JP3067240B2 - Phase shift detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase shift detecting circuit suitable for application to a time axis correcting device of a video signal reproducing device, for example.

[0002]

2. Description of the Related Art Conventionally, for example, in a video signal reproducing apparatus of a beta cam format, a video signal in which a chroma signal and a luminance signal are component-recorded separately on a tape by four heads is reproduced. I have to. The recording format is as shown in FIG.
14 shows the case of the NTSC system, and FIG. 14B shows the case of the PAL or SECAM system. As shown in FIG. 14A, in recording an NTSC video signal, a luminance signal Y and a chroma signal are recorded alternately on a recording surface of a tape with different azimuth angles. The video track angle θ is 4.6790, the track width C of the chroma signal is 71 to 75 μm, the track Y track of the luminance signal Y and the chroma signal C
Of the track C between tracks 78.5 to 82.
5 μm, and the lower edge of the video track is 880 μm to 10 μm.
The width N of the track Y of the luminance signal Y is 71 μm to 75 μm, and the overlap O is 2 μm.
The track offset P between the track Y track of the luminance signal Y and the track C track of the chroma signal C is 4399 μm, the video track pitch Q is 161 μm, and the control head distance S is 366 μm.
00 to 36800 μm, and the audio head distance T
Is set to 180903 to 18933 μm, and the lower limit Y of the effective video width W is set to 1233 to 1258 μm. Also,
As shown in FIG. 14B, in the recording of the video signal of the PAL or SECAM system, the overlap O is 2391 μm.
m, and the track offset P between the track Y track of the luminance signal Y and the track C track of the chroma signal C is 4
399 μm, and the video track pitch Q is 166 μm.
m. The other components are the same as in the case of the NTSC system described above. Among the video signals component-recorded as described above, the luminance signal Y is subjected to signal processing such as time axis correction after FM demodulation and de-emphasis. On the other hand, since the chroma signal is recorded after being compressed by Ｒ for RY and BY, it is expanded by a factor of two in the reproduction system, and after being subjected to signal processing such as time axis correction, it is encoded. Is done. This time axis correction is performed by converting the reproduced video signal from A-D
The digital data is converted into digital data by a converter, and this digital data is written to a memory with a write clock using a write phase reference signal formed based on a reproduction synchronization signal separated from a reproduction video signal, and the read phase reference signal is read. This is performed by reading digital data written in the memory with a read clock as a phase reference. At the same time, after the later-described dropout processing and gray replacement processing are performed,
The luminance signal Y and the chroma signal C are mixed and supplied to a monitor or the like as a color video signal. When the video signal is reproduced by such a video signal reproducing apparatus, a loss of the reproduced video signal, that is, a so-called dropout may occur. When this dropout occurs, the dropout is detected by a circuit for detecting the dropout, and the dropout signal is used to interpolate the dropout portion of the video signal with the preceding data. When performing a so-called search operation for reproducing at a higher speed than the normal reproduction speed, a guard band is detected by a dropout signal, and a video signal corresponding to the detected guard band is gray-replaced by a so-called gray-replacement process. And output it. In guard band detection, the period of the falling edge of the reproduced horizontal synchronizing signal is determined by dividing the read clock by half.
Counting is performed using the frequency-divided signal obtained by frequency division to obtain average horizontal cycle data for reproduction. Based on the average horizontal cycle data, the next falling edge of the reproduction horizontal synchronization signal is predicted. And
Based on the prediction, an average period detection signal is generated, and the average period detection signal is latched with a reproduced horizontal synchronization signal guarded by a dropout signal to form a guard band signal. Then, based on the guard band signal, the video signal corresponding to the guard band portion (low level “0”) is
So-called gray replacement processing is used to perform gray replacement and output. As shown in FIG. 15A,
When a dropout of three horizontal cycles occurs in the reproduced video signal during reproduction, this causes the reproduction horizontal synchronizing signal to be 4, 5,
And 6 lines are missing. The GH signal at this time is shown in FIG.
B. The dropout signal is shown in FIG.
C. At this time, since the guard band signal is formed using the reproduced horizontal synchronizing signal as a clock, FIG.
As shown in FIG. 5D, when the reproduced horizontal synchronizing signal is lost, it is pre-held and the guard band, that is, the portion which is originally low level "0" becomes high level "1", and the seven lines on which the reproduced horizontal synchronizing signal appears are displayed. Guard band in the eyes,
That is, the guard band is released at the ninth line of the reproduced horizontal synchronizing signal at which the GH signal starts to be output at the low level “0”, that is, the high level becomes “1”. In this case, the originally appropriate guard band signal is as shown in FIG. 15F. Therefore, a part that should originally be a guard band during the gray replacement processing is not determined to be a guard band, and the gray replacement processing is not performed. Therefore, the OR signal obtained by ORing the dropout signal and the guard band signal is used as the guard band signal. Further, at the time of reproduction by a search operation at a speed of ± 30 times or more, the reproduced horizontal synchronizing signal is used as a GH signal, and all the low level “0” portions of the guard band signal are replaced with gray.

[0003]

As described above, conventionally, the guard band signal is formed based on the average horizontal period of the falling edge of the reproduced horizontal synchronizing signal. By the way, for example, the reference of the phase in the luminance signal Y of the beta cam format is the rising edge of the reproduced horizontal synchronization signal. Therefore, for example, as shown in FIG. 8A, the rising edge of the reproduced horizontal synchronizing signal has been removed by dropout (FIG. 8C) (tc in FIG. 8A).
8D), as shown in FIG. 8D, the GH signal also has a portion tc that has been similarly removed and a portion that is not detected as a guard band portion occurs, thereby causing a so-called curved portion in the projected image. There was an inconvenience. In addition, ± 3
At the time of reproduction by a high-speed search operation at 0x speed or more, since the reproduced horizontal synchronizing signal is a GH signal, similarly, there is an inconvenience that a projected image has a curved portion.

[0004] The present invention has been made in view of the above, with even if the rising edge of the reproduced horizontal synchronizing signal when the search operation is scraped to allow replacement optimal gray, high-speed search operation to allow replacement optimal gray when, so as not to cause a so-called image disturbance is intended to provide a phase shift detector circuit that can out movies the extremely high quality images.

[0005]

The present invention phase shifting detecting circuit [Means for Solving the Problems] is as shown in FIGS. 1 to 13, for example, de of the reproduction synchronization signal
Detects dropout and outputs dropout detection signal
Drop-out detecting means 6 and the reproduction synchronizing signal
Pulse width detecting means 4, 5, 8-12, 14 for detecting a horizontal synchronizing pulse width to generate a pulse width detection signal;
17 and the pulse width detecting means 4, 5, 8 to 1
A pulse width detection signal from 2, 14 and 17, drop
By latching the out detection signal, a signal indicating the phase shift of the reproduction synchronization signal is obtained.

