System for the conversion of digital television signals with an insertion of interactive menu

摘要

The system includes a digital decoding module (30) which provides on-screen display (OSD) and main-picture (I) data streams which are mixed (34) and multiplexed (40). An encoding module (36) contains D/A converters (28,38) and a block (39) which performs common functions for two data stream encoders (27,37). These common functions include the generation of clock and chrominance subcarrier signals and the optimisation of the encoding function by minimising the required number of integrated circuits and connections. The sampling rates of the multiplexer and demultiplexer (41) correspond to twice the control frequency (F) of the mixer.