The 8520 Digital Video Noise Reducer is an optional sub module for use with the 8500 Video Processing Frame Synchronizer. The noise reduction process is downstream from the 8500 Proc Amp controls. The 8520 can be used with any video input source. It only adds 4 microseconds to the throughput delay of the 8500, so it does not introduce problems with system timing.
The 8520 is motion-and scene-adaptive. It removes unwanted noise and artifacts, making it perfect for MPEG compression preprocessing and satellite or ENG feeds.
Several forms of noise reduction are employed to ensure the best possible performance. Recursive Temporal Noise filtering includes Simple Recursive, Motion Adaptive and Motion Adaptive with Impulse Filters. Controls are provided for maximum signal-to-noise improvement and for noise threshold. These can be set manually or run in automatic mode.
Motion Adaptive Recursive Noise filtering works on a pixel-by-pixel basis, comparing the current frame to frames that have already been filtered. If the change that is detected is small, it is considered noise, while if it is large, it is considered motion or a scene change. The detection process uses an LMMSE (Linear Minimum Mean Square Error) filtering algorithm to evaluate the presence of motion. Combining this algorithm with recursive temporal filters preserves fine detail while reducing noise in the presence of motion, including rapidly moving objects and scene changes. Motion trails are minimized while avoiding hard motion failures that some adaptive noise filters can exhibit.
User controls for the Motion Adaptive Recursive Filter include a Noise Threshold, based on how much noise is present in the incoming signal, and Maximum Signal to Noise Improvement, based on how much noise removal is desired. The threshold setting can be automatic or user-adjustable. When set to automatic, the noise level of the input signal is measured and the threshold is set accordingly. This simplifies the setup of the noise reducer and makes it responsive to varying input signal-to-noise levels. This minimizes the need for operator intervention to accommodate feeds of differing quality.
When the combined Motion Adaptive Recursive and Impulse Noise Filter is selected, temporal impulse noise-filtering is used to remove high level, narrow noise impulses, without reducing fine stationary detail.
A special Luma Tie mode reduces dot crawl artifacts from composite originated material by identifying cross-color and cross-luminance effects as unwanted noise. The Show Noise output mode displays what areas of the picture are being affected by the noise-reducer. Noise is represented by white or black, while unaffected areas are represented in gray. This handy mode makes it easy to set optimum adjustments for the material being processed. The Split Screen mode lets you compare the processed output to the original signal.
Complete control of the 8520 is provided through the Avenue Control System. Memory registers allow you to store configurations for easy recall.