[0006]

According to the present invention, the pulse width detecting means is provided.
The pulse width detection signals from 4, 5, 8 to 12, 14, and 17 , and the dropout from dropout detection means 6
By latching the detection signal, a signal indicating the phase shift of the reproduction synchronization signal is obtained. For example, when applied to a time axis correction device of a video signal reproduction device, the reproduction horizontal synchronization signal Even if the rising edge of the GH signal is cut off, it is possible to perform the optimum gray replacement by the signal indicating the phase shift, and to guard the rising edge of the GH signal during the high-speed search operation to perform the optimum gray replacement. Thus, an extremely high quality image can be displayed without causing so-called image disorder.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the phase shift detecting circuit according to the present invention will be described below in detail with reference to FIG. This figure 1
Indicates a synchronization signal detection circuit including a phase shift detection circuit. In FIG. 1, reference numeral 1 denotes an input terminal to which a read clock is supplied. The read clock from the input terminal 1 is supplied to a frequency dividing circuit 4 and an average pulse width detecting circuit 17 to be described later.
Supplied to The frequency dividing circuit 4 divides the read clock from the input terminal 1 by 例 え ば, for example, and divides the ク ロ ッ ク frequency of the read clock (hereinafter simply referred to as a frequency-divided signal) into a horizontal period count circuit. 5 and an average pulse width detection circuit 17 described later. The horizontal period counting circuit 5 counts the period of the falling edge of the reproduced horizontal synchronizing signal (see FIG. 2A) using the reference signal from the frequency dividing circuit 4, and outputs the horizontal period data signal obtained by this counting to a timing generator 8 described later. It is supplied to the average horizontal period detection circuit 10 by the load signal. The average horizontal cycle detection circuit 10 receives a horizontal cycle data signal from the horizontal cycle count circuit 5 and an average horizontal cycle latch data signal from an average horizontal cycle data latch circuit 9 described later based on a switch signal from the timing generator 8. , And as a result, an average horizontal cycle data signal is obtained and supplied to the average horizontal cycle data latch circuit 9 and the average cycle detection signal generation circuit 11, respectively. The average horizontal cycle data latch circuit 9 includes an average horizontal cycle detection circuit 10
The average horizontal period data signal is smoothed based on the sample and hold signal from the timing generator 8,
The smoothed average horizontal cycle latch data signal is supplied to an average horizontal cycle detection circuit.

The average period detection signal generation circuit 11 generates a signal based on a reset signal from the timing generator 8.
An average period detection signal (see FIG. 2B) having a pulse of, for example, ± 1 μs before and after the predicted arrival position of the falling edge of the next reproduced horizontal synchronizing signal from the average horizontal period data signal from the average horizontal period detection circuit. The average period detection signal is generated and supplied to the gate circuit 12 and an average period detection circuit 13 described later. The gate circuit 12 obtains a gated guard sync signal by gating a guard sync signal from the gate circuit 7 described later with an average period detection signal from the average period detection signal generation circuit 11, and outputs the gated guard sync signal to the switch 14. The first guard band signal (see FIG. 2G) is supplied to one fixed contact 14a and latches the average period detection signal at the falling edge of the guard sync signal from the gate circuit 7 to generate a first guard band signal (see FIG. 2G). Mix guard band signal generation circuit 2 for converting the band signal
Supply 0.

Here, the above-mentioned guard sync signal will be described. Reference numeral 2 denotes a dropout signal detected in the reproduced RF signal (a signal in which a dropout of the reproduced video signal is detected)
The dropout signal supplied to the input terminal 2 is supplied to a dropout stretch circuit 6. This dropout stretch circuit 6
Extends the trailing edge of the dropout signal supplied via the input terminal 2 by, for example, 2 μs, and supplies the trailing edge dropout signal (see FIG. 2E) to the gate circuit 7 and a phase detection circuit 18 described later, respectively. I do. 3
Is an input terminal to which a reproduced horizontal synchronizing signal is supplied. The reproduced horizontal synchronizing signal supplied to this input terminal 3 is supplied to a gate circuit 7. The gate circuit 7 gates the reproduced horizontal synchronizing signal from the input terminal 3 with the dropout signal from the dropout stretch circuit 6. As a result, the above-mentioned guard sync signal is generated. The guard sync signal from the gate circuit 7 is supplied to the timing generator 8, the gate circuit 12 and the switch 14 already described above.
Are supplied to the other fixed contact 14b and the average period detecting circuit 13 described later. As described above, the timing generator 8 generates a load signal, a switch signal, a sample-and-hold signal, a reset signal, and the like based on the guard sync signal from the gate circuit 7 and the frequency-divided signal from the frequency-divider circuit 4. The average period detection circuit 13 latches the guard sync signal from the gate circuit 7 at the falling edge of the average period detection signal from the average period detection signal generation circuit 11 to obtain a second guard band signal (see FIG. 2H). The second guard band signal is supplied to the mixed guard band signal generation circuit 20.

The switch 14 changes the movable contact 14c of the switch 14 to one fixed contact 14a or the other fixed contact 14a in response to a mode signal supplied to the control input terminal 15 and becoming "0" at, for example,. +-. 30.times. The switch 14 is connected to a gated guard sync signal supplied to one fixed contact 14a of the switch 14 or a guard sync signal supplied to the other fixed contact 14b of the switch 14 by a GH signal (G is a gate , H are supplied to an output terminal 16 as horizontal synchronizing signals, and are also supplied to an average pulse width detection circuit 17 described later. The average pulse width detection circuit 17 outputs the gated guard sync signal or guard sync signal from the switch 14, ie, GH
The average pulse width of the signal (refer to FIG. 2F) is detected based on the read clock from the input terminal 1 and the detected value (count value) is used to determine, for example, ± 0.5 μs before and after the predicted rising edge of the next GH signal. A third guard band signal (see FIG. 2I) is generated by latching the pulse width detection signal at the rising edge of the GH signal, and the third guard band signal is phase-shifted as described later. The signals are supplied to the detection circuit 18 and the mix guard band signal generation circuit 20, respectively.

