namespace ARDOUR {
class Session;
+/**
+ * @class Slave
+ *
+ * @brief The class Slave can be used to sync ardours tempo to an external source
+ * like MTC, MIDI Clock, etc.
+ *
+ * The name of the class may be a bit misleading: A subclass of Slave actually
+ * acts as a master for Ardour, that means Ardour will try to follow the
+ * speed and transport position of the implementation of Slave.
+ * Therefor 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.
+ * (Otherwise Session:average_slave_delta will become negative, and
+ * the transport will move silently)
+ * </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 negative or greater than the resolution, sound will stop
+ * (Session::follow_slave label silent_motion)
+ */
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; }
};
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 */
+
+ /// 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;
float accumulator[accumulator_size];
int32_t accumulator_index;
- bool have_first_accumulated_speed;
- float average;
+
+ /// the running average of current_midi_clock_frame_duration
+ float average_midi_clock_frame_duration;
void reset ();
void start (MIDI::Parser& parser, nframes_t timestamp);
void update_midi_clock (MIDI::Parser& parser, nframes_t timestamp);
void read_current (SafeTime *) const;
+ /// whether transport should be rolling
bool _started;
+
+ /// is true if the MIDI Start message has just been received until
+ /// the first call of speed_and_position(...)
+ bool _starting;
};
class ADAT_Slave : public Slave
: session (s)
, ppqn (ppqn)
, accumulator_index (0)
- , average (0.0)
+ , average_midi_clock_frame_duration (0.0)
{
rebind (p);
reset ();
// for the first MIDI clock event we dont have any past
// data, so we assume a sane tempo
if(last.timestamp == 0) {
- midi_clock_frame = one_ppqn_in_frames;
+ current_midi_clock_frame_duration = one_ppqn_in_frames;
} else {
- midi_clock_frame = now - last.timestamp;
+ current_midi_clock_frame_duration = now - last.timestamp;
}
// moving average over incoming intervals
- accumulator[accumulator_index++] = (float) midi_clock_frame;
+ accumulator[accumulator_index++] = (float) current_midi_clock_frame_duration;
if(accumulator_index == accumulator_size)
accumulator_index = 0;
- average = 0.0;
+ average_midi_clock_frame_duration = 0.0;
for(int i = 0; i < accumulator_size; i++)
- average += accumulator[i];
- average /= accumulator_size;
+ average_midi_clock_frame_duration += accumulator[i];
+ average_midi_clock_frame_duration /= accumulator_size;
#if 1
std::cerr
<< " got MIDI Clock message at time " << now
<< " session time: " << session.engine().frame_time()
- << " real delta: " << midi_clock_frame
+ << " real delta: " << current_midi_clock_frame_duration
<< " reference: " << one_ppqn_in_frames
- << " average: " << average
+ << " average: " << average_midi_clock_frame_duration
<< std::endl;
#endif
+
+
current.guard1++;
- current.position += midi_clock_frame;
+ current.position += current_midi_clock_frame_duration * (one_ppqn_in_frames / average_midi_clock_frame_duration);
current.timestamp = now;
current.guard2++;
return;
}
- midi_clock_frame = 0;
+ current_midi_clock_frame_duration = 0;
- session.request_transport_speed(one_ppqn_in_frames / average);
+ session.request_transport_speed(one_ppqn_in_frames / average_midi_clock_frame_duration);
current.guard1++;
current.position = 0;
current.timestamp = now;
current.guard2++;
_started = true;
+ _starting = true;
}
void
{
std::cerr << "MIDIClock_Slave got stop message" << endl;
- midi_clock_frame = 0;
+ current_midi_clock_frame_duration = 0;
current.guard1++;
current.position = 0;
pos = 0;
return true;
}
-
+
nframes_t now = session.engine().frame_time();
nframes_t frame_rate = session.frame_rate();
cerr << " now: " << now << " last: " << last.timestamp;
- speed = one_ppqn_in_frames / average;
+ speed = one_ppqn_in_frames / average_midi_clock_frame_duration;
cerr << " final speed: " << speed;
if (now > last.timestamp) {
// so we interpolate position according to speed
nframes_t elapsed = now - last.timestamp;
cerr << " elapsed: " << elapsed << " elapsed (scaled) " << elapsed * speed;
- pos = last.position + elapsed * speed;
- last.position = pos;
+ nframes_t delta = elapsed * speed;
+ pos = last.position + delta;
} else {
// A new MIDI clock message has arrived this cycle
pos = last.position;
cerr << " position: " << pos;
cerr << endl;
-
+
+ // we want start on frame 0 on the first call after a MIDI start
+ if(_starting) {
+ pos = 0;
+ _starting = false;
+ }
+
return true;
}
projects / ardour.git / commitdiff