SYSTEM FOR MULTIPLEXING PCM DATA WITH VIDEO DATA

Abstract

When video signals are transmitted in a telemetry system it is usually necessary to simultaneously transmit other basic data such as temperature, pressure, audio, etc. In recent years these video/data telemetry systems have been implemented by transmitting the video through an analog link and the digital data through a parallel separate digital channel. Most recently it has become practical to transmit video signals by digital means, and this makes it possible to digitally multiplex the narrowband data with the wider band video. This results in a large reduction in system complexity since both data streams are transmitted over one channel rather than two. This paper describes a particular technical approach to multiplexing data and video which supports PCM data rates up to 60 kilobits per second. The approach has the advantage that PCM data is only embedded into the Video data as required. This results in the maximum utilization of the bandwidth of the transmission link. An airborne device has been developed which implements the video encoding and data multiplexing function. The paper describes the general multiplexing concept, the communication protocol, and the particular implementation. A description of the video encoding system, including the data multiplexing option, can be found in the “Draft Standard for Digital Transmission of Television Images” - RCC/TCG 209