Skip to content

Latest commit

 

History

History
102 lines (68 loc) · 3.1 KB

HydrogenProject.md

File metadata and controls

102 lines (68 loc) · 3.1 KB
Raw

Make a system that can take a Hydrogen songe (*.h2song) and a Jack

Timebase feed and play the Hydrogen song into a Jack audio pipe

Use: ~/hydrogen/src/player/

hydrogen/src/core/Hydrogen.h defines Hydrogen::tempo enum that defines Jack:

		/** Hydrogen will disregard all internal tempo settings and
			uses the ones provided by the JACK server instead. This
			mode is only used in case the JACK audio driver is used,
			JACK timebase support is activated in the Preferences, and
			an external timebase master is registered to the JACK
			server.*/
		Jack = 2

It looks like this is set in the song file.

If the song mode is Song::Mode::Song then if getJackTimebaseState() == JackAudioDriver::Timebase::Slave tempo is Tempo::Jack. (See Hydrogen.cpp:1340)

The default mode for a song is: Song::Mode::Pattern

The mode of a song is set by: std::shared_ptr<Song> Song::loadFrom( XMLNode* pRootNode, bool bSilent ) Song.cpp:257 by calling void Song::setMode( Song::Mode mode )

Jack Timebase

Thie link indicates that there is a master and there are slaves

Properties

From this reading the Python source code

  • Beats per bar

  • Beat type (?)

  • BPM

  • Ticks per beat

Timebase Master

From this website:

The timebase master continuously updates extended position information, counting beats, timecode, etc. If no [Jack] client is registered as timebase master, frame numbers will be the only position information available.

The timebase master registers a callback that updates position information while the transport is rolling.

Its [the calback?] output affects the following process cycle. [What is a process cycle?]

This function [the callback?] is called immediately after the process callback in the same thread whenever the transport is rolling, or when any client has set a new position in the previous cycle. [What is the "process callback"?]

The first cycle after jack_set_timebase_callback() is also treated as a new position, or the first cycle after jack_activate() if the client had been inactive.

typedef int  (*JackTimebaseCallback)(jack_transport_state_t state,
                                     jack_nframes_t nframes,
                                     jack_position_t *pos,
                                     int new_pos,
                                     void *arg);

When a new client takes over, the former timebase callback is no longer called. Taking over the timebase may be done conditionally, in which case the takeover fails when there is a master already. The existing master can release it voluntarily, if desired.

int  jack_set_timebase_callback (jack_client_t *client,
                                 int conditional,
                                 JackTimebaseCallback timebase_callback,
                                 void *arg);
int  jack_release_timebase(jack_client_t *client);

Timebase Client