The phase detection circuit 18 generates a phase detection signal for extracting an edge serving as a phase reference.
The fourth guard band signal (see FIG. 2J) is obtained by latching the drop-out signal, and the fourth guard band signal is supplied to the mixed guard band signal generation circuit 20 and the generated phase detection signal is output to the output terminal 19. To supply. The mixed guard band signal generation circuit 20 includes a first guard band signal from the gate circuit 12, a second guard band signal from the average period detection circuit 13, a third guard band signal from the average pulse width detection circuit 17, and a phase detection circuit. The AND of all the fourth guard band signals is taken, a mixed guard band signal is generated, and this mixed guard band signal is supplied to the output terminal 21. The above-described frequency dividing circuit 4, horizontal count circuit 5, dropout stretch circuit 6, gate circuit 7, timing generator 8, average horizontal cycle data latch circuit 9, average horizontal cycle detection circuit 10, average cycle detection signal generation circuit 11, gate Circuit 1
2, a switch 14 and an average pulse width detection circuit 17 constitute a phase shift detection circuit.

Next, the operation of the above-described synchronization signal detection circuit will be described with reference to the timing chart of FIG.
In FIG. 2, for example, as shown in FIG. 2E, assuming that dropout occurs over 3H (horizontal period), the reproduced horizontal synchronizing signal is 4, 5 as shown in FIG. 2A.
And the sixth is missing. At this time, in the gate circuit 12, since the average period detection signal is latched at the falling edge of the guard sync signal from the gate circuit 7, the fourth, fifth and sixth reproduction horizontal synchronization signals are pre-held and the guard band Will not be determined. Therefore, as shown in FIG. 2G, the first guard band signal from the gate circuit 12 becomes a low level “0” which is the guard band at the seventh of the reproduced horizontal synchronization signal, and the GH signal shown in FIG. When the gated guard sync signal output from the circuit 12 starts to fall, the ninth of the reproduced horizontal synchronizing signal becomes a high level "1" at which the guard band is released. As described in FIG. 1, the gated guard sync signal is formed as follows. That is, a load signal based on the guard sync signal from the gate circuit 7 is generated by the timing generator 8, and the horizontal cycle count circuit 5 is divided by the frequency divider circuit until the count value is loaded by the load signal. By counting the signals (frequency-divided signals of the read clock), the period of the falling edge of the reproduced horizontal synchronization signal is counted. Then, this count value is smoothed by the average horizontal cycle data latch circuit 9 and the average horizontal cycle detection circuit 10, and is used as average horizontal cycle data. And the average period detection signal generation circuit 11
Predicts the arrival position of the next rising edge of the reproduced horizontal synchronizing signal from the average horizontal cycle data, and generates an average cycle detection signal in which pulses of ± 1 μs are set before and after that. Further, the guard sync signal is gated by the average period detection signal. A guard sync signal gated in this way is formed. In this example, ± 10
In the reproduction mode at the double speed or lower, the guard sync signal is not recognized as a gated guard sync signal unless the guard sync signal is continuously included in the pulse portion of the average period detection signal. Accordingly, as shown in FIGS. 2F and 2A, the eighth portion of the reproduced horizontal synchronizing signal of the GH signal does not become active, that is, does not become low level “0”.

As shown in FIGS. 2H and 2B, the second guard band signal is supplied to the average period detecting circuit 13 by a guard sync signal from the gate circuit 7 at the falling edge of the average period detecting signal from the average period detecting circuit 11. It is formed by being latched. Now, since the phase reference of the luminance signal Y in the beta cam format is the rising edge of the reproduced horizontal synchronizing signal, the GH obtained based on the average horizontal period of the rising edge of the reproduced horizontal synchronizing signal as in the related art. As shown in FIGS. 2A and 2F, some of the signals have a rising edge cut off by dropout in a portion corresponding to the eleventh and fifteenth portions of the reproduced horizontal synchronization signal. Was the cause. Therefore, the third guard band signal is obtained by detecting, as a guard band, a state in which the trailing edge of the reproduced horizontal synchronizing signal has been removed due to dropout, and the third guard band signal is, as shown in FIGS. The pulse width detection signal generated by the average pulse width detection circuit 17 is formed by latching at the rising edge of the guard sync signal from the gate circuit 7. That is, as shown in FIG. 2F, the average pulse width detection circuit 17 reads out the pulse width of the GH signal from the switch 14 in the low level “0” section and counts it with the clock to detect the average pulse width of the GH signal. Then, the arrival position of the next rising edge of the GH signal is predicted from this count value, and a pulse of ± 0.5 μs is made before and after the corresponding portion. As described above, by latching the pulse width detection signal generated by the average pulse width detection circuit 17 at the rise of the guard sync signal from the gate circuit 7, the edge eroded by the dropout in the GH signal (reproduction) The line (corresponding to the eleventh of the horizontal synchronizing signal) is set as a guard band as shown in FIG. 2I.

On the other hand, the fourth guard band signal also detects a state in which the trailing edge of the reproduced horizontal synchronizing signal has been removed due to dropout as a guard band. This fourth guard band signal is shown in FIGS. 2D and 2J. Thus, at the rise of the phase detection signal generated by the phase detection circuit 18,
It is formed by latching the dropout signal from the dropout stretch circuit 6. This is because an edge (corresponding to the fifteenth reproduction horizontal synchronization signal) of the GH signal which cannot be detected by the pulse width detection circuit 17 described above occurs. Therefore, by latching the dropout signal from the dropout stretch circuit 6 at the rising edge of the phase detection signal generated by the phase detection circuit 18, the edge eroded by the dropout in the GH signal (the fifteenth of the reproduced horizontal synchronization signal). (Corresponding to) is a guard band as shown in FIG. 2J.

Thus, the first to fourth guard band signals are formed. Here, since the above-described average period detection signal is a signal that predicts the arrival position of the guard sync signal, as shown in FIGS. 2A and 2B, if there is a third horizontal synchronizing signal of the reproduced horizontal synchronizing signal, An average period detection signal is set in a portion corresponding to the next fourth. Therefore, the guard band can be determined from the portion corresponding to the fourth portion of the reproduced horizontal synchronizing signal, and the second guard band signal can be formed as shown in FIG. 2H. However, as shown in FIGS. 2A and 2H, the guard band is released in the portion corresponding to the eighth portion of the reproduced horizontal synchronization signal. Therefore, it is necessary to AND the first guard band signal and the second guard band signal shown in FIG. 2G. Also, it is necessary to perform an AND operation on the third and fourth guard band signals. Therefore, in the mix guard band signal generation circuit 20 shown in FIG.
The fourth guard band signal is ANDed to generate a mixed guard band signal as shown in FIG. 2K. The mix guard band signal generation circuit 20 includes a control signal from the input terminal 15, an average period detection signal from the average period detection signal generation circuit 11, a signal indicating the tape running direction from the video signal reproducing apparatus main body, and a chroma signal. A signal for performing switch control with the signal C and the luminance signal Y,
The signal lines of the guard sync signal from the gate circuit 7 and the dropout signal from the dropout stretch circuit are shown and described with reference to FIG. FIG. 3 shows an enlarged waveform of a signal related to guard band detection in the luminance signal Y, and FIG. 4 shows an enlarged waveform of a signal related to guard band detection in the chroma signal C.

