Method for developing a key signal for descrambling in television broadcasting
AssigneePioneer Electronic Corporation
InventorsYoshifumi Saeki, Shigeru Watanabe, Ryuichi Todoroki
Life of this patent
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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.
Claims11
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.
Dependencies are inferred from the claim text.