fix and improve MTC-slave

 - MTC-speed average (MIDI thread)
   * base timing on quarter-frames
   * replace hann-window average with a DLL
 - MTC/engine alignment
   * replace 1st order PI-controller with 2nd order DLL

The 2nd DLL is needed because the jack-process callback effectively
quantizes the transport-speed to integer audio-frames (speed * nframes).
This leaves a delta on every cycle because the remainder from previous
cycles is not compensated for.

Theoretically it is possible to merge the two DLLs into one.
However, with callbacks coming from by two independent threads
it is cleaner to track the MTC and JACK engine-alignment speeds
independently.

git-svn-id: svn://localhost/ardour2/branches/3.0@13226 d708f5d6-7413-0410-9779-e7cbd77b26cf

1 files changed, 19 insertions, 11 deletions

diff --git a/libs/ardour/ardour/slave.h b/libs/ardour/ardour/slave.h
index 1602b8bc8e..be6b966560 100644
--- a/libs/ardour/ardour/slave.h
+++ b/libs/ardour/ardour/slave.h
@@ -32,8 +32,6 @@
 #include "midi++/parser.h"
 #include "midi++/types.h"
 
-class PIChaser;
-
 namespace MIDI {
 	class Port;
 }
@@ -243,7 +241,6 @@ class MTC_Slave : public Slave {
 	MIDI::Port* port;
 	PBD::ScopedConnectionList port_connections;
 	bool        can_notify_on_unknown_rate;
-	PIChaser* pic;
 
 	static const int frame_tolerance;
 
@@ -253,18 +250,28 @@ class MTC_Slave : public Slave {
 	MIDI::byte     last_mtc_fps_byte;
 	framepos_t     window_begin;
 	framepos_t     window_end;
-	framepos_t     last_mtc_timestamp;
-	framepos_t     last_mtc_frame;
+	framepos_t     first_mtc_timestamp;
 	bool           did_reset_tc_format;
 	TimecodeFormat saved_tc_format;
-	size_t         speed_accumulator_size;
-	double*        speed_accumulator;
-	size_t         speed_accumulator_cnt;
-	bool           have_first_speed_accumulator;
-	double         average_speed;
 	Glib::Threads::Mutex    reset_lock;
 	uint32_t       reset_pending;
 	bool           reset_position;
+	int            transport_direction;
+	int            busy_guard1;
+	int            busy_guard2;
+
+	/* DLL - chase MTC */
+	double t0; ///< time at the beginning of the MTC quater frame
+	double t1; ///< calculated end of the MTC quater frame
+	double e2; ///< second order loop error
+	double b, c, omega; ///< DLL filter coefficients
+
+	/* DLL - sync engine */
+	int    engine_dll_initstate;
+	double te0; ///< time at the beginning of the engine process
+	double te1; ///< calculated sync time
+	double ee2; ///< second order loop error
+	double be, ce, oe; ///< DLL filter coefficients
 
 	void reset (bool with_pos);
 	void queue_reset (bool with_pos);
@@ -276,7 +283,8 @@ class MTC_Slave : public Slave {
 	void read_current (SafeTime *) const;
 	void reset_window (framepos_t);
 	bool outside_window (framepos_t) const;
-	void process_apparent_speed (double);
+	void init_mtc_dll(framepos_t, double);
+	void init_engine_dll (framepos_t, framepos_t);
 };
 
 class MIDIClock_Slave : public Slave {