Video noise reduction system

DETAILED DESCRIPTION The present invention has application in the field of film to video tape conversation, but works in conjunction with any video signal from which it is desired to reduce noise which results from film granularity, circuitry imperfections and other sources which cause random signal degradation.
The present invention assumes that such noise is random from frame to frame, and within a particular area of a frame in which noise is to be reduced, the corresponding area in adjacent frames is similar.
The present invention operates by selectively and non-recursively averaging between 2 and 9 frames of video.
That is, once an average is established for a set of video frames, that result is not fed back and used to calculate an average for a subsequent set of video frames.
By such averaging, since the noise is random, it is filtered out leaving only the desired picture.
The averaging is performed only on areas of the picture which are close in both amplitude and/or color in adjacent frames.
In this connection, in cases where there is no motion or scene change between adjacent frames, the entire picture corresponding to such frames can be processed according to the present invention.
In the prior art, it is known that noise in a video signal can be reduced by recursively combining, on a frame by frame basis, portions of an image which are stationery from frame to frame.
In a particular technique disclosed by Lowry et al.
, in U.
S.
Pat.
No.
4,107,736, in a color system, conventional luminance and chroma separation methods, which are used for the moving portions of the picture, are replaced in the stationery portions by an opposite phase frame comparison method.
This patent is directed to a technique for determining which portions of pairs of adjacent frames are stationery and which portions are moving and then averaging those portions of the pairs of adjacent frames which are stationary.