Noise is reduced in a video system by applying motion compensated temporal
filtering using previously generated motion vectors and adaptive spatial
filtering at scene change frames. Various types of noise can be
introduced into video prior to compression and transmission. Artifacts
arise from recording and signal manipulation, terrestrial or orbital
communications, or during decoding. Noise introduced prior to image
compression interferes with performance and subsequently impairs system
performance. While filtering generally reduces noise in a video image, it
can also reduce edge definition leading to loss of focus. Filtering can
also tax system throughput, since increased computational complexity
often results from filtering schemes. Furthermore, the movement of
objects within frames, as defined by groups of pixels, complicates the
noise reduction process by adding additional complexity. In addition to
improvements made to FIR spatial filtering, the present invention
improves on previous filtering techniques by using Infinite Impulse
Response (IR) temporal filtering to reduce noise while maintaining edge
definition. It also uses motion vectors previously calculated as part of
the first-pass image encoding or alternatively by transcoding to reduce
computational complexity for P-frame and B-frame image preprocessing.
Single stage P-frame temporal noise filtering and double stage B-frame
temporal noise filtering are presented.