a/libs/ardour/audioengine.cc
+++ b/libs/ardour/audioengine.cc
@@ -136,9 +136,13 @@ _thread_init_callback (void * /*arg*/)
 	*/
 
 	PBD::notify_gui_about_thread_creation (pthread_self(), X_("Audioengine"), 4096);
-#ifdef WITH_JACK_MIDI
 	MIDI::JACK_MidiPort::set_process_thread (pthread_self());
-#endif // WITH_JACK_MIDI
+}
+
+static void
+ardour_jack_error (const char* msg)
+{
+	error << "JACK: " << msg << endmsg;
 }
 
 int
@@ -188,6 +192,8 @@ AudioEngine::start ()
 			jack_set_timebase_callback (_priv_jack, 0, _jack_timebase_callback, this);
 		}
 
+		jack_set_error_function (ardour_jack_error);
+
 		if (jack_activate (_priv_jack) == 0) {
 			_running = true;
 			_has_run = true;
@@ -1121,12 +1127,6 @@ AudioEngine::remove_all_ports ()
 	ports.flush ();
 }
 
-static void
-ardour_jack_error (const char* msg)
-{
-	error << "JACK: " << msg << endmsg;
-}
-
 int
 AudioEngine::connect_to_jack (string client_name)
 {
@@ -1148,8 +1148,6 @@ AudioEngine::connect_to_jack (string client_name)
 		jack_client_name = jack_get_client_name (_priv_jack);
 	}
 
-	jack_set_error_function (ardour_jack_error);
-
 	return 0;
 }
 
diff --git a/libs/ardour/enums.cc b/libs/ardour/enums.cc
index 870c60eec7..4b82950f3e 100644
--- a/libs/ardour/enums.cc
+++ b/libs/ardour/enums.cc
@@ -18,6 +18,7 @@
 */
 
 #include "pbd/enumwriter.h"
+#include "midi++/types.h"
 
 #include "ardour/audiofilesource.h"
 #include "ardour/audioregion.h"
@@ -40,6 +41,7 @@
 using namespace std;
 using namespace PBD;
 using namespace ARDOUR;
+using namespace MIDI;
 
 void
 setup_enum_writer ()
@@ -115,7 +117,9 @@ setup_enum_writer ()
 	WaveformShape _WaveformShape;
 	QuantizeType _QuantizeType;
 	Session::PostTransportWork _Session_PostTransportWork;
-		
+	Session::SlaveState _Session_SlaveState;
+	MTC_Status _MIDI_MTC_Status;
+
 #define REGISTER(e) enum_writer->register_distinct (typeid(e).name(), i, s); i.clear(); s.clear()
 #define REGISTER_BITS(e) enum_writer->register_bits (typeid(e).name(), i, s); i.clear(); s.clear()
 #define REGISTER_ENUM(e) i.push_back (e); s.push_back (#e)
@@ -305,6 +309,16 @@ setup_enum_writer ()
 	REGISTER_CLASS_ENUM (Session::Event, AutoLoop);
 	REGISTER (_Session_Event_Type);
 
+	REGISTER_CLASS_ENUM (Session, Stopped);
+	REGISTER_CLASS_ENUM (Session, Waiting);
+	REGISTER_CLASS_ENUM (Session, Running);
+	REGISTER (_Session_SlaveState);
+
+	REGISTER_ENUM (MTC_Stopped);
+	REGISTER_ENUM (MTC_Forward);
+	REGISTER_ENUM (MTC_Backward);
+	REGISTER (_MIDI_MTC_Status);
+
 	REGISTER_CLASS_ENUM (Session, PostTransportStop);
 	REGISTER_CLASS_ENUM (Session, PostTransportDisableRecord);
 	REGISTER_CLASS_ENUM (Session, PostTransportPosition);
diff --git a/libs/ardour/mtc_slave.cc b/libs/ardour/mtc_slave.cc
index 4ca86236b7..9e566367bc 100644
--- a/libs/ardour/mtc_slave.cc
+++ b/libs/ardour/mtc_slave.cc
@@ -22,6 +22,7 @@
 #include <sys/types.h>
 #include <unistd.h>
 #include "pbd/error.h"
+#include "pbd/enumwriter.h"
 #include "pbd/failed_constructor.h"
 #include "pbd/pthread_utils.h"
 
