| 摘要 |
PROBLEM TO BE SOLVED: To selectively provide video service to a pay broadcast system subscriber by restoring a ciphered video signal which is transmitted from a cable TV and a cable broadcast system into an original signal so as to permit it to be viewed. SOLUTION: A video signal decoding device separates a synchronizing signal and data from the ciphered video signal, generates a control signal with the separated synchronizing signal and data as reference, removes the virtual synchronizing signal from the ciphered video signal by the control signal and, then, executes non-inversion and inversion amplification by on-inversion/inversion amplifiers 21a, 21b/24a, 24b. Then, the non-inversion and inversion-amplified video signal is inverted by the control signal after selection and the original synchronizing signal is restored. The restored video signal is repeatedly non- inversion and inversion-amplified and, then, the synchronizing signal which is selectively removed at the time of ciphering is selectively restored so that the signal is easily restored to the original video signal even when the video signal is ciphered by a virtual synchronizing signal inserting system. |
