JPH0244887A - Time base variation correction device - Google Patents

Abstract

PURPOSE:To remove the time base variation component by detecting the presence of burst in a reproduced decoded video signal, and sampling the phase comparison output of a burst signal by using this detection signal. CONSTITUTION:A burst detection circuit 44 detects the presence of the burst signal in the reproduced decoded video signal, and a burst phase difference detection circuit 45 detects the phase difference of the burst signal. Then, when the burst signal in the reproduced decoded video signal is normal, the burst phase difference detection circuit 45 outputs a signal corresponding to the phase difference of the burst signal. Besides, in the case an amplitude becomes small because of drop-out, etc., too, it outputs the signal Z that a normal value is held without outputting a wrong signal X. Thus, the time base variation component can be removed without causing the malfunction of a coarse TBC and a fine TBC.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a time axis fluctuation correction device for removing a time axis fluctuation component of a reproduced decoded video signal reproduced from a recording medium in an image reproducing apparatus such as a VTR or a video disc. Regarding.

2. Prior Art As a conventional time axis fluctuation correction device, for example, Japanese Patent Laid-Open No. 6
A method disclosed in Japanese Patent No. 0-216691 [Time axis fluctuation correction device] is known. Hereinafter, a conventional time axis fluctuation correction device will be described with reference to the drawings.

FIG. 5 shows a block diagram of a conventional time axis fluctuation correction device. In FIG. 5, 10 is an input terminal of the device;
20 is an output terminal of the device; 30 is a variable delay element 3 composed of a CCD or the like; a horizontal synchronization separation circuit that extracts a horizontal synchronization signal from the reproduced decoded video signal and also generates a burst gate signal; A horizontal phase difference detection circuit detects a phase error of a synchronization signal, 35 is a phase compensation circuit composed of an active filter, etc., and 36 is a voltage controlled oscillation circuit (VCO) whose oscillation frequency can be changed by voltage. Further, 40 is a phase correction circuit that corrects the phase shift of the color subcarrier of the reproduced decoded video signal, 41 is a burst separation circuit that extracts a burst signal from the reproduced decoded video signal, and 42 is a burst signal that detects the phase error of the burst signal. A phase difference detection circuit, 43 a reference signal generation circuit that generates a reference horizontal synchronization signal and a reference burst signal, 33 an adder, and 34 a low pass filter (LPF).

In FIG. 5, a variable delay element 30, a horizontal synchronization separation circuit 31, a horizontal phase difference detection circuit 32, a low-pass filter (L
Coarse TB with seven broncs: PF) 33, adder 34, phase compensation circuit 35, and voltage controlled oscillation circuit (VCO) 36.
C, and the time axis fluctuation component included in the reproduced decoded video signal is determined by the phase shift of the burst signal (maximum approximately 140 ns).
) to remove the following. In addition, a fine TBC is composed of three blocks: a phase compensation circuit 40, a burst M circuit 41, and a burst phase difference detection circuit 42, and a coarse TBC removes the phase shift of the burst signal to below the degree (maximum approximately 140 ns). To remove time axis fluctuation components in a reproduced decoded video signal with higher accuracy.

The operation of the conventional time axis fluctuation correction device configured as described above will be described below with reference to FIG.

A reproduced decoded video signal including a time axis fluctuation component inputted from an input terminal 10 of the apparatus passes through a variable delay element 30 and is sent to a horizontal synchronization separation circuit 31, a burst separation circuit 41, and a phase correction circuit 40. The horizontal synchronization separation circuit 31 separates the horizontal synchronization signal in the reproduced decoded video signal and sends it to the horizontal phase difference detection circuit 32 , and also generates a burst gate signal and sends it to the burst separation circuit 41 .

