@@ -69,6 +69,7 @@
    std::string api_user;  ///< Web UI user.
    std::string api_pass;  ///< Web UI password.
    std::string pin_file;  ///< When set, write the PIN here and let someone else approve it.
    std::string audio_out;  ///< When set, write the decoded audio there as a WAV, to analyze it offline.
    std::string state_dir {"e2e-client"};  ///< Directory for the client identity.
    int width {1280};  ///< Stream width.
    int height {800};  ///< Stream height.
@@ -590,7 +591,46 @@
   * @brief Write the last frame as a binary PPM.
   *
   * @param path Output path.
   */
  /**
   * @brief Write the decoded audio as a 16-bit WAV, so it can be measured or listened to.
   *
   * @param path Output path; nothing is written when empty.
   */
  void write_wav(const std::string &path) {
    std::lock_guard lock {audio.mutex};
    if (path.empty() || audio.pcm.empty() || audio.channels <= 0) {
      return;
    }
    const auto rate = (std::uint32_t) audio.sample_rate;
    const auto channels = (std::uint16_t) audio.channels;
    const auto data_bytes = (std::uint32_t) (audio.pcm.size() * 2);
    std::ofstream out {path, std::ios::binary};
    auto u32 = [&](std::uint32_t v) {
      out.write(reinterpret_cast<const char *>(&v), 4);
    };
    auto u16 = [&](std::uint16_t v) {
      out.write(reinterpret_cast<const char *>(&v), 2);
    };
    out.write("RIFF", 4);
    u32(36 + data_bytes);
    out.write("WAVEfmt ", 8);
    u32(16);
    u16(1);  // PCM
    u16(channels);
    u32(rate);
    u32(rate * channels * 2);
    u16((std::uint16_t) (channels * 2));
    u16(16);
    out.write("data", 4);
    u32(data_bytes);
    for (float sample : audio.pcm) {
      const auto clamped = std::clamp(sample, -1.0f, 1.0f);
      const auto value = (std::int16_t) std::lround(clamped * 32767.0f);
      out.write(reinterpret_cast<const char *>(&value), 2);
    }
  }
  void write_ppm(const std::string &path) {
    std::lock_guard lock {state.mutex};
    if (path.empty() || state.rgb.empty()) {
@@ -624,6 +664,7 @@
      {"--wait-file", &opts.wait_file},
      {"--input", &opts.input},
      {"--pin-file", &opts.pin_file},
      {"--audio-out", &opts.audio_out},
    };
    std::map<std::string, int *> ints {
      {"--port", &opts.port},
@@ -856,6 +897,7 @@
  const auto elapsed = std::chrono::duration<double>(std::chrono::steady_clock::now() - stream_start).count();
  write_ppm(opts.out);
  write_wav(opts.audio_out);
  if (input_thread.joinable()) {
    input_thread.join();
  }