initial commit

2 files changed, 180 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..d0fba61
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+dbmeasure
+*.o
diff --git a/dbmeasure.c b/dbmeasure.c
new file mode 100644
index 0000000..c6d2c1d
--- /dev/null
+++ b/dbmeasure.c
@@ -0,0 +1,178 @@
+/*-*- 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;
+}