JPH02252385A - Video tape recorder - Google Patents

Abstract

PURPOSE:To facilitate to delay a drop-out detection pulse by compensating the drop-out of a delayed luminance signal according to the delayed drop-out detection pulse. CONSTITUTION:When the drop-out of an FM luminance signal 100 is detected by a drop-out detection circuit 2, the drop-out detection pulse 300 is inputted to an adder 12. A chrominance signal 200 and the pulse 300 are synthesized, and delayed by a TBC circuit 6 for chrominance signal. A TBC controlled synthesized signal is separated by a signal separation circuit 11, and a delayed drop-out detection signal 301 is inputted to a drop-out compensation circuit 4 for luminance signal and a drop-out compensation circuit 9 for chrominance signal. On the other hand, the chrominance signal 200 is inputted to a frequency conversion circuit 7, and after being converted into the chrominance signal of a base band, it is inputted to the compensation circuit 9. The luminance signal demodulated by a demodulation circuit 3 is inputted to the compensation circuit 4 after being delayed by a TBC circuit 5 for luminance signal. According ly, the compensation circuit 4 compensates the drop-out of the luminance signal according to the signal 301, and outputs the luminance signal free from the drop-out to the adder 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Field of Industrial Application) The present invention relates to a pulse delay circuit constituting a time base collector circuit used in a video tape recorder (VTR).

(Prior Art) In general, a time base collector circuit (hereinafter abbreviated as TBC) is a circuit that delays a video signal of a VTR or the like in advance using a delay element, and then changes the amount of delay to It has a function of correcting time axis errors related to signals and the like. An example of this 780 circuit is a 780 circuit using COD used in laser discs, laser vision, and the like. On a laser disc, a video signal that is a mixture of a luminance signal (Y)/chrominance signal (C) is directly FM modulated and recorded, so TBC
is applied to the Y/C mixed video signal. On the other hand, in a home VTR, the brightness signal is FM modulated,
Since color signals are recorded after low-frequency conversion, TBG is generally applied to luminance signals and color signals separately. In this household ■choR, the TBG of the laser disk after Y/C mixing.
However, some VTRs have a terminal called an S terminal that outputs the luminance signal and color signal separately, and in such cases, after applying TBG, the luminance signal is output again. An inconvenience arises in that the signal and color signal must be separated.

By the way, when the above-mentioned 780 circuit is installed in a home VTR, a problem arises as to how to perform dropout compensation. That is, in the luminance signal system, TBC is
Therefore, it is necessary to perform dropout detection using the reproduced FM luminance signal, and this requires delaying the dropout detection pulse by TBC. However, if this method is adopted, dropout compensation can be used to mask one day's worth of skew that occurs during high-speed cue/review playback in the standard mode and cannot be corrected by TBC. On the other hand, in a VTR that applies TBG after dropout compensation, delay processing to the dropout detection pulse is not necessary, but the mask processing described above cannot be performed. In addition, in the color signal system of a VTR, due to problems with the band of the variable delay line and sensitivity to phase fluctuations, the low frequency side of the color signal
It is common to apply TBC at 29KH7. However, chrominance signal dropout compensation is performed on the 3.58 MHz baseband side. This is because color rotor processing is performed on the 629Kl-12 side, and color dropout compensation cannot be performed. Therefore, a delay in the dropout detection pulse is required. However, since the pulse width of the dropout detection pulse indicates the dropout compensation period, it is difficult to delay it, and the delay caused by a flip-flop or the like cannot respond to time compensation by the TBC.

