Setting Client Callbacks

Detailed Description

JACK allows to register numerous callback functions for various purposes. The most important ones are listed in this group. Note that there are however also other callbacks on other JACK API parts. The most important callback, which usually every JACK client application implements, is registered with jack_set_process_callback(). With the latter your application provides a function that is periodically called to process audio & MIDI.

Note

All callbacks must be registered before you call jack_activate() for your client. Subsequent registration of callbacks is only possible by suspending your client with jack_deactivate().

Functions
int	jack_set_thread_init_callback (jack_client_t *client, JackThreadInitCallback thread_init_callback, void *arg) JACK_OPTIONAL_WEAK_EXPORT
void	jack_on_shutdown (jack_client_t *client, JackShutdownCallback shutdown_callback, void *arg) JACK_OPTIONAL_WEAK_EXPORT
void	jack_on_info_shutdown (jack_client_t *client, JackInfoShutdownCallback shutdown_callback, void *arg) JACK_WEAK_EXPORT
int	jack_set_process_callback (jack_client_t *client, JackProcessCallback process_callback, void *arg) JACK_OPTIONAL_WEAK_EXPORT
int	jack_set_freewheel_callback (jack_client_t *client, JackFreewheelCallback freewheel_callback, void *arg) JACK_OPTIONAL_WEAK_EXPORT
int	jack_set_buffer_size_callback (jack_client_t *client, JackBufferSizeCallback bufsize_callback, void *arg) JACK_OPTIONAL_WEAK_EXPORT
int	jack_set_sample_rate_callback (jack_client_t *client, JackSampleRateCallback srate_callback, void *arg) JACK_OPTIONAL_WEAK_EXPORT
int	jack_set_client_registration_callback (jack_client_t *client, JackClientRegistrationCallback registration_callback, void *arg) JACK_OPTIONAL_WEAK_EXPORT
int	jack_set_port_registration_callback (jack_client_t *client, JackPortRegistrationCallback registration_callback, void *arg) JACK_OPTIONAL_WEAK_EXPORT
int	jack_set_port_connect_callback (jack_client_t *client, JackPortConnectCallback connect_callback, void *arg) JACK_OPTIONAL_WEAK_EXPORT
int	jack_set_port_rename_callback (jack_client_t *client, JackPortRenameCallback rename_callback, void *arg) JACK_OPTIONAL_WEAK_EXPORT
int	jack_set_graph_order_callback (jack_client_t *client, JackGraphOrderCallback graph_callback, void *) JACK_OPTIONAL_WEAK_EXPORT
int	jack_set_xrun_callback (jack_client_t *client, JackXRunCallback xrun_callback, void *arg) JACK_OPTIONAL_WEAK_EXPORT

Function Documentation

int jack_set_thread_init_callback	(	jack_client_t *	client,
		JackThreadInitCallback	thread_init_callback,
		void *	arg
	)

Tell JACK to call thread_init_callback once just after the creation of the thread in which all other callbacks will be handled.

The code in the supplied function does not need to be suitable for real-time execution.

NOTE: this function cannot be called while the client is activated (after jack_activate has been called.)

Returns

0 on success, otherwise a non-zero error code, causing JACK to remove that client from the process() graph.

void jack_on_shutdown	(	jack_client_t *	client,
		JackShutdownCallback	shutdown_callback,
		void *	arg
	)

Parameters

client	pointer to JACK client structure.
function	The jack_shutdown function pointer.
arg	The arguments for the jack_shutdown function.

Register a function (and argument) to be called if and when the JACK server shuts down the client thread. The function must be written as if it were an asynchonrous POSIX signal handler — use only async-safe functions, and remember that it is executed from another thread. A typical function might set a flag or write to a pipe so that the rest of the application knows that the JACK client thread has shut down.

NOTE: clients do not need to call this. It exists only to help more complex clients understand what is going on. It should be called before jack_client_activate().

NOTE: if a client calls this AND jack_on_info_shutdown(), then in case of a client thread shutdown, the callback passed to this function will not be called, and the one passed to jack_on_info_shutdown() will.

NOTE: application should typically signal another thread to correctly finish cleanup, that is by calling "jack_client_close" (since "jack_client_close" cannot be called directly in the context of the thread that calls the shutdown callback).

Deprecated:

It is recommended to use jack_on_info_shutdown() instead, which provides detailed informations about the exact reason why the client has been closed by the JACK server.

void jack_on_info_shutdown	(	jack_client_t *	client,
		JackInfoShutdownCallback	shutdown_callback,
		void *	arg
	)

Parameters

client	pointer to JACK client structure.
function	The jack_info_shutdown function pointer.
arg	The arguments for the jack_info_shutdown function.

Register a function (and argument) to be called if and when the JACK server shuts down the client thread. The function must be written as if it were an asynchonrous POSIX signal handler — use only async-safe functions, and remember that it is executed from another thread. A typical function might set a flag or write to a pipe so that the rest of the application knows that the JACK client thread has shut down.

NOTE: clients do not need to call this. It exists only to help more complex clients understand what is going on. It should be called before jack_client_activate().

NOTE: if a client calls this AND jack_on_shutdown(), then in case of a client thread shutdown, the callback passed to jack_on_info_shutdown() will be called.

