c-ai-conversation/audio.c

#include "audio.h"

static void print_pcm_state(snd_pcm_t *pcm_handle) {
  snd_pcm_state_t state = snd_pcm_state(pcm_handle);
  const char *state_name = snd_pcm_state_name(state);
  printf("State of pcm handle: %s\n", state_name);
}

int audio_play(char *buf, size_t byte_count) {
  printf("going to play audio of %d bytes of data\n", (int)byte_count);

  snd_pcm_t *pcm_handle;
  // The total frames in the buffer is how many bytes divided by 2 because
  // of linear16 encoding, one channel
  size_t total_frames = byte_count / 2;

  int err;
  err = snd_pcm_open(&pcm_handle, ALSA_SPEAKER_HARDWARE_DEVICE,
                     SND_PCM_STREAM_PLAYBACK, 0);
  if (err < 0) {
    fprintf(stderr, "unable to open playback device");
    return err;
  }
  print_pcm_state(pcm_handle);

  const char *name = snd_pcm_name(pcm_handle);
  printf("found this device: %s\n", name);

  snd_pcm_info_t *pcm_info;
  snd_pcm_info_malloc(&pcm_info);
  err = snd_pcm_info(pcm_handle, pcm_info);
  if (err < 0) {
    snd_pcm_close(pcm_handle);
    printf("unable to get info of pcm device");
    return -1;
  }
  name = snd_pcm_info_get_name(pcm_info);
  if (err < 0) {
    printf("unable to get card info");
    snd_pcm_close(pcm_handle);
    snd_pcm_info_free(pcm_info);
    return -1;
  }
  printf("got pcm name: %s \n", name);

  print_pcm_state(pcm_handle);
  snd_pcm_info_free(pcm_info);
  if ((err = snd_pcm_set_params(pcm_handle, SND_PCM_FORMAT_S16_LE,
                                SND_PCM_ACCESS_RW_INTERLEAVED, 1, 48000, 1,
                                500000)) < 0) { /* 0.5sec */
    printf("Playback open error: %s\n", snd_strerror(err));
    exit(EXIT_FAILURE);
  }

  // we want to read in a chunk of data and writei to the pcm
  size_t frames_written = 0;
  size_t frames_in_each_chunk = 1024; // how many frames to read per chunk (2048
                                      // bytes since each frame is 2 bytes)
  while (frames_written < total_frames) {
    size_t frames_to_write =
        frames_in_each_chunk < (total_frames - frames_written)
            ? frames_in_each_chunk
            : (total_frames - frames_written);
    // We move the pointer x2 because each frame is 2 bytes so the next audio
    // sample is 16 bits forward, not 8
    char *start_ptr = buf + (frames_written * 2);
    snd_pcm_sframes_t result =
        snd_pcm_writei(pcm_handle, start_ptr, frames_to_write);
    if (result < 0) {
      result = snd_pcm_recover(pcm_handle, result, 0);
      if (result < 0) {
        printf("snd_pcm_writei failed: %s\n", snd_strerror(result));
        break;
      }
    }

    if (result > 0 && result < frames_to_write) {
      printf("Short write \n");
    }

    frames_written += result;
  }

  /* pass the remaining samples, otherwise they're dropped in close */
  err = snd_pcm_drain(pcm_handle);
  if (err < 0) {
    printf("snd_pcm_drain failed: %s\n", snd_strerror(err));
  }
  snd_pcm_close(pcm_handle);

  return 0;
}

char *audio_capture(uint seconds) {
  char *output_file = "output.pcm";

  snd_pcm_t *pcm_handle = NULL;

  int err;
  err = snd_pcm_open(&pcm_handle, ALSA_MIC_HARDWARE_DEVICE,
                     SND_PCM_STREAM_CAPTURE, 0);
  if (err < 0) {
    printf("unable to open pcm device");
    return NULL;
  }
  print_pcm_state(pcm_handle);

  const char *name = snd_pcm_name(pcm_handle);
  printf("found this device: %s\n", name);

