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/*-*- Mode: C; c-file-style: "linux"; indent-tabs-mode: nil; c-basic-offset: 8 -*-*/
#include <math.h>
#include <stdlib.h>
#include <asoundlib.h>
static float *generate_signal(unsigned n_samples, double amplitude, double frequency) {
float *r;
unsigned i;
if (!(r = malloc(n_samples * sizeof(float))))
return NULL;
for (i = 0; i < n_samples; i++)
r[i] = amplitude * sin(((double) i*frequency*M_PI*2)/(double) n_samples);
return r;
}
static float *generate_silence(unsigned n_samples) {
float *r;
if (!(r = calloc(n_samples, sizeof(float))))
return NULL;
return r;
}
static snd_pcm_t *open_device(const char *name, snd_pcm_stream_t stream, unsigned rate) {
snd_pcm_t *d;
int r;
snd_pcm_hw_params_t *hw;
snd_pcm_hw_params_alloca(&hw);
if ((r = snd_pcm_open(&d, name, stream, 0)) < 0) {
fprintf(stderr, "Cannot open audio device %s: %s\n", name, snd_strerror(r));
goto finish;
}
if ((r = snd_pcm_hw_params_any(d, hw)) < 0) {
fprintf(stderr, "Cannot initialize hardware parameters: %s\n", snd_strerror(r));
goto finish;
}
if ((r = snd_pcm_hw_params_set_access(d, hw, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
fprintf(stderr, "Cannot set access type (%s)\n", snd_strerror(r));
goto finish;
}
if ((r = snd_pcm_hw_params_set_format(d, hw, SND_PCM_FORMAT_FLOAT_LE)) < 0) {
fprintf(stderr, "cannot set sample format (%s)\n", snd_strerror(r));
goto finish;
}
if ((r = snd_pcm_hw_params_set_rate(d, hw, rate, 0)) < 0) {
fprintf(stderr, "cannot set sample rate (%s)\n", snd_strerror(r));
goto finish;
}
if ((r = snd_pcm_hw_params_set_channels(d, hw, 2)) < 0) {
fprintf(stderr, "cannot set channel count (%s)\n", snd_strerror(r));
goto finish;
}
if ((r = snd_pcm_hw_params(d, hw)) < 0) {
fprintf(stderr, "cannot set parameters (%s)\n", snd_strerror(r));
goto finish;
}
return d;
finish:
if (d)
snd_pcm_close(d);
return NULL;
}
static double compute_level(const float *buffer, float *sum, unsigned n_samples, unsigned iteration) {
unsigned i;
double max = 0.0;
for (i = 0; i < n_samples; i++) {
sum[i] += buffer[i];
if (sum[i] > max)
max = sum[i];
}
return max / (double) iteration;
}
int main(int argc, char *argv[]) {
int ret = 1;
snd_pcm_sframes_t n;
float *signal = NULL, *silence = NULL, *buffer = NULL, *sum = NULL;
snd_pcm_t *input = NULL, *output = NULL;
unsigned rate = 44100;
unsigned skip_input = 0, skip_output = 0;
double frequency = 440.0, amplitude = 0.5;
unsigned iteration;
if (argc < 2) {
fprintf(stderr, "Need to specify device.\n");
goto finish;
}
if (!(output = open_device(argv[1], SND_PCM_STREAM_PLAYBACK, rate)))
goto finish;
if (!(input = open_device(argv[1], SND_PCM_STREAM_CAPTURE, rate)))
goto finish;
if (!(silence = generate_silence(rate))) {
fprintf(stderr, "Failed to generate silence.\n");
goto finish;
}
if (!(signal = generate_signal(rate, amplitude, frequency))) {
fprintf(stderr, "Failed to generate signal.\n");
goto finish;
}
if (!(buffer = malloc(rate * sizeof(float)))) {
fprintf(stderr, "Failed to allocate buffer.\n");
goto finish;
}
if (!(sum = calloc(rate, sizeof(float)))) {
fprintf(stderr, "Failed to allocate sum buffer.\n");
goto finish;
}
for (iteration = 1;; iteration ++) {
if ((n = snd_pcm_writei(output, silence + skip_input, rate - skip_input)) < 0) {
fprintf(stderr, "Cannot write samples: %s\n", snd_strerror(n));
goto finish;
}
skip_input += n;
if (skip_input == rate)
skip_input = 0;
if ((n = snd_pcm_readi(output, buffer + skip_output, rate - skip_output)) < 0) {
fprintf(stderr, "Cannot read samples: %s\n", snd_strerror(n));
goto finish;
}
skip_output += n;
if (skip_output == rate) {
double level;
skip_output = 0;
level = compute_level(buffer, sum, rate, iteration);
fprintf(stderr, "Iteration %u, level is %g.\n", iteration, level);
}
}
ret = 0;
finish:
if (input)
snd_pcm_close(input);
if (output)
snd_pcm_close(output);
free(signal);
free(silence);
free(buffer);
free(sum);
return ret;
}
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