The horizontal phase difference detection circuit 32 uses the reference horizontal synchronization signal generated by the reference signal generation circuit 43 and the horizontal synchronization separation circuit 3.
1 detects the phase difference between the reproduced decoded video signal and the horizontal synchronizing signal and sends it to the adder 34. Further, the burst separation circuit 41 separates the burst signal in the reproduced decoded video signal and sends it to the burst phase difference detection circuit 42 . The burst phase difference detection circuit 42 detects the phase difference between the reference burst signal generated by the reference signal generation circuit 43 and the burst signal in the reproduced decoded video signal sent from the burst signal separation circuit 41, The 6LPF 33, which is sent to the LPF 33 and the phase correction circuit 40, extracts only the low frequency component of the burst phase difference signal and sends it to the adder 34. Adder 3
4, the horizontal synchronization phase difference signal sent from the horizontal phase difference detection circuit 32 and the low frequency component of the burst phase difference signal sent from the LPF 33 are added and sent to the phase compensation circuit 35.

In the phase compensation circuit 35, the adder 3
The phase difference signal from 4 is amplified and phase compensated, and
Send to C036.

VCO36 is a voltage controlled oscillation circuit, and phase compensation circuit 3
The oscillation frequency is changed according to the phase difference signal sent from 5. The variable delay element 30 changes the amount of delay in response to changes in the oscillation frequency of the VCO 36, and removes time axis fluctuation components in the reproduced decoded video signal. On the other hand, the phase correction circuit 4
0, by changing the phase of the color subcarrier according to the burst phase difference signal detected by the burst phase difference detection circuit 42, the time axis fluctuation component in the reproduced decoded video signal is
Remove with precision. The reason why the burst phase difference signal detected by the burst phase difference detection circuit 42 is returned to the coarse TBC via the LPF 33 is to enable the phase correction circuit 40 to operate within the phase difference of the burst signal (maximum ±140ns). It is. Further, the reference signal generation circuit 43 generates a reference burst signal and a horizontal synchronization signal by frequency-dividing a signal generated using a crystal oscillator.

The above configuration constitutes a time axis variation correction device, and the reproduced decoded video signal containing the time axis variation component inputted from the input terminal 10 of the device is converted into coarse TBC and fine TBC.
As a result, the time axis fluctuation component is removed, and the output terminal 2 of the device is
0, a composite video signal synchronized with the reference burst signal and the reference horizontal synchronization signal generated by the reference signal generation circuit 43 is output.

Problems to be Solved by the Invention However, in the conventional time axis fluctuation correction device configured as described above, a phase comparison operation is always performed on the Haas) signal in the reproduced decoded video signal, and this burst phase difference is Since the signal is used to drive the variable delay element 30 and phase correction circuit 4o shown in FIG. 5, the amplitude of the burst signal in the reproduced decoded video signal may become small or disappear due to dropouts, etc. If this happens, the phase comparison operation of the burst signal will malfunction, and the variable delay element 30 and phase correction circuit 40 shown in FIG. The problem was that it became impossible to do so.

The present invention has been made in view of the above points, and even when the amplitude of the burst signal in the reproduced decoded video signal is disturbed, the phase difference signal of the burst signal is not greatly disturbed, and the appropriate time axis can be adjusted. The present invention provides an apparatus for correcting fluctuations.

Means for Solving the Problems In order to solve the above problems, the time axis fluctuation correction device of the present invention includes a burst detection circuit in the reproduced decoded video signal system, detects the presence or absence of a burst signal, and detects the presence or absence of a burst signal using this detection signal. , the phase difference signal of the burst signal is sampled, and when a burst signal in the reproduced decoded video signal is detected, the phase difference signal of the burst signal is sampled and output, and the phase difference signal in the reproduced decoded video signal is sampled and output. If a burst signal is not detected, the normal state is held (previous value held) without sampling the phase difference signal of the burst signal (this prevents the phase difference signal of the burst signal from being disturbed. It is something to prevent.

