KR0167997B1 - The preprocessing circuit for time axis compensation - Google Patents

Abstract

A circuit for processing an image signal in connection with a TBC includes conversion means for digitally converting a luminance demodulated signal according to an applied clock frequency and outputting the same to a TBC memory; Synchronizing separation means for outputting a synchronizing frequency, phase synchronizing means for outputting a phase synchronizing signal in response to the horizontal synchronizing frequency applied from the synchronizing separation means and the clock frequency applied from the TBC, and dividing it at a predetermined ratio; Decoding means for generating a color difference signal by phase shifting the color signal converted into the component according to the phase synchronizing signal, and multiplexing and applying the color difference signal applied to the decoding means in response to a selection signal applied from TBC. It consists of multiplexing conversion means for digitally converting and outputting The.

Description

Preprocessing Circuit for Timebase Correction

1 is a pre-processing circuit diagram of time-base correction located in front of a conventional time base corrector (TBC).

2 is a preprocessing circuit diagram for time-base correction according to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal processing apparatus such as a VTR, and more particularly, to a preprocessing circuit for enabling efficient TBC.

In general, a TBC circuit for time-base correction is used to remove interleaving and jitter components of luminance and color signals in the processing of digital video signals. The need for pre-processing emerges.

Referring to FIG. 1, a conventional technology is briefly described. For example, when a video signal reproduced from a head of a VTR or the like is a VHS, a low-conversion (629 KHZ) color signal is superimposed on an FM luminance signal. It is a signal.

The Y / C separator 2 separates the signal applied from the head into Y (luminance signal) and C (color signal), respectively, with a comb filter or the like.

The Y signal output from the Y / C separator 2 is applied to the luminance signal demodulator 4 and output as an FM demodulated luminance signal.

The C signal output from the Y / C separator 2 is converted by the second frequency converter 6 into a color signal with a high frequency (3,58MHZ) component at low frequency.

Here, the high frequency conversion of the second frequency converter 6 is performed by the PPL method, and the error frequency separated by the color burst separator 10, that is, the component of fsc ± Δfs is determined by the phase comparator 12. Phase comparison with (3,58MHZ) and an error voltage corresponding to the phase difference is applied to the FS control generator 14. Accordingly, the FS controlled oscillator 14 oscillates fs ± Δfs frequency and is applied to the first frequency converter 16 in response thereto. The first frequency converter 16 outputs a frequency of fsc + fs ± Δfs to the second frequency converter 6 by mixing the fs ± Δfs and the fsc.

However, in case of time-base correction of the Y and C signals applied through the mixer 8 in the component type TBC, there is a jitter component ± ΔFH in the Y signal, but a jitter component in the 3,58MHZ of the C signal. It can be seen that there is no interleaving for Y / C because there is no.

In other words, the carrier color signal is superimposed on the luminance signal when the TBC is performed because there is no interleaving between Y / C, resulting in serious deterioration of image quality, and it is difficult to perform digital processing after the TBC.

In addition, even though there is no jitter, the color signal sometimes causes jitter components by performing TBC. As described above, the preprocessing of the TBC shear with a composite rather than a component is performed by another digital process (for example, multi-screen or A problem has arisen in performing the PIP screen).

Accordingly, an object of the present invention is to provide a preprocessing circuit for time-base calibration that can solve the above conventional problems.

Another object of the present invention is to provide a pre-processing circuit for time-base calibration, which is simple in construction and suitable for digital processing at a later stage.

Another object of the present invention is to provide a preprocessing circuit for a TBC that can improve the deterioration of image quality.

According to the present invention for achieving the above object, the conversion means for digitally converting the luminance demodulated signal from the luminance signal demodulator in accordance with the applied clock frequency to the TBC memory, and horizontally by synchronously separating the luminance demodulated signal Synchronous separation means for outputting a synchronous frequency and a vertical synchronous frequency, and a phase synchronous signal for outputting a phase synchronous signal in response to the horizontal synchronous frequency applied from the synchronous separation means and the clock frequency applied from the TBC and dividing it at a predetermined ratio Means for decoding the color signal converted into a high frequency component according to the phase synchronization signal to generate a color difference signal, and multiplexing and applying the color difference signal applied to the decoding means in response to a selection signal applied from the TBC. Multiplexing by digitally converting and outputting the clock frequency Ring means is provided in the front end TBC.

The above objects of the present invention can be achieved by the above means.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is an overall block diagram of the present invention, wherein the TBC unit 100 is the time base calibrator described above.

The input signal commonly input to the A / D converter 20 and the sync separator 22 is a signal output from the luminance signal demodulator of FIG. 1 described above, and the signal input from the color decoder 30 is of FIG. It is the signal output from the 2 frequency converter.

In addition, the internal display terminal of the TBC unit 100 will be described. M1 and M2 are memory input terminals composed of RAMs or the like in the TBC unit 100 and are usually about 8 bits.

WC means the light control frequency and is also provided as the sampling clock of the A / D converter 20 and the A / D converter 34 and is also applied as one side input frequency of the PLL 24.

In this case, the frequency of the WC is usually 910 (fH ± ΔfH).

The frequency divider 26 connected to the PLL 24 adjusts the frequency of the high frequency converted color signal output from the second frequency converter in response to 910 (fH ± ΔfH), that is, fsc ± CBW at 0 ° and 90 °. Two color difference signals RY and BY are output by phase shifting as the frequency of the divider.

Therefore, the color difference signal is multiplexed by the multiplexer 32 and input to the A / D converter 34.

The A / D converter 34 outputs 8-bit digital data to the memory of the TBC unit 100 in response to the clock frequency WC.

By this preprocessing, the color difference signal has the jitter component ΔfH like the Y signal, so that a complete Y / C interleave is established.

Accordingly, it can be seen that better TBC can be achieved by processing the entire interleaving already at the previous stage of the TBC unit 100 to prevent deterioration of image quality.

As described above, the present invention has the advantage that accurate Y-C interleaving can be made at the TBC shear, so that correct time-base correction can be made, and thus the reproduction quality is improved.

Claims (3)

A circuit for processing a video signal in connection with a TBC, comprising: conversion means for digitally converting a luminance demodulated signal according to an applied clock frequency and outputting it to a memory for a TBC; Synchronizing separation means for outputting a vertical synchronizing frequency, phase synchronizing means for outputting a phase synchronizing signal in response to the horizontal synchronizing frequency applied from the synchronizing separating means and the clock frequency applied from the TBC, and dividing it at a predetermined ratio; Decoding means for generating a color difference signal by phase shifting a color signal converted into a high frequency component according to the phase synchronization signal, and multiplexing and applying a color difference signal applied to the decoding means in response to a selection signal applied from a TBC. Multiplexed conversion means for digitally converting and outputting the clock frequency Circuit characterized by a name. 2. The circuit of claim 1 wherein the circuit is connected to a front end of the TBC to perform pretreatment. 2. The circuit according to claim 1, wherein the multiplexing means comprises a multiplexer for multiplexing the chrominance signal and an A / D converter for digitally converting the output of the multiplexer to an applied clock frequency.