FIG. 16 shows an enlarged view of a portion of the video record location of FIG. In FIG. 16, θ1 is 4.68111 degrees, θ2 is 4.6 degrees, and θ3 is 1
At 5.3311, the distance between the center of the track Y track of the luminance signal Y and the center of the track C track of the chroma signal C is 165.7 μm. The forward direction of the luminance signal Y will be described. During normal reproduction, the head h moves from the position a to the position b at an angle of θ2. On the other hand, during reproduction by the search operation, the head h moves from the position a to the position c. By the way, x shown in the figure is 45.7 sin (15.3311 degrees).
3.8 μm. Since the track length becomes 114.98 mm, the track length becomes 11 by 114.98 cos (4.68 degrees).
4.60 mm. This 114.60 mm is converted to 312.
When divided by 5H (the number of Hs in one track in the PAL system), the length of 1H is approximately 366.7 μm. Then, the ratio of x to the length of 1H is approximately 11.9%. Therefore, as shown in FIG. 17, at the time of reproduction in the forward direction by the search operation of the luminance signal Y, the GH signal (FIG. 17A) arrives earlier than the position in the normal reproduction, so that the write phase reference signal (FIG. 17B) Is surely reset, and a normal image can be output from seven lines of the GH signal. However, as shown in FIG. 18, during the reproduction in the reverse direction by the search operation of the luminance signal Y, the GH signal (FIG. 18A) arrives later than the position in the normal reproduction, so that the write phase reference signal (FIG. 18B) ) Are not reset by 7 lines of the GH signal. As described above, the luminance signal Y and the chroma signal C
Are recorded on the tape with the azimuth angle changed, so that when the reproduction is performed by the search operation of the chroma signal, FIGS.
The opposite phenomenon to that described in FIG. Therefore, some processing must be performed on the guard band signal by the luminance signal Y and the chroma signal C. FIG. 5 illustrates an example of the mix guard band signal generation circuit 20 described in FIG. 1 that performs such processing. In FIG. 5, reference numeral 26 denotes an input terminal to which a first guard band signal is supplied; 22, an input terminal to which a second guard band signal is supplied; 23, an input terminal to which a third guard band signal is supplied; This is an input terminal to which a 4-guard band signal is supplied. The first, second, third, and fourth guard band signals from these input terminals 26, 22, 23, and 24 are supplied to a guard band detection circuit 25, respectively. The guard band detection circuit 25 has input terminals 26, 22, 23 and 2
4 and the AND of all of the first, second, third, and fourth guard band signals respectively supplied as signals, and uses this as a mixed guard band signal by a 1H (one horizontal cycle) stretching circuit 29 and one of the switches 27. Each is supplied to the fixed contact 27a. The 1H stretching circuit 29 converts the mixed guard band signal from the guard band detecting circuit 25 into 1 based on the average period detection signal supplied to the clock input terminal.
H (one horizontal period), and the average period detection signal expanded by 1H is applied to the other fixed contact 2 of the switch 27.
7b. When a signal from a switch 32 to be described later is at a low level "0", the switch 27 connects the movable contact 27c of the switch 27 to one fixed contact 27a of the switch 27, and the signal from the switch 32 is at a high level. In the case of "1", the movable contact 27c of the switch 27 is connected to the other fixed contact 27b, and the mixed guard band signal supplied to one and the other fixed contacts 27a and 27b of the switch 27 is expanded by 1H. One of the average period detection signals
Is supplied to one of the fixed contacts 41a. Reference numeral 34 denotes an input terminal to which a guard sync signal from the gate circuit 7 is supplied;
Reference numeral 5 denotes an input terminal to which a dropout signal from the dropout stretch circuit 6 is supplied. A guard sync signal and a dropout signal are supplied to the high-speed guard band detection circuit 36 via these input terminals 34 and 35, respectively. This high-speed guard band detection circuit 36 has an input terminal 3
An average period detection signal is obtained based on the guard sync signal and the dropout signal from 4 and 35, a guard band signal is formed based on the average period detection signal, and the guard band signal is connected to one fixed contact 39a of the switch 39. And 2
An H (two horizontal periods) enlargement circuit 38 is supplied to each of them.
The 2H stretching circuit 38 stretches the guard band signal from the high-speed guard band detecting circuit 36 by 2H (two horizontal periods) based on the guard sync signal supplied from the gate circuit 7 via the input terminal 37, and stretches the guard band signal. The guard band signal is supplied to the other fixed contact 39 of the switch 39.
b. This switch 39 is a switch 3 described later.
When the signal from switch 2 is at low level "0", the movable contact 39c of switch 39 is connected to one fixed contact 39a of switch 39. When the signal from switch 32 is at high level "1", The movable contact 3 of this switch 39
9c is connected to the other fixed contact 39b.
One of the guard band signal supplied to one and the other fixed contacts 39a and 39b of 9 and the guard band signal expanded by 2H are supplied to the other fixed contact 41b of the switch 41.

Reference numeral 30 denotes an input terminal to which a high level "1" is supplied when the tape traveling direction is reverse, that is, reverse, and a low level "0" is supplied when the tape traveling direction is forward, that is, forward. An input terminal to which a low level “0” is supplied when the tape running direction is reverse, ie, reverse, and a high level “1” when the tape running direction is forward, ie, forward, Is a terminal to which a control signal which becomes high level "1" and becomes low level "0" in case of a chroma signal is inputted. A switch 32 has one fixed contact 32a of the switch 32.
Is supplied with a signal of the high level "1" or low level "0" indicating the above-described reverse or forward, and the other fixed contact 32b of the switch 32 has the high level "1" or the low level indicating the above-described forward or reverse. A signal of level “0” is supplied. When the control signal from the input terminal 33 is at a high level "1", the switch 32 connects the movable contact 32c of the switch 32 to one fixed contact 32a, and the control signal from the input terminal 33 is at a low level. When "0", this switch 32
Is connected to the other fixed contact 32b.
The signal from the switch 32 is supplied as a control signal to the switches 27 and 39, respectively. Switch 42
Indicates that the control signal from the input terminal 40 is high level "1" (±
When the speed is 30 times or less), the movable contact 41c of the switch 41 is connected to one fixed contact 41a of the switch 41, and the control signal from the input terminal 40 is low level "0".
In the case of (more than ± 30 times speed), the movable contact 41c of the switch 41 is connected to the other fixed contact 41b of the switch 41, and the signal from the switch 27 or the switch 39 is supplied to the output terminal 42.