@@ -30,7 +31,7 @@
 #include "ardour/slave.h"
 #include "ardour/session.h"
 #include "ardour/audioengine.h"
-#include "ardour/cycles.h"
+#include "ardour/pi_controller.h"
 
 #include "i18n.h"
 
@@ -45,8 +46,14 @@ MTC_Slave::MTC_Slave (Session& s, MIDI::Port& p)
 {
 	can_notify_on_unknown_rate = true;
 	did_reset_tc_format = false;
+
+	pic = new PIController (1.0, 8);
 	
 	last_mtc_fps_byte = session.get_mtc_timecode_bits ();
+	mtc_frame = 0;
+
+	speed_accumulator_size = 16;
+	speed_accumulator = new double[speed_accumulator_size];
 
 	rebind (p);
 	reset ();
@@ -57,6 +64,15 @@ MTC_Slave::~MTC_Slave()
 	if (did_reset_tc_format) {
 		session.config.set_timecode_format (saved_tc_format);
 	}
+	delete pic;
+	delete [] speed_accumulator;
+}
+
+bool 
+MTC_Slave::give_slave_full_control_over_transport_speed() const
+{
+	return true; // for PiC control */
+	// return false; // for Session-level computed varispeed
 }
 
 void
@@ -68,6 +84,8 @@ MTC_Slave::rebind (MIDI::Port& p)
 
 	port = &p;
 
+	cerr << "Bind to port MTC messages\n";
+
 	connections.push_back (port->input()->mtc_time.connect (mem_fun (*this, &MTC_Slave::update_mtc_time)));
 	connections.push_back (port->input()->mtc_qtr.connect (mem_fun (*this, &MTC_Slave::update_mtc_qtr)));
 	connections.push_back (port->input()->mtc_status.connect (mem_fun (*this, &MTC_Slave::update_mtc_status)));
@@ -76,34 +94,8 @@ MTC_Slave::rebind (MIDI::Port& p)
 void
 MTC_Slave::update_mtc_qtr (Parser& /*p*/, int which_qtr, nframes_t now)
 {
-	DEBUG_TRACE (DEBUG::MTC, string_compose ("qtr frame %1 at %2, valid-for-time? %3\n", which_qtr, now, qtr_frame_messages_valid_for_time));
-
-	if (qtr_frame_messages_valid_for_time) {
-
-		if (which_qtr != 7) {
-
-			/* leave position and speed updates for the last
-			   qtr frame message of the 8 to be taken
-			   care of in update_mtc_time(), invoked
-			   by the Parser right after this.
-			*/
-
-			nframes_t qtr;
-			
-			qtr = (long) (session.frames_per_timecode_frame() / 4);
-			mtc_frame += qtr;
-			
-			double speed = compute_apparent_speed (now);
-			
-			current.guard1++;
-			current.position = mtc_frame;
-			current.timestamp = now;
-			current.speed = speed;
-			current.guard2++;
-		}
-
-		last_inbound_frame = now;
-	}
+	DEBUG_TRACE (DEBUG::MTC, string_compose ("qtr frame %1 at %2\n", which_qtr, now));
+	last_inbound_frame = now;
 }
 
 void
@@ -116,7 +108,8 @@ MTC_Slave::update_mtc_time (const byte *msg, bool was_full, nframes_t now)
 	Timecode::Time timecode;
 	TimecodeFormat tc_format;
 	bool reset_tc = true;
-	
+	nframes64_t window_root = -1;
+
 	DEBUG_TRACE (DEBUG::MTC, string_compose ("full mtc time known at %1, full ? %2\n", now, was_full));
 	
 	timecode.hours = msg[3];
@@ -175,24 +168,28 @@ MTC_Slave::update_mtc_time (const byte *msg, bool was_full, nframes_t now)
 	DEBUG_TRACE (DEBUG::MTC, string_compose ("MTC time timestamp = %1 TC %2 = frame %3 (from full message ? %4)\n", 
 						 now, timecode, mtc_frame, was_full));
 
-	if (was_full) {
+	if (was_full || outside_window (mtc_frame)) {
 
 		session.timecode_to_sample (timecode, mtc_frame, true, false);
 		session.request_locate (mtc_frame, false);
 		session.request_transport_speed (0);
-		update_mtc_status (MIDI::Parser::MTC_Stopped);
-
+		update_mtc_status (MIDI::MTC_Stopped);
+		window_root = mtc_frame;
+		
 		reset ();
 
