Method and system for estimating sharpness metrics based on local edge kurtosis
AssigneeKoninklijke Philips Electronics N.V.
InventorsJorge E Caviedes, Sabri Gurbuz
Life of this patent
Estimating the term…
Abstract
The present invention relates to a method and system for evaluating the quality of video data without gaining access to the source data. The system is configured to estimate sharpness metrics by detecting edge pixels and enclosing them with 8×8 pixel blocks. For each block, the sharpness according to the Kurtosis of the DCT is computed. The final metric is the average sharpness of the blocks in the edge profile and includes a robust combination of spatial and frequency domain information.
Claims12
A method for evaluating the sharpness quality of video data, the method comprising the steps of:
- (a) receiving an input video frame;
- (b) obtaining an edge image comprised of edge pixels for said input video frame;
- (c) assigning each edge pixel of a selected portion of said edge image to a center of an 8×8 block;
- (d) performing a discrete cosine transform (DCT) on said 8×8 block to produce a set of DCT coefficients;
- (e) normalizing said DCT coefficients of said 8×8 block to obtain a bivariate probability-density function;
- and,
- (f) calculating kurtosis of said normalized DCT coefficients to produce a sharpness metric.
An apparatus for evaluating the sharpness quality of video data, comprising:
- an edge-detecting means, adapted to receive an input video frame for obtaining an edge image comprised of edge pixels for said input video frame;
- a segmenting means for receiving said input video frame and assigning each edge pixel of a selected portion of said edge image to an 8×8 block without duplication and with the option of centering the edge pixels on the block;
- and,
- a Kurtosis estimator for performing a discrete cosine transform (DCT) on said 8×8 block to produce a set of DCT coefficients, normalizing said DCT coefficients of said 8×8 block to obtain a bivariate probability-density function, and estimating the Kurtosis thereof.
A signal processor, responsive to an input video frame for evaluating the sharpness quality, comprising:
- an input portion, an output portion, and a processing unit coupled between said input and said output portion, said processing unit constructed and adapted to receive said input video frame;
- obtain an edge image comprised of edge pixels for said input video frame;
- assign each edge pixel of a selected portion of said edge image to a center of an 8×8 block;
- perform a discrete cosine transform (DCT) on said 8×8 block to produce a set of DCT coefficients;
- normalize said DCT coefficients of said 8×8 block to obtain a bivariate probability-density function;
- and, calculate kurtosis of said normalized DCT coefficients to produce a sharpness metric.
Dependencies are inferred from the claim text.