* changed transport speed in session and slaves from float to double

* added some comments


git-svn-id: svn://localhost/ardour2/branches/3.0@4394 d708f5d6-7413-0410-9779-e7cbd77b26cf

12 files changed, 68 insertions, 55 deletions

diff --git a/libs/ardour/ardour/diskstream.h b/libs/ardour/ardour/diskstream.h
index 955f2ed8e7..24655a1d41 100644
--- a/libs/ardour/ardour/diskstream.h
+++ b/libs/ardour/ardour/diskstream.h
@@ -277,9 +277,13 @@ class Diskstream : public SessionObject
 	nframes_t            wrap_buffer_size;
 	nframes_t            speed_buffer_size;
 
-	uint64_t                  last_phase;
-	uint64_t                  phi;
-	uint64_t                  target_phi;
+	uint64_t             last_phase;
+	
+	/// diskstream speed in 40.24 fixed point math
+	uint64_t             phi;
+	
+	/// target diskstream speed in 40.24 fixed point math
+	uint64_t             target_phi;
 	
 	nframes_t            file_frame;		
 	nframes_t            playback_sample;
diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index 81134d16fd..9d12aa79b8 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -170,9 +170,9 @@ class Session : public PBD::StatefulDestructible
 
 		Type           type;
 	    Action         action;
-	    nframes_t action_frame;
-	    nframes_t target_frame;
-	    float          speed;
+	    nframes_t      action_frame;
+	    nframes_t      target_frame;
+	    double         speed;
 
 	    union {
 			void*                ptr;
@@ -187,7 +187,7 @@ class Session : public PBD::StatefulDestructible
 	    list<AudioRange>     audio_range;
 	    list<MusicRange>     music_range;
 
-	    Event(Type t, Action a, nframes_t when, nframes_t where, float spd, bool yn = false)
+	    Event(Type t, Action a, nframes_t when, nframes_t where, double spd, bool yn = false)
 		    : type (t),
 		      action (a),
 		      action_frame (when),
@@ -388,9 +388,9 @@ class Session : public PBD::StatefulDestructible
 	void set_session_end (nframes_t end) { end_location->set_start(end); _end_location_is_free = false; }
 	void use_rf_shuttle_speed ();
 	void allow_auto_play (bool yn);
-	void request_transport_speed (float speed);
+	void request_transport_speed (double speed);
 	void request_overwrite_buffer (Diskstream*);
-	void request_diskstream_speed (Diskstream&, float speed);
+	void request_diskstream_speed (Diskstream&, double speed);
 	void request_input_change_handling ();
 
 	bool locate_pending() const { return static_cast<bool>(post_transport_work&PostTransportLocate); }
@@ -572,7 +572,7 @@ class Session : public PBD::StatefulDestructible
 	void        request_slave_source (SlaveSource);
 	bool        synced_to_jack() const { return Config->get_slave_source() == JACK; }
 
-	float       transport_speed() const { return _transport_speed; }
+	double      transport_speed() const { return _transport_speed; }
 	bool        transport_stopped() const { return _transport_speed == 0.0f; }
 	bool        transport_rolling() const { return _transport_speed != 0.0f; }
 
