JPH0783496B2 - Video tape recorder - Google Patents

Description

The present invention relates to a low frequency conversion color recording type helical scan video tape recorder.

[Conventional technology]

Generally, in a low frequency conversion color recording type helical scan video tape recorder, the phase of the low frequency conversion color signal is changed according to a predetermined rule for each track of the video tape (90 degrees every 1H in a predetermined direction). Rotation), the spectrum of color signals does not overlap between adjacent tracks, and crosstalk interference is removed. Then, as a color phase processing control signal for designating the changing direction (rotation direction) of the low-frequency conversion color signal phase, the state is changed in accordance with the change of the rotation phase of the drum for recording and reproducing the signal on the video tape wound around the outer circumference. A drum flip-flop signal (hereinafter, abbreviated as DFF signal) whose signal level changes is used.

The DFF signal causes a slight phase shift with respect to the vertical synchronization signal of the video signal due to fluctuations in the drum servo, tracking adjustment during playback, and subtle shifts in the drum servo lock phase during recording and playback. Therefore, the state change point of the color phase processing control signal, that is, the switching point of the rotation direction instruction changes.

In order to solve such a problem, the DFF signal and the sync signal included in the video signal are received and adjusted so that the state changes at a predetermined timing with respect to the sync signal.
A color phase processing control method has been proposed in which the F signal is used as a color phase processing control signal during recording and reproduction.

By the way, at present, in the processing switching method at the switching point of the color phase change rule, that is, the state change point (transition point) of the color phase processing control signal, as shown in FIG. There are a "in-situ inversion" method of inverting the rotation and a "reset inversion" method of having a reset phase and resetting the phase immediately after switching and then inverting the rotation.

FIG. 8 shows a conventional configuration example of a color phase processing device on the recording side and the reproducing side of a video tape. As shown in this figure,
A recording color phase processing circuit 202 and a reproduction color phase processing circuit 204 are provided on the recording side and the reproducing side of the video tape 200, respectively. Recording color phase processing circuit 202
And the reproduction color phase processing circuit 204 performs the opposite process to restore the color phase. Further, the comb filter including the 1H delay circuit 206 and the adder circuit 208 adds the output of the reproduction color phase processing circuit 204 and the output of the 1H delay circuit 206 which delays this output by one horizontal scanning period (1H). hand,
Cancel crosstalk.

FIG. 9 shows that the color phase change rule is switched by using the “reset inversion” method during recording (that is, the color phase processing control is switched) and the color phase change rule is changed by using the “in-situ inversion” method during reproduction. The output of the recording color phase processing circuit 202 when switching (that is, switching the color phase processing control), and when the switching points at the time of recording and reproduction are matched,
The output of the reproduction color phase processing circuit 204 and the output of the addition circuit 208 are shown.

That is, the recording color phase processing circuit 202 sets the phase (hereinafter simply referred to as color phase) S11 of the low frequency conversion color signal to 1
Rotate by 90 degrees for each H to make color phase S12,
Store on magnetic tape 200. The direction of this rotation is switched at a predetermined timing for each field in accordance with the recording color phase processing control signal.

The color phase S13 of the signal reproduced from the magnetic tape 200 is
In the reproduction color phase processing circuit 204, the original color phase S14 is returned according to the reproduction color phase processing control signal.

The color phase S14 is added to the color phase S16 delayed by 1H by the 1H delay circuit 206 in the adder 208 to obtain the color phase S1.
6

[Problems to be Solved by the Invention]

In the color phase processing control method proposed above, color phase processing control is performed except when this method is adopted for both recording and reproduction (that is, in the case of recording / reproduction by the same device and compatible reproduction of this method). Switching points are misaligned, causing color misregistration or color disappearance during playback.

Further, if the color phase processing switching method at the time of recording is different from that at the time of reproducing, color shift occurs as shown in FIG. 9 even if the switching points match.

It is an object of the present invention to provide a video tape recorder that prevents the occurrence of color misregistration or color disappearance even if the switching point of the color phase change rule, that is, the switching point of the color phase processing control is deviated during recording and reproduction. To aim.

Another object of the present invention is to provide a video tape recorder that prevents the occurrence of color misregistration even when the color phase processing switching method at the time of recording is different from that at the time of reproducing.

