Video transmission system

• US 4,694,489 A
• Filed: 07/10/1986
• Issued: 09/15/1987
• Est. Priority Date: 12/22/1983
• Status: Expired due to Fees

• Current Assignee: Frederiksen, Jeffrey E.
• Original Assignee: Frederiksen, Jeffrey E.
• Inventors: Frederiksen, Jeffrey E.
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US06/884,213
• Time in Patent Office: 432 Days
• Field of Search: 358/120, 358/119, 358/122, 358/123, 380/10, 380/20
• US Class Current: 380/212
• CPC Class Codes: H04N 7/085 the inserted signal being digital
• CPC Class Codes: H04N 7/1696 by changing or reversing the order of active picture signal portions

Abstract

A subscriber cable television system uses predominantly digital signal processing techniques and has extremely high security and an increased capacity for transmitting program and customer data to individual decoder units. For ease of data handling, two-channel audio, video, and high capacity program and customer data are multiplexed for transmission on the composite video signal. The decoder unit employs a system timing circuit which precisely synchronizes the sample times on the received composite video signal to the chroma burst, regardless of whether the video information is for a color or black-and-white program. An improved time-warp and segment scrambling method is disclosed along with means for suppressing the undesirable effects of discontinuities in the scrambled video signal. The digital audio is transmitted as scrambled most significant bits in low resolution samples and unscrambled least significant bits in a high resolution remainder sample. The system timing circuit has a horizontal sync detector accommodating variable line length such as is provided by some video recording apparatus. The clock to the horizontal counter is selectively phase-reversed in response to early or late horizontal sync so that the timing resolution is twice the clock period. An improved self-adjusting threshold detector and other means are disclosed for detecting a "20 IEEE" suppressed horizontal sync so that the full range of video modulation may be used more effectively. Circuitry is also disclosed for transmitting the customer and program information in a multi-level correlative signalling format in order to more effectively use the band width of the entire television channel.

Claims

1. In a video transmission system providing secure transmission of a video signal over a communications channel for reception by designated customers, synchronization information indicating the starting positions of video lines and customer data for designating individual customers permitted to receive the video signal,

a decoder having means for detecting the synchronization information and thereupon generating horizontal sync pulses indicating the starting positions of the video lines, wherein the improvement comprises,

at least a portion of the customer data for a particular customer is transmitted in a preassigned time slot in a video line including a record number preassigned to the particular customer, and

the decoder has a customer memory programmed with a customer identification number including a programmed customer record number and a programmed customer time slot identifier, and means for latching the customer data from a video line having a record number matching the programmed customer record number, the customer data being latched from the video line at a time slot indicated by the programmed customer time slot identifier.

2. For use in a video transmission system providing secure transmission of a video signal over a communications channel for reception by designated customers, wherein said video signal includes a plurality of video lines, said video lines including synchronization information indicating the starting positions of the video lines, and some of said video lines each including a preselected record number and preselected customer data for reception by designated individual customers, the preselected customer data being arranged in time slots so that the customer data for an individual customer is transmitted in a respective preassigned one of said time slots,

a decoder comprising means for detecting the synchronization information and thereupon generating horizontal sync pulses indicating the starting positions of the video lines, a customer memory programmed with a customer identification number including a programmed customer record number and a programmed customer time slot identifier, and means operative upon a match between the programmed customer record number and the record number in a video line for latching the customer data in the video line at a time slot indicated by the programmed customer time slot identifier.