US 2003/0169375 A1 · Method for detecting grid in block-based compressed video

Abstract

A grid detector detects the existence and the location of grids in DCT compressed videos. When a grid is detected in the input video, a post-processor is turned on and the de-blocking processing is applied on the grid detected by the grid detector. When no grid is detected, indicating that the input video is either an uncompressed video or an already de-blocked video, post-processing turned off to avoid degrading the picture quality. To detect grids, the grid detector: (a) computes horizontal and vertical second derivatives for all pixels of the image; (b) generates horizontal second derivative zero-crossing mask and vertical second derivative zero-crossing mask by marking the those pixels whose second derivatives have opposite signs with respect to their horizontal or vertical neighboring pixels'; (c) applies horizontal and vertical integral projections to the horizontal and vertical zero-crossing masks respectively; (d) generates the local maximum masks by locating the local maximum of the two projected 1-D signals; and (e) determines grid location by computing the positions of the local maximum masks.

Claims28

Dependent claims

A method of processing video signals representing video image frames comprising pixels, to detect the existence and the positions of a block grid in each frame resulting from block-based transform coding, wherein the video signal value is a function f of pixel positions in each frame, comprising the steps of:

(i) computing a horizontal second derivative ƒh″ and a vertical second derivative ƒv″, for the function ƒ at multiple pixel position in the frame;
(ii) determining the zero-crossings of the second derivative and generating horizontal and vertical second derivative zero-crossing masks;
(iii) computing a horizontal integral projection of the horizontal zero-crossing mask to generate a horizontal projected one dimensional signal, and computing a vertical integral projection of the vertical zero-crossing mask to generate a vertical projected one dimensional signal;
(iv) generating a local maximum mask for each of the two projected one dimensional signals;
and
(v) determining the grid block boundary position by computing the locations of the local maximum masks in the frame.

3 more elements

A grid detector system for processing video signals representing video image frames comprising pixels, to detect the existence and the positions of a block grid in each frame resulting from block-based transform coding, wherein the video signal value is a function f of pixel positions in each frame, comprising:

(a) a mask generator that determines the second derivative f″ of the function f at pixel positions for a set of pixels in the frame, wherein the second derivative f″ indicates a change in the relative value of neighboring pixels, and determines the zero-crossings of the second derivative and generates a second derivative zero-crossing mask;
(b) an integral projector that computes an integral projection of the zero-crossing mask to generate a projected one dimensional signal;
(c) a local maximum identifier that determines the local maximum for the projected one dimensional signals, and generates a corresponding local mask;
and
(d) a position detector that determines the grid block boundary position by computing the location of the local maximum mask in the frame.

2 more elements

Dependencies are inferred from the claim text.

Method for detecting grid in block-based compressed video

Life of this patent

Method for detecting grid in block-based compressed video

Life of this patent

Abstract

Claims28