RM Signetics rescaler — Page
Video scaler fits picture to random window
Horizontal and vertical filtering maximizes picture quality at arbitrary
resolution
The SAA7186 is a down-scaling IC for video images. It accepts 30 frames/s
digitized video input in the CCIR industry-standard YUV 4:2:2 format. The
IC scales the signal, does vertical and horizontal filtering, and
converts the signal to RGB. The independent horizontal and vertical
filters allow interpolation for each new pixel, rather than dropping
pixels to get the requisite number. Thus the picture quality in a reduced
window will be as good as the source and resolution allow. The device
conforms to the company's Digital Video Architecture, which means it will
play with existing video-processing equipment hosted on PCs and Macintosh
computers. All devices in the family can be controlled by an I
bus from a host microcontroller. The down-sampler's most obvious use is as
a display-window generator in a video editor. The editor could have
controls on screen, with a window for the video stream in process (see
diagram). The output can be 15- or 24-bit RGB, 16-bit YUV, or gray scale.
Anti-gamma correction is done by ROM lookup table on the RGB data. At full
speed, the chip can handle up to 768 pixels x 576 lines/frame. Without
vertical processing, it can resize 1,023 x 1,023-pixel screens. (SAA7186
in 100-pin plastic, $40 ea/100–available now.) Signetics Co., Sunnyvale,
CA Stephen Solari 408-991-4577
CAPTION:
The SAA7186 down-sampling converter can provide a window view of a video
stream in an editing system made up of other video-processing parts, all
controlled by I
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