Simple alsa API example. Get the min and max number of channels supported by capture audio device and other values.

capture_nb_chan.c

/* 
* file:           capture_nb_chan.c
* description:    Simple alsa API example. Get the min and max number of channels supported by capture audio device and other values.
* doc:            https://www.alsa-project.org/alsa-doc/alsa-lib/index.html
* install asound: apt-get install libasound2
*                 apt-get install libasound2-dev
* compile:        gcc -o capture_nb_chan capture_nb_chan.c -lasound
* execute:        ./capture_nb_chan
* expected output (something similar to) :
*                                         Min channels: 2. (0)
*                                         Max channels: 2. (0)
*										  										...
*/

#include <stdio.h>
#include <alsa/asoundlib.h>

int main(int argc, char* argv[])
{
  int err;
  snd_pcm_t             *capture_handle;
  snd_pcm_hw_params_t   *hw_params;
  unsigned int min, max;

  // Open audio device
  if ((err = snd_pcm_open (&capture_handle, "hw:0,0", SND_PCM_STREAM_CAPTURE, 0)) < 0)
    exit (1);

  // Allocate hardware parameters
  if ((err = snd_pcm_hw_params_malloc (&hw_params)) < 0)
    exit (1);

  // Initialize parameters
  if ((err = snd_pcm_hw_params_any (capture_handle, hw_params)) < 0)
    exit (1);

  // Get min and max number of channels
  err = snd_pcm_hw_params_get_channels_min(hw_params, &min);
  if (err < 0)
    exit (1);
  fprintf(stdout, "Min channels: %u. (%d)\n", min, err);
  err = snd_pcm_hw_params_get_channels_max(hw_params, &max);
  if (err < 0)
    exit (1);
  fprintf(stdout, "Max channels: %u. (%d)\n", max, err);
  
  // Get min and max sample rate
  err = snd_pcm_hw_params_get_rate_min(hw_params, &min, 0);
  if (err < 0)
    exit (1);
  fprintf(stdout, "Min sample rate: %u. (%d)\n", min, err);
  err = snd_pcm_hw_params_get_rate_max(hw_params, &max, 0);
  if (err < 0)
    exit (1);
  fprintf(stdout, "Max sample rate: %u. (%d)\n", max, err);
}