Stmicroelectronics S.r.l.

Marco Ferretti

Mauro De Ponti

Vittorio Peduto

Matteo Boffadossi

Fabio Brognara

A method of compressing a stream of pixel data relative a two-dimensional object, pixels of which are scanned by rows from a source device to a receiver device, includes defining an extended context window to include a pair of pixels following a last encoded pixel on the row being scanned and the respective triplets of neighboring pixels belonging to the preceding row. The method includes defining a first distinct context array of pixels of the extended context window for the pixel of the pair immediately following the last encoded pixel, and a second context array of pixels of the extended context window for the other pixel of the pair. An extended context value relative to each pixel of the pair is calculated, and the extended context value relative to a first pixel immediately following the last encoded pixel is compared with an extended threshold. If the extended context value is less than the extended threshold, then encoding the first and second pixels of the pair, and if the extended context value relative to the first pixel of the pair exceeds the extended threshold, then carrying out simultaneously a parallel processing and encoding of both pixels according to an encoding routine.

Loss-less compression of still images at enhanced speed

A method for generating sequences of memory addresses for a memory buffer having N*M locations includes making a first address and a last address of every sequence respectively equal to 0 and to N*M&#x2212;1, assigning a first sequence of addresses, and each address but a last address of another sequence of addresses is generated by multiplying a corresponding address of a previous sequence by N, and performing a modular reduction of this product with respect to N*M&#x2212;1. The method further includes calculating a greatest bit length of every address, and calculating an auxiliary constant as the modular reduction with respect to N*M&#x2212;1 of the power of two raised to twice the greatest bit length. Each sequence of addresses includes storing an auxiliary parameter equal to an N+1address of the current sequence, computing a first factor as the modular product with respect to N*M&#x2212;1 of the auxiliary constant based upon a ratio between the auxiliary parameter and the power of two raised to the greatest bit length, and generating all addresses but the last of a sequence by performing the Montgomery algorithm using the first factor and an address index varying from 0 to N*M&#x2212;2 as factors of the Montgomery algorithm, and with the quantity N*M&#x2212;1 as modulus of the Montgomery algorithm, and the greatest bit length as the number of iterations of the Montgomery algorithm.

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Pavia, Italy

Marco Ferretti