Patent ID: 6233283
Filing Date: 2001-05-15
Classification: H04N

Abstract:
A layered encoder for coding an image represented by a video signal defined by a continuous stream of successive-in-time video frames containing macro blocks having a plurality of picture elements and for compensating for errors in transmission of a subject macro block in a current frame by considering human visual perception limitations, said video signal being coded onto a base layer and an error resilience layer of a coded video signal, said encoder comprising:an input port for receiving the current frame of the video signal, the current frame containing the image of an object;a perceptual preprocessor connected to said input port and receiving, as input signals, the subject macro block of the current frame and a delayed, quantized version of a prior macro block of a prior adjacent-in-time frame and corresponding to the subject macro block, and generating a determining output signal for comparing, in the event an error in transmission of the subject frame is detected, a difference between picture element intensity values of the object in the subject macro block and picture element intensity values of the object in the prior macro block to predetermined conditions representing limitations in human visual perception;a motion estimator connected to said input port and to said perceptual preprocessor for estimating, based at least in part on said predetermined conditions, possible motion of the object by comparing a position of the object in the prior macro block to the position of the object in the subject macro block, said motion estimator receiving as input signals said subject macro block, the delayed, quantized version of the prior macro block, and the determining output signal;a motion compensator for compensating for possible motion of the object from the prior macro block to the subject macro block, said motion compensator receiving as input signals the delayed, quantized version of the prior macro block and a signal from said motion estimator, and outputting a motion compensation signal; anda subtractor for producing an error signal by subtracting picture element intensity values of the picture elements in the prior macro block from picture element intensity values of the picture elements in the subject macro block;said perceptual preprocessor determining whether said error signal is to be incorporated in one or more of a base layer and an error resilience layer of a coded video signal so that video data contained in the subject macro block for which errors in transmission have been detected will be re-transmitted to a receiver based upon human visual perception limitations considered by said perceptual preprocessor.