jack1/example-clients/simple_client.c

#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>

#include <jack/jack.h>

jack_port_t *input_port;
jack_port_t *output_port;

int
process (jack_nframes_t nframes, void *arg)

{
	jack_default_audio_sample_t *out = (jack_default_audio_sample_t *) jack_port_get_buffer (output_port, nframes);
	jack_default_audio_sample_t *in = (jack_default_audio_sample_t *) jack_port_get_buffer (input_port, nframes);

	memcpy (out, in, sizeof (jack_default_audio_sample_t) * nframes);
	
	return 0;      
}

int
srate (jack_nframes_t nframes, void *arg)

{
	printf ("the sample rate is now %lu/sec\n", nframes);
	return 0;
}

void
error (const char *desc)
{
	fprintf (stderr, "JACK error: %s\n", desc);
}

void
jack_shutdown (void *arg)
{
	exit (1);
}

int
main (int argc, char *argv[])
{
	jack_client_t *client;
	const char **ports;

	if (argc < 2) {
		fprintf (stderr, "usage: jack_simple_client <name>\n");
		return 1;
	}

	/* tell the JACK server to call error() whenever it
	   experiences an error.  Notice that this callback is
	   global to this process, not specific to each client.
	
	   This is set here so that it can catch errors in the
	   connection process
	*/
	jack_set_error_function (error);

	/* try to become a client of the JACK server */

	if ((client = jack_client_new (argv[1])) == 0) {
		fprintf (stderr, "jack server not running?\n");
		return 1;
	}

	/* tell the JACK server to call `process()' whenever
	   there is work to be done.
	*/

	jack_set_process_callback (client, process, 0);

	/* tell the JACK server to call `srate()' whenever
	   the sample rate of the system changes.
	*/


	jack_set_sample_rate_callback (client, srate, 0);

	/* tell the JACK server to call `jack_shutdown()' if
	   it ever shuts down, either entirely, or if it
	   just decides to stop calling us.
	*/

	jack_on_shutdown (client, jack_shutdown, 0);

	/* display the current sample rate. once the client is activated 
	   (see below), you should rely on your own sample rate
	   callback (see above) for this value.
	*/

	printf ("engine sample rate: %lu\n", jack_get_sample_rate (client));

	/* create two ports */

	input_port = jack_port_register (client, "input", JACK_DEFAULT_AUDIO_TYPE, JackPortIsInput, 0);
	output_port = jack_port_register (client, "output", JACK_DEFAULT_AUDIO_TYPE, JackPortIsOutput, 0);

	/* tell the JACK server that we are ready to roll */

	if (jack_activate (client)) {
		fprintf (stderr, "cannot activate client");
		return 1;
	}

	/* connect the ports. Note: you can't do this before
	   the client is activated, because we can't allow
	   connections to be made to clients that aren't
	   running.
	*/


	if ((ports = jack_get_ports (client, NULL, NULL, JackPortIsPhysical|JackPortIsOutput)) == NULL) {
		fprintf(stderr, "Cannot find any physical capture ports\n");
		exit(1);
	}

	if (jack_connect (client, ports[0], jack_port_name (input_port))) {
		fprintf (stderr, "cannot connect input ports\n");
	}

	free (ports);
	
	if ((ports = jack_get_ports (client, NULL, NULL, JackPortIsPhysical|JackPortIsInput)) == NULL) {
		fprintf(stderr, "Cannot find any physical playback ports\n");
		exit(1);
	}

	if (jack_connect (client, jack_port_name (output_port), ports[0])) {
		fprintf (stderr, "cannot connect output ports\n");
	}

	free (ports);

	/* Since this is just a toy, run for a few seconds, then finish */

	sleep (10);
	jack_client_close (client);
	exit (0);
}