@@ -1023,8 +1023,8 @@ class Session : public PBD::StatefulDestructible
 	Location*                start_location;
 	Slave*                  _slave;
 	bool                    _silent;
-	volatile float          _transport_speed;
-	float                   _last_transport_speed;
+	volatile double         _transport_speed;
+	double                  _last_transport_speed;
 	bool                     auto_play_legal;
 	nframes_t               _last_slave_transport_frame;
 	nframes_t                maximum_output_latency;
@@ -1419,8 +1419,8 @@ class Session : public PBD::StatefulDestructible
 	void locate (nframes_t, bool with_roll, bool with_flush, bool with_loop=false);
 	void start_locate (nframes_t, bool with_roll, bool with_flush, bool with_loop=false);
 	void force_locate (nframes_t frame, bool with_roll = false);
-	void set_diskstream_speed (Diskstream*, float speed);
-	void set_transport_speed (float speed, bool abort = false);
+	void set_diskstream_speed (Diskstream*, double speed);
+	void set_transport_speed (double speed, bool abort = false);
 	void stop_transport (bool abort = false);
 	void start_transport ();
 	void realtime_stop (bool abort);
diff --git a/libs/ardour/ardour/slave.h b/libs/ardour/ardour/slave.h
index 07d7a4cf6a..1f2610e028 100644
--- a/libs/ardour/ardour/slave.h
+++ b/libs/ardour/ardour/slave.h
@@ -105,7 +105,7 @@ class Slave {
 	 * @param position - The transport position requested
 	 * @return - The return value is currently ignored (see Session::follow_slave)
 	 */
-	virtual bool speed_and_position (float& speed, nframes_t& position) = 0;
+	virtual bool speed_and_position (double& speed, nframes_t& position) = 0;
 	
 	/**
 	 * reports to ARDOUR whether the Slave is currently synced to its external 
@@ -174,7 +174,7 @@ class MTC_Slave : public Slave, public sigc::trackable {
 	~MTC_Slave ();
 
 	void rebind (MIDI::Port&);
-	bool speed_and_position (float&, nframes_t&);
+	bool speed_and_position (double&, nframes_t&);
 
 	bool locked() const;
 	bool ok() const;
@@ -194,12 +194,12 @@ class MTC_Slave : public Slave, public sigc::trackable {
 	nframes_t   last_inbound_frame;      /* when we got it; audio clocked */
 	MIDI::byte  last_mtc_fps_byte;
 
-	float       mtc_speed;
+	double      mtc_speed;
 	nframes_t   first_mtc_frame;
 	nframes_t   first_mtc_time;
 
 	static const int32_t accumulator_size = 128;
-	float   accumulator[accumulator_size];
+	double   accumulator[accumulator_size];
 	int32_t accumulator_index;
 	bool    have_first_accumulated_speed;
 
@@ -216,7 +216,7 @@ class MIDIClock_Slave : public Slave, public sigc::trackable {
 	~MIDIClock_Slave ();
 
 	void rebind (MIDI::Port&);
-	bool speed_and_position (float&, nframes_t&);
+	bool speed_and_position (double&, nframes_t&);
 
 	bool locked() const;
 	bool ok() const;
@@ -289,7 +289,7 @@ class ADAT_Slave : public Slave
 	ADAT_Slave () {}
 	~ADAT_Slave () {}
 
-	bool speed_and_position (float& speed, nframes_t& pos) {
+	bool speed_and_position (double& speed, nframes_t& pos) {
 		speed = 0;
 		pos = 0;
 		return false;
@@ -307,7 +307,7 @@ class JACK_Slave : public Slave
 	JACK_Slave (jack_client_t*);
 	~JACK_Slave ();
 
-	bool speed_and_position (float& speed, nframes_t& pos);
+	bool speed_and_position (double& speed, nframes_t& pos);
 
 	bool starting() const { return _starting; }
 	bool locked() const;
@@ -319,7 +319,7 @@ class JACK_Slave : public Slave
 
   private:
 	jack_client_t* jack;
-	float speed;
+	double speed;
 	bool _starting;
 };
 
diff --git a/libs/ardour/audio_diskstream.cc b/libs/ardour/audio_diskstream.cc
index 8ba1825759..dbd16e920b 100644
--- a/libs/ardour/audio_diskstream.cc
+++ b/libs/ardour/audio_diskstream.cc
@@ -785,8 +785,17 @@ AudioDiskstream::process (nframes_t transport_frame, nframes_t nframes, nframes_
 			nframes_t i = 0;
 
