Documentation:Modules/jack

 JACK audio input (access_jack)
      --jack-input-caching <integer>
                                 Caching value in ms
          Make VLC buffer audio data captured from jack for the specified
          length in milliseconds.
      --jack-input-use-vlc-pace, --no-jack-input-use-vlc-pace
                                 Pace (default disabled)
          Read the audio stream at VLC pace rather than Jack pace. (default
          disabled)
      --jack-input-auto-connect, --no-jack-input-auto-connect
                                 Auto Connection (default disabled)
          Automatically connect VLC input ports to available output ports.
          (default disabled)

 JACK audio output (jack)
      --jack-auto-connect, --no-jack-auto-connect
                                 Automatically connect to writable clients
                                 (default disabled)
          If enabled, this option will automatically connect sound output to
          the first writable JACK clients found. (default disabled)
      --jack-connect-regex <string>
                                 Connect to clients matching
          If automatic connection is enabled, only JACK clients whose names
          match this regular expression will be considered for connection.

vlc -p jack --advanced --help-verbose