A CAQ Bandwidth Reduction System For RPV Video Transmission

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Abstract
A bandwidth compression system for the transmission of video images from remotely piloted vehicles has been built and demonstrated. Novel features of this system are the use of the Constant Area Quantization (CAQ) technique to obtain spatial bit rate reduction of 6:1 and a rugged and compact scan convertor, based on a core memory, to accommodate temporal frame rate reduction. Based on the ability of the human eye to perceive more detail in high contrast regions than in low, the CAQ method transmits higher resolution in the former areas. The original six-bit digitized video is converted to a three level signal by the quanti-zing circuit and then Huffman - encoded to exploit its statistical properties and reduce it further to one-bit per pixel. These circuits operate on one line of the picture at a time, and can handle information at full video (10 MHz) rate. The compressed information when received on the ground is stored in coded form in a two-frame (500,000 bit) digital core memory. One frame of the memory is filled while the other is being displayed and then the two are interchanged. Decoding and reconstruction of the video are performed between the memory and the display.

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