namespace ARDOUR {
class Session;
+/**
+ * @class Slave
+ *
+ * @brief The Slave interface can be used to sync ARDOURs tempo to an external source
+ * like MTC, MIDI Clock, etc.
+ *
+ * The name of the interface may be a bit misleading: A subclass of Slave actually
+ * acts as a time master for ARDOUR, that means ARDOUR will try to follow the
+ * speed and transport position of the implementation of Slave.
+ * Therefore it is rather that class, that makes ARDOUR a slave by connecting it
+ * to its external time master.
+ */
class Slave {
public:
Slave() { }
virtual ~Slave() {}
- virtual bool speed_and_position (float&, nframes_t&) = 0;
+ /**
+ * This is the most important function to implement:
+ * Each process cycle, Session::follow_slave will call this method.
+ * and after the method call they should
+ *
+ * Session::follow_slave will then try to follow the given
+ * <emph>position</emph> using a delay locked loop (DLL),
+ * starting with the first given transport speed.
+ * If the values of speed and position contradict each other,
+ * ARDOUR will always follow the position and disregard the speed.
+ * Although, a correct speed is important so that ARDOUR
+ * can sync to the master time source quickly.
+ *
+ * For background information on delay locked loops,
+ * see http://www.kokkinizita.net/papers/usingdll.pdf
+ *
+ * The method has the following precondition:
+ * <ul>
+ * <li>
+ * Slave::ok() should return true, otherwise playback will stop
+ * immediately and the method will not be called
+ * </li>
+ * <li>
+ * when the references speed and position are passed into the Slave
+ * they are uninitialized
+ * </li>
+ * </ul>
+ *
+ * After the method call the following postconditions should be met:
+ * <ul>
+ * <li>
+ * The first position value on transport start should be 0,
+ * otherwise ARDOUR will try to locate to the new position
+ * rather than move to it
+ * </li>
+ * <li>
+ * the references speed and position should be assigned
+ * to the Slaves current requested transport speed
+ * and transport position.
+ * </li>
+ * <li>
+ * Slave::resolution() should be greater than the maximum distance of
+ * ARDOURs transport position to the slaves requested transport position.
+ * </li>
+ * <li>Slave::locked() should return true, otherwise Session::no_roll will be called</li>
+ * <li>Slave::starting() should be false, otherwise the transport will not move until it becomes true</li> *
+ * </ul>
+ *
+ * @param speed - The transport speed requested
+ * @param position - The transport position requested
+ */
+ virtual bool speed_and_position (float& speed, nframes_t& position) = 0;
+
+ /**
+ * reports to ARDOUR whether the Slave is currently synced to its external
+ * time source.
+ *
+ * @return - when returning false, the transport will stop rolling
+ */
virtual bool locked() const = 0;
+
+ /**
+ * reports to ARDOUR whether the slave is in a sane state
+ *
+ * @return - when returning false, the transport will be stopped and the slave
+ * disconnected from ARDOUR.
+ */
virtual bool ok() const = 0;
+
+ /**
+ * reports to ARDOUR whether the slave is in the process of starting
+ * to roll
+ *
+ * @return - when returning false, transport will not move until this method returns true
+ */
virtual bool starting() const { return false; }
+
+ /**
+ * @return - the timing resolution of the Slave - If the distance of ARDOURs transport
+ * to the slave becomes greater than the resolution, sound will stop
+ */
virtual nframes_t resolution() const = 0;
+
+ /**
+ * @return - when returning true, ARDOUR will wait for one second before transport
+ * starts rolling
+ */
virtual bool requires_seekahead () const = 0;
+
+ /**
+ * @return - when returning true, ARDOUR will use transport speed 1.0 no matter what
+ * the slave returns
+ */
virtual bool is_always_synced() const { return false; }
};
SafeTime current;
nframes_t mtc_frame; /* current time */
nframes_t last_inbound_frame; /* when we got it; audio clocked */
+ MIDI::byte last_mtc_fps_byte;
float mtc_speed;
nframes_t first_mtc_frame;
bool locked() const;
bool ok() const;
+ bool starting() const;
nframes_t resolution() const;
- bool requires_seekahead () const { return true; }
+ bool requires_seekahead () const { return false; }
private:
Session& session;
MIDI::Port* port;
std::vector<sigc::connection> connections;
+ /// pulses per quarter note for one MIDI clock frame (default 24)
int ppqn;
+
+ /// the duration of one ppqn in frame time
double one_ppqn_in_frames;
+ /// the time stamp and transport position of the last inbound MIDI clock message
SafeTime current;
- nframes_t midi_clock_frame; /* current time */
- nframes_t last_inbound_frame; /* when we got it; audio clocked */
-
- float midi_clock_speed;
- nframes_t first_midi_clock_frame;
- nframes_t first_midi_clock_time;
-
- static const int32_t accumulator_size = 128;
- float accumulator[accumulator_size];
+ /// since current.position is integral, we need to keep track of decimal places
+ /// to be precise
+ double current_position;
+
+ /// The duration of the current MIDI clock frame in frames
+ nframes_t current_midi_clock_frame_duration;
+ /// the timestamp of the last inbound MIDI clock message
+ nframes_t last_inbound_frame;
+
+ /// how many MIDI clock frames to average over
+ static const int32_t accumulator_size = 4;
+ double accumulator[accumulator_size];
int32_t accumulator_index;
- bool have_first_accumulated_speed;
+
+ /// the running average of current_midi_clock_frame_duration
+ double average_midi_clock_frame_duration;
void reset ();
- void start (MIDI::Parser& parser);
- void stop (MIDI::Parser& parser);
- void update_midi_clock (MIDI::Parser& parser);
+ void start (MIDI::Parser& parser, nframes_t timestamp);
+ void stop (MIDI::Parser& parser, nframes_t timestamp);
+ // we can't use continue because it is a C++ keyword
+ void contineu (MIDI::Parser& parser, nframes_t timestamp);
+ void calculate_one_ppqn_in_frames_at(nframes_t time);
+ void update_midi_clock (MIDI::Parser& parser, nframes_t timestamp);
void read_current (SafeTime *) const;
+ bool stop_if_no_more_clock_events(nframes_t& pos, nframes_t now, SafeTime& last);
+
+ /// whether transport should be rolling
bool _started;
+
+ /// is true if the MIDI Start message has just been received until
+ /// the first MIDI Clock Event
+ bool _starting;
};
class ADAT_Slave : public Slave
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