title: Sound Recording & Play on Raspberry Pi Using ALSA in C
body: <p>I am trying to record sound and play it in a C program.
  just like using those terminal lines:</p>
  
  <pre><code>arecord -D plughw:0 -r 16000 sample.wav
  </code></pre>
  
  <p>for record, and later on</p>
  
  <pre><code>aplay sample.wav
  </code></pre>
  
  <p>to play the sound.</p>
  
  <p>I used this code:</p>
  
  <pre><code>/*
  
  
  This example reads from the default PCM device
  and writes to standard output for 5 seconds of data.
  
  
  */
  
  
  /* Use the newer ALSA API */
  #define ALSA_PCM_NEW_HW_PARAMS_API
  
  
  #include &lt;alsa/asoundlib.h&gt;
  
  
  int main() {
    long loops;
    int rc;
    int size;
    snd_pcm_t *handle;
    snd_pcm_hw_params_t *params;
    unsigned int val;
    int dir;
    snd_pcm_uframes_t frames;
    char *buffer;
  
  
    /* Open PCM device for recording (capture). */
    rc = snd_pcm_open(&amp;handle, "default",
                      SND_PCM_STREAM_CAPTURE, 0);
    if (rc &lt; 0) {
      fprintf(stderr,
              "unable to open pcm device: %s\n",
              snd_strerror(rc));
      exit(1);
    }
  
  
    /* Allocate a hardware parameters object. */
    snd_pcm_hw_params_alloca(&amp;params);
  
  
    /* Fill it in with default values. */
    snd_pcm_hw_params_any(handle, params);
  
  
    /* Set the desired hardware parameters. */
  
  
    /* Interleaved mode */
    snd_pcm_hw_params_set_access(handle, params,
                        SND_PCM_ACCESS_RW_INTERLEAVED);
  
  
    /* Signed 16-bit little-endian format */
    snd_pcm_hw_params_set_format(handle, params,
                                SND_PCM_FORMAT_S16_LE);                                 
  
  
    /* Two channels (stereo) */
    snd_pcm_hw_params_set_channels(handle, params, 2);                                 
  
  
    /* 44100 bits/second sampling rate (CD quality) */
    val = 44100;                                                     
    snd_pcm_hw_params_set_rate_near(handle, params,
                                    &amp;val, &amp;dir);
  
  
    /* Set period size to 32 frames. */
    frames = 32;
    snd_pcm_hw_params_set_period_size_near(handle,
                                params, &amp;frames, &amp;dir);
  
  
    /* Write the parameters to the driver */
    rc = snd_pcm_hw_params(handle, params);
    if (rc &lt; 0) {
      fprintf(stderr,
              "unable to set hw parameters: %s\n",
              snd_strerror(rc));
      exit(1);
    }
  
  
    /* Use a buffer large enough to hold one period */
    snd_pcm_hw_params_get_period_size(params,
                                        &amp;frames, &amp;dir);
    size = frames * 4; /* 2 bytes/sample, 2 channels */
    buffer = (char *) malloc(size);
  
  
    /* We want to loop for 5 seconds */
    snd_pcm_hw_params_get_period_time(params,
                                           &amp;val, &amp;dir);
    loops = 5000000 / val;
  
  
    while (loops &gt; 0) {
      loops--;
      rc = snd_pcm_readi(handle, buffer, frames);
      if (rc == -EPIPE) {
        /* EPIPE means overrun */
        fprintf(stderr, "overrun occurred\n");
        snd_pcm_prepare(handle);
      } else if (rc &lt; 0) {
        fprintf(stderr,
                "error from read: %s\n",
                snd_strerror(rc));
      } else if (rc != (int)frames) {
        fprintf(stderr, "short read, read %d frames\n", rc);
      }
      rc = write(1, buffer, size);
      if (rc != size)
        fprintf(stderr,
                "short write: wrote %d bytes\n", rc);
    }
  
  
    snd_pcm_drain(handle);
    snd_pcm_close(handle);
    free(buffer);
  
  
    return 0;
  }
  </code></pre>
  
  <p>I compile this file this way:</p>
  
  <pre><code>gcc -o recorder -lasound recorder.c
  </code></pre>
  
  <p>and run it:</p>
  
  <pre><code>./recorder &lt; sample.wav
  </code></pre>
  
  <p>if I try to play this with "aplay sample.wav" it's making a terrible noisy sound.
  but if I use "aplay -t raw -f S16_LE -c2 -r44100 sample.wav"
  it works good.</p>
  
  <p>what I do wrong and if there is an easy way to capture audio and play it on Raspberry Pi?</p>
  
  <p>Thank You for Your time.</p>