research_and_development/ai-conversation/audio_capture.c

#include <stdio.h>
#include <stdlib.h>
#include <alsa/asoundlib.h>
#include <alsa/control.h>
#include <alsa/pcm.h>
#include <curl/curl.h>

// NOTE: find this via `arecord -l`
#define ALSA_MIC_HARDWARE_DEVICE "hw:3"

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);
}

size_t write_callback(void *contents, size_t size, size_t nmemb, void *userp) {
    size_t total_size = size * nmemb;
    printf("%.*s", (int)total_size, (char*)contents);
    return total_size;
}

void test_request() {
  CURL *curl;
  CURLcode res;
  curl = curl_easy_init();

  if (curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://www.google.com");
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_callback);

    res = curl_easy_perform(curl);
    if (res != CURLE_OK)
    {
      fprintf(stderr, "curl failed: %s\n", curl_easy_strerror(res));
      return;
    }

    curl_easy_cleanup(curl);
  }
}

int main() {
    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 -1;
    }
    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);

    snd_pcm_hw_params_t *params;
    err = snd_pcm_hw_params_malloc(&params);
    if (err < 0) {
        fprintf(stderr, "unable to mallow hw params");
        return -1;
    }
    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 -1;
    }

    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 -1;
    }

    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 -1;
    }

    print_pcm_state(pcm_handle);

    const uint seconds_to_capture = 5;
    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.pcm", "wb");
    if (file == NULL) {
      perror("Error opening file");
      return 1;
    }
    while (snd_pcm_readi(pcm_handle, (void *)buf, period_size) > 0 && periods_read < periods_to_read) {
        printf("======READING FRAMES========\n");

        // 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);

        printf("\n");
        periods_read++;
    }

    // TODO: keep appending above frames into one buffer, and send to deepgram

    fclose(file);
    free((void *)buf);
    snd_pcm_close(pcm_handle);
    snd_pcm_hw_params_free(params);

    return 0;
}