The discussion about video standards for live processing has been summarised as:

  1. Codec: Motion.jpg (for interlaced footage) or Photo.jpg.
  2. Compression ratio/quality: Quality 80 is a decent baseline for.jpg, though you can crank as high as 97 to improve quality.
  3. Keyframes: Encode a keyframe on every frame so it’s ‘scratch-ready’.
  4. Alpha channels: For video containing alpha channels, PNG is the format of choice.

Sounds like more or less the same conclusion that has been reached in the Jitter forum, when this question comes up there once in a while.