Patent ID: 7010041
Filing Date: 2006-03-07
Classification: H04N

Abstract:
1. A process for generating an output MPEG bitstream from an MPEG input bitstream, said output MPEG bitstream having at least one entity chosen among syntax, resolution, and bitrate modified with respect to said input bitstream, the process comprising: distinguishing, in said input bitstream, non-affecting portions that substantially do not affect variation in bitrate and affecting portions that substantially do affect variation in bitrate; when said syntax is to be modified between said input bitstream and said output bitstream, subjecting said non-affecting portions of said input bitstream to translation of said syntax into the syntax of said output bitstream and transferring said non-affecting portions subjected to syntax translation to said output bitstream; when said resolution is to be modified between said input bitstream and said output bitstream, subjecting said non-affecting portions of said input bitstream to translation of said resolution into the resolution of said output bitstream and transferring said non-affecting portions subjected to the resolution translation to said output bitstream; transferring said affecting portions from said input bitstream to said output bitstream in substantial absence of processing operations when said resolution is left unaltered between said input bitstream and said output bitstream; and when said resolution is modified between said input bitstream and said output bitstream, subjecting said affecting portions of said input bitstream to a filtering in the domain of the discrete cosine transform, then transferring said affecting portions subjected to filtering in the domain of the discrete cosine transform to said output bitstream; and carrying out a scaling of a motion field to enable association with pixel macroblocks having a resolution corresponding to the modified resolution of said output bitstream when said resolution is to be modified between said input bitstream and said output bitstream, wherein said scaling of the motion field includes an operation of applying to motion vectors associated with said input bitstream a transformation that correlates the motion vectors to a given number of motion vectors associated with at least one of the macroblocks; wherein said at least one of the macroblocks is from a set made up of: macroblocks that are to be merged into a new macroblock; and macroblocks that surround the ones that are to be merged into the new macroblock; wherein said transformation applied to the motion vectors associated with said input bitstream comprises the operations of: multiplying said motion vectors by respective weighting factors; accumulating the results of the above multiplication; and dividing the results accumulated by the sum of said weighting factors.