US4794643A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for developing a key signal for descrambling in television broadcasting
Assignee: Pioneer Corp
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Filing: 1983-06-30
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Granted: 1988-12-27
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Expires: 2003-06-30
Abstract
Abstract A scrambling method for TV pictures avoids deterioration of the reproduced picture by level compressing only selected horizontal flyback portions according to a randomly selected pattern to prevent synchronization at the receiver. Key signals are added repetitively to a plurality of horizontal synch signals in one frame so as to enable descrambling of the picture at the decoder, even if noise or data error interferes with one or more of the signals.
Inventors
- 👤 Yoshifumi Saeki
- 👤 Shigeru Watanabe
- 👤 Ryuichi Todoroki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 17:35
CPC Classifications
H; H04; H04N; H04N7/00; H04N7/16; H04N7/162; H04N7/167; H04N7/1675; H04N7/171; H04N7/1713
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
155 words
In a television broadcasting method wherein vertical synchronizing signals are developed as outputs at predetermined intervals, a plurality of horizontal synchronizing signals are developed between said vertical synchronizing signals and video signals are modulated and developed between said horizontal synchronizing signals, the improvement comprising: selectively level compressing ones of said horizontal synchronizing signals so as to effect scrambling of each field of a TV picture signal; and generating a key signal for descrambling said each field of said TV picture signal, wherein a plurality of said key signals for descrambling which correspond to a plurality of fields including a particular field and subsequent fields are superposed, within said particular field, on a selected plurality of horizontal synchronizing signals between consecutive ones of said vertical synchronizing signals, wherein ones of said plurality of said key signals which are not available for descrambling the particular field in which they are superposed are available for descrambling subsequent fields.
Claim 2
Dependent Claim
155 words
In a television broadcasting method wherein vertical synchronizing signals are developed as outputs at predetermined intervals, a plurality of horizontal synchronizing signals are developed between said vertical synchronizing signals and video signals are modulated and developed between said horizontal synchronizing signals, the improvement comprising: selectively level compressing ones of said horizontal synchronizing signals so as to effect scrambling of each field of a TV picture signal; and generating a key signal for descrambling said each field of said TV picture signal, wherein a plurality of said key signals for descrambling which correspond to a plurality of fields including a particular field and subsequent fields are superposed, within said particular field, on a selected plurality of horizontal synchronizing signals between consecutive ones of said vertical synchronizing signals, wherein ones of said plurality of said key signals which are not available for descrambling the particular field in which they are superposed are available for descrambling subsequent fields.
Claim 3
Dependent Claim
39 words
A method according to claim 1, wherein said each frame of said TV picture signal is divided into a plurality of portions, and each portion is independently scrambled or left as it is in accordance with said each frame.
Claim 4
Dependent Claim
32 words
A method according to claim 2, including periodically generating random numbers for generating said key signals, and holding a plurality of said random numbers for said plurality of frames in a memory.
Claim 5
Dependent Claim
23 words
A method according to claim 3, including processing said random numbers through shift register means to control performance of said level compressing step
Claim 6
Dependent Claim
32 words
A method according to claim 3, including checking, at a decoder portion, the content of said key signals derived from a portion of said TV picture signal not subjected to level compression.
Claim 7
Dependent Claim
27 words
A method according to claim 5, including decoding said scrambled TV picture signal using said derived key signals as indicators for signal portions to be level expanded.
Claim 8
Dependent Claim
38 words
A method according to claim 1, wherein said key signals are superposed on at least 10 horizontal synchronizing signals following said vertical synchronizing signals and include information for decoding said plurality of fields of said TV picture signal.
Claim 9
Dependent Claim
46 words
A method according to claim 1, wherein said plurality of horizontal sychronizing signals include a flyback signal indicative of a horizontal flyback interval, said method including the steps of level-compressing said flyback signal before it is broadcast, and level-expanding said flyback signal after it is received.
Claim 10
Dependent Claim
40 words
A method according to claim 1, including the steps of demodulating said plurality of key signals in series, checking the demodulated key signals for accuracy, and outputting said demodulated key signals in parallel to a memory if they are accurate.
Claim 11
Dependent Claim
44 words
A method according to claim 9, including the step of, when said demodulated key signals are not accurate, shifting contents of said memory so as to output previously stored descramblingg information corresponding to one of said plurality of fields being descrambled at the time.
Claim 12
Dependent Claim
16 words
A method according to claim 1, wherein a number of said plurality of fields is five.
References Cited (Backward Citations)
US2603714A
Cited
US4319273A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-12-27 | 1992-06-27 | 1992-12-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-12-27 | 1996-06-27 | 1996-12-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-12-27 | 2000-06-27 | 2000-12-27 | $7700.00 | Window Closed / Lapsed |