Now, this mix guard band signal generating circuit 20 is used in a luminance signal processing system,
In addition, when the speed is ± 30 times or less, a high-level “1” signal is supplied to the input terminal 30 and a low-level “0” signal is supplied to the input terminal 31. Then, the control signal from the input terminal 33 becomes high level “1”, and the switch 32
Is connected to the fixed contact 32a of the switch 32. As a result, a high-level "1" signal from the switch 32 is supplied to the switches 27 and 39, respectively, and the movable contact 27c of the switch 27 is connected to the switch 2
7 is connected to the other fixed contact 27b, and the movable contact 39c of the switch 39 is connected to the other fixed contact 3 of the switch 39.
9b. Thus, 1H via switch 27
The 1H extended mix guard band signal from the extending circuit 29 is applied to one fixed contact 41 of the switch 41.
a, and the guard band signal expanded by 2H from the 2H expansion circuit 38 is supplied to the switch 4.
1 and is supplied to the other fixed contact 41b. On the other hand, the movable contact 41c of the switch 41 is connected to one of the fixed contacts 41a by a control signal of a high level "1" from the input terminal 40.
Connected to. The output terminal 42 is supplied with the 1H stretched mix guard band signal from the 1H stretching circuit 29.

Next, this mix guard band signal generation circuit 20 is used in a luminance signal processing system, and when the speed is less than ± 30 times the speed in the forward direction, a low-level “0” signal is supplied to the input terminal 30. , An input terminal 31 is supplied with a high-level "1" signal. And input terminal 3
3 is at a high level "1", and the movable contact 32c of the switch 32 is connected to the fixed contact 32a of the switch 32.
Connected to. As a result, a low-level "0" signal from the switch 32 is supplied to the switches 27 and 39, respectively, and the movable contact 27c of the switch 27 is connected to one fixed contact 27a of the switch 27.
Nine movable contacts 39c are connected to one fixed contact 39a of the switch 39. Thus, the mixed guard band signal from the guard band detection circuit 25 is supplied to one fixed contact 41a of the switch 41 via the switch 27, and the guard band signal from the high speed guard band detection circuit 36 is supplied to the other of the switch 41. Fixed contact 41b
Supplied to On the other hand, the movable contact 41 of the switch 41
“c” is connected to one fixed contact 41 a by a control signal of a high level “1” from the input terminal 40. The output terminal 42 is supplied with a mixed guard band signal from the guard band detection circuit 25.

Next, this mix guard band signal generation circuit 20 is used in a luminance signal processing system,
When the speed is ± 30 times or more, a high-level “1” signal is supplied to the input terminal 30 and a low-level “0” signal is supplied to the input terminal 31. Then, the control signal from the input terminal 33 becomes high level “1”, and the switch 32
Is connected to the fixed contact 32a of the switch 32. As a result, a high-level "1" signal from the switch 32 is supplied to the switches 27 and 39, respectively, and the movable contact 27c of the switch 27 is connected to the switch 2
7 is connected to the other fixed contact 27b, and the movable contact 39c of the switch 39 is connected to the other fixed contact 3 of the switch 39.
9b. Thus, 1H via switch 27
The 1H extended mix guard band signal from the extending circuit 29 is applied to one fixed contact 41 of the switch 41.
a, and the guard band signal expanded by 2H from the 2H expansion circuit 38 is supplied to the switch 4.
1 and is supplied to the other fixed contact 41b. On the other hand, the movable contact 41c of the switch 41 is connected to the other fixed contact 41b by a low level “0” control signal from the input terminal 40.
Connected to. The output terminal 42 is supplied with the guard band signal expanded by 2H from the 2H expansion circuit 38.

Next, this mix guard band signal generation circuit 20 is used in a luminance signal processing system, and when the speed is higher than ± 30 times speed in the forward direction, a signal of low level “0” is supplied to the input terminal 30. , An input terminal 31 is supplied with a high-level "1" signal. And the input terminal 33
The control signal becomes high level "1", and the movable contact 32c of the switch 32 becomes the fixed contact 32a of the switch 32.
Connected to. As a result, a low-level "0" signal from the switch 32 is supplied to the switches 27 and 39, respectively, and the movable contact 27c of the switch 27 is connected to one fixed contact 27a of the switch 27.
Nine movable contacts 39c are connected to one fixed contact 39a of the switch 39. Thus, the mixed guard band signal from the guard band detection circuit 25 is supplied to one fixed contact 41a of the switch 41 via the switch 27, and the guard band signal from the high speed guard band detection circuit 36 is supplied to the other of the switch 41. Fixed contact 41b
Supplied to On the other hand, the movable contact 41 of the switch 41
“c” is connected to the other fixed contact 41 b by a low-level “0” control signal from the input terminal 40. The output terminal 42 is supplied with a guard band signal from the high-speed guard band detection circuit 36.

Next, when this mix guard band signal generating circuit 20 is used in a chroma signal processing system and the reverse direction and the speed is ± 30 times or less, a high level “1” signal is supplied to the input terminal 30. Then, a signal of low level “0” is supplied to the input terminal 31. Then, the control signal from the input terminal 33 becomes low level “0”, and the movable contact 32 c of the switch 32 becomes the fixed contact 32 of the switch 32.
b. As a result, a low-level "0" signal from the switch 32 is supplied to the switches 27 and 39, respectively, and the movable contact 27c of the switch 27 is connected to one fixed contact 27a of the switch 27. 39c is connected to one fixed contact 39a of the switch 39. Thus, the mixed guard band signal from the guard band detection circuit 25 is supplied to one fixed contact 41a of the switch 41 via the switch 27, and the guard band signal from the high speed guard band detection circuit 36 is supplied to the other of the switch 41. Fixed contact 41
b. On the other hand, the movable contact 4 of the switch 41
1c is connected to one fixed contact 41a by a control signal of high level "1" from the input terminal 40. The output terminal 42 is supplied with a mixed guard band signal from the guard band detection circuit 25.