Effect of the present invention With the above-described configuration, the phase difference signal of the burst signal in the reproduced decoded video signal is sampled or held according to the state of the burst signal, and the amplitude of the burst signal is disturbed due to dropout or the like. , or if it disappears, the phase difference signal of the burst signal is held at its normal value and output, so the operation of the phase correction circuit and variable delay element is not disturbed, and the phase difference signal of the burst signal is output for an appropriate time. Axis fluctuations can be corrected.

Example Below, regarding a time axis fluctuation correction device according to an example of the present invention,
This will be explained with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In FIG. 1, 10 is an input terminal of the device, 20 is an output terminal of the device, 30 is a variable delay element composed of a CCD, etc., 31 is a horizontal synchronizing signal taken out from a reproduced decoded video signal, and a burst gate. 32 is a horizontal phase difference detection circuit that detects the phase error of the horizontal sync signal; 33 is a low-pass filter (LPF);
), 34 is an adder, 35 is a phase compensation circuit composed of an active filter, etc., and 3G is a voltage controlled oscillation circuit (VCO) whose oscillation frequency can be varied by voltage. Also, 4
0 is a phase correction circuit that corrects the phase of the color subcarrier of the reproduced decoded video signal, 41 is a burst separation circuit that extracts a burst signal from the reproduced decoded video signal, and 43 is a reference signal that generates a reference horizontal synchronization signal and a burst signal. Generation circuit, 4
4 is a burst detection circuit that detects the presence or absence of a burst signal in the reproduced decoded video signal, and 45 is a burst phase difference detection circuit that detects a phase error of the burst signal.

In FIG. 1, blocks labeled with the same numbers as in FIG. 5 indicate the same circuit blocks.

The operation of the time axis fluctuation correction device of the present invention configured as described above will be described below with reference to FIG. 1.

In FIG. 1, a variable delay element 30, a horizontal synchronization separation circuit 31, a horizontal phase difference detection circuit 32, a low-pass filter (L
Coarse TB with seven blocks: PF) 33, adder 34, phase compensation circuit 35, and voltage controlled oscillation circuit (VCO) 36.
C, and the time axis fluctuation component included in the reproduced decoded video signal is determined by the phase shift of the burst signal (maximum approximately 140 ns).
) to remove the following.

In addition, a fine TBC is composed of four blocks: a phase correction circuit 40, a burst separation circuit 41, a burst detection circuit 44, and a burst phase difference detection circuit 45. In a coarse TBC, the phase shift of the burst signal is about 140 ns (maximum). To further accurately remove time axis fluctuation components in a reproduced decoded video signal that have been removed to the extent below.

The coarse TBC has exactly the same configuration as the conventional time axis fluctuation correction device shown in FIG.
After adding the horizontal synchronization phase difference signal obtained by detecting the phase difference of the υ1 signal and the low-frequency component of the burst phase difference signal obtained by the fine TBC and performing phase compensation and amplification, the voltage controlled oscillation circuit (VC○ ) 36 and the delay amount of the variable delay element 30, the time axis fluctuation component included in the reproduced decoded video signal is removed to a level equal to or less than the phase shift of the burst signal (maximum approximately 140 ns).

On the other hand, in the fine TBC, first, the reproduced decoded video signal from which the time axis fluctuation component has been removed to below the phase shift of the burst signal (maximum approximately 140 ns) is inputted in the coarse TBC, and is sent to the phase correction circuit 4o. The signal is also sent to the burst separation circuit 41 and the burst detection circuit 44. The burst separation circuit 41 separates the burst signal in the reproduced decoded video signal and sends it to the burst phase difference detection circuit 45 as a reproduced burst signal. In addition, the burst detection circuit 4
4 detects a burst signal in the reproduced decoded video signal,
A zumbling pulse is sent to the burst phase difference detection circuit 45. The burst phase difference detection circuit 45 uses the reproduced burst signal from the burst separation circuit 41 and the reference signal generation circuit 4.
3, and if a burst signal is detected in the reproduced decoded video signal in response to the sampling pulse from the burst detection circuit 44, sampling is performed and the reproduction is performed. If a burst signal in the decoded video signal is not detected, the previous value is held and the phase correction circuit 40 and low-pass filter (L
PF) 33. The phase correction circuit 40 accurately corrects the time axis fluctuation of the reproduced decoded video signal by changing the phase of the color subcarrier in the reproduced decoded video signal.