 	} else {
-
 			
 		/* we've had the first set of 8 qtr frame messages, determine position
-			   and allow continuing qtr frame messages to provide position
-			   and speed information.
+		   and allow continuing qtr frame messages to provide position
+		   and speed information.
 		*/
 		
-		qtr_frame_messages_valid_for_time = true;
+		/* do a careful conversion of the timecode value to a position
+		   so that we take drop/nondrop and all that nonsense into 
+		   consideration.
+		*/
+
 		session.timecode_to_sample (timecode, mtc_frame, true, false);
 		
 		/* We received the last quarter frame 7 quarter frames (1.75 mtc
@@ -203,56 +200,84 @@ MTC_Slave::update_mtc_time (const byte *msg, bool was_full, nframes_t now)
 		
 		mtc_frame += (long) (1.75 * session.frames_per_timecode_frame()) + session.worst_output_latency();
 
+
 		if (now) {
-			double speed = compute_apparent_speed (now);
-			
+
+			if (last_mtc_timestamp == 0) {
+
+				last_mtc_timestamp = now;
+				last_mtc_frame = mtc_frame;
+
+			} else {
+
+				if (give_slave_full_control_over_transport_speed()) {
+					/* PIC 
+					 * 
+					 * its not the average, but we will assign it to current.speed below
+					 */
+					
+					average_speed = pic->get_ratio (session.audible_frame() - mtc_frame);
+					
+				} else {
+
+					/* Non-PiC 
+					 */
+
+					nframes64_t time_delta = (now - last_mtc_timestamp);
+					
+					if (time_delta != 0) {
+						double apparent_speed = (mtc_frame - last_mtc_frame) / (double) (time_delta);
+						
+						process_apparent_speed (apparent_speed);
+						DEBUG_TRACE (DEBUG::Slave, string_compose ("apparent speed was %1 average is now %2\n", apparent_speed, average_speed));
+					} else {
+						DEBUG_TRACE (DEBUG::Slave, string_compose ("no apparent calc, average is %1\n", average_speed));
+					}
+					
+					/* every second, recalibrate the starting point for the speed measurement */
+					if (mtc_frame - last_mtc_frame > session.frame_rate()) {
+						last_mtc_timestamp = now;
+						last_mtc_frame = mtc_frame;
+					}
+				}
+			}
+
 			current.guard1++;
 			current.position = mtc_frame;
 			current.timestamp = now;
-			current.speed = speed;
+			current.speed = average_speed;
 			current.guard2++;
+			window_root = mtc_frame;
 		}
 	}
 
 	if (now) {
 		last_inbound_frame = now;
 	}
+
+	if (window_root >= 0) {
+		reset_window (window_root);
+	}
 }
 
-double
-MTC_Slave::compute_apparent_speed (nframes64_t now)
+void
+MTC_Slave::process_apparent_speed (double this_speed)
 {
-	if (current.timestamp != 0) {
-		
-		double speed = (double) ((mtc_frame - current.position) / (double) (now - current.timestamp));
-		DEBUG_TRACE (DEBUG::MTC, string_compose ("instantaneous speed = %1 from %2 / %3\n",
-							 speed, mtc_frame - current.position, now - current.timestamp));
-		
-		/* crude low pass filter/smoother for speed */
+	DEBUG_TRACE (DEBUG::MTC, string_compose ("speed cnt %1 sz %2 have %3\n", speed_accumulator_cnt, speed_accumulator_size, have_first_speed_accumulator));
 
-		accumulator[accumulator_index++] = speed;
-		
-		if (accumulator_index >= accumulator_size) {
-			have_first_accumulated_speed = true;
-			accumulator_index = 0;
+	if (speed_accumulator_cnt >= speed_accumulator_size) {
+		have_first_speed_accumulator = true;
+		speed_accumulator_cnt = 0;
+	}
+
+	speed_accumulator[speed_accumulator_cnt++] = this_speed;
+
+	if (have_first_speed_accumulator) {
+		average_speed = 0.0;
+		for (size_t i = 0; i < speed_accumulator_size; ++i) {
+			average_speed += speed_accumulator[i];
 		}
-		
-		if (have_first_accumulated_speed) {
-			double total = 0;
-			
-			for (int32_t i = 0; i < accumulator_size; ++i) {
-				total += accumulator[i];
-			}
-			
-			speed = total / accumulator_size;
-			DEBUG_TRACE (DEBUG::MTC, string_compose ("speed smoothed to %1\n", speed));
-		} 
-
-		return speed;
-		
-	} else {
-		
-		return 0;
+		average_speed /= speed_accumulator_size;
 	}
 }
 
