openYCoCg

It’s the story of an experimental video codec, built on the Y′COCG colour space and designed for restoration purposes. We do use the unofficial FourCC «YCOG» for this video codec.

This video codec is developed since early 2014 by Reto Kromer, who first presented it publicly in 2015, but the C library was called «openYCoCg» only two years later.1 An alpha is currently tested. The source code and its brew formula will be freely available on our GitHub repository, as soon as a public beta will be released.

A Little Context

  • When working with the old colour processes, used in the during the first half century of cinema, it’s often more effective to handle independently, on one hand, the luma Y′ and, on the other hand, the chroma C1 and C2 components.
  • Working with CO and CG is easier than working with the common CB and CR, because the de-correlation of the colour planes is better and the transcoding from and to R′G′B′ is faster. Therefore one can see quicker the results on modern monitors.

Alpha

An alpha release is currently tested by some restoration facilities and archives located in Asia, Europe and North America (often by using a plug-in for the Diamant-Film restoration suite). At present, it supports two different bit-depths:

  • 16-bit per channel Y′COCG for actual work;
  • 24-bit per channel Y′COCG primarily for research purposes on file formats for the future.

Note

1
Older names include «YOG1», «YOG2» and «YOG3» and have been used also as unofficial FourCC – in case one should come across those files in the wild…

2018–01–03