Television system with a digital data rate.

摘要

This system is of the type in which a digital data transmission is associated with the analogue transmission of the video signal. It is to be compatible with conventional D2-MAC packet receivers. The conventional D2-MAC offers a digital rate of 2050 packets/s (D-MAC offers twice this). To increase the digital rate of a D2-MAC channel data can be transmitted at the 20.25 MHz frequency (D frequency) with frame blanking: an additional capacity of 1400 packets/s is obtained. For certain applications this capacity is still insufficient. The invention uses "mixed" packets comprising a part at the D frequency and a part at the D2 frequency, which are obtained by bit by bit juxtaposition of two consecutive packets of the same service. The same continuity index is imposed on the two basic packets. In this way, the two hiders are identical and after juxtaposition everything occurs as if the D2-D was formed by a 23 bit header at the D2 frequency with contents at the D frequency. These packets can be transmitted in digital bursts of the video lines, and not only with frame blanking. <IMAGE>