Patent ID: 7515638

Claim:
A process for estimating the noise level of video images before coding in which: at least one current input image is stored; a blockwise motion estimation is performed so as to produce, blockwise, quantities representative of motion-compensated image variations, on the basis of a current input image and of at least one input image stored previously; and a global noise level is determined for each image as a function of at least certain of the quantities representative of motion-compensated image variations, called first quantities, wherein a local noise level is determined for each block of the image as a function of the difference between a mean displaced frame difference and a local displaced frame difference, both calculated during blockwise motion estimation, and as a function of the ratio of said difference to the mean displaced frame difference, wherein the local noise level is determined: by decreasing the value of said global noise level, if said difference is positive, and, by increasing the value of said global noise level, if said difference is negative; and wherein, if said difference is positive, the local noise level is determined by: subtracting from said global noise level the product of said ratio and a first predefined parameter if said difference is below a first predefined threshold, and subtracting from said global noise level half the value of said first predefined parameter otherwise.