[Means for Solving the Problems]

The video tape recorder according to claim 1 changes the phase of the low-frequency conversion color signal for each track based on a predetermined rule so that the spectrums of the color signals do not overlap between adjacent tracks. In a video tape recorder, a reproduction color phase processing means for changing the phase of the low-frequency conversion color signal at the time of reproduction based on a predetermined rule and outputting a reproduction color signal having the original phase, and a predetermined rule for recording. Detecting means for detecting a phase error of the reproduction color signal generated during reproduction due to a deviation between the switching point of the reproduction color and the switching point of a predetermined rule during reproduction, and the reproduction color according to the detection signal of the phase color output from the detection means. Control correction means for correcting the phase of the signal, and comb-filtering the reproduced color signal output from the control correction means to cancel the crosstalk. And a killing means.

In the video tape recorder according to claim 2, the control correction means includes a timing means for setting a fixed period associated with the vertical synchronizing signal obtained from the reproduced video signal, and a phase error detection signal only for the fixed period. And a gate means for taking out.

A video tape recorder according to claim 3, wherein a plurality of video reproducing heads, a head switching circuit for switching these head outputs to supply to the video reproducing circuit, and a drum for reproducing a signal from the tape wound around the outer circumference are provided. The head switching control signal is sent to the head switching circuit as a drum flip-flop signal adjusted so that the state change point of the drum flip-flop signal that changes according to the change in the rotational phase is shifted to a position after the range of a certain period. And a head switching control circuit supplied as.

In the video tape recorder according to claim 4, the gate means extracts only the first phase error within a fixed period, and the control correction means follows a fixed rule from the time when the error detection signal is generated to the time when the head switching control signal is generated. It is characterized in that the reproduction color phase is corrected.

[Work]

In the video tape recorder according to the first aspect, since the color phase error is detected and corrected to the correct phase, it is possible to prevent the occurrence of color disappearance and color misregistration.

In the video tape recorder according to the second aspect of the present invention, the phase error detection signal can be taken out only during a certain period associated with the vertical synchronizing signal.

In the video tape recorder according to the third aspect, since the switching of the reproducing head can be shifted after the phase error is detected, the head is not switched during the color phase correction.

In the video tape recorder according to the fourth aspect, only the first detected phase error is used, and the correction is thereafter performed according to a certain rule. Therefore, only the first phase error correction is delayed.

〔Example〕

FIG. 1 shows the configuration of an embodiment of a video tape recorder according to the present invention. This embodiment is an example in which recording and reproduction are performed by an "in-situ reversal" method. The reproduction color phase processing circuit 4 has the same function as the conventional reproduction color phase processing circuit 204 of FIG. 8 and receives the reproduction low frequency conversion color signal and the reproduction color phase processing control signal for instructing the phase rotation direction, The phase of the gamut conversion color signal is changed to the rotation direction instructed by the color phase processing control signal based on a predetermined rule as in the case described above. That is, the reproduction color phase processing circuit 4 rotates, for example, the phase of the reproduction low-frequency conversion color signal by 90 degrees counterclockwise (or clockwise) in each horizontal scanning period (1H), and the reproduction color phase If the processing control signal indicates counterclockwise (or clockwise), all phases of the color signal are returned to their original phases. That is, the phase of the color signal is returned to the original phase before being changed by the recording color signal processing. The reproduction color phase processing circuit 4 constitutes reproduction color phase processing means.

The color phase adjusting device 5 receives the output of the reproduction color phase processing circuit 4 and switches the color phase processing control signal at the time of recording, that is, the color phase changing rule at the time of recording.
A detection circuit 50 for detecting an error in a reproduction color phase caused at the time of reproduction due to a deviation from a switching point of the color phase processing control signal at the time of reproduction, that is, a switching point of the color phase changing rule at the time of reproduction, and a detection means are constituted. A control circuit 60 which receives a phase error detection signal output from the detection circuit 50 and outputs a correction control signal according to a predetermined logic, and an output of the reproduction color phase processing circuit 4 according to the correction control signal output from the control circuit 60. And a correction circuit 70 for correcting the phase of the reproduction color signal.

The control circuit 60 and the correction circuit 70 constitute control correction means.

The arrangement position of the color phase adjusting device 5 is a position after the reproduction low frequency conversion color signal is converted to, for example, 3.58 MHz and the color phase processing is performed, and the crosstalk is canceled by the comb filter processing. Must be in previous position.
This is because if the comb filter process is performed, the line having the phase error is added to the lines before and after, and the hue is deviated or the level is reduced, so that the phase error cannot be detected. Therefore, the color phase adjusting device 5
As shown in FIG. 1, it is connected to the next stage of the reproduction color phase processing circuit 4, which is the preceding stage of the reproduction comb filter (which constitutes the canceling means) including the 1H delay circuit 6 and the adding circuit 8. To be done. The functions of the 1H delay circuit 6 and the adder circuit 8 are the same as those of the 1H delay circuit 206 and the adder circuit 2 shown in FIG.
Same as 08.

