Method and device for processing a sequence of video images
US7822202B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jan 25, 2007 |
| Grant date | Oct 26, 2010 |
| Priority date | — |
| Expiry date | Aug 25, 2029 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N2005/91392
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
The invention discloses a new modulation scheme to prevent illegal copy in movie theaters. None of the existing modulation schemes make the right assumptions to modelize a camcorder device. In such classical schemes, camcorders are always considered as sampling devices without taking into account the effects of shutter speed. The shutter of the camcorder is classically compared to a low-pass filter. As a result, modulation effects can be easily removed by setting up shutter speed to low values (low cutoff frequency). The right mathematical modelization of the shutter effect shows that, in the spectral domain, the behavior of the camcorder is close to a cardinal sine function with a main lobe and sidelobes. Consequently, according to the invention, it is proposed to select a modulation frequency that not only generates visual artifacts once recorded by the camcorder under shutter-free conditions, but that can also generate artifacts despite low shutter speed settings by going through sidelobe of the shutter spectrum.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.