An RGB digital video signal destined to be displayed on a display such as a liquid crystal display (LCD) is converted from the RGB colour space to the YUV colour space. The signal converted into the YUV colour space is subjected to at least a processing operation selected among a sub-sampling operation (24) and a data compression operation (26). The signal is then stored in a memory and the signal read from said memory (12) is then subjected to at least a return operation (28, 30) complementary to the aforesaid processing operation (24, 26). The signal subjected to the aforesaid return operation is lastly reconverted from the YUV colour space to the RGB colour space, thus being susceptible to be displayed on the display.