System for receiving and decoding digital signals in accordance with two image definition levels

A system for receiving and decoding digital signals having two image definition levels, a higher image definition level and a lower image definition level, the system comprising:

• a) a sub-assembly for receiving the digital signals and including i) a first channel decoder for decoding signals of the higher definition level ii) a second channel decoder for decoding signals of the lower definition level, said first and second channel decoders being coupled in parallel and iii) a switch coupled to the first and second channel decoders for selecting one of said channel decoders;
• b) a source decoding sub-assembly for decoding the signals from the selected channel decoder and being arranged to decode both the higher and the lower definition levels;
• c) an error detector coupled to the source decoding sub-assembly for detecting perturbations in the received digital signals and for providing an output signal which indicates the level of perturbations in the received signals;
• and
• d) a decision circuit coupled to the error detector for controlling the switch in accordance with the output signal and for controlling the source decoding sub-assembly to decode the higher definition level if the first channel decoder is selected and the lower definition level if the second channel decoder is selected.