FIG. 2 shows the detection circuit 50, the control circuit 60, and the detection circuit 50 shown in FIG.
A specific configuration example of the correction circuit 70 is shown. Detection circuit 50
Is a phase detection for phase-detecting the output signal S1 (FIG. 3) by comparing the output signal S1 of the reproduction color phase processing circuit 4 with the color subcarrier fsc of 3.58 MHz supplied from the reference oscillation circuit (not shown). It has a circuit 52. Phase detection circuit
The output S3 of 52 (FIG. 3) is at a low level when the signal S1 is not out of phase and is at a high level when the signal S1 is out of phase by 180 degrees, that is, when there is a phase error. The output of the phase detection circuit 52 is the detection circuit 50.
Low pass filter (LPF) 54 and comparator 56 in
Is connected to the data input of a latch 62 provided in the control circuit 60 via. The low-pass filter 54 removes unnecessary high frequency components, and the comparator 56 compares the signal from the low-pass filter 54 with a predetermined reference voltage to shape the waveform.

The control circuit 60 includes a first timer 61, a latch 62, a vertical synchronization signal (V-SYNC) detection circuit 63, a second timer 64, a gate 65 and a toggle circuit 66. The first timer 61 receives the reproduction composite synchronization (C-SYNC) signal and supplies the center pulse S4 (FIG. 3) of the color burst to the clock input of the latch 62. The latch 62 latches at the timing of the phase error detection signal (waveform shaping signal of the signal S3) and the clock input pulse S4 input from the detection circuit 50, and the latch pulse S5.
(Fig. 3) is generated from the Q output.

The vertical sync signal detection circuit 63 detects the vertical sync signal from the reproduced C-SYNC signal. The second timer 64 receives the vertical synchronization signal detected by the vertical synchronization signal detection circuit 63, and outputs 1
Once in the field, at a predetermined timing, for example 10.5H
To 3.0H (H is horizontal scanning period) width gate pulse S6
(Fig. 3) is output. Vertical sync signal detection circuit 63 and second
The timer 64 constitutes the timing means.

The gate 65 receives the Q output S5 of the latch 62 and the gate pulse S6 output from the second timer 64, and after the gate pulse S6, the output S5 of the latch 62 first becomes the high level, and after the gate pulse S6. Gate output that goes high to the edge
Generate S7 (Fig. 3). The toggle circuit 66 receives the output S7 of the gate 65 and the horizontal synchronizing signal in the reproduced C-SYNC signal, inverts it to a high level at the edge of the output S7 to a high level, and then inputs the horizontal synchronizing signal every time. Output flipped to
Generate S8 (Fig. 3).

The high level output signal S8 of the toggle circuit 66 is a correction control signal indicating that the reproduction color phase processing output S1 should be shifted by 180 degrees, and the low level output signal S8 changes the phase of the reproduction color phase processing output S1. It is a correction control signal indicating that there is no need to change.

The correction circuit 70 includes a 0-degree phase shifter 71 that directly outputs the reproduction color phase processing output S1 without changing the phase thereof, and a 90-degree phase shifter 72 that shifts the phase of the reproduction color phase processing output S1 by 90 degrees. It is supplied from the control circuit 60 and a 180 degree phase shifter 73 that shifts the phase of the reproduction color phase processing output S1 by 180 degrees, a 270 degree phase shifter 74 that shifts the phase of the reproduction color phase processing output S1 by 270 degrees. A switch 75 for selecting any one of the four phase shifters 71, 72, 73 and 74 according to the correction control signal S8.

The switch 75 selects the 180-degree phase shifter 73 when receiving the high-level correction control signal S8 from the control circuit 60, that is, the toggle circuit 66, and selects the 180-degree phase shifter 73 when receiving the low-level correction control signal S8. Select 71.

FIG. 3 shows a case where the embodiment shown in FIG. 1 and FIG. 2 shows a video tape recorded by switching the recording color phase processing control signal at a position 6.5H before the vertical synchronizing signal. The following shows the signal waveform of each part when reproduced by a reproducing device in which the reproduction color phase processing control signal switches at a position 3.0H before the synchronization signal.