 			// Linearly interpolate into the alt buffer
-			// using 40.24 fixp maths (swh)
-
+			// using 40.24 fixp maths
+			//
+			// Fixedpoint is just an integer with an implied scaling factor. 
+			// In 40.24 the scaling factor is 2^24 = 16777216,  
+			// so a value of 10*2^24 (in integer space) is equivalent to 10.0. 
+			//
+			// The advantage is that addition and modulus [like x = (x + y) % 2^40]  
+			// has no rounding errors and no drift, and just requires a single integer add.
+			// (swh)
+
+			// phi = fixed point speed
 			if (phi != target_phi) {
 				phi_delta = ((int64_t)(target_phi - phi)) / nframes;
 			} else {
@@ -795,7 +804,7 @@ AudioDiskstream::process (nframes_t transport_frame, nframes_t nframes, nframes_
 
 			for (chan = c->begin(); chan != c->end(); ++chan) {
 
-				float fr;
+				Sample fractional_part;
 				ChannelInfo* chaninfo (*chan);
 
 				i = 0;
@@ -803,10 +812,10 @@ AudioDiskstream::process (nframes_t transport_frame, nframes_t nframes, nframes_
 
 				for (nframes_t outsample = 0; outsample < nframes; ++outsample) {
 					i = phase >> 24;
-					fr = (phase & 0xFFFFFF) / 16777216.0f;
+					fractional_part = (phase & 0xFFFFFF) / 16777216.0f;
 					chaninfo->speed_buffer[outsample] = 
-						chaninfo->current_playback_buffer[i] * (1.0f - fr) +
-						chaninfo->current_playback_buffer[i+1] * fr;
+						chaninfo->current_playback_buffer[i] * (1.0f - fractional_part) +
+						chaninfo->current_playback_buffer[i+1] * fractional_part;
 					phase += phi + phi_delta;
 				}
 				
diff --git a/libs/ardour/diskstream.cc b/libs/ardour/diskstream.cc
index 334e4336af..afd5d21470 100644
--- a/libs/ardour/diskstream.cc
+++ b/libs/ardour/diskstream.cc
@@ -109,6 +109,7 @@ Diskstream::init (Flag f)
 	wrap_buffer_size = 0;
 	speed_buffer_size = 0;
 	last_phase = 0;
+	// speed = 1 in 40.24 fixed point math
 	phi = (uint64_t) (0x1000000);
 	target_phi = phi;
 	file_frame = 0;
diff --git a/libs/ardour/jack_slave.cc b/libs/ardour/jack_slave.cc
index 40729d3370..b7160489ff 100644
--- a/libs/ardour/jack_slave.cc
+++ b/libs/ardour/jack_slave.cc
@@ -34,7 +34,7 @@ using namespace sigc;
 JACK_Slave::JACK_Slave (jack_client_t* j)
 	: jack (j)
 {
-	float x;
+	double x;
 	nframes_t p;
 	/* call this to initialize things */
 	speed_and_position (x, p);
@@ -63,7 +63,7 @@ JACK_Slave::ok() const
 }
 
 bool 
-JACK_Slave::speed_and_position (float& sp, nframes_t& position) 
+JACK_Slave::speed_and_position (double& sp, nframes_t& position) 
 {
 	jack_position_t pos;
 	jack_transport_state_t state;
diff --git a/libs/ardour/midi_clock_slave.cc b/libs/ardour/midi_clock_slave.cc
index ec5dc3e5c9..f1ec1ad924 100644
--- a/libs/ardour/midi_clock_slave.cc
+++ b/libs/ardour/midi_clock_slave.cc
@@ -133,8 +133,8 @@ MIDIClock_Slave::update_midi_clock (Parser& parser, nframes_t timestamp)
 
 		// calculate loop error
 		// we use session.transport_frame() instead of t1 here
-		// because t1 is used to calculate the transport speed, and since this
-		// is float, the loop will compensate for accumulating rounding errors
+		// because t1 is used to calculate the transport speed,
+		// so the loop will compensate for accumulating rounding errors
 		e = (double(last_position) - double(session.transport_frame())) 
 		    / double(session.frame_rate());
 		
