ace_recorder.c

#include <stdint.h>
#define DR_WAV_IMPLEMENTATION
#define nchannels 2
#include "../../dr_wav.h"
#include <linux/if_packet.h>
#include <netinet/if_ether.h>
#include <netinet/in.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

struct sockaddr saddr;

struct audio_packet {

  uint8_t source_mac[6];
  uint8_t dest_mac[6];
  uint8_t ether_type[2];
  int8_t samples[65][3]; // 64 Channels+Sync
};
const uint8_t source[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
const uint8_t destination[] = {0x00, 0x04, 0xC4};

int kbhit() {
  struct timeval tv;
  fd_set fds;
  tv.tv_sec = 0;
  tv.tv_usec = 0;
  FD_ZERO(&fds);
  FD_SET(STDIN_FILENO, &fds); // STDIN_FILENO is 0
  select(STDIN_FILENO + 1, &fds, NULL, NULL, &tv);
  return FD_ISSET(STDIN_FILENO, &fds);
}

int main(int argc, char **argv) {
  drwav_data_format format;
  drwav wav;
  int8_t tempFrames[4096][nchannels][3];
  if (argc < 2) {
    printf("No output file specified.\n");
    return -1;
  }

  format.container = drwav_container_riff;
  format.format = DR_WAVE_FORMAT_PCM;
  format.channels = nchannels;
  format.sampleRate = 48000;
  format.bitsPerSample = 24;
  if (!drwav_init_file_write(&wav, argv[1], &format, NULL)) {
    printf("Failed to open file.\n");
    return -1;
  }
  int sock_r, saddr_len, buflen;

  unsigned char *buffer = (unsigned char *)malloc(65536);
  memset(buffer, 0, 65536);

  sock_r = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
  if (sock_r < 0) {
    printf("error in socket, run as super user\n");
    return -1;
  }
  int i, wave_channel, ace_channel = 0;
  uint8_t lastSync;
  printf("Recording, press ENTER to stop .... \n");
  while (!kbhit()) {
    // recvfrom reads one entire packet
    buflen =
        recvfrom(sock_r, buffer, 65536, 0, &saddr, (socklen_t *)&saddr_len);
    // the frame size of an ACE Packet is always 235 when not using VLAN
    if (buflen == 235) {
      struct audio_packet *audio = (struct audio_packet *)buffer;
      // memcmp returns 0 if equal
      if (!memcmp(audio->source_mac, source, 6) &&
          !memcmp(audio->dest_mac, destination, 3)) {
          uint8_t SyncByte=(audio->samples[0][2] & 0xf0) >> 4 |
                                (audio->samples[0][2] & 0x0f) << 4;  
        if (!(SyncByte == lastSync + 4)){
          printf("lost Packet detected\n");
        }
        lastSync = SyncByte== 0x7c ? 0x3c : SyncByte;
        for (int c = 0; c < nchannels; c++) {
          // on ACE the bits are weirdly shifted so we shift the back
          tempFrames[i][c][0] = (audio->samples[1 + c][0] & 0xf0) >> 4 |
                                (audio->samples[1 + c][0] & 0x0f) << 4;
          tempFrames[i][c][1] = (audio->samples[1 + c][1] & 0xf0) >> 4 |
                                (audio->samples[1 + c][1] & 0x0f) << 4;
          tempFrames[i][c][2] = (audio->samples[1 + c][2] & 0xf0) >> 4 |
                                (audio->samples[1 + c][2] & 0x0f) << 4;
        }
        i++;
        if (i == 4096) {
          drwav_write_pcm_frames_be(&wav, 4096, tempFrames);
          i = 0;
        }
      }
    } else {
      printf("Received Packet of wrong length: %u\n", buflen);
    }
  }

  close(sock_r); // use signals to close socket
  drwav_uninit(&wav);

  return 0;
}