@@ -271,16 +296,16 @@ MTC_Slave::handle_locate (const MIDI::byte* mmc_tc)
 }
 
 void
-MTC_Slave::update_mtc_status (MIDI::Parser::MTC_Status status)
+MTC_Slave::update_mtc_status (MIDI::MTC_Status status)
 {
 	/* XXX !!! thread safety ... called from MIDI I/O context
 	   and process() context (via ::speed_and_position())
 	*/
 
+
+	DEBUG_TRACE (DEBUG::MTC, string_compose ("new MTC status %1\n", enum_2_string (status)));
 	switch (status) {
 	case MTC_Stopped:
-		mtc_frame = 0;
-
 		current.guard1++;
 		current.position = mtc_frame;
 		current.timestamp = 0;
@@ -290,27 +315,22 @@ MTC_Slave::update_mtc_status (MIDI::Parser::MTC_Status status)
 		break;
 
 	case MTC_Forward:
-		mtc_frame = 0;
-
 		current.guard1++;
 		current.position = mtc_frame;
 		current.timestamp = 0;
 		current.speed = 0;
 		current.guard2++;
-
 		break;
 
 	case MTC_Backward:
-		mtc_frame = 0;
-
 		current.guard1++;
 		current.position = mtc_frame;
 		current.timestamp = 0;
 		current.speed = 0;
 		current.guard2++;
-
 		break;
 	}
+	
 }
 
 void
@@ -365,7 +385,7 @@ MTC_Slave::speed_and_position (double& speed, nframes64_t& pos)
 		pos = last.position;
 		session.request_locate (pos, false);
 		session.request_transport_speed (0);
-		update_mtc_status (MIDI::Parser::MTC_Stopped);
+		update_mtc_status (MIDI::MTC_Stopped);
 		reset();
 		DEBUG_TRACE (DEBUG::MTC, "MTC not seen for 1/4 second - reset\n");
 		return false;
@@ -384,7 +404,7 @@ MTC_Slave::speed_and_position (double& speed, nframes64_t& pos)
 		if (last.timestamp && (now > last.timestamp)) {
 			elapsed = (nframes_t) floor (last.speed * (now - last.timestamp));
 			DEBUG_TRACE (DEBUG::MTC, string_compose ("last timecode received @ %1, now = %2, elapsed frames = %3 w/speed= %4\n",
-								 last.timestamp, now, elapsed, speed));
+								 last.timestamp, now, elapsed, last.speed));
 		} else {
 			elapsed = 0; /* XXX is this right? */
 		}
@@ -422,7 +442,42 @@ MTC_Slave::reset ()
 	current.timestamp = 0;
 	current.speed = 0;
 	current.guard2++;
-	accumulator_index = 0;
-	have_first_accumulated_speed = false;
-	qtr_frame_messages_valid_for_time = false;
+
+	window_begin = 0;
+	window_end = 0;
+	last_mtc_frame = 0;
+	last_mtc_timestamp = 0;
+
+	average_speed = 0;
+	have_first_speed_accumulator = false;
+	speed_accumulator_cnt = 0;
+
+	pic->out_of_bounds();
+}
+
+void
+MTC_Slave::reset_window (nframes64_t root)
+{
+	window_begin = root;
+
+	if (session.slave_state() == Session::Running) {
+		window_end = root + (session.frames_per_timecode_frame() * 2);
+	} else {
+		window_end = root + seekahead_distance ();
+	}
+
+	DEBUG_TRACE (DEBUG::MTC, string_compose ("legal MTC window now %1 .. %2\n", window_begin, window_end));
+}
+
+nframes64_t
+MTC_Slave::seekahead_distance () const
+{
+	/* 1 second */
+	return session.frame_rate();
+}
+
+bool
+MTC_Slave::outside_window (nframes64_t pos) const
+{
+	return ((pos < window_begin) || (pos > window_end));
 }
diff --git a/libs/ardour/session_midi.cc b/libs/ardour/session_midi.cc
index d205cc1ca8..b05cfc83a2 100644
--- a/libs/ardour/session_midi.cc
+++ b/libs/ardour/session_midi.cc
@@ -1261,7 +1261,7 @@ Session::midi_thread_work ()
 			}
 
