Time base corrector
AssigneeSony Corporation
InventorMitsugu Yoshihiro
Life of this patent
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Abstract
A time base corrector for correcting time base fluctuations in a video signal is effective to remove both low frequency time base fluctuations and repetitive high frequency time base fluctuations repeating at the field period of the video signal. The time base corrector includes a memory having a plurality of addresses for storing residual phase error data corresponding to iundividual horizontal lines of each field period. A control circuit supplies corresponding residual phase error data from the memory to be used in compensating a present phase error signal whereby the high frequency time base fluctuations may be removed, and further mixes the present phase error signal with corresponding residual phase error data to generate new residual phase error data for storage in the memory in place of the original residual phase error data.
Claims16
A time base corrector for correcting time base fluctuations in a video signal containing a horizontal synchronizing signal and being reproduced from a recording medium, comprising:
- a write clock generator for generating a write clock signal having said time base fluctuations of the reproduced video signal;
- a memory unit for storing the reproduced video signal in response to the write clock signal;
- and
- a read clock generator for generating a read clock signal supplied to said memory unit to read the stored reproduced video signal from said memory unit, characterized in that said write clock generator comprises:
- voltage controlled oscillator means for generating an oscillating output signal;
- frequency divider means for frequency dividing said oscillating output signal to provide a frequency divided output;
- phase comparator means for comparing phases of said frequency divided output and said horizontal synchronizing signal of said reproduced video signal to provide a comparison output;
- low pass filter means for filtering said comparison output to provide a filtered output;
- analog-to-digital converter means for converting said comparison output to digital data;
- memory means having a plurality of addresses for storing residual phase error data;
- control means supplied with the converted digital data for mixing, in a predetermined ratio, said converted digital data and corresponding residual phase error data read from a selected one of said addresses in said memory means to generate new residual phase error data and to store said new residual phase error data at said selected address;
- digital-to-analog converter means for converting said residual phase error data read out from said selected address in said memory means to an analog control voltage;
- and
- adder means for adding together said filtered output of said low pass filter means and said analog control voltage to form a voltage control signal for controlling said voltage controlled oscillator means.
A method for correcting time base fluctuations in a video signal containing a horizontal synchronizing signal and being reproduced from a recording medium, said method comprising the steps of:
- generating a write clock signal having said time base fluctuations of the reproduced video signal;
- storing the reproduced video signal in response to the write clock signal;
- and
- generating a read clock signal for reading out the stored reproduced video signal, said method characterized in that said step of generating said write clock signal comprises:
- generating a voltage controlled oscillating output signal;
- frequency dividing said oscillating output signal to provide a frequency divided output;
- comparing a phase of said frequency divided output with a phase of said horizontal synchronizing signal of said reproduced video signal to provide a comparison output;
- low pass filtering said comparison output to provide a filtered output;
- converting said comparison output to digital data;
- storing residual phase error data at a plurality of addresses;
- converting residual phase error data read out from a selected one of said addresses to an analog control voltage;
- mixing in a predetermined ratio said converted digital data and corresponding residual phase error data from the selected address to generate new residual phase error data;
- storing said new residual phase error data in the selected address;
- and
- adding together said filtered output and said analog control voltage to form a voltage control signal to control the generation of said oscillating output signal.
Dependencies are inferred from the claim text.