Furthermore, the reference signal generation circuit 43 obtains a reference burst signal and a reference horizontal synchronization signal by dividing the oscillation frequency of the crystal oscillator.

The second part is a block diagram showing details of the burst detection circuit 44 and the burst phase difference detection circuit 45 in the time-base fluctuation correction apparatus of the present invention shown in FIG. Also, Figure 3 shows
FIG. 4 is a signal line diagram showing the operation of the burst detection circuit 44 of the time-base fluctuation correction device of the present invention shown in FIG. 2, and FIG. 4 is a signal line diagram showing the operation of the detection circuit 45. FIG.

In FIG. 2, 44 is an input terminal to which the output video signal of the variable delay line 30 shown in FIG. An input terminal 451 is not shown in FIG. 1 and is an input terminal to which the output terminal of the burst separation circuit 41 is input manually.
52 is an input terminal into which a reference burst signal generated by the reference signal generating circuit 43 shown in FIG. 1 is input; 456 is an input terminal;
An output terminal for outputting the output signal of the burst phase difference detection circuit 45 shown in FIG. 1, 443 a band pass filter (BPF) for extracting the color signal, 444 an amplifier for amplifying the amplitude of the color signal, 445 for periods other than the burst period The burst gate 0446 that sets the signal to GND potential is an absolute value circuit (ABS) that takes the absolute value of the signal, 447 is a comparator that compares it with a reference potential and outputs the comparison result, and 448 is a low-pass circuit that extracts low-frequency components. A filter (LPF) 453 is a phase comparator that detects the phase difference between the burst signal in the reproduced video signal and a reference burst signal, 454 is a switch that samples the comparison output of the phase comparator 453, and 455 is a switch 454 This is a capacitor that holds the sampling output.

Hereinafter, the operation of the burst detection circuit 250 will be described first with reference to FIGS. 2 and 3. The reproduced decoded video signal (signal A in FIG. 3) inputted from the input terminal 441 shown in FIG.
is extracted.

(Signal B in Figure 3) Next, after being amplified by an amplifier 444 to stabilize the operation of the next stage,
The voltage is fixed at the CND potential except during the burst period, and converted into an absolute value by an absolute value circuit (ABS) 446 to become a signal C (signal C in FIG. 3). Next, the signal C is compared with the reference voltage Vo by a comparator 447 and becomes a signal D (signal D in FIG. 3).

Furthermore, a low-pass filter (LPF) 448 extracts a low frequency component of the signal to form a signal E (third V signal E), which becomes a control signal for a switch 454.

This control signal E is obtained by comparing the signal C with the reference voltage 0 in the comparator 447 in FIG. 2, as shown in the signal C shown in FIG. A) The amplitude of the burst signal in
When the signal C becomes small as shown in section b of the signal A shown in the figure,
The amplitude of signal C shown in FIG. 3 becomes smaller, and the signal C shown in FIG.
There is no longer a section larger than o, and no zumbling pulse appears in section b, as in signal E shown in FIG.

At this time, the signal Z at the output terminal 456 shown in FIG.
The state is shown in FIG. The operation of the burst phase difference detection circuit 45 in FIG. 2 will be described below with reference to FIGS. 2 and 4. The burst signal in the reproduced decoded video signal inputted from the input terminal 451 and the reference burst signal inputted from the input terminal 452 are phase-compared by a phase comparator 453, and a signal χ (signal X in FIG. 4) is obtained. . This signal X is sampled by a switch 454 and a capacitor 455 to become a signal Z (signal Z in FIG. 4).