Next, this mix guard band signal generation circuit 20 is used in a chroma signal processing system, and when the speed is less than ± 30 times the speed in the forward direction, a signal of low level “0” is supplied to the input terminal 30. , An input terminal 31 is supplied with a high-level "1" signal. And input terminal 3
3 becomes low level "0", and the movable contact 32c of the switch 32 becomes the fixed contact 32b of the switch 32.
Connected to. As a result, a high-level "1" signal from the switch 32 is supplied to the switches 27 and 39, respectively, and the movable contact 27c of the switch 27 is connected to the other fixed contact 27b of the switch 27.
Nine movable contacts 39c are connected to the other fixed contact 39b of the switch 39. Thus, the 1H-stretched mix guard band signal from the 1H-stretching circuit via the switch 27 is applied to one fixed contact 41 of the switch 41.
a, and the guard band signal expanded by 2H from the 2H expansion circuit 38 is supplied to the switch 4.
1 and is supplied to the other fixed contact 41b. On the other hand, the movable contact 41c of the switch 41 is connected to one of the fixed contacts 41a by a control signal of a high level "1" from the input terminal 40.
Connected to. The output terminal 42 is supplied with the 1H stretched mix guard band signal from the 1H stretching circuit 29.

Next, when this mix guard band signal generating circuit 20 is used in a chroma signal processing system and the reverse direction and the speed is ± 30 times or more, a high level “1” signal is supplied to the input terminal 30. Then, a signal of low level “0” is supplied to the input terminal 31. Then, the control signal from the input terminal 33 becomes low level “0”, and the movable contact 32 c of the switch 32 becomes the fixed contact 32 of the switch 32.
b. As a result, a low-level "0" signal from the switch 32 is supplied to the switches 27 and 39, respectively, and the movable contact 27c of the switch 27 is connected to one fixed contact 27a of the switch 27. 39c is connected to one fixed contact 39a of the switch 39. Thus, the mixed guard band signal from the guard band detection circuit 25 is supplied to one fixed contact 41a of the switch 41 via the switch 27, and the guard band signal from the high speed guard band detection circuit 36 is supplied to the other of the switch 41. Fixed contact 41
b. On the other hand, the movable contact 4 of the switch 41
1c is connected to the other fixed contact 41b by a low-level "0" control signal from the input terminal 40. The output terminal 42 is supplied with a guard band signal from the high-speed guard band detection circuit 36.

Next, this mix guard band signal generating circuit 20 is used in a chroma signal processing system, and when the speed is higher than ± 30 times speed in the forward direction, a signal of low level “0” is supplied to the input terminal 30. , An input terminal 31 is supplied with a high-level "1" signal. And input terminal 3
3 becomes low level "0", and the movable contact 32c of the switch 32 becomes the fixed contact 32b of the switch 32.
Connected to. As a result, a high-level "1" signal from the switch 32 is supplied to the switches 27 and 39, respectively, and the movable contact 27c of the switch 27 is connected to the other fixed contact 27b of the switch 27.
Nine movable contacts 39c are connected to the other fixed contact 39b of the switch 39. Thus, the 1H-stretched mix guard band signal from the 1H-stretching circuit via the switch 27 is applied to one fixed contact 41 of the switch 41.
a, and the guard band signal expanded by 2H from the 2H expansion circuit 38 is supplied to the switch 4.
1 and is supplied to the other fixed contact 41b. On the other hand, the movable contact 41c of the switch 41 is connected to the other fixed contact 41b by a low level “0” control signal from the input terminal 40.
Connected to. The output terminal 42 is supplied with the guard band signal expanded by 2H from the 2H expansion circuit 38. When the mixed guard band signal generating circuit 20 is used in the chroma signal processing system, particularly when the projected image is monochrome at ± 30 × speed or more, the control by the video signal reproducing device supplied to the input terminal 40 is performed. The signal remains at high level "1".

As is apparent from the above description, when the mix guard band signal generating circuit 20 is used in a chroma signal processing system of a time axis correcting device of a video signal reproducing device, which will be described later, the 1H stretching circuit is used during the forward operation. 29, the mix guard band signal is extended by 1H and output, so that the minimum gray replacement can be performed, thereby obtaining an extremely high quality image. Also, when the mix guard band signal generation circuit 20 is used in a luminance signal processing system of a time axis correction device of a video signal reproducing device described later, 1H is used during a reverse operation.
The mix guard band signal is expanded by 1H and output by the expansion circuit 29, so that the minimum gray replacement can be performed, thereby obtaining an extremely high quality image.

In the mixed guard band signal generating circuit 20, as described above, when the speed is less than ± 30 times the average period based on the guard sync signal and the dropout signal, the control signal from the input terminal 40 is used. A detection signal is obtained, and a guard band signal formed based on the average period detection signal is output. When the speed is higher than +30 times (forward), an average period detection signal is obtained based on the guard sync signal and the dropout signal. A guard band signal formed based on this average period detection signal is output. When the speed is higher than -30 times (reverse), the guard band signal from the high-speed guard band detection circuit 36 is expanded by 2H based on the guard sync signal. The signal is output as a guard band signal. As shown in FIG. 6, since the average horizontal period of the reproduced horizontal synchronizing signal (FIG. 6A) is observed in the case of -30 times speed (reverse) or higher, the high-speed guard band detection circuit 36 described in FIG.
The average period detection signal (FIG. 6E) can be taken from the line. However, as described above, since eight lines are not reset for the writing reference due to the azimuth, the guard band signal (FIG. 6D) from the high-speed guard band detection circuit 36 is expanded by 2H, as shown in FIG. 6F. A guard band signal is formed. At +30 times speed or higher, the high-speed guard band detection circuit 36 can obtain the average period detection signal (FIG. 6C) from the seven lines of the reproduced horizontal synchronization signal shown in FIG. 6A.
A guard band signal as shown in FIG. 6D can be formed based on the average period detection signal.

As described above, when the speed is higher than +30 times (forward), an average period detection signal is obtained based on the guard sync signal and the dropout signal, and a guard band signal formed based on the average period detection signal is output. West,
When the speed is higher than -30 times (reverse), a signal obtained by extending the guard band signal from the high-speed guard band detection circuit 36 by 2H based on the guard sync signal is output as a guard band signal. An extremely high quality image can be obtained even at the time of high-speed reproduction of 30 times or more in the direction.

Next, the average pulse width detection circuit 17 described with reference to FIG. 1 will be described with reference to FIG. 7, reference numeral 100 denotes an input terminal to which a read clock is supplied. The read clock is supplied to the pulse width count circuit 101 and the timing generator 104 via the input terminal 100. The timing generator 104 receives a load signal, a switch signal, a sample hold signal, and a reset signal based on a read clock supplied from the input terminal 100 and a GH signal from the switch 14 described in FIG. Generate a signal. The generated load signal is supplied to the pulse width counting circuit 101, the switch signal is supplied to the average pulse width detection circuit 103, the sample hold signal is supplied to the average pulse width data latch circuit 102, and the reset signal is supplied to the pulse width detection signal. It is supplied to the generation circuit 105.
The pulse width counting circuit 101 counts the low level “0” section of the GH signal from the input terminal 106 based on the load signal from the timing generator 104 and the read clock from the input terminal 100, and obtains the count by this counting. The supplied pulse width data is supplied to the average pulse width detection circuit 103. This average pulse width detection circuit 103
Is the average pulse width latch data from the average pulse width data latch circuit 102 and the timing generator 104
Average pulse width data based on the switch signal
This average pulse width data is converted to a pulse width detection signal generation circuit 1
05. The pulse width detection signal generation circuit 105
Based on the average pulse width data from the average pulse width detection circuit 103 and the reset signal from the timing generator 104, the arrival position of the rising edge of the GH signal from the input terminal 106 is predicted. A pulse width detection signal having a 0.5 μm pulse is generated, and the generated pulse width detection signal is supplied to the third guard band signal generation circuit 107.

