git.sesse.net Git - pitch/blob - linux_audio.cpp

   1 #include <stdio.h>
   2 #include <string.h>
   3 #include <stdlib.h>
   4 #include <math.h>
   5 #include <unistd.h>
   6 #include <fcntl.h>
   7 #include <sys/ioctl.h>
   8 #include <linux/soundcard.h>
   9 #include <alsa/asoundlib.h>
  10 #include "linux_audio.h"
  11
  12 snd_pcm_t *get_dsp_handle(int sample_rate)
  13 {
  14         int err;
  15         snd_pcm_t *handle;
  16         snd_pcm_hw_params_t *hw_params;
  17
  18         if ((err = snd_pcm_open(&handle, "plughw:0,0", SND_PCM_STREAM_CAPTURE, 0)) < 0) {
  19                 fprintf(stderr, "cannot open audio device plughw:0,0: %s\n",
  20                         snd_strerror(err));
  21                 exit(1);
  22         }
  23
  24         if ((err = snd_pcm_hw_params_malloc(&hw_params)) < 0) {
  25                 fprintf(stderr, "cannot allocate hardware parameter structure: %s\n",
  26                         snd_strerror(err));
  27                 exit(1);
  28         }
  29
  30         if ((err = snd_pcm_hw_params_any(handle, hw_params)) < 0) {
  31                 fprintf(stderr, "cannot initialize hardware parameter structure: %s\n",
  32                         snd_strerror(err));
  33                 exit(1);
  34         }
  35
  36         if ((err = snd_pcm_hw_params_set_access(handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
  37                 fprintf(stderr, "cannot set access type: %s\n",
  38                         snd_strerror(err));
  39                 exit(1);
  40         }
  41
  42         if ((err = snd_pcm_hw_params_set_format(handle, hw_params, SND_PCM_FORMAT_S16_LE)) < 0) {  // FIXME
  43                 fprintf(stderr, "cannot set sample format: %s\n",
  44                         snd_strerror(err));
  45                 exit(1);
  46         }
  47
  48         if ((err = snd_pcm_hw_params_set_rate(handle, hw_params, sample_rate, 0)) < 0) {
  49                 fprintf(stderr, "cannot set sample rate: %s\n",
  50                         snd_strerror(err));
  51                 exit(1);
  52         }
  53
  54         if ((err = snd_pcm_hw_params_set_channels(handle, hw_params, 1)) < 0) {
  55                 fprintf(stderr, "cannot set channel count: %s\n",
  56                         snd_strerror(err));
  57                 exit(1);
  58         }
  59
  60         if ((err = snd_pcm_hw_params(handle, hw_params)) < 0) {
  61                 fprintf(stderr, "cannot set parameters: %s\n",
  62                         snd_strerror(err));
  63                 exit(1);
  64         }
  65
  66         snd_pcm_hw_params_free(hw_params);
  67
  68         if ((err = snd_pcm_prepare(handle)) < 0) {
  69                 fprintf(stderr, "cannot prepare audio interface for use: %s\n",
  70                         snd_strerror(err));
  71                 exit(1);
  72         }
  73
  74         return handle;
  75 }
  76
  77 #if 1
  78 void read_chunk(snd_pcm_t *handle, short *in, unsigned num_samples)
  79 {
  80         int ret;
  81         int samples_left = num_samples;
  82
  83         while (samples_left > 0) {
  84                 ret = snd_pcm_readi(handle, in, samples_left);
  85                 if (ret == 0) {
  86                         printf("EOF\n");
  87                         exit(0);
  88                 }
  89                 if (ret == -EPIPE) {
  90                         fprintf(stderr, "ALSA underrun\n");
  91                         snd_pcm_prepare(handle);
  92                         continue;
  93                 }
  94                 if (ret < 0) {
  95                         fprintf(stderr, "snd_pcm_readi: %s\n", snd_strerror(ret));
  96                         exit(1);
  97                 }
  98                 in += ret;
  99                 samples_left -= ret;
 100         }
 101 }
 102 #else
 103 // make a pure 440hz sine for testing
 104 void read_chunk(snd_pcm_t *handle, short *in, unsigned num_samples)
 105 {
 106         static double theta = 0.0;
 107         for (unsigned i = 0; i < num_samples; ++i) {
 108                 in[i] = 32768.0 * cos(theta);
 109                 theta += 2.0 * M_PI * 440.0 / double(SAMPLE_RATE);
 110         }
 111 }
 112 #endif
 113
 114 void write_sine(int dsp_fd, double freq, unsigned num_samples, unsigned sample_rate)
 115 {
 116         static double theta = 0.0;
 117         short buf[num_samples];
 118
 119         for (unsigned i = 0; i < num_samples; ++i) {
 120                 buf[i] = short(cos(theta) * 16384.0);
 121                 theta += 2.0 * M_PI * freq / double(sample_rate);
 122         }
 123
 124         write(dsp_fd, buf, num_samples * sizeof(short));
 125 }
 126