 			if (pfd[p].revents & POLLIN) {
-				DEBUG_TRACE (DEBUG::MidiIO, string_compose ("MIDI fd # %1 has data ready\n", p));
+				DEBUG_TRACE (DEBUG::MidiIO, string_compose ("MIDI fd # %1 has data ready @ %2\n", p, now));
 				fds_ready++;
 				ports[p]->parse (now);
 			}
diff --git a/libs/ardour/session_process.cc b/libs/ardour/session_process.cc
index e270a7c3ec..4142490af6 100644
--- a/libs/ardour/session_process.cc
+++ b/libs/ardour/session_process.cc
@@ -461,7 +461,7 @@ Session::reset_slave_state ()
 	average_slave_delta = 1800;
 	delta_accumulator_cnt = 0;
 	have_first_delta_accumulator = false;
-	slave_state = Stopped;
+	_slave_state = Stopped;
 }
 
 bool
@@ -483,7 +483,6 @@ Session::follow_slave (nframes_t nframes)
 	nframes64_t slave_transport_frame;
 	nframes_t this_delta;
 	int dir;
-	bool starting;
 
 	if (!_slave->ok()) {
 		stop_transport ();
@@ -493,7 +492,7 @@ Session::follow_slave (nframes_t nframes)
 
 	_slave->speed_and_position (slave_speed, slave_transport_frame);
 
-	DEBUG_TRACE (DEBUG::Slave, string_compose ("Slave @ %2 speed %1\n", slave_speed, slave_transport_frame));
+	DEBUG_TRACE (DEBUG::Slave, string_compose ("Slave position %1 speed %2\n", slave_transport_frame, slave_speed));
 
 	if (!_slave->locked()) {
 		DEBUG_TRACE (DEBUG::Slave, "slave not locked\n");
@@ -508,7 +507,7 @@ Session::follow_slave (nframes_t nframes)
 		dir = -1;
 	}
 
-	if ((starting = _slave->starting())) {
+	if (_slave->starting()) {
 		slave_speed = 0.0f;
 	}
 
@@ -524,21 +523,23 @@ Session::follow_slave (nframes_t nframes)
 
 	} else {
 
-		/* TC source is able to drift relative to us (slave)
-		   so we need to keep track of the drift and adjust
-		   our speed to remain locked.
+		/* if we are chasing and the average delta between us and the
+		   master gets too big, we want to switch to silent
+		   motion. so keep track of that here.
 		*/
 
-		calculate_moving_average_of_slave_delta(dir, this_delta);
+		if (_slave_state == Running) {
+			calculate_moving_average_of_slave_delta(dir, this_delta);
+		}
 	}
 
-	track_slave_state (slave_speed, slave_transport_frame, this_delta, starting);
+	track_slave_state (slave_speed, slave_transport_frame, this_delta);
 
-	DEBUG_TRACE (DEBUG::Slave, string_compose ("slave state %1 @ %2 speed %3 cur delta %4 starting %5\n",
-						   slave_state, slave_transport_frame, slave_speed, this_delta, starting));
+	DEBUG_TRACE (DEBUG::Slave, string_compose ("slave state %1 @ %2 speed %3 cur delta %4 avg delta %5\n",
+						   _slave_state, slave_transport_frame, slave_speed, this_delta, average_slave_delta));
 		     
 
-	if (slave_state == Running && !_slave->is_always_synced() && !config.get_timecode_source_is_synced()) {
+	if (_slave_state == Running && !_slave->is_always_synced() && !config.get_timecode_source_is_synced()) {
 
 		if (_transport_speed != 0.0f) {
 
@@ -548,7 +549,6 @@ Session::follow_slave (nframes_t nframes)
 
 			float delta;
 
-#ifdef USE_MOVING_AVERAGE_OF_SLAVE
 			if (average_slave_delta == 0) {
 				delta = this_delta;
 				delta *= dir;
@@ -556,52 +556,38 @@ Session::follow_slave (nframes_t nframes)
 				delta = average_slave_delta;
 				delta *= average_dir;
 			}
-#else
-			delta = this_delta;
-			delta *= dir;
-#endif
 
