Function audioBroadcastThread

src/stream.cpp:1651–1753

  }

  void audioBroadcastThread(udp::socket &sock) {
    auto shutdown_event = mail::man->event<bool>(mail::broadcast_shutdown);
    auto packets = mail::man->queue<audio::packet_t>(mail::audio_packets);

    audio_packet_t audio_packet;
    fec::rs_t rs {reed_solomon_new(RTPA_DATA_SHARDS, RTPA_FEC_SHARDS)};
    crypto::aes_t iv(16);

    // For unknown reasons, the RS parity matrix computed by our RS implementation
    // doesn't match the one Nvidia uses for audio data. I'm not exactly sure why,
    // but we can simply replace it with the matrix generated by OpenFEC which
    // works correctly. This is possible because the data and FEC shard count is
    // constant and known in advance.
    const unsigned char parity[] = {0x77, 0x40, 0x38, 0x0e, 0xc7, 0xa7, 0x0d, 0x6c};
    memcpy(rs.get()->p, parity, sizeof(parity));

    audio_packet.rtp.header = 0x80;
    audio_packet.rtp.packetType = 97;
    audio_packet.rtp.ssrc = 0;

    // Audio traffic is sent on this thread
    platf::adjust_thread_priority(platf::thread_priority_e::high);

    while (auto packet = packets->pop()) {
      if (shutdown_event->peek()) {
        break;
      }

      TUPLE_2D_REF(channel_data, packet_data, *packet);
      auto session = (session_t *) channel_data;

      auto sequenceNumber = session->audio.sequenceNumber;
      auto timestamp = session->audio.timestamp;

      *(std::uint32_t *) iv.data() = util::endian::big<std::uint32_t>(session->audio.avRiKeyId + sequenceNumber);

      auto &shards_p = session->audio.shards_p;

      auto bytes = encode_audio(session->config.encryptionFlagsEnabled & SS_ENC_AUDIO, packet_data, shards_p[sequenceNumber % RTPA_DATA_SHARDS], iv, session->audio.cipher);
      if (bytes < 0) {
        BOOST_LOG(error) << "Couldn't encode audio packet"sv;
        break;
      }

      BOOST_LOG(verbose) << "Audio [seq "sv << sequenceNumber << ", pts "sv << timestamp << "] ::  send..."sv;

      audio_packet.rtp.sequenceNumber = util::endian::big(sequenceNumber);
      audio_packet.rtp.timestamp = util::endian::big(timestamp);

      session->audio.sequenceNumber++;
      session->audio.timestamp += session->config.audio.packetDuration;

      auto peer_address = session->audio.peer.address();
      try {
        auto send_info = platf::send_info_t {
          (const char *) &audio_packet,
          sizeof(audio_packet),
          (const char *) shards_p[sequenceNumber % RTPA_DATA_SHARDS],