@@ -242,7 +242,7 @@ MIDIClock_Slave::stop_if_no_more_clock_events(nframes_t& pos, nframes_t now)
 }
 
 bool
-MIDIClock_Slave::speed_and_position (float& speed, nframes_t& pos)
+MIDIClock_Slave::speed_and_position (double& speed, nframes_t& pos)
 {
 	if (!_started || _starting) {
 		speed = 0.0;
@@ -257,15 +257,14 @@ MIDIClock_Slave::speed_and_position (float& speed, nframes_t& pos)
 	}
 
 	// calculate speed
-	double speed_double = ((t1 - t0) * session.frame_rate()) / one_ppqn_in_frames;
-	speed = float(speed_double);
+	speed = ((t1 - t0) * session.frame_rate()) / one_ppqn_in_frames;
 	
 	// calculate position
 	if (engine_now > last_timestamp) {
 		// we are in between MIDI clock messages
 		// so we interpolate position according to speed
 		nframes_t elapsed = engine_now - last_timestamp;
-		pos = nframes_t (last_position + double(elapsed) * speed_double);
+		pos = nframes_t (last_position + double(elapsed) * speed);
 	} else {
 		// A new MIDI clock message has arrived this cycle
 		pos = last_position;
diff --git a/libs/ardour/mtc_slave.cc b/libs/ardour/mtc_slave.cc
index 1a8cd589da..e45e760251 100644
--- a/libs/ardour/mtc_slave.cc
+++ b/libs/ardour/mtc_slave.cc
@@ -257,13 +257,13 @@ MTC_Slave::ok() const
 }
 
 bool 
-MTC_Slave::speed_and_position (float& speed, nframes_t& pos)
+MTC_Slave::speed_and_position (double& speed, nframes_t& pos)
 {
 	nframes_t now = session.engine().frame_time();
 	SafeTime last;
 	nframes_t frame_rate;
 	nframes_t elapsed;
-	float speed_now;
+	double speed_now;
 
 	read_current (&last);
 
@@ -287,7 +287,7 @@ MTC_Slave::speed_and_position (float& speed, nframes_t& pos)
 
 	frame_rate = session.frame_rate();
 
-	speed_now = (float) ((last.position - first_mtc_frame) / (double) (now - first_mtc_time));
+	speed_now = (double) ((last.position - first_mtc_frame) / (double) (now - first_mtc_time));
 
 	accumulator[accumulator_index++] = speed_now;
 
@@ -297,7 +297,7 @@ MTC_Slave::speed_and_position (float& speed, nframes_t& pos)
 	}
 
 	if (have_first_accumulated_speed) {
-		float total = 0;
+		double total = 0;
 
 		for (int32_t i = 0; i < accumulator_size; ++i) {
 			total += accumulator[i];
diff --git a/libs/ardour/session_process.cc b/libs/ardour/session_process.cc
index 08f614db07..6247a4d654 100644
--- a/libs/ardour/session_process.cc
+++ b/libs/ardour/session_process.cc
@@ -465,7 +465,7 @@ Session::transport_locked () const
 bool
 Session::follow_slave (nframes_t nframes, nframes_t offset)
 {
-	float slave_speed;
+	double slave_speed;
 	nframes_t slave_transport_frame;
 	nframes_t this_delta;
 	int dir;
diff --git a/libs/ardour/session_transport.cc b/libs/ardour/session_transport.cc
index 9163dfd5ea..0649d16848 100644
--- a/libs/ardour/session_transport.cc
+++ b/libs/ardour/session_transport.cc
@@ -74,14 +74,14 @@ Session::request_slave_source (SlaveSource src)
 }
 
 void
-Session::request_transport_speed (float speed)
+Session::request_transport_speed (double speed)
 {
 	Event* ev = new Event (Event::SetTransportSpeed, Event::Add, Event::Immediate, 0, speed);
 	queue_event (ev);
 }
 
 void
-Session::request_diskstream_speed (Diskstream& ds, float speed)
+Session::request_diskstream_speed (Diskstream& ds, double speed)
 {
 	Event* ev = new Event (Event::SetDiskstreamSpeed, Event::Add, Event::Immediate, 0, speed);
 	ev->set_ptr (&ds);
@@ -628,7 +628,7 @@ Session::start_locate (nframes_t target_frame, bool with_roll, bool with_flush,
 {
 	if (synced_to_jack()) {
 