 #ifndef NDEBUG
-	if (slave_speed != 0.0) {
-		DEBUG_TRACE (DEBUG::Slave, string_compose ("delta = %1 speed = %2 ts = %3 M@%4 S@%5 avgdelta %6\n",
-							   (int) (dir * this_delta),
-							   slave_speed,
-							   _transport_speed,
-							   _transport_frame,
-							   slave_transport_frame, 
-							   _transport_frame,
-							   average_slave_delta));
-	}
+			if (slave_speed != 0.0) {
+				DEBUG_TRACE (DEBUG::Slave, string_compose ("delta = %1 speed = %2 ts = %3 M@%4 S@%5 avgdelta %6\n",
+									   (int) (dir * this_delta),
+									   slave_speed,
+									   _transport_speed,
+									   _transport_frame,
+									   slave_transport_frame, 
+									   average_slave_delta));
+			}
 #endif
-			if (fabs(delta) > 2048) {
-				nframes64_t jump_to = slave_transport_frame + lrintf (_current_frame_rate/5.0f);
-				/* too far off, so locate and keep rolling */
-				DEBUG_TRACE (DEBUG::Slave, string_compose ("slave delta %1 is too big, locate to %2\n", 
-									   delta, jump_to));
-				request_locate (jump_to, true);
-				return false;
+			
+			if (_slave->give_slave_full_control_over_transport_speed()) {
+				set_transport_speed (slave_speed, false, false);
 			} else {
 				float adjusted_speed = slave_speed + (delta /  float(_current_frame_rate));
-				
-				if (_slave->give_slave_full_control_over_transport_speed()) {
-					request_transport_speed (slave_speed);
-				} else {
-					request_transport_speed (adjusted_speed);
-					DEBUG_TRACE (DEBUG::Slave, string_compose ("adjust using %1 towards %2 ratio %3 current %4 slave @ %5\n",
-										   delta, adjusted_speed, adjusted_speed/slave_speed, _transport_speed,
-										   slave_speed));
-				}
+				request_transport_speed (adjusted_speed);
+				DEBUG_TRACE (DEBUG::Slave, string_compose ("adjust using %1 towards %2 ratio %3 current %4 slave @ %5\n",
+									   delta, adjusted_speed, adjusted_speed/slave_speed, _transport_speed,
+									   slave_speed));
 			}
 			
-			if (abs(average_slave_delta) > (long) _slave->resolution()) {
-				cerr << "average slave delta greater than slave resolution, going to silent motion\n";
+			if (abs(average_slave_delta) > _slave->resolution()) {
+				cerr << "average slave delta greater than slave resolution (" << _slave->resolution() << "), going to silent motion\n";
 				goto silent_motion;
 			}
 		}
 	}
 
 
-	if (!starting && !non_realtime_work_pending()) {
+	if (_slave_state == Running && !non_realtime_work_pending()) {
 		/* speed is set, we're locked, and good to go */
 		return true;
 	}
@@ -645,24 +631,24 @@ Session::calculate_moving_average_of_slave_delta(int dir, nframes_t this_delta)
 }
 
 void
-Session::track_slave_state (float slave_speed, nframes_t slave_transport_frame, nframes_t this_delta, bool starting)
+Session::track_slave_state (float slave_speed, nframes_t slave_transport_frame, nframes_t this_delta)
 {
 	if (slave_speed != 0.0f) {
 
 		/* slave is running */
 
-		switch (slave_state) {
+		switch (_slave_state) {
 		case Stopped:
 			if (_slave->requires_seekahead()) {
-				slave_wait_end = slave_transport_frame + _current_frame_rate;
+				slave_wait_end = slave_transport_frame + _slave->seekahead_distance ();
 				DEBUG_TRACE (DEBUG::Slave, string_compose ("slave stopped, but running, requires seekahead to %1\n", slave_wait_end));
+				/* we can call locate() here because we are in process context */
 				locate (slave_wait_end, false, false);
-				slave_state = Waiting;
-				starting = true;
+				_slave_state = Waiting;
 
 			} else {
 
-				slave_state = Running;
+				_slave_state = Running;
 
 				Location* al = _locations.auto_loop_location();
 
@@ -678,13 +664,24 @@ Session::track_slave_state (float slave_speed, nframes_t slave_transport_frame,
 			break;
 
 		case Waiting:
+		default:
+			break;
+		}
+
+		if (_slave_state == Waiting) {
+
 			DEBUG_TRACE (DEBUG::Slave, string_compose ("slave waiting at %1\n", slave_transport_frame));
 
 			if (slave_transport_frame >= slave_wait_end) {
 
 				DEBUG_TRACE (DEBUG::Slave, string_compose ("slave start at %1 vs %2\n", slave_transport_frame, _transport_frame));
 