This third guard band signal generation circuit 107
Latches the pulse width detection signal from the pulse width detection signal generation circuit 105 at the rising edge of the GH signal from the input terminal 106 to generate a third guard band signal.
The guard band signal is supplied to the mixed guard band signal generation circuit 20 described with reference to FIG. As shown in FIG. 8, the reproduced horizontal synchronization signal (FIG. 8A)
8C, and a portion tc where the edge of the reproduced horizontal synchronizing signal is removed occurs, the average period detection signal is not affected as shown in FIG. 8B, but the GH signal (FIG. 8C) is not affected. 8D), a portion tc with a sharpened edge is generated in the same portion as the reproduced horizontal synchronization signal. However, as shown in FIG. 8E, the pulse width detection signal
Since the signal corresponds to the pulse width of the H signal, the third guard band signal (FIG. 8F) has a low level “0” at the portion corresponding to the portion tc of the GH signal whose edge has been removed. Therefore, the portion of the projected image that has been curved is replaced with gray.

Next, referring to FIG. 9, the synchronization signal detecting circuit including the phase shift detecting circuit described with reference to FIGS. 1, 5 and 7 is applied to a time axis correcting device of a video signal reproducing device. An example will be described. In FIG. 9, reference numeral 50 denotes an input terminal to which a reproduced video signal (luminance video signal) from a video signal reproducing apparatus main body (not shown) is supplied, and a reproduced video signal from the input terminal 50 (hereinafter simply referred to as video data). (Described) are supplied to an A / D converter (analog-digital converter) 52 and a sync separation / PLL (phase locked loop) circuit 51. The A / D converter 52 converts a luminance signal from the input terminal 50 into, for example, an 8-bit digital signal using a write clock from the synchronization separation / PLL circuit 51, and supplies the digital signal to a luminance signal processing circuit 53. I do. On the other hand, the sync separation / PLL circuit 51 separates the sync signal from the luminance signal from the input terminal 50, locks the phase, generates a write clock and a write phase reference signal, and sends the reproduced sync signal to the sync signal detection circuit 53. The write clock is supplied to the A / D converter 52 and the cancel circuit 5.
4. Supply to the insert circuit 55, the memory controller 56 and the memory 57, respectively.

The synchronization signal detection circuit 53 including the phase shift detection circuit already described with reference to FIGS. 1, 5 and 7 supplies a guard sync signal and a phase detection signal to the synchronization separation / PLL circuit 51 and drops the signal to the insert circuit 55. Out signal and guard band signal, and a decision circuit 5 described later.
9 is supplied with a guard band signal. Cancel circuit 54
Performs drop-out processing and pre-processing for gray replacement based on the write clock from the sync separation / PLL circuit 51. That is, if the upper 7 bits of the 8-bit video data (luminance signal-based reproduced video data signal) from the A / D converter 52 are all "0", this data is set to "00000010", and this is used as the data as an insert circuit. 55. The insert circuit 55 converts the video data whose data is “00000010” from the video data from the cancel circuit 54 into a drop-out signal (corresponding to drop-out processing) or a guard band signal (for gray replacement processing) from the synchronization signal detection circuit 53. Signal), a signal in which all 8 bits are “0”, that is, “0000” corresponding to the dropout process.
0000 "data (hereinafter simply referred to as dropout processing data) or the least significant 8 bits are" 1 "
, Ie, data of “00000001” corresponding to the gray replacement processing (hereinafter simply referred to as gray replacement processing data). Then, the insert circuit 55 supplies the converted dropout processing data, gray replacement processing data, or unconverted normal video data to the memory 57.

The memory controller 56 has a sync separation / PL
A write control signal is generated based on a write clock and a write phase reference signal from the L circuit 51, and the write control signal is supplied to the memory 57. On the other hand, the memory controller 56 includes a read reference signal generation circuit 61
A read control signal is generated based on the read clock and the read phase reference signal, and the read control signal is supplied to the memory 57. Therefore, writing of video data (dropout processing data or gray replacement processing data) to the memory 57 is performed by the memory controller 5.
6 according to the write control signal from the sync separation / PLL
Reading of video data (including dropout processing data and gray replacement processing data) from the memory 57 is performed in accordance with a reading control signal from the memory controller 56 in accordance with a writing clock from the circuit 51.
This is performed using a read clock from the read reference signal generation circuit 61. Readout reference signal generation circuit 61
Is a detection circuit 58 and an output processing circuit 60 in addition to the memory controller 56, the memory 57 and the synchronization signal detection circuit 53
Also supply a read clock.

The video data (including the drop-out processing data and the gray replacement processing data) read from the memory 57 is supplied to the detection circuit 58. The detection circuit 58 detects whether the video data from the memory 57 is normal video data, dropout processing data, or gray replacement processing data based on a read clock from the read reference signal generation circuit 61. If the video data is the dropout processing data, a dropout detection signal is supplied to the determination circuit 59. If the video data from the memory 57 is the gray replacement processing data, a gray replacement detection signal is supplied to the determination circuit 59. The video data from the memory 57 is supplied to the output processing circuit 60. The judgment circuit 59 includes a dropout detection signal or a gray replacement detection signal from the detection circuit 58, a control signal supplied from the video / tape recorder main unit via the input terminal 73 and indicating a reproduction speed of less than ± 3 times, and the memory controller 56. Based on the read control signal, the timing of the dropout processing, the timing of the gray replacement processing, and the detection of the first line of the guard band are performed, and the output detection circuit 60 outputs the dropout processing timing signal or the gray replacement timing. Providing a processing signal. The output processing circuit 60 performs dropout processing or gray replacement processing of video data from the detection circuit 58 based on the dropout processing timing signal or gray replacement timing processing signal from the determination circuit 59, and outputs the video data subjected to these processings. Is supplied to the addition circuit 70 via the DA converter 62.

