Accept ffmpeg input and output params separately.

[kapoorlakshya]

Accept input/output params separately to appropriately place them in the parsed (final) command.

advanced = {
  input:  {
    framerate:   30,
    pix_fmt:     'yuv420p',
    video_size:  '1280x720',
    show_cursor: 1
  },
  output: {
    framerate: 15,
    pix_fmt:   'yuv420p'
  },
  log:    'recorder.log',
  loglevel: 'level+debug', # For FFmpeg
}