Patent ID: 7388913

Claim:
A method of transmitting a bit stream representing digitalized images to a user which requires a reduction of the bit stream, the method comprising: encoding the digitalized images in a compressed discrete cosine transform (DCT) domain using DCTs of length N/2 to produce a first encoded bitstream of coefficients; receiving in a transcoder the first encoded bit stream; undersampling in the transcoder, by removing selected ones of the coefficients, the compressed digitalized images represented by the first encoded bitstream by a certain factor in each dimension; and calculating, from the remaining coefficients, DCTs of length N×N, each of the DCTs of length N×N calculated directly from four adjacent DCT coefficient blocks of size N/2×N/2 of the remaining coefficients, for each of the digitalized images, N being a positive, even integer to produce a second encoded bitstream; and transmitting from the transcoder the second encoded bit stream to the user.