Therefore, in the past, dropout delay was not detected, but TBC was applied after compensating for the dropout of the luminance signal system.
In addition, a circuit as shown in FIG. 4 is used, which does not perform dropout compensation for the color signal system. That is, after the reproduced signal from the tape is amplified by a preamplifier, the reproduced signal processing circuit 1 separates the FM luminance signal and the low frequency conversion color signal, and the FMI! The degree signal 100 is input to the dropout detection circuit 2, and the low frequency conversion color signal 200 is input to the color signal 7.
80 circuit 6. The dropout detection circuit 2 detects dropout of the input FM 1 degree signal and outputs a detection pulse 300 to the luminance signal dropout compensation circuit 4. The FM luminance signal that has passed through the dropout detection circuit 2 is demodulated by the demodulation circuit 3 and then input to the dropout compensation circuit 4 for luminance signals, where the dropout detection pulse input from the dropout detection circuit 2 is 3
00 to compensate for the dropout of the luminance signal. In this way, the luminance signal whose dropout has been compensated for is delayed by 30 M seconds in the luminance signal TBC circuit 5 and then output to the adder 8. On the other hand, the color signal input to the color signal 780 circuit 6 is delayed by approximately 30 μs, and then converted into a baseband color signal by the frequency conversion circuit 7 and output to the adder 8. As a result, the adder 8 adds the luminance signal and the color signal to form a video signal, which is output to the next stage. In such a circuit, the dropout detection pulse 300 is not delayed. Therefore, in the luminance signal dropout compensation circuit 4, there is a problem that the dropout compensation signal does not enter a part that completely coincides with the dropout position, and the above-mentioned masking process cannot be performed.

FIG. 5 is an example of a conventional circuit in which TBC is applied before dropout compensation. The FM luminance signal 100 separated by the reproduced signal processing circuit 1 of this example is demodulated by the demodulation circuit 3 after its dropout is detected by the dropout detection circuit 2. The demodulated luminance signal is delayed by about 30 μs in the luminance signal TBC circuit 5, and then its dropout is compensated for in the luminance signal dropout compensation circuit 4, and then outputted by the adder circuit 8. Here, a dropout detection pulse 30 is generated at the timing when the dropout detection circuit 2 detects a dropout of the luminance signal.
0 is delayed by about 30 μs in the dropout delay circuit 10 and then output to the luminance signal dropout compensation circuit 4 and the chrominance signal dropout compensation circuit 9. Therefore, in the luminance signal dropout compensation circuit 4, dropout compensation is performed using the delayed dropout detection pulse. On the other hand, the color signal separated in the reproduced signal processing circuit 1 is delayed by about 30 μs in the color signal 780 circuit 6, and then sent to the frequency conversion circuit 7 for baseband (3,
58MH7) color signal. The baseband color signal is subjected to dropout compensation in the color signal dropout compensation circuit 9 based on the delayed dropout detection pulse, and then output to the adder 8 . In adder 8, after TBC is applied, the dropout-compensated luminance signal and chrominance signal are combined to form a video signal, and this video signal is output to the next stage. However, as described above, this circuit has the disadvantage that it is difficult to delay in the dropout pulse delay circuit, making the circuit configuration difficult.

(Problem to be Solved by the Invention) As described above, in order to mask one day's worth of skew that cannot be corrected by TBC that occurs during standard mode cue/review picture search, the luminance signal system In a circuit configuration in which TBC is applied before dropout compensation, TBC is applied to the dropout detection pulse.
minute delay is required. However, this delay is difficult, and even if it were possible, there was a drawback that the dropout detection pulse could not be accurately delayed by the TBC delay. Therefore, there is a circuit configuration in which TBC is applied after dropout compensation for the luminance signal system, but dropout compensation for the chrominance signal system is not performed, but this circuit has the drawback that the above-mentioned mask cannot be performed. Therefore, the present invention eliminates the above-mentioned drawbacks, and aims to reduce the TBC applied to the luminance signal before dropout compensation.
It is an object of the present invention to provide a VTR equipped with a circuit that can easily and accurately delay a dropout detection pulse by a delay amount of .

[Structure of the Invention] (Means for Solving the Problems) The present invention has a function of demodulating a frequency modulated luminance signal reproduced from a tape and then delaying the demodulated luminance signal through a first analog time base collector circuit. In the video tape recorder, the video tape recorder operates in conjunction with dropout detection means for detecting dropout of the reproduction frequency variable UA luminance signal and outputting a dropout detection pulse, and the first analog time base collector circuit. a second delaying the dropout detection pulse outputted from the dropout detection means by
and an analog time base collector circuit for performing dropout compensation of the luminance signal delayed by the first analog time base collector circuit based on a dropout detection pulse delayed by the second analog time base collector circuit. It has a configuration including an out compensation means.

