Time base correction apparatus
AssigneeVictor Company of Japan, Ltd.
InventorsTsuneo Ubukata, Hiroshi Takeshita
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Abstract
An apparatus for compensating a time base error of a video signal. A reference signal of no time base error is generated. A difference between a frequency of the reference signal and a frequency of a horizontal synchronizing signal included in an input analog video signal is detected and then a difference signal is outputted. In response to the difference signal, a phase of the reference signal is controlled. The video signal is sampled, based on the reference signal the phase of which is controlled, thus the video signal is converted into a digital signal in which the difference is cancelled. The digital signal is stored in a memory. And the stored digital signal is read out, based on the reference signal.
Claims3
An apparatus for compensating for a time base error of a video signal, in which an input video signal sampled by a first clock signal corresponding with a time base error of the input video signal is stored in memory means and read out therefrom by a second clock signal having a fixed frequency, the apparatus comprising:
- signal generation means for generating a master clock signal having a constant frequency;
- signal output means for detecting a difference between a standard and an interval of a synchronizing signal of the input video signal of the basis of the master clock signal, to output a difference signal indicating the difference;
- control means responsive to the difference signal for controlling a phase of an intermediate signal on the basis of the master clock signal, thus to output the first clock signal;
- sampling means for sampling the input video signal by the first clock signal;
- and
- clock generating means for generating the second clock signal derived from the master clock signal;
- wherein, the signal output means comprises:
- a counter for down-counting from a predetermined number by the master clock signal in the interval of the synchronizing signal included in the input video signal, to output a pulse signal according to a difference between a counted number of the master clock signal and the predetermined number;
- and
- a comparator for comparing the predetermined number and the number of the master clock signal counted during the interval of the synchronizing signal, to output a positive signal when the predetermined number is smaller than the counted number, and to output a negative signal when the predetermined number is larger than the counted number.
An apparatus for compensating for a time base error of a video signal, in which an input video signal sampled by a first clock signal corresponding with a time base error of the input video signal is stored in memory means and read out therefrom by a second clock signal having a fixed frequency, comprising:
- signal generation means for generating a master clock signal having a constant frequency;
- signal output means for detecting a difference between a standard and an interval of a synchronizing signal of the input video signal of the basis of the master clock signal, to output a difference signal indicating the difference, said signal output means comprising:
- a counter for down-counting from a predetermined number by the master clock signal in the interval of the synchronizing signal included in the input video signal, to output a pulse signal according to a difference between a counted number of the master clock signal and the predetermined number;
- and
- a comparator for comparing the predetermined number and the number of the master clock signal counted during the interval of the synchronizing signal, to output a positive signal when the predetermined number is smaller than the counted number, and to output a negative signal when the predetermined number is larger than the counted number;
- control means responsive to the difference signal for controlling a phase of an intermediate signal on the basis of the master clock signal, thus to output the first clock signal;
- sampling means for sampling the input video signal by the first clock signal;
- clock generating means for generating the second clock signal derived from the master clock signal;
- the control means comprises second signal generation means for generating the intermediate signal containing a specific number of pulse trains obtained from frequency division of the master clock signal and having the same phase difference;
- selection means for selecting a pulse train from the intermediate signal having a phase closest to a phase of the synchronizing signal included in the input video signal, and responsive to the positive or negative signal and a pulse of the pulse signal for changing the selected pulse train from the intermediate signal, to output the first clock signal.
Dependencies are inferred from the claim text.