System for formatting digital signals to be transmitted
US4729020A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 1, 1987 |
| Grant date | Mar 1, 1988 |
| Priority date | — |
| Expiry date | Jun 1, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N19/93
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
In a preferred embodiment, a computer is employed to control the system. The system initially accepts analog signals and converts them into digital signals, which are then compressed, at a DPCM encoder, into a three bit code. Thereafter the once compressed signals are further compressed in accordance with a variable length code. The twice compressed digital signals are transmitted through formatter circuitry whereat a tag is added to indicate (in addition to other information) what forms of compression have been employed on the digital signals which follow the tag. The twice compressed and tagged digital signals are forwarded to a buffer storage device. The role of the buffer storage is to keep a relatively constant supply of data signals so that there is a relatively constant supply of pels moving to the transmitter at a constant frequency. The computer monitors the buffer fullness and the rate at which it is being loaded or is emptying. In response to such monitoring the system compresses more lines of digitized video or compresses less lines of digitized video. Additional compression can be effected by horizontal subsampling or by changing the first DPCM coding operation from a …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.