diff options
author | Hans Baier <hansfbaier@googlemail.com> | 2008-10-29 07:17:07 +0000 |
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committer | Hans Baier <hansfbaier@googlemail.com> | 2008-10-29 07:17:07 +0000 |
commit | 75e918080093a6ca88abe010c07d883afc697520 (patch) | |
tree | 0ac621b5dd7c863bce98871b69d60cee0e798d31 /libs/ardour/ardour/slave.h | |
parent | a1a3dc05ad480ee7cf25ad628b3477461f5709d7 (diff) |
* added documentaion to libs/ardour/slave.h
* first roughly working midi clock slave
git-svn-id: svn://localhost/ardour2/branches/3.0@4025 d708f5d6-7413-0410-9779-e7cbd77b26cf
Diffstat (limited to 'libs/ardour/ardour/slave.h')
-rw-r--r-- | libs/ardour/ardour/slave.h | 126 |
1 files changed, 121 insertions, 5 deletions
diff --git a/libs/ardour/ardour/slave.h b/libs/ardour/ardour/slave.h index 0685e66436..80fac38a2a 100644 --- a/libs/ardour/ardour/slave.h +++ b/libs/ardour/ardour/slave.h @@ -36,17 +36,119 @@ namespace MIDI { 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; } }; @@ -124,18 +226,27 @@ class MIDIClock_Slave : public Slave, public sigc::trackable { 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); @@ -143,7 +254,12 @@ class MIDIClock_Slave : public Slave, public sigc::trackable { 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 |