Implement basic measurement logic

1 files changed, 111 insertions, 24 deletions

diff --git a/dbmeasure.c b/dbmeasure.c
index c6d2c1d..f9140c8 100644
--- a/dbmeasure.c
+++ b/dbmeasure.c
@@ -30,10 +30,12 @@ static snd_pcm_t *open_device(const char *name, snd_pcm_stream_t stream, unsigne
         snd_pcm_t *d;
         int r;
         snd_pcm_hw_params_t *hw;
+        snd_pcm_uframes_t t;
+        snd_output_t *output = NULL;
 
         snd_pcm_hw_params_alloca(&hw);
 
-        if ((r = snd_pcm_open(&d, name, stream, 0)) < 0) {
+        if ((r = snd_pcm_open(&d, name, stream, SND_PCM_NONBLOCK)) < 0) {
                 fprintf(stderr, "Cannot open audio device %s: %s\n", name, snd_strerror(r));
                 goto finish;
         }
@@ -44,36 +46,58 @@ static snd_pcm_t *open_device(const char *name, snd_pcm_stream_t stream, unsigne
         }
 
         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));
+                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));
+                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));
+                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));
+        if ((r = snd_pcm_hw_params_set_channels(d, hw, 1)) < 0) {
+                fprintf(stderr, "Cannot set channel count: %s\n", snd_strerror(r));
+                goto finish;
+        }
+
+        t = rate;
+        if ((r = snd_pcm_hw_params_set_buffer_size_near(d, hw, &t)) < 0) {
+                fprintf(stderr, "Cannot set buffer size: %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));
+                fprintf(stderr, "Cannot set parameters: %s\n", snd_strerror(r));
+                goto finish;
+        }
+
+        if ((r = snd_output_stdio_attach(&output, stderr, 0)) < 0) {
+                fprintf(stderr, "Cannot attach to stderr: %s\n", snd_strerror(r));
+                goto finish;
+        }
+
+        if ((r = snd_pcm_dump(d, output)) < 0) {
+                fprintf(stderr, "Cannot dump status: %s\n", snd_strerror(r));
                 goto finish;
         }
 
+        snd_output_close(output);
+
         return d;
 
 finish:
         if (d)
                 snd_pcm_close(d);
 
+        if (output)
+                snd_output_close(output);
+
+
         return NULL;
 }
 
@@ -93,13 +117,15 @@ static double compute_level(const float *buffer, float *sum, unsigned n_samples,
 
 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;
+        unsigned rindex = 0, windex = 0;
         double frequency = 440.0, amplitude = 0.5;
-        unsigned iteration;
+        unsigned iteration = 0;
+        int icount, ocount;
+        struct pollfd *pollfd;
+        int e;
 
         if (argc < 2) {
                 fprintf(stderr, "Need to specify device.\n");
@@ -132,30 +158,91 @@ int main(int argc, char *argv[]) {
                 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));
+        if ((icount = snd_pcm_poll_descriptors_count(input)) <= 0 ||
+            (ocount = snd_pcm_poll_descriptors_count(output)) <= 0) {
+                fprintf(stderr, "Failed to determine number of pollfd descriptors.\n");
+                goto finish;
+        }
+
+        if (!(pollfd = calloc(icount + ocount, sizeof(struct pollfd)))) {
+                fprintf(stderr, "Failed to allocate pollfd array.\n");
+                goto finish;
+        }
+
+        if ((e = snd_pcm_prepare(input)) < 0 ||
+            (e = snd_pcm_prepare(output)) < 0) {
+                fprintf(stderr, "snd_pcm_prepare() failed: %s\n", snd_strerror(e));
+                goto finish;
+        }
+
+        if ((e = snd_pcm_start(input)) < 0) {
+                fprintf(stderr, "snd_pcm_start() failed: %s\n", snd_strerror(e));
+                goto finish;
+        }
+
+        for (;;) {
+                snd_pcm_sframes_t n;
+                unsigned short irevents, orevents;
+
+                if (snd_pcm_poll_descriptors(input, pollfd, icount) != icount ||
+                    snd_pcm_poll_descriptors(output, pollfd+icount, ocount) != ocount) {
+                        fprintf(stderr, "ALSA changed its mind about number of file descriptors.");
                         goto finish;
                 }
 
-                skip_input += n;
-                if (skip_input == rate)
-                        skip_input = 0;
+                if (poll(pollfd, icount+ocount, -1) < 0) {
+                        fprintf(stderr, "poll() failed: %s\n", strerror(errno));
+                        goto finish;
+                }
 
-                if ((n = snd_pcm_readi(output, buffer + skip_output, rate - skip_output)) < 0) {
-                        fprintf(stderr, "Cannot read samples: %s\n", snd_strerror(n));
+                if ((e = snd_pcm_poll_descriptors_revents(input, pollfd, icount, &irevents)) < 0 ||
+                    (e = snd_pcm_poll_descriptors_revents(output, pollfd+icount, ocount, &orevents)) < 0) {
+                        fprintf(stderr, "Cannot get revents: %s\n", snd_strerror(e));
                         goto finish;
                 }
 
-                skip_output += n;
-                if (skip_output == rate) {
-                        double level;
+                if (orevents) {
+                        if ((n = snd_pcm_writei(output, signal + windex, rate - windex)) < 0) {
+
+                                if (snd_pcm_recover(output, n, 0) < 0) {
+                                        fprintf(stderr, "Cannot write samples: %s\n", snd_strerror(n));
+                                        goto finish;
+                                } else
+                                        continue;
+                        }
+
+                        windex += n;
+                        if (windex == rate)
+                                windex = 0;
+                }
+
+
+                if (irevents)  {
+                        if ((n = snd_pcm_readi(input, buffer + rindex, rate - rindex)) < 0) {
+
+                                if (snd_pcm_recover(input, n, 0) < 0) {
+                                        fprintf(stderr, "Cannot read samples: %s\n", snd_strerror(n));
+                                        goto finish;
+                                }
+
+                                if ((e = snd_pcm_start(input)) < 0) {
+                                        fprintf(stderr, "snd_pcm_start() failed: %s\n", snd_strerror(e));
+                                        goto finish;
+                                }
+
+                                continue;
+                        }
 
-                        skip_output = 0;
+                        rindex += n;
+                        if (rindex == rate) {
+                                double level;
 
-                        level = compute_level(buffer, sum, rate, iteration);
+                                rindex = 0;
 
-                        fprintf(stderr, "Iteration %u, level is %g.\n", iteration, level);
+                                iteration++;
+                                level = compute_level(buffer, sum, rate, iteration);
+                                fprintf(stderr, "Iteration %u, level is %g.\n", iteration, level);
+                        }
                 }
         }