A skeleton program to get data from Jack Audio Connection Kit

/***************************************************************************

* jack-skeleton
* 
* This program is a skeleton program to use to get data from a Jack 
* source to process.
*
* Written:
*  May 2013
*  by Rob Frohne
*  e-mail: Rob "dot" Frohne "at sign" wallawalla "dot" edu
* 
****************************************************************************/

/* To build this program, you must have jack audio connection kit installed.

* At the command prompt:
* $ gcc jack-skeleton.c -ljack -o jack-skeleton
*/

/*

*  This program is free software; you can redistribute it and/or modify
*  it under the terms of the GNU General Public License as published by
*  the Free Software Foundation; either version 2 of the License, or
*  (at your option) any later version.
*
*  This program is distributed in the hope that it will be useful,
*  but WITHOUT ANY WARRANTY; without even the implied warranty of
*  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*  GNU General Public License for more details.
*
*  You should have received a copy of the GNU General Public License
*  along with this program; if not, write to the Free Software
*  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/

1. include <jack/jack.h>
2. include <stdio.h>
3. include <unistd.h>
4. include <sys/types.h>
5. include <sys/stat.h>
6. include <math.h>
7. include <errno.h>
8. include <fcntl.h>
9. include <stdlib.h>
10. include <getopt.h>
11. include <string.h>

/* global jack variables. */ jack_client_t *test_client; jack_port_t *audio_input_port_left, *audio_input_port_right;

/* To use this command, you need to $ jack-skeleton

* assuming those are the options you want.
* Options are:
* -? for help
* -v or --verbose for verbose response.
*/

/* Flag set by ‘--verbose’. */ static int verbose_flag; // Specify options and their syntax static struct option long_options[] = { /* These options set a flag. */ {"verbose", no_argument, &verbose_flag, 1}, {"brief", no_argument, &verbose_flag, 0}, /* These options don't set a flag. We distinguish them by their indices. */ {"help", no_argument, 0, '?'}, {0, 0, 0, 0} };

/* Close things opened. */ void cleanup(void) { if(test_client != NULL) { jack_deactivate(test_client); jack_client_close(test_client); } }

/* This is the function that is called when and if jackd shuts down. */ void jack_shutdown (void *arg) { fprintf (stderr, "JACK shutdown\n"); cleanup(); abort(); }

/* This is the callback process that gets data from jack.*/ int process(jack_nframes_t number_of_frames, void *arg) { //Use static variables if you want to save things between calls to // this process. jack_default_audio_sample_t *sample_buffer_left = (jack_default_audio_sample_t *) jack_port_get_buffer(audio_input_port_left, number_of_frames);

jack_default_audio_sample_t *sample_buffer_right = (jack_default_audio_sample_t *) jack_port_get_buffer(audio_input_port_right, number_of_frames);

jack_nframes_t i; //This is where you get your data in the format that the program using /dev/dsp needs it. for(i = 0; i < number_of_frames; i++){ // This is where you process your data. } return 0; }

int main (int argc, char *argv[]){

int error;

char * fifo_name = PIPE_NAME;

// Iterate over options and handle each one as appropriate int c; // The function getopt_long stores the option index here. int option_index = 0;

while ( (c = getopt_long ( argc, argv, "v?f:", long_options, &option_index )) != -1 ) { switch ( c ) { case 0: // If this option set a flag, do nothing else now. if ( long_options[option_index].flag != 0 ) break;

case 'v': verbose_flag = 1; break;

case '?':

default : printf( "Options are: \n" "-v or --verbose for verbose output\n" "Typing EOF (ctrl-D) (ctrl-capitol D, to be exact) will end the program.\n"); exit ( 0 ); } } //Create a new jack client, then make sure everything went ok. test_client = jack_client_open("Test Client",(jack_options_t)(!JackServerName),NULL); if (test_client == 0) {

   	fprintf(stderr,"Cannot connect to the jackd as a client.\n");
   	cleanup();
   	return 1;
 	}
 	  	/* Set up Jack */
 	//Set up the jack shutdown routine in case we want to do something special on shutdown of jack.
 	jack_on_shutdown (test_client, jack_shutdown, 0);

//Create and register new audio input ports. audio_input_port_left = jack_port_register(test_client, "Audio FIFO Port_left", JACK_DEFAULT_AUDIO_TYPE, JackPortIsInput, 0); if (audio_input_port_left == NULL) { fprintf(stderr, "Error: jack_port_register returned NULL for left channel.\n"); cleanup(); return 1; }

audio_input_port_right = jack_port_register(test_client, "Audio FIFO Port_right", JACK_DEFAULT_AUDIO_TYPE, JackPortIsInput, 0); if (audio_input_port_right == NULL) { fprintf(stderr, "Error: jack_port_register returned NULL for right channel.\n"); cleanup(); return 1; }

//Tell the jackd server what function call when it wants more audio data. if((error = jack_set_process_callback(test_client, process, &pipe_handle)) != 0) { fprintf(stderr, "Jack could not set the callback, (error %i).\n", error); cleanup(); return 1; }

//Tell jack it's ok to start asking us for audio data. if((error = jack_activate(test_client)) != 0) { fprintf(stderr, "Jack could not activate the client (error %i).\n", error); cleanup(); return 1; } else if(verbose_flag) fprintf(stderr,"Activated client.\n");

//Connect the ports. if (jack_connect (test_client,"system:capture_1", jack_port_name (audio_input_port_left))) {

       fprintf (stderr, "cannot connect port: system:capture_1\n");
   }
   else if(verbose_flag) fprintf(stderr, "Connected to port: system:capture_1\n");

if (jack_connect (test_client,"system:capture_2", jack_port_name (audio_input_port_right))) {

       fprintf (stderr, "cannot connect port: system:capture_2\n");
   }
   else if(verbose_flag) fprintf(stderr, "Connected to port: system:capture_2\n");

while(getchar() != EOF){ //Quit on ctrl-D. }

/* Close things opened. */ cleanup();

return 0; }