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/* See LICENSE file for copyright and license details. */
#include "common.h"
#include <alsa/asoundlib.h>
#include <math.h>
/* TODO add support for 12, 14, 18 and 20, 22 kHz in addition to 16 kHz as well as custom frequencies */
/* TODO add support for selecting output device and backend */
/* TODO add support for selecting volume */
/* TODO add support for pausing and exiting */
/* TODO prefer loudspeakers over headphones */
/* TODO use bus to listen for incoming phone calls and pause when arriving */
#define UTYPE uint32_t
#define SMAX INT32_MAX
#define FORMAT SND_PCM_FORMAT_U32
#define SAMPLE_RATE 52000 /* Hz */
#define LATENCY 100000 /* µs */
USAGE("");
int
main(int argc, char *argv[])
{
UTYPE *buffer;
snd_pcm_uframes_t i, buflen, wavelen;
snd_pcm_sframes_t n;
snd_pcm_t *sound_handle = NULL;
double freq = 16000;
double volume = (double)0.1f, imul, omul;
int r;
NOFLAGS(argc);
/* Set up audio */
r = snd_pcm_open(&sound_handle, "default", SND_PCM_STREAM_PLAYBACK, 0);
if (r < 0)
eprintf("snd_pcm_open: %s\n", snd_strerror(r));
if (!sound_handle)
eprintf("snd_pcm_open:");
/* Configure audio */
r = snd_pcm_set_params(sound_handle, FORMAT, SND_PCM_ACCESS_RW_INTERLEAVED, 1 /* channels */,
SAMPLE_RATE, 1 /* allow resampling? */, LATENCY);
if (r < 0)
eprintf("snd_pcm_set_params: %s\n", snd_strerror(r));
/* Generate tone */
buflen = wavelen = (snd_pcm_uframes_t)((double)SAMPLE_RATE / freq);
if ((snd_pcm_uframes_t)freq > 1)
buflen *= (snd_pcm_uframes_t)freq;
buffer = emallocn((size_t)buflen, sizeof(*buffer), 0);
omul = volume * SMAX * 2;
#ifdef __GNUC__
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wunsuffixed-float-constants"
#endif
imul = 2 * M_PI * freq / (double)SAMPLE_RATE;
#ifdef __GNUC__
# pragma GCC diagnostic pop
#endif
for (i = 0; i < wavelen; i++)
buffer[i] = (UTYPE)(sin(imul * (double)i) * omul + SMAX);
for (i = wavelen; i < buflen; i += wavelen)
memcpy(&buffer[i], &buffer[0], wavelen * sizeof(UTYPE));
/* Play tone */
for (;;) {
n = snd_pcm_writei(sound_handle, buffer, buflen);
if (n < 0)
n = snd_pcm_recover(sound_handle, (int)n, 0 /* do not print error reason? */);
if (n < 0)
eprintf("snd_pcm_writei: %s\n", snd_strerror((int)n));
if (n > 0 && (snd_pcm_uframes_t)n < buflen)
eprintf("short write from snd_pcm_writei\n");
}
snd_pcm_close(sound_handle);
return 0;
}
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