When neither the recording color processing control signal nor the reproduction color phase processing control signal is switched, there is no phase error in the reproduction color phase processing output S1 and the output of the phase detection circuit 52.
S3 remains low.

If the reproduction color phase processing control signal is not switched even though the recording color processing control signal is switched, a phase error occurs in the reproduction color phase processing output S1, and the output S3 of the phase detection circuit 52 becomes high level. The output S8 of the toggle circuit 66 goes high, and the control circuit 60 outputs the reproduction color phase processing.
A correction control signal indicating that the phase of S1 should be shifted by 180 degrees is output. In response, switch 70 turns 180 degree phase shifter 7
Select 3.

In the next horizontal scanning period, the output S8 of the toggle circuit 66 becomes low level, and the control circuit 60 outputs a correction control signal indicating that the phase of the reproduction color phase processing output S1 should be left unchanged. In response to this, the switch 70 selects the 0-degree phase shifter 71.

In the above-described embodiment, the phase error is not detected and corrected every horizontal scanning period (1H), but only the first phase error is detected and then corrected according to a certain rule (that is, every horizontal scanning period). Are corrected as if they had the same phase error) due to the following reasons (1) and (2).

Reason for (1) Since phase detection is performed at the burst center, a delay of half the burst (about 1.1 μsec) occurs, as shown in FIG. To deal with this, as shown in FIG. 5, 1 μse
An equalizer (EQ) 90 of about c must be inserted before and after the correction circuit 70, which is not practical in terms of cost and performance.

Reason for (2) As shown in FIG. 3 and the upper part of FIG. 6, in the case of the “in-situ inversion” method at the time of recording and at the “in-situ inversion” method at the time of reproduction, the color at the time of recording and reproduction When the switching point of the phase processing control signal is deviated, the phase error in the deviated period is "180
, 0 degrees, 180 degrees ", the same phase error appears every other horizontal scanning period.

In this way, the same phase error appears every other horizontal scanning period not only in the "in-situ inversion" method during recording and in the "in-situ inversion" method during reproduction.

For example, as shown in the middle part of FIG. 6, one horizontal scanning period is "90 degrees, 270 degrees, 90 degrees" in the case of "reset inversion" method during recording and "in-situ inversion" method during reproduction. Every same phase error appears. Also, as shown in the lower part of FIG. 6, “270 degrees, 90 degrees, 270 degrees” is used in the case of “reset inversion” method during recording and “in-situ inversion” method during reproduction.
Thus, the same phase error may appear every other horizontal scanning period. That is, if the color phase processing control signal (rotation direction) is not switched in the screen at the time of reproduction, no matter what method is used for switching, an error occurs which is inverted every horizontal scanning period from the first error.

As is apparent from (2) above, by knowing the phase and position of the error that appears first, correction is performed according to the rule that the phase is inverted every horizontal scanning period from that point to the switching point of the reproduction color phase processing control signal. If you do the first one
The problem of detection delay in the horizontal scanning period remains, but the problem of (1) above can be solved. An automatic phase control device (APC) such as a color television does not respond so fast as to follow a burst error in one horizontal scanning period. Therefore, even if half of the first horizontal scanning period is delayed, it is practically impossible. There is no problem.

In the embodiment of FIGS. 1 and 2, the gate signal S7 is set because the switching point of the color phase control signal (6.5
This is to prevent malfunction by making the embodiment operate only near (± 1.5 H).

In the embodiment shown in FIGS. 1, 2, and 3, the “in-situ reversal” method is used for recording and the “in-situ reversal” method is used for reproduction.
Since the present invention is applied to the case of the system, when the correction control signal S8 is at the low level, the switch 75 causes the 0 degree phase shifter 71 to operate.
Select and switch when the correction control signal S8 is at high level.
Although 75 selects the 180-degree phase shifter 73, in the case of the "reverse inversion" method at the time of recording and the "in-situ inversion" method at the time of reproduction shown in the middle part of Fig. 6, the correction control signal S8 is at a low level. Switch 75 selects the 270-degree phase shifter 74, and when the correction control signal S8 is high level, the switch 75 switches the 90-degree phase shifter.
72 should be selected. In the case of the "reset inversion" method at the time of recording and the "in-situ inversion" method at the time of recording at the bottom of FIG. 6, the switch 75 selects the 90-degree phase shifter 72 when the correction control signal is at the low level, and the correction control is performed. The switch 75 may select the 270-degree phase shifter 74 when the signal is at the high level.