This signal Z is sampled with the control signal E shown in Part 3, so if a burst signal is detected in the reproduced decoded video signal like the signal Z shown in Figure 4, it is sampled and output. , if a burst signal in the reproduced decoded video signal is not detected, the normal state value is held.

As described above, according to this embodiment, the burst phase difference detection circuit 45 shown in FIG. Even if the amplitude becomes small due to dropout, etc., it will not output the incorrect signal The coarse TBC and fine TBC shown in FIG. 1 can remove time axis fluctuation components without malfunctioning.

As described in detail, the time axis fluctuation correction device according to the present invention has a configuration that detects the presence or absence of a burst in a reproduced decoded video signal, and uses this detection signal to sample the phase comparison output of the burst signal. By doing this, even if the amplitude of the burst in the reproduced decoded video signal becomes small due to dropout or the like or disappears, the phase comparison output of the burst signal will be output while holding the normal value. Therefore, coarse TBC and fine TBC can remove time axis fluctuation components without malfunctioning, and their practical effects are great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an outline of the time axis fluctuation correction device according to the present invention, and FIG. 2 is a block diagram showing the outline of the time axis fluctuation correction device according to the present invention shown in FIG. 1. A block diagram showing the details of one embodiment of the phase difference detection circuit-u field, FIG. 3 is a signal line diagram showing the operation of the burst detection circuit shown in FIG. 2, and FIG. Signal diagram showing the operation of the burst phase difference detection circuit, No. 5
The figure is a block diagram schematically showing a conventional time axis fluctuation correction device. 10...Input terminal, 20...Output terminal, 30...Variable delay element, 31...Horizontal synchronization separation circuit, 32...Horizontal phase difference Detection circuit, 33
...Low pass filter (LPF), 34...
... Adder, 35 ... Phase compensation circuit, 36.
... Voltage controlled oscillation circuit, 40 ... Phase correction circuit, 41 ... Burst separation circuit, 4245.
...Burst phase difference detection circuit, 43...
Reference signal generation circuit, 44... Burst detection circuit, 441, . 442... Burst detection circuit 44
input terminals, 451, 452...input terminals of the burst phase difference detection circuit 45, 456...output terminals of the Haas I-phase difference detection circuit 45, 443...
・Band pass filter (BPF), 444... Amplifier, 445... Burst gate, 446...
... Absolute value circuit (ABS), 447 ... Comparator, 448 ... Low pass filter (L
PF), 453... Phase comparator, 454...
...Switch, 455...Capacitor, A.
...Band pass filter (BPF) in Figure 2
Input signal of 443, B... Output signal of band pass filter (BPF) 443 in FIG. 2, C...
. . . Output signal of the absolute value circuit (ABS) 446 in FIG. 2, D . . . Comparator 44 in FIG. 2
7 output signal, E... Output signal of low pass filter (LPF) 44B in FIG. 2, X...
The output signal of the phase comparator 453 in FIG. 2, Z...
. . . Output signal of the burst phase difference detection circuit 45 in FIG. 2.

Claims (2)

[Claims] (1) A time axis fluctuation correction device that removes time axis fluctuations by controlling the delay amount of a variable delay element provided in the reproduced decoded video signal system according to the time axis fluctuation component in the reproduced decoded video signal. an extraction means for extracting a burst signal from the reproduced decoded video signal; a reference signal generation means for generating a reference burst signal; and a combination of the burst signal extracted by the extraction means and the reference signal generation means generated by the reference signal generation means. a phase difference detection means for detecting a phase difference with a reference burst signal, a burst detection means for detecting the presence or absence of a burst signal in the reproduced decoded video signal; 1. A time axis fluctuation correction device comprising a hold means for sampling and holding the output of the detection means. (2) A claim characterized in that the burst detection means for detecting the presence or absence of a burst signal is comprised of absolute value means for taking the absolute value of the signal and reference potential comparison means for comparing with a reference potential. The time axis fluctuation correction device according to item (1).