-		float sp;
+		double sp;
 		nframes_t pos;
 
 		_slave->speed_and_position (sp, pos);
@@ -799,16 +799,16 @@ Session::locate (nframes_t target_frame, bool with_roll, bool with_flush, bool w
  * @param abort
  */
 void
-Session::set_transport_speed (float speed, bool abort)
+Session::set_transport_speed (double speed, bool abort)
 {
 	if (_transport_speed == speed) {
 		return;
 	}
 
 	if (speed > 0) {
-		speed = min (8.0f, speed);
+		speed = min (8.0, speed);
 	} else if (speed < 0) {
-		speed = max (-8.0f, speed);
+		speed = max (-8.0, speed);
 	}
 
 	if (transport_rolling() && speed == 0.0) {
@@ -875,11 +875,11 @@ Session::set_transport_speed (float speed, bool abort)
 			return;
 		}
 
-		if (speed > 0.0f && _transport_frame == current_end_frame()) {
+		if (speed > 0.0 && _transport_frame == current_end_frame()) {
 			return;
 		}
 
-		if (speed < 0.0f && _transport_frame == 0) {
+		if (speed < 0.0 && _transport_frame == 0) {
 			return;
 		}
 
@@ -889,7 +889,7 @@ Session::set_transport_speed (float speed, bool abort)
 		   before the last stop, then we have to do extra work.
 		*/
 
-		if ((_transport_speed && speed * _transport_speed < 0.0f) || (_last_transport_speed * speed < 0.0f) || (_last_transport_speed == 0.0f && speed < 0.0f)) {
+		if ((_transport_speed && speed * _transport_speed < 0.0) || (_last_transport_speed * speed < 0.0) || (_last_transport_speed == 0.0f && speed < 0.0f)) {
 			post_transport_work = PostTransportWork (post_transport_work | PostTransportReverse);
 			last_stop_frame = _transport_frame;
 		}
@@ -1144,7 +1144,7 @@ Session::reverse_diskstream_buffers ()
 }
 
 void
-Session::set_diskstream_speed (Diskstream* stream, float speed)
+Session::set_diskstream_speed (Diskstream* stream, double speed)
 {
 	if (stream->realtime_set_speed (speed, false)) {
 		post_transport_work = PostTransportWork (post_transport_work | PostTransportSpeed);
diff --git a/libs/surfaces/control_protocol/basic_ui.cc b/libs/surfaces/control_protocol/basic_ui.cc
index b88e002374..a0eeda5a96 100644
--- a/libs/surfaces/control_protocol/basic_ui.cc
+++ b/libs/surfaces/control_protocol/basic_ui.cc
@@ -184,12 +184,12 @@ BasicUI::next_marker ()
 }
 
 void
-BasicUI::set_transport_speed (float speed)
+BasicUI::set_transport_speed (double speed)
 {
 	session->request_transport_speed (speed);
 }
 
-float
+double
 BasicUI::get_transport_speed ()
 {
 	return session->transport_speed ();
diff --git a/libs/surfaces/control_protocol/control_protocol/basic_ui.h b/libs/surfaces/control_protocol/control_protocol/basic_ui.h
index c8b5a2a0b6..279d1c6394 100644
--- a/libs/surfaces/control_protocol/control_protocol/basic_ui.h
+++ b/libs/surfaces/control_protocol/control_protocol/basic_ui.h
@@ -50,8 +50,8 @@ class BasicUI {
 	void ffwd ();
 	void transport_stop ();
 	void transport_play (bool jump_back = true);
-	void set_transport_speed (float speed);
-	float get_transport_speed ();
+	void set_transport_speed (double speed);
+	double get_transport_speed ();
 
 	jack_nframes_t transport_frame ();
 	void locate (jack_nframes_t frame, bool play = false);