| US 7,515,638 B2 | ||
| Device and process for estimating noise level, noise reduction system and coding system comprising such a device | ||
| Olivier Le Meur, Talensac (France); Jean-Yves Babonneau, L'Hermitage (France); and Georges Joulaud, Liffré (France) | ||
| Assigned to Nextream France, Cergy Saint-Christophe (France) | ||
| Appl. No. 10/487,197 PCT Filed Aug. 06, 2002, PCT No. PCT/EP02/08810 § 371(c)(1), (2), (4) Date Feb. 19, 2004, PCT Pub. No. WO03/019947, PCT Pub. Date Mar. 06, 2003. |
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| Claims priority of application No. 01 10977 (FR), filed on Aug. 21, 2001. | ||
| Prior Publication US 2004/0179602 A1, Sep. 16, 2004 | ||
| Int. Cl. H04N 7/12 (2006.01) | ||
| U.S. Cl. 375—240.27 [375/240.29; 375/240.12; 375/240.24] | 2 Claims |
| 1. 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.
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