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/* beepALSA.c -- Neale Pickett 8/2007 */
/* A lot of code taken from the beepOSS.c, which said: */
/* * A lot of code taken from the beepSun.c */
/*
Implementation of beep for ALSA.
*/
#include <alsa/asoundlib.h>
#include <math.h>
static char *device = "default";
#include "beep.h"
#define RATE (44100) /* 44.1K samples = 1 second (CD quality) */
#define RAMP (RATE * 5 / 1000) /* 5 millisecond ramp */
#define MAXTIME (2 * RATE) /* 2 seconds max tone time */
static int err;
static snd_pcm_t *handle;
static snd_pcm_sframes_t frames;
static int channels = 1; /* 1=mono, 2=stereo */
static float silence[2*MAXTIME];
static float soundbuf[2*(MAXTIME - RAMP)];
static float ramp_down[2*RAMP];
int BeepInit (void)
{
int i;
/*
* Initialize the sound of silence
*/
for (i = 0; i < 2*MAXTIME; i++) {
silence[i] = 0;
}
/*
* Set up ALSA
*/
if ((err = snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
printf("Playback open error: %s\n", snd_strerror(err));
return 1; /* Not OK */
}
if ((err = snd_pcm_set_params(handle,
SND_PCM_FORMAT_FLOAT,
SND_PCM_ACCESS_RW_INTERLEAVED,
channels,
RATE,
1,
500000)) < 0) { /* 0.5sec */
printf("Playback open error: %s\n", snd_strerror(err));
return 1; /* Not OK */
}
BeepWait();
return 0; /* OK */
}
int Beep (int time, int volume, int pitch)
{
static int last_pitch = -1, last_n = -1, last_volume = -1;
int i, n, first_len, down_len, cycle;
double dt;
/*
* Finagle the number of samples
*/
n = (time / 1000.) * RATE; /* Number samples in tone time */
n = n < MAXTIME ? n : MAXTIME; /* clip to buffer size */
n = n < 2 * RAMP ? 2 * RAMP : n; /* leave room for ramps */
/*
* Catch stupidity
*/
if (pitch <= 0) {
volume = 0;
}
if (volume <= 0) {
snd_pcm_writei(handle, silence, channels*n);
} else {
/*
* clip to Nyquist
* (Of course this means that if you ask for too high a frequency you
* just get silence, since you sample all the zero-crossings of the
* sine wave.)
*/
pitch = pitch < RATE / 2 ? pitch : RATE / 2;
cycle = ((RATE + 1.e-6) / pitch); /* samples per cycle */
if (cycle > MAXTIME / 2) {
cycle = MAXTIME / 2;
}
/* round down length of (rampup + mesa top) to integral cycle */
first_len = ((n - RAMP) / cycle) * cycle;
if (first_len < cycle) {
first_len = cycle;
}
if (first_len > MAXTIME - RAMP) {
first_len = MAXTIME - RAMP;
}
/* round down length of (rampdown) to integral cycle */
down_len = ((RAMP) / cycle) * cycle;
if (down_len < cycle) {
down_len = cycle;
}
if (down_len > RAMP) {
down_len = RAMP;
}
/*
* Can we just reuse what we had before?
*/
if (pitch != last_pitch || n > last_n || volume != last_volume) {
last_pitch = pitch;
last_n = n;
last_volume = volume;
dt = 2. * M_PI / cycle; /* sine scale factor */
/* Ramp up; begin with silence */
for (i = 0; i < RAMP; i++) {
soundbuf[i*channels] = ((float)i / RAMP) * (volume/100.0) * sin(i * dt);
if (channels == 2)
soundbuf[i*channels+1] = soundbuf[i*channels];
}
/* Mesa top */
for (i = RAMP; i < first_len; i++) {
soundbuf[i*channels] = (volume/100.0) * sin(i * dt);
if (channels == 2) {
soundbuf[i*channels+1] = soundbuf[i*channels];
}
}
/* Ramp down; end with silence */
for (i = 0; i < down_len; i++) {
ramp_down[i*channels] = (1. - ((float)i / RAMP)) * (volume/100.0) * sin(i * dt);
if (channels == 2) {
ramp_down[i*channels+1] = ramp_down[i*channels];
}
}
}
snd_pcm_writei(handle, soundbuf, channels*first_len);
snd_pcm_writei(handle, ramp_down, channels*down_len);
}
return 0;
}
int BeepWait (void)
{
return 0;
}
int BeepCleanup (void)
{
return 0;
}
int BeepResume (void)
{
return 0;
}
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