Hello all, I'm struggling a bit with getting libao to work in C on Debian (Squeeze, kernel 2.6.38.5, driver is Alsa). I've got this slightly modified test script and it seems to work fine on my internal soundcard (it opens the device and plays a test tone). However, when trying to do the same trick on an external USB-dac (tried two different models), it gives an "Input/output error". I've tried different settings, but as far as I can see there is not really that much to set (especially if it plays on one soundcard but not the other, dev=hw:1 should suffice). Does anyone have a suggestion on how to get this to work? Kind regards, Maarte /* * * ao_example.c * * Written by Stan Seibert - July 2001 * * Legal Terms: * * This source file is released into the public domain. It is * distributed without any warranty; without even the implied * warranty * of merchantability or fitness for a particular * purpose. * * Function: * * This program opens the default driver and plays a 440 Hz tone for * one second. * * Compilation command line (for Linux systems): * * gcc -lao -ldl -lm -o ao_example ao_example.c * */ #include <stdio.h> #include <ao/ao.h> #include <math.h> #include <string.h> #include <errno.h> #define BUF_SIZE 4096 int main(int argc, char *argv[]) { ao_device *device; ao_sample_format format; ao_option option; int default_driver; char *buffer; int buf_size; int sample; float freq = 440.0; int i; char *option_key = "dev"; char *option_value = "hw:0"; option.key = option_key; option.value = option_value; option.next = NULL; if (argc >= 1) option.value = argv[1]; /* -- Initialize -- */ fprintf(stderr, "libao example program\n"); ao_initialize(); /* -- Setup for default driver -- */ default_driver = ao_default_driver_id(); char *format_matrix = "L,R"; format.matrix = format_matrix; format.bits = 16; format.channels = 2; format.rate = 44100; format.byte_format = AO_FMT_LITTLE; /* -- Open driver -- */ device = ao_open_live(default_driver, &format, &option); if (device == NULL) { fprintf(stderr, "Error opening device: %s\n", strerror (errno)); return 1; } /* -- Play some stuff -- */ buf_size = format.bits/8 * format.channels * format.rate; buffer = calloc(buf_size, sizeof(char)); for (i = 0; i < format.rate; i++) { sample = (int)(0.75 * 32768.0 * sin(2 * M_PI * freq * ((float) i/format.rate))); /* Put the same stuff in left and right channel */ buffer[4*i] = buffer[4*i+2] = sample & 0xff; buffer[4*i+1] = buffer[4*i+3] = (sample >> 8) & 0xff; } ao_play(device, buffer, buf_size); /* -- Close and shutdown -- */ ao_close(device); ao_shutdown(); return (0); }