Processing of color video signals
US4979022A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 14, 1989 |
| Grant date | Dec 18, 1990 |
| Priority date | — |
| Expiry date | Sep 14, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/262
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for keying digital color TV signals without exceeding the normal sampling frequency (13.5 MHz) and without obtaining a degraded image. A digital keying signal and a digital color TV signal are supplied to upsamplers (10,12), respectively, which double the sampling frequency of the incoming signal by linear interpolation. The 27 MHz sampled outputs are keyed in multiplier (14). In one line to a switch (24) the 27 MHz, 12 MHz bandwidth keyed signal is passed through low pass filter (16) and demultiplexer (18). The latter removes each alternate sample to provide a 13.5 MHz signal of 6 MHz bandwidth. In a second line to the switch the keyed signal is demultiplexed to provide a signal which would have resulted without upsampling, which is then delayed (22). Edge detector (26) senses high frequency keying signals and controls switch (24). In the absence of such high frequency keying signals the signal to the second line to the switch is taken. Only the presence of high frequency keying is the signal to the first line employed. The invention is thus "transparent" to the viewer in the absence of high frequency keys.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.