Incidentally, in a video tape recorder having a plurality of video reproducing heads and a head switching circuit (not shown) for switching the head outputs and supplying them to the video reproducing circuit, a video tape wound around the outer periphery is used. The state change point of the drum flip-flop whose state changes according to the change of the rotation phase of the drum that reproduces the signal is set for the period set by the gate output S7 in FIG. It is preferable to provide a head switching control circuit that supplies a drum flip-flop signal adjusted so as to be shifted to a position later than (ends at a point) to the head switching circuit as a head switching control signal. By doing so, the video heads are not switched during the phase error correction period, and malfunctions can be prevented.

Further, when such a head switching control circuit is provided, it is preferable that the correction of the phase error is cascaded until the time point when the head switching control signal is generated.

〔The invention's effect〕

According to the video tape recorder of claim 1, even if the switching point of the color phase changing rule at the time of recording and the switching point of the color phase changing rule at the time of reproducing are deviated, the color at the time of recording and reproducing is changed. Even if the phase change rule switching method is different,
The phase error can be accurately detected and corrected, and color misregistration and color disappearance can be prevented.

According to the video tape recorder of the second aspect, it is possible to detect the phase error only in the vicinity of the switching point of the color phase control signal and prevent the malfunction.

According to the video tape recorder of the third aspect, the switching of the video head is not performed within the phase error correction period, and the malfunction can be prevented.

According to the video tape recorder of the fourth aspect, the delay of the phase error correction can be limited to only the first phase error, and the hardware can be simplified and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a video tape recorder of the present invention, and FIG. 2 is a detection circuit 5 of FIG.
0, a block diagram showing a concrete configuration example of the control circuit 60 and the correction circuit 70, FIG. 3 is a waveform diagram of signals of respective parts of FIG. 2,
FIG. 4 is an explanatory diagram of the delay of the detection circuit 50 of FIG. 3, FIG. 5 is a block diagram showing an example of the configuration for coping with the delay shown in FIG. 4, and FIG. Timing chart showing an example of phase error pattern when adopting the switching method,
FIG. 7 is an explanatory view of the “in-situ inversion” method and the “reset inversion” method for switching the color phase processing, and FIG. 8 is
FIG. 9 is a block diagram showing a configuration example of a conventional video tape recorder on the recording side and the reproducing side, and FIG. 9 is a vector diagram of signals of respective parts in FIG. 5 ... Color phase adjustment device, 50 ... Detection circuit, 52 ... Phase detection circuit, 60 ... Control circuit, 61, 64 ... Timer, 62 ...
… Latch, 63 …… Vertical sync signal detection circuit, 65 …… Gate, 66 …… Toggle circuit, 70 …… Correction circuit, 71,72,73,74
...... 0 degree, 90 degree, 180 degree, 270 degree phase shifter, 75 …… switch.

Claims (4)

[Claims] 1. A video tape recorder in which the phase of the low-frequency conversion color signal is changed for each track based on a predetermined rule so that the spectrums of the color signals do not overlap between adjacent tracks. At this time, the reproduction color phase processing means for changing the phase of the low-pass conversion color signal based on the predetermined rule to output the reproduction color signal having the original phase, and the switching point of the predetermined rule at the time of recording. And detecting means for detecting an error in the phase of the reproduced color signal that occurs during reproduction due to a deviation between the switching point of the predetermined rule during reproduction and the reproduction according to the phase error detection signal output from the detecting means. Control correction means for correcting the phase of the color signal and comb-filtering the reproduced color signal output from the control correction means to eliminate the crosstalk. A video tape recorder equipped with a means for offsetting. 2. The control correction means includes timing means for setting a fixed period associated with a vertical synchronizing signal obtained from a reproduced video signal, and gate means for extracting the phase error detection signal only during the fixed period. The video tape recorder according to claim 1, further comprising: 3. A plurality of video reproducing heads, a head switching circuit for switching these head outputs to supply them to a video reproducing circuit, and a change in the rotational phase of a drum for reproducing a signal from the tape wound around the outer circumference. The state change point of the drum flip-flop signal that changes according to the state is adjusted so as to be shifted to a position after the range of the fixed period, and the drum flip-flop signal is supplied to the head switching circuit as a head switching control signal. The video tape recorder according to claim 2, further comprising: 4. The gate means extracts only the first phase error within the certain period, and the control correction means follows the certain rule from the time when the error detection signal is generated to the time when the head switching control signal is generated. The video tape recorder according to claim 3, wherein the reproduction color phase is corrected.