Chroma dots are visual artifacts caused by displaying an unfiltered PAL analogue colour video signal on a black-and-white television or monitor.
Chroma dots were once regarded as undesirable picture noise, but recent advances in computer technology have allowed them to be used to reconstruct the original colour signal from black-and-white recordings, providing a means to re-colour material where the original colour copy is lost.
Example of the chroma dot reconstruction: Analogue colour video signals comprise two components: luminance and chrominance.
He theorised that it might be possible to use the chroma dots to reconstruct the original colour signal,[1] and in 2007, set up a working group[2] to carry out further research.
In 2008, it was announced[3] that members of the working group had successfully managed to restore the Dad's Army episode "Room at the Bottom" using information from the chroma dot patterning.