Patent ID: 6023295
Filing Date: 2000-02-08
Classification: H04N

Abstract:
A recompression and decompression method according to an adaptive differential pulse code modulation scheme (ADPCM) for a stream of digital data representing an MPEG decoded digital video signal, before being stored in a video memory and during reading of said data from said video memory, respectively, to be then processed by a video processor generating three video signals controlling a display monitor, the recompression and decompression method for reducing the video memory requirement of an MPEG video decoder, the method comprising the steps of:defining an ADPCM processing window including a predetermined block of adjacent pels belonging to a same horizontal video line;calculating moduli of a difference between every two adjacent pels for each processing window;detecting a maximum value of a set of values of the moduli of the differences between adjacent pels for each processing window;storing the detected current maximum value of each processing window in a register;comparing said current maximum value stored with a predetermined number of thresholds defining as many ranges of said value corresponding to a number of selectable addresses of a look-up table containing a corresponding number of sets of quantization parameters;selecting an address as a function of the range to which said current maximum value belongs;loading a parametric quantizer with the set of quantization parameters read from said look-up table as a function of said address; andupdating said current maximum value stored for each new block of input pels as identified by said processing window.