Archive for the ‘chroma’ Category

Cineform and Alpha Channels

Friday, August 31st, 2012

The full (paid) version of GoPro-Cineform Neo (as I have) does support alpha channels.

(A colleague initially thought otherwise – but that impression turned out to be based on info from old forum threads)


Chroma Upsampling (Chroma Interpolation)

Friday, August 31st, 2012

Shooting green-screen onto a 4:2:0 chroma-subsampled format, intending of course to use it for chroma-keying.  Obvious disadvantage is green-ness of green-screen only gets sampled at quarter-resolution.  Not a show-stopper, given my target deliverable is standard definition, but anyhow, towards perfectionism, is there any way to up-sample to 4:4:4 i.e. full definition colour?

It does occur to me that something more sophisticated than chroma blur ought to be possible, broadly along the lines of edge-following methods employed in resizing. What’s out there?

  • Simplest method, that most people seem to use, is chroma-blur.  That’s only the chroma, not the luma.
  • Searching around, Graham Nattress has analysed the problem and seems to have produced a more mathematical approach.  But it’s only available (at time of writing) for Final Cut (which of course is Mac-only at present).

Some tools that “promise” upsampling, but I wonder by what methods:

  • GoPro-CineForm intermediate.  The codec settings include an option to up-sample to 4:4:4
  • Adobe Premiere, but only if a Color Corrector effect employed.
    • But the crucial thing here, regarding the usefulness of this, is whether it uses any better method than chroma blur.

Some questions:

  •  Does Adobe have anything built-in to do something Nattress-like nowadays?
  • DaVinci Resolve?
  • Boris?