Universal digital TV codec—unicodec

Abstract

The UNICODEC, developed under the INTELSAT R & D Program, is a TV codec which can transmit and receive any standard signal of NTSC, PAL, or SECAM, by using 15 Mb/s or 30 Mb/s transmission rates (switchable) with two high quality sound channels and one voice circuit. These rates include rate 239/255 BCH FEC for video information. The codec uses the 4:2:2 digital interface for component coding based on CCIR Recommendation 601. The UNICODEC can provide the flexibility to deal with the composite coding now needed in mixed analogue/digital networks, but can also handle either composite NTSC, PAL, SECAM or MAC (multiplexed analogue components), or digital component signals (Y, R‐Y, B‐Y) in the future. The key technique used here is called MAP (median adaptive prediction) coding, which is one of the adaptive DPCM methods for accurate and simple control in high quality TV transmission; one prediction out of three (interframe, intrafield or interfield) is transmitted without the need for many control bits. There is also a refresh mode for burst error or synchronization recovery. The UNICODEC is expected to provide double capacity with higher quality pictures compared to conventional analogue transmission (FM in 18 MHz). Alternatively, smaller size antennas may be used. This paper describes the objectives of the development of the UNICODEC, its main features and results of field tests.