Method for detecting grid in block-based compressed video
US7218794B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 10, 2003 |
| Grant date | May 15, 2007 |
| Priority date | — |
| Expiry date | Apr 30, 2025 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/21
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.