(Function) In the video tape recorder of the present invention, the dropout detection means performs dropout detection of the frequency modulated luminance signal by generating a dropout detection pulse, and transmits the generated dropout detection pulse to the second analog time base collector circuit. Output to. The second analog time base collector circuit delays the dropout detection pulse output from the dropout detection means by operating in conjunction with the first analog time base collector circuit that delays the demodulated luminance signal. . The dropout compensation means performs dropout compensation of the luminance signal delayed by the first analog time base collector circuit based on the dropout detection pulse delayed by the second analog time base collector circuit.

(Example) An example of the present invention will be described below with reference to the drawings, in which the same parts as those of the conventional example are denoted by the same reference numerals. Figure 1 shows the VT of the present invention.
This is a block diagram showing one embodiment of R. 1 is the FMt1 degree signal 1 from the playback signal played by the video head.
a reproduction signal processing circuit for separating color signals 200 and 200;
3 is a demodulation circuit that demodulates the FMiW intensity signal; 4 is a lower dropout compensation circuit for the luminance signal that compensates for the dropout portion of the demodulated luminance signal; 5 6 is a TBC circuit for a luminance signal that extends the time of the luminance signal; 6 is a TBC circuit for a chrominance signal that delays the chrominance signal; 7 is a frequency conversion circuit that converts the frequency of the low-pass conversion color signal into a baseband color signal; an adder that adds a luminance signal and a chrominance signal to produce a video signal; 9 a chrominance signal dropout compensation circuit that performs dropout compensation on a baseband chrominance signal; 1;
1 is a signal separation circuit that separates the color signal and the dropout detection pulse, and 12 is an adder that adds the color signal and the dropout detection pulse.

Next, the operation of this embodiment will be explained. The playback signal played by the video head is amplified by a preamplifier, etc., and then input to the playback signal processing circuit 1, where FMi\i
It is separated into a color signal 100 and a low frequency converted color signal 200.

After the dropout of the FM 1 degree signal 100 is detected by the dropout detection circuit 2, it is demodulated by the demodulation circuit 3. On the other hand, in the dropout detection circuit 2, FMi! A dropout detection pulse 300 generated when a dropout of the i-degree signal 100 is detected is input to the adder 12 . Since the color signal 200 separated by the reproduced signal processing circuit 1 is also input to this adder 12, the color signal 200 and the dropout detection pulse 300 are combined here, and this combined signal is used as the color signal TBC. It is delayed in circuit 6. In this way, the TBC-applied composite signal is separated by the signal separation circuit 11, and the delayed dropout detection signal 301 is input to the luminance signal dropout compensation circuit 4 and the chrominance signal dropout compensation circuit 9. . On the other hand, the color signal 200 is input to the frequency conversion circuit 7, where it is converted to a baseband color signal, and then input to the color signal dropout compensation circuit 9. Demodulation circuit 3 described above
The luminance signal demodulated is delayed by the luminance signal TBC circuit 5 and then input to the luminance signal dropout compensation circuit 4. Therefore, the luminance signal dropout compensation circuit 4 is configured to use the dropout detection signal 3 inputted separately.
Perform dropout compensation of the luminance signal based on 01,
The obtained luminance signal without dropout is output to the adder 8. In addition, the color signal dropout compensation circuit 9 performs dropout compensation based on the aforementioned dropout detection signal @301 that is input separately to the baseband color signal, and the resulting dropout-free luminance signal is sent to the adder. Output to 8. The adder 8 adds the input luminance signal and color signal to form a video signal, which is output to the next stage.

