COMPRESSION TECHNIQUES FOR VIDEO TELEMETRY

Abstract

As the role of television in the aerospace industry has expanded so has the need for video telemetry. In most cases it is important that the video signal be encrypted due to the sensitive nature of the data. Since this means that the signal must be transmitted in digital form, video compression technology must be employed to minimize the transmitted bit rate while maintaining the picture quality at an acceptable level. The basic compression technique which has been employed recently, with successful results, is a combination of Differential PCM and Variable Length coding (DPCM/VLC). This technique has been proposed to the Range Commanders Council to become a possible standard. The purpose of this paper is to compare the basic DPCM/VLC technique with alternative coding technologies. Alternative compression techniques which will be reviewed include Transform coding, Vector Quantization, and Bit Plane coding. All candidate techniques will be viewed as containing four elements -- signal conditioning, signal processing, quantization, and variable length coding. All four techniques will be evaluated and compared from the stand point of compression ratio and picture quality.