These are what I'm thinking to implement in near future.

Common

• select program and preview as a source
• multi-threading to avoid dropping frames or interleave frame to process and scatter the steps of calculation to frames.
• dock to show all of them easily
• select area by mouse
• scale filter

Vectorscope

• features from FFmpeg
  • mode; gray, color, etc.
  • intensity
  • envelope
  • graticule (On/off is implemented but color has not been configurable yet.)
  • graticule-flags; name, white, black
  • opacity
  • bgopacity
  • thresholds
  • colorspace
  • tint
• skin tone line
• use effect to convert to YUV for performance
• zoom (like Kdenlive)

Waveform

• features from FFmpeg
  • mode; row, column
  • intensity
  • mirror (Scene item can be flipped.)
  • display; overlay, stack, parade.
  • components
  • envelope
  • filter
  • graticule
  • graticule-flags
  • opacity
  • scale; digital, millivolts, ire
  • bgopacity
  • tint
  • format; RGB, YUV

Histogram

• features from FFmpeg
  • level-heights
  • scale-heights
  • display-mode; stack, parade, overlay
  • level-mode; linear, logarithmic
  • components
  • fgopacity
  • bgopacity

Others

• Zebra
• False color