Patent ID: 7436889

Claim:
In a video management system that has access to a video stream that is generated using quantization and inter-picture motion compensation, the video management system further compressing the video stream by requantizing pictures within the video stream, the video management system providing the further compressed video stream to a decoder, a method of at least partially avoiding generational error at the decoder introduced by the requantization, the method comprising the following: accessing a reference picture that has been previously quantized; performing inverse quantization on the reference picture: performing requantization on the reference picture using a coarser quantization scale than a quantization scale originally used to perform quantization on the reference picture; storing information representing the error generated due to the requantization of the reference picture; accessing a predictive picture that depends on the reference picture; and calculating an altered predictive picture that would compensate for the error generated due to the requantization of the reference picture using the information representing the error; wherein the predictive picture is a first predicative picture and the altered predictive picture is a first altered predictive picture, and wherein the method further comprises: performing requantization on the first altered predictive picture using a coarser quantization scale than a quantization scale originally used to perform quantization on the first predictive picture; storing information representing the error generated due to the requantization of the first altered predictive picture; and accessing a second predictive picture that depends on the first predictive picture; and calculating a second altered predictive picture that would compensate for the error generated due to the requantization of the first altered predictive picture using the information representing the error generated due to the requantization of the first altered predictive picture.