Patent ID: 7580578

Claim:
A method of forming a compressed transcoded digital image signal from a compressed original digital image signal which comprises digital data organized in blocks, the compression of the original signal comprising at least one step of spatio-frequency transformation of the original signal and a step of coding the data blocks of said transformed signal, said method using a processor to perform the steps of: selecting a data block in one of the compressed signals between the compressed transcoded digital image signal and the compressed original digital image signal, said selecting comprising identifying the spatial position of said data block in the selected compressed signal, identifying, in the non selected compressed signal, the spatial position of a dual data block which corresponds to the data block selected having regard to a given geometric transformation applied to this block, decoding the data block belonging to the compressed original signal, applying the given geometric transformation to the data block thus decoded, coding the geometrically transformed data block, and inserting the first data block thus coded in the compressed transcoded image signal at the position of its dual block.