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Controlling & querying JACK server operation
Creating & manipulating clients » The non-callback API » Setting Client Callbacks

## Topics

| Creating & manipulating ports

## Functions

int | jack_set_freewheel (jack_client_t *client, int onoff) JACK_OPTIONAL_WEAK_EXPORT
int | jack_set_buffer_size (jack_client_t *client, jack_nframes_t nframes) JACK_OPTIONAL_WEAK_EXPORT
jack_nframes_t | jack_get_sample_rate (jack_client_t *) JACK_OPTIONAL_WEAK_EXPORT
jack_nframes_t | jack_get_buffer_size (jack_client_t *) JACK_OPTIONAL_WEAK_EXPORT
int | jack_engine_takeover_timebase (jack_client_t *) JACK_OPTIONAL_WEAK_DEPRECATED_EXPORT
float | jack_cpu_load (jack_client_t *client) JACK_OPTIONAL_WEAK_EXPORT

## Detailed Description

## Function Documentation

## jack_cpu_load()

float jack_cpu_load | ( | jack_client_t * | client | ) |

Returns
  the current CPU load estimated by JACK. This is a running average of the time it takes to execute a full process cycle for all clients as a percentage of the real time available per cycle determined by the buffer size and sample rate.

References jack_cpu_load(), and JACK_OPTIONAL_WEAK_EXPORT.

Referenced by jack_cpu_load().

## jack_engine_takeover_timebase()

int jack_engine_takeover_timebase | ( | jack_client_t * |  | ) |

Old-style interface to become the timebase for the entire JACK subsystem.

Deprecated
  This function still exists for compatibility with the earlier transport interface, but it does nothing. Instead, see transport.h and use jack_set_timebase_callback().

Returns
  ENOSYS, function not implemented.

References jack_engine_takeover_timebase().

Referenced by jack_engine_takeover_timebase().

## jack_get_buffer_size()

jack_nframes_t jack_get_buffer_size | ( | jack_client_t * |  | ) |

Returns
  the current maximum size that will ever be passed to the process_callback. It should only be used before the client has been activated. This size may change, clients that depend on it must register a bufsize_callback so they will be notified if it does.

See also
  jack_set_buffer_size_callback()

References jack_get_buffer_size(), and JACK_OPTIONAL_WEAK_EXPORT.

Referenced by jack_get_buffer_size().

## jack_get_sample_rate()

jack_nframes_t jack_get_sample_rate | ( | jack_client_t * |  | ) |

Returns
  the sample rate of the jack system, as set by the user when jackd was started.

References jack_get_sample_rate(), and JACK_OPTIONAL_WEAK_EXPORT.

Referenced by jack_get_sample_rate().

## jack_set_buffer_size()

int jack_set_buffer_size | ( | jack_client_t * | client,
|  | jack_nframes_t | nframes )

Change the buffer size passed to the process_callback.

This operation stops the JACK engine process cycle, then calls all registered bufsize_callback functions before restarting the process cycle. This will cause a gap in the audio flow, so it should only be done at appropriate stopping points.

See also
  jack_set_buffer_size_callback()

Parameters

  client | pointer to JACK client structure.
  nframes | new buffer size. Must be a power of two.

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

References JACK_OPTIONAL_WEAK_EXPORT, and jack_set_buffer_size().

Referenced by jack_set_buffer_size().

## jack_set_freewheel()

int jack_set_freewheel | ( | jack_client_t * | client,
|  | int | onoff )

Start/Stop JACK's "freewheel" mode.

When in "freewheel" mode, JACK no longer waits for any external event to begin the start of the next process cycle.

As a result, freewheel mode causes "faster than realtime" execution of a JACK graph. If possessed, real-time scheduling is dropped when entering freewheel mode, and if appropriate it is reacquired when stopping.

IMPORTANT: on systems using capabilities to provide real-time scheduling (i.e. Linux kernel 2.4), if onoff is zero, this function must be called from the thread that originally called jack_activate(). This restriction does not apply to other systems (e.g. Linux kernel 2.6 or OS X).

Parameters

  client | pointer to JACK client structure
  onoff | if non-zero, freewheel mode starts. Otherwise freewheel mode ends.

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

References JACK_OPTIONAL_WEAK_EXPORT, and jack_set_freewheel().

Referenced by jack_set_freewheel().