  snd_pcm_info_t *pcm_info;
  snd_pcm_info_malloc(&pcm_info);
  err = snd_pcm_info(pcm_handle, pcm_info);
  if (err < 0) {
    snd_pcm_close(pcm_handle);
    printf("unable to get info of pcm device");
    return NULL;
  }
  name = snd_pcm_info_get_name(pcm_info);
  if (err < 0) {
    printf("unable to get card info");
    snd_pcm_close(pcm_handle);
    snd_pcm_info_free(pcm_info);
    return NULL;
  }
  printf("got pcm name: %s \n", name);

  print_pcm_state(pcm_handle);
  snd_pcm_info_free(pcm_info);

  snd_pcm_hw_params_t *params;
  err = snd_pcm_hw_params_malloc(&params);
  if (err < 0) {
    fprintf(stderr, "unable to mallow hw params");
    return NULL;
  }
  err = snd_pcm_hw_params_any(pcm_handle, params);
  if (err < 0) {
    fprintf(stderr, "unable to find ranges for hw device");
    snd_pcm_close(pcm_handle);
    snd_pcm_hw_params_free(params);
    return NULL;
  }

  uint period_size = 1024;
  uint buffer_size = 4096;
  uint channel_count = 1;
  uint bytes_per_sample = 2; // FORMAT_S16_LE
  uint samples_per_second = 48000;
  snd_pcm_hw_params_set_access(pcm_handle, params,
                               SND_PCM_ACCESS_RW_INTERLEAVED);
  snd_pcm_hw_params_set_channels(pcm_handle, params, channel_count);
  snd_pcm_hw_params_set_buffer_size(pcm_handle, params, buffer_size);
  snd_pcm_hw_params_set_format(pcm_handle, params, SND_PCM_FORMAT_S16_LE);
  snd_pcm_hw_params_set_rate(pcm_handle, params, samples_per_second, 0);
  snd_pcm_hw_params_set_periods(pcm_handle, params, period_size, 0);

  err = snd_pcm_hw_params(pcm_handle, params);
  if (err < 0) {
    fprintf(stderr, "unable to prepare pcm\n");
    snd_pcm_close(pcm_handle);
    snd_pcm_hw_params_free(params);
    return NULL;
  }

  print_pcm_state(pcm_handle);

  err = snd_pcm_start(pcm_handle);
  if (err < 0) {
    fprintf(stderr, "unable to start pcm");
    snd_pcm_close(pcm_handle);
    snd_pcm_hw_params_free(params);
    return NULL;
  }

  print_pcm_state(pcm_handle);

  const uint seconds_to_capture = seconds;
  const uint periods_to_read =
      (samples_per_second * seconds_to_capture) / period_size;
  char *buf = malloc(period_size * channel_count * bytes_per_sample);
  uint periods_read = 0;
  /* Read one period at a time from the hardware buffer
   *  We set the hardware buffer to read 4096 frames.
   *  The period size is 1024 frames.
   *  Each period is 2048 BYTES because each frame is 2 bytes.
   *  Each frame is 2 bytes because of 1 channel, and 16 bit format
   */
  FILE *file = fopen(output_file, "wb");
  if (file == NULL) {
    perror("Error opening file");
    return NULL;
  }
  printf("======READING FRAMES for 5 seconds========\n");
  while (snd_pcm_readi(pcm_handle, (void *)buf, period_size) > 0 &&
         periods_read < periods_to_read) {
    // Because each frame is 2 bytes (format/bit rate), cast to int16
    // int16_t *samples = (int16_t *)buf;
    // for (int i = 0; i < period_size; i++) {
    //     printf("%d ", samples[i]);
    // }

    fwrite(buf, sizeof(int16_t), period_size, file);
    periods_read++;
  }
  printf("done capturing audio\n");

  fclose(file);

  free(buf);
  snd_pcm_close(pcm_handle);
  snd_pcm_hw_params_free(params);

  return output_file;
}