NOTE: application should typically signal another thread to correctly finish cleanup, that is by calling "jack_client_close" (since "jack_client_close" cannot be called directly in the context of the thread that calls the shutdown callback).

int jack_set_process_callback	(	jack_client_t *	client,
		JackProcessCallback	process_callback,
		void *	arg
	)

Tell the Jack server to call process_callback whenever there is work be done, passing arg as the second argument.

The code in the supplied function must be suitable for real-time execution. That means that it cannot call functions that might block for a long time. This includes malloc, free, printf, pthread_mutex_lock, sleep, wait, poll, select, pthread_join, pthread_cond_wait, etc, etc.

NOTE: this function cannot be called while the client is activated (after jack_activate has been called.)

Returns

0 on success, otherwise a non-zero error code.

int jack_set_freewheel_callback	(	jack_client_t *	client,
		JackFreewheelCallback	freewheel_callback,
		void *	arg
	)

Tell the Jack server to call freewheel_callback whenever we enter or leave "freewheel" mode, passing arg as the second argument. The first argument to the callback will be non-zero if JACK is entering freewheel mode, and zero otherwise.

All "notification events" are received in a seperated non RT thread, the code in the supplied function does not need to be suitable for real-time execution.

NOTE: this function cannot be called while the client is activated (after jack_activate has been called.)

Returns

0 on success, otherwise a non-zero error code.

int jack_set_buffer_size_callback	(	jack_client_t *	client,
		JackBufferSizeCallback	bufsize_callback,
		void *	arg
	)

Tell JACK to call bufsize_callback whenever the size of the the buffer that will be passed to the process_callback is about to change. Clients that depend on knowing the buffer size must supply a bufsize_callback before activating themselves.

All "notification events" are received in a seperated non RT thread, the code in the supplied function does not need to be suitable for real-time execution.

NOTE: this function cannot be called while the client is activated (after jack_activate has been called.)

Parameters

client	pointer to JACK client structure.
bufsize_callback	function to call when the buffer size changes.
arg	argument for bufsize_callback.

Returns

0 on success, otherwise a non-zero error code

int jack_set_sample_rate_callback	(	jack_client_t *	client,
		JackSampleRateCallback	srate_callback,
		void *	arg
	)

Tell the Jack server to call srate_callback whenever the system sample rate changes.

All "notification events" are received in a seperated non RT thread, the code in the supplied function does not need to be suitable for real-time execution.

NOTE: this function cannot be called while the client is activated (after jack_activate has been called.)

Returns

0 on success, otherwise a non-zero error code

int jack_set_client_registration_callback	(	jack_client_t *	client,
		JackClientRegistrationCallback	registration_callback,
		void *	arg
	)

Tell the JACK server to call client_registration_callback whenever a client is registered or unregistered, passing arg as a parameter.

All "notification events" are received in a seperated non RT thread, the code in the supplied function does not need to be suitable for real-time execution.

NOTE: this function cannot be called while the client is activated (after jack_activate has been called.)

Returns

0 on success, otherwise a non-zero error code

int jack_set_port_registration_callback	(	jack_client_t *	client,
		JackPortRegistrationCallback	registration_callback,
		void *	arg
	)

Tell the JACK server to call registration_callback whenever a port is registered or unregistered, passing arg as a parameter.

All "notification events" are received in a seperated non RT thread, the code in the supplied function does not need to be suitable for real-time execution.

NOTE: this function cannot be called while the client is activated (after jack_activate has been called.)

Returns

0 on success, otherwise a non-zero error code

int jack_set_port_connect_callback	(	jack_client_t *	client,
		JackPortConnectCallback	connect_callback,
		void *	arg
	)

Tell the JACK server to call connect_callback whenever a port is connected or disconnected, passing arg as a parameter.

All "notification events" are received in a seperated non RT thread, the code in the supplied function does not need to be suitable for real-time execution.

NOTE: this function cannot be called while the client is activated (after jack_activate has been called.)

Returns

0 on success, otherwise a non-zero error code

int jack_set_port_rename_callback	(	jack_client_t *	client,
		JackPortRenameCallback	rename_callback,
		void *	arg
	)

Tell the JACK server to call rename_callback whenever a port is renamed, passing arg as a parameter.

All "notification events" are received in a seperated non RT thread, the code in the supplied function does not need to be suitable for real-time execution.

NOTE: this function cannot be called while the client is activated (after jack_activate has been called.)

Returns

0 on success, otherwise a non-zero error code

int jack_set_graph_order_callback	(	jack_client_t *	client,
		JackGraphOrderCallback	graph_callback,
		void *
	)

Tell the JACK server to call graph_callback whenever the processing graph is reordered, passing arg as a parameter.

All "notification events" are received in a seperated non RT thread, the code in the supplied function does not need to be suitable for real-time execution.

NOTE: this function cannot be called while the client is activated (after jack_activate has been called.)

Returns

0 on success, otherwise a non-zero error code

int jack_set_xrun_callback	(	jack_client_t *	client,
		JackXRunCallback	xrun_callback,
		void *	arg
	)

Tell the JACK server to call xrun_callback whenever there is a xrun, passing arg as a parameter.

All "notification events" are received in a seperated non RT thread, the code in the supplied function does not need to be suitable for real-time execution.

NOTE: this function cannot be called while the client is activated (after jack_activate has been called.)

Returns

0 on success, otherwise a non-zero error code