FIG. 2 is a circuit diagram showing a detailed example of the adder 11 described above. The color signal 200 is inputted via the capacitor C1 to the variable delay line (COD> that constitutes the color signal TBC circuit 6. By the way, since the input of the COD is a bias input, it is inputted by the resistors R1 and R2. A bias voltage obtained by dividing V.0 is applied to the input of the COD.On the other hand, the input of this COD is connected to the collector side of the transistor TY (S) via the resistor R capacitor C2. Tr1, the resistor 3 and the capacitor C2 form a switch circuit.Therefore, a dropout detection pulse 300 is applied to the base of the transistor Tr1.
If this Trl is switched by applying
The input of D has a color signal of 200 and a dropout pulse of 50.
A superimposed signal appears and is input to the COD.

According to this embodiment, the dropout detection pulse 300 that detects a dropout in the FM 1 degree signal is used as the color signal 7
80 circuit 6, and this delayed dropout detection pulse 301 is used to compensate for the dropout of the luminance signal that has already been subjected to TBC, so the luminance signal is delayed in the luminance signal TBC circuit 5. The dropout detection pulse 300 can be accurately and easily delayed by the same amount as the dropout detection pulse 300@. Therefore, the standard mode queue/
Dropout compensation can also be used to mask one day's worth of skew that occurs during review and picture search and cannot be corrected by TBC.

FIG. 3 is a block diagram showing another embodiment of the present invention. In this example, a dropout pulse TBC circuit 13 is provided which specifically delays the dropout pulse detected by the dropout detection circuit 2.
The dropout detection pulse 301 delayed at T
The signal is input to the dropout compensation circuit 4 for the li degree signal and the dropout compensation circuit 9 for the chrominance signal, and has the same effect as the previous embodiment. Note that the TBC circuit 13 for dropout pulses has 78 circuits for luminance signals and color signals.
It operates in conjunction with the 0 circuit.

[Effects of the Invention] As described above, the VTR of the present invention has the effect of easily delaying the dropout detection pulse exactly by the TBC delay before compensating for the dropout of the luminance signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the VTR of the invention, FIG. 2 is a circuit diagram showing a detailed example of the adder shown in FIG. 1, and FIG. 3 is another embodiment of the invention. A block diagram showing
Figure 4 is a block diagram showing an example of a conventional VTR;
The figure is a block diagram showing another example of a conventional VTR. 1... Reproduction signal processing circuit 2... Dropout detection circuit 4... TBC circuit for luminance signal 5... Dropout compensation circuit for luminance signal 6... 780 circuit for color signal 8.11...・Addition circuit 9...Color signal dropout pulse compensation circuit 10・
... Signal separation circuit 12 ... TBC circuit agent for dropout pulse
Patent Attorney Nori Chika Yudo Hiroshi Uji

Claims (2)

[Claims] (1) In a video tape recorder having a function of demodulating a frequency modulated luminance signal reproduced from a tape and then delaying this demodulated luminance signal through a first analog time base collector circuit, a drop of the reproduced frequency modulated luminance signal is provided. a dropout detection means for detecting a dropout and outputting a dropout detection pulse; and a dropout detection means that operates in conjunction with the first analog time base collector circuit to detect the dropout detection pulse output from the dropout detection means. a second analog time base collector circuit to delay and a luminance delayed by the first analog time base collector circuit based on a dropout detection pulse delayed by the second analog time base collector circuit; A video tape recorder comprising dropout compensation means for compensating for signal dropouts. (2) In a video tape recorder having a function of demodulating a frequency modulated luminance signal reproduced from a tape and then delaying the demodulated luminance signal through an analog time base collector circuit for luminance signals, dropout of the frequency modulated luminance signal is provided. dropout detection means for performing detection by generating a dropout detection pulse; signal synthesis means for synthesizing the dropout detection pulse outputted from the dropout detection means and the low-pass conversion color signal; an analog time base collector circuit for color signals that delays a composite signal output from the means; a signal separation means that separates a dropout detection pulse from the composite signal output from the analog time base collector circuit; A video tape recorder comprising dropout compensation means for compensating for dropout of the luminance signal delayed by the luminance signal analog time base collector circuit based on the separated dropout detection pulse.