-				slave_state = Running;
+				_slave_state = Running;
+
+				/* now perform a "micro-seek" within the disk buffers to realign ourselves
+				   precisely with the master.
+				*/
+
 
 				bool ok = true;
 				nframes_t frame_delta = slave_transport_frame - _transport_frame;
@@ -713,13 +710,9 @@ Session::track_slave_state (float slave_speed, nframes_t slave_transport_frame,
 				average_slave_delta = 0L;
 				this_delta = 0;
 			}
-			break;
-
-		default:
-			break;
 		}
 
-		if (slave_state == Running && _transport_speed == 0.0f) {
+		if (_slave_state == Running && _transport_speed == 0.0f) {
 			DEBUG_TRACE (DEBUG::Slave, "slave starts transport\n");
 			start_transport ();
 		}
@@ -738,7 +731,7 @@ Session::track_slave_state (float slave_speed, nframes_t slave_transport_frame,
 			force_locate (slave_transport_frame, false);
 		}
 
-		slave_state = Stopped;
+		_slave_state = Stopped;
 	}
 }
 
diff --git a/libs/ardour/session_state.cc b/libs/ardour/session_state.cc
index 86a317d1d1..bcc3afbb05 100644
--- a/libs/ardour/session_state.cc
+++ b/libs/ardour/session_state.cc
@@ -263,7 +263,7 @@ Session::first_stage_init (string fullpath, string snapshot_name)
 	average_slave_delta = 1800; // !!! why 1800 ????
 	have_first_delta_accumulator = false;
 	delta_accumulator_cnt = 0;
-	slave_state = Stopped;
+	_slave_state = Stopped;
 
 	_engine.GraphReordered.connect (mem_fun (*this, &Session::graph_reordered));
 
diff --git a/libs/ardour/wscript b/libs/ardour/wscript
index 48cd6ccb6f..bf850ebeab 100644
--- a/libs/ardour/wscript
+++ b/libs/ardour/wscript
@@ -132,6 +132,7 @@ libardour_sources = [
 	'onset_detector.cc',
 	'panner.cc',
 	'pcm_utils.cc',
+	'pi_controller.cc',
 	'playlist.cc',
 	'playlist_factory.cc',
 	'plugin.cc',
diff --git a/libs/midi++2/midi++/parser.h b/libs/midi++2/midi++/parser.h
index b8364cc025..365f2fb46a 100644
--- a/libs/midi++2/midi++/parser.h
+++ b/libs/midi++2/midi++/parser.h
@@ -116,12 +116,6 @@ class Parser : public sigc::trackable {
 
 	/* MTC */
 
-	enum MTC_Status {
-		MTC_Stopped = 0,
-		MTC_Forward,
-		MTC_Backward
-	};
-
 	MTC_FPS mtc_fps() const { return _mtc_fps; }
 	MTC_Status  mtc_running() const { return _mtc_running; }
 	const byte *mtc_current() const { return _mtc_time; }
diff --git a/libs/midi++2/mtc.cc b/libs/midi++2/mtc.cc
index 74b528e5e3..a49f469d2b 100644
--- a/libs/midi++2/mtc.cc
+++ b/libs/midi++2/mtc.cc
@@ -226,7 +226,7 @@ Parser::process_mtc_quarter_frame (byte *msg)
 	/* time code is looking good */
 
 #ifdef DEBUG_MTC
-	cerr << "for quarter frame " << which_quarter_frame << " byte = " << hex << (int) msg[1] << dec << endl;
+	// cerr << "for quarter frame " << which_quarter_frame << " byte = " << hex << (int) msg[1] << dec << endl;
 #endif
 
 	switch (which_quarter_frame) {
@@ -276,6 +276,10 @@ Parser::process_mtc_quarter_frame (byte *msg)
 
 	} 
 	
+#ifdef DEBUG_MTC
+	cerr << "Emit MTC Qtr\n";
+#endif
+
 	mtc_qtr (*this, which_quarter_frame, _timestamp); /* EMIT_SIGNAL */
 
 	// mtc (*this, &msg[1], msglen - 1);