Set Top Box

Attempts at analog high-definition television (MUSE, HD-MAC) have shown that, in the final analysis, the public is much more sensitive to the quantity of programs available and the quality of their content, than to the quality of the image itself. Now that the analog terrestrial network was saturated, digital could come into play. The first digital television broadcasts to the general public took place in 1994 in the United States with the DirecTV (satellite) project. Success was immediate, with a million subscribers within a year of launch. In Europe, the digital adventure began at the end of 1991 with the DVB (Digital Video Broadcasting) project, based on MPEG-2 compression. Canal+ launched its first regular broadcasts on the ASTRA 1E satellite in April 1996.

In addition, the development of mobile telephony has brought back the problem of analog terrestrial television, which takes up a considerable amount of bandwidth, although not all existing channels are actually used. In fact, the echoes of analog broadcasting prevent the use of adjacent channels and the N + 3 and N – 3 channels. Digital broadcasting would be the solution to recover all this wasted bandwidth. The launch of digital terrestrial television in France is scheduled for 2003; analog television will eventually disappear.

The digital decoder (or Set Top Box: STB) is a prerequisite for the arrival of digital TV sets (i.e. with integrated decoders). It consists of a hardware base driven by real-time embedded software. It has benefited from advances in component integration and hardware miniaturization. The case has retained its original size, but the volume of its contents has been almost quadrupled. Only the power supply has remained more or less the same size.

For obvious reasons of confidentiality, we can't go into the details of the decoder, but we will show here the overall operation of the Integrated Receiver Decoder (IRD).