Method and apparatus for extracting binary signals included in vertical blanking intervals of video signals

Claim 2

Apparatus for extracting binary signals occurring in an information signal reproduced from a tape transported at variable velocity past a transducer rotated at a predictable constant speed, each binary signal having a selected number of bits at regular intervals with certain of the bits forming a known bit pattern in each binary signal, and each binary signal having a bit rate which varies as the rate of reproduction of the information signal, comprising: means (71) for generating a control signal having a rate proportional to the velocity at which the tape is transported past the transducer; a clock generator (104) responsive to the control signal for generating a clock signal having a rate corresponding to the bit rate at which the binary signal is reproduced from the tape by the transducer; and a binary signal detector (106,108) coupled to receive the reproduced information signal, and responsive to said clock signal and the occurrence of the known bit pattern for detecting the occurrence of the binary signal in the received information signal.

Claim 3

Apparatus for extracting a binary signal including a known bit pattern occurring in the vertical blanking intervals of a video signal reproduced from a tape transported past a rotating transducer, the apparatus comprising: means (71) for generating a control signal having a rate proportional to the velocity at which the tape is transported past the transducer; a clock generator (104) responsive to the control signal and arranged to compute, and to generate a clock signal having a rate corresponding to the bit rate at which the binary signal is reproduced from the tape by the transducer; means (66) responsive to the video signal reproduced by the transducer for generating a stream of binary data therefrom having a first or second level according as said video signal has an amplitude above or below a reference level; and a binary signal detector (106,108) coupled to receive the stream of binary data and the clock signal, said detector being responsive to said clock signal and the occurrence of said bit pattern of the binary signal for detecting the occurrence of the binary signal in the received stream of binary data.

Claim 4

Apparatus for extracting a binary signal including a known bit pattern occurring in the vertical blanking intervals of a video signal reproduced from a tape transported past a rotating transducer, the apparatus comprising: means (71) for generating a control signal having a rate proportional to the velocity at which the tape is transported past the transducer; a clock generator (104) responsive to the control signal and arranged to compute, and to generate a clock signal having a rate corresponding to the bit rate at which the binary signal is reproduced from the tape by the transducer; means (66) responsive to the video signal reproduced by the transducer for generating a stream of binary data therefrom having a first or second level according as said video signal has an amplitude above or below a reference level; and a binary signal detector (106,108) coupled to receive the stream of binary data and the clock signal, said detector being responsive to said clock signal and the occurrence of said bit pattern of the binary signal for detecting the occurrence of the binary signal in the received stream of binary data.

Claim 5

Apparatus according to claim 1 wherein said means for generating a control signal comprises a tachometer coupled to the transported tape or to a capstan which drives the tape.

Claim 6

Apparatus according to claim 2 or claim 3 in which the clock generator comprises a tape speed detector (130) responsive to the control signal to provide a signal representing the speed of the tape and means (200-210) for modifying this signal in accordance with a presumed fixed speed of the transducer to provide a signal denoting the relative velocity of the tape and the transducer and a pulse generator responsive to this signal to generate the clock signal.

Claim 7

Apparatus according to claim 4 wherein said tape speed detector (130) comprises: a decrementing counter (150) responsive to a reference clock for generating a tape speed detector clock; and an incrementing counter (156) responsive to the control signal for producing the tape speed signal, the up counter being reset by the tape speed detector clock.

Claim 8

Apparatus according to any of claims 2 to 5 further comprising means (120) for selectively inhibiting the clock signal.

Claim 9

Apparatus according to claim 6 further comprising means for activating said inhibit means outside the vertical blanking interval.

Claim 10

Apparatus according to claim 7 further comprising means for activating said inhibit means during selected periods within the vertical blanking interval.

Claim 15

A method according to claim 10 wherein the bits forming the known bit pattern are distributed over a specified interval in each binary signal, and the examining steps includes periodically examining successive intervals of the reproduced information signal with the examined interval at least equal to the specified interval; each successive interval of reproduced information signal examined displaced from a previously examined interval of reproduced information signal by an amount corresponding to a bit interval of the binary signal.