As described above, in the beta cam system, the write phase reference in the search operation is, for example, shown in FIG. 10 due to the azimuth in the tape format.
It becomes as shown in. Here, for example, when there is a dropout (FIG. 10C) from line 2 to line 6 of the horizontal synchronizing signal of the reproduced video signal, the reproduced horizontal synchronizing signal becomes 3
You cannot take from line to line 6. At this time, the guard band portion corresponds to three to six lines of the reproduced horizontal synchronization signal as shown in FIG. 10D.
Therefore, as shown as tx in FIG. 10B, writing is not performed for a predetermined amount. At this time, if the video signal is projected on the screen of a monitor or the like without performing the gray processing on the read side after being read from the memory 57, as shown in FIG. Are projected as previously written data tx. If the memory 57 is a so-called line memory, the data tx moves on the screen of the monitor, resulting in an image that is very hard to see visually. The numbers 1 to 8 on the left correspond to the numbers 1 to 8 described in the reproduced horizontal synchronization signal of FIG. 10A, respectively. Also, d is the dropout part,
This corresponds to the drop-out portion shown in FIG. 10C, and g is a guard band portion, which corresponds to the guard band portion shown in FIG. 10D.

However, the decision circuit 59 described above uses the timing of the read control signal generated by the memory controller 56 based on the read phase reference signal {read reference horizontal synchronization signal (FIG. 12A)} as shown in FIG. A guard band portion as shown in FIG. 12C is detected for the output, and a dropout processing timing signal and a gray replacement processing timing signal are supplied to the output processing circuit 60 in response to the detection. Therefore, when a video signal is projected on the screen of a monitor or the like after dropout processing or gray replacement processing is performed on the read side after reading from the memory 57, writing is not performed as shown in FIG. The predetermined portion is not displayed as the previously written data tx, but is displayed as the gray-substituted portion tb. The numerals 1 to 8 on the left correspond to the numerals 1 to 8 described in the reference horizontal synchronization signal of FIG. 12A, respectively. In addition, ta is a dropout processing part, and corresponds to the dropout processing part ta of the dropout part shown in FIG. 12B and the guard band part shown in FIG. 12C, and tb is a gray replacement processing part shown in FIG. 12C. This corresponds to the gray replacement processing part tb of the guard band part. Also, the judgment circuit 59
In the case where the guard band portion is equal to or longer than two horizontal periods of the reference horizontal synchronization signal, as shown in FIG. 13C, the first one horizontal period of the guard band portion is video data one horizontal period before, and a so-called drop A dropout processing timing signal is supplied to the output processing circuit so that the output processing is performed. Then, as shown in FIGS. 2K, 6D and 6F, the output circuit 60 performs a gray replacement process (shown as tb in each figure) on the video signal portion corresponding to the guard band portion of the guard band signal. When the portion extends over two horizontal periods, a portion of the video signal corresponding to the first one horizontal period of the guard band portion is called video data one horizontal period earlier, so-called dropout processing (referred to as ta in each drawing). Shown). Therefore,
As shown in FIG. 13, a dropout processing part t of the dropout part shown in FIG.
a and the dropout processing part ta of the guard band part shown in FIG. 12C is subjected to the dropout processing and is displayed (shown as ta in the figure), and the gray processing part tb of the guard band part shown in FIG. It is projected.

Further, the judgment circuit 59 has an input terminal 73
When a signal indicating a search operation at a speed of ± 3 times or less becomes active, the above-described so-called line dropout processing is not performed. The reason for this is that, when performing a so-called line drop-out process when the guard band portion is equal to or more than two horizontal periods as described above during a low-speed search of ± 3 × speed or less, because of the low-speed search, it is displayed on the screen of a monitor or the like. This is because the projected image has four lines of the same video data including ODD and EVEN, which makes it easy to visually discriminate and makes the image hard to see.

Next, the circuit of the chroma signal system will be described. The input terminal 64 is supplied with a reproduced video signal (a chroma video signal). The reproduced video signal (hereinafter simply referred to as video data) is supplied to a chroma signal processing circuit 65 via an input terminal 64. Since the chroma signal processing circuit 65 has substantially the same circuit configuration as the luminance signal processing circuit 72, illustration and detailed description thereof are omitted. The video data (color difference signals RY and BY) signal-processed by the chroma signal processing circuit 65 are converted into analog signals by DA converters 66 and 67, respectively, and supplied to an encoder circuit 68. The encoder circuit 68 is based on the reference subcarrier signal obtained by the reference subcarrier signal generation circuit 69 based on the read clock supplied from the reference signal generation circuit 61 and the color difference signals RY and BY. Then, a chroma signal is obtained, and this chroma signal is supplied to the adding circuit 70. The adder circuit 70 outputs D-
Brightness signal from A converter 62 and encoder circuit 6
The chroma signals from 8 are added to obtain a color video signal, and this color video signal is supplied to an output terminal 71. The color video signal is supplied to, for example, a monitor connected to the video signal reproducing device via an output circuit or the like of the video signal reproducing device main body, and is projected as an extremely high quality image on the monitor screen of the monitor. . It is assumed that the above-described chroma signal processing circuit 65 also performs the same guard band detection, dropout processing, and gray replacement processing as the luminance signal processing circuit 72.

As is clear from the above, in this example,
When the mix guard band signal generation circuit 20 is used in the chroma signal processing system of the time axis correction device of the video signal reproducing device, the 1H stretching circuit 29 extends the mix guard band signal by 1 H during the forward operation and outputs the signal. As a result, the minimum gray replacement can be performed, thereby obtaining an extremely high quality image. When the mix guard band signal generation circuit 20 is used in the luminance signal processing system of the time axis correction device of the video signal reproducing device, the 1H stretching circuit 29 stretches the mix guard band signal by 1 H during the reverse operation and outputs the result. As a result, the minimum gray replacement can be performed, so that an extremely high quality image can be obtained.

When the speed is higher than +30 times (forward), an average period detection signal is obtained based on the guard sync signal and the dropout signal, and a guard band signal formed based on the average period detection signal is output. -30
When the speed is higher than the double speed (reverse), a signal obtained by extending the guard band signal from the high-speed guard band detection circuit 36 by 2H based on the guard sync signal is output as a guard band signal. Even at high speed playback of 30 times speed or more,
Extremely high quality images can be obtained. Further, in the synchronization signal detection circuit 53, since the guard band detection is performed based on the read clock and the read phase reference signal, even if the previous data remains in the memory 57, the corresponding portion of this data is grayed out. Can be replaced,
As a result, so-called image disturbance does not occur in the projected image. Further, when the guard band portion is equal to or more than two horizontal periods of the reference horizontal synchronization signal, the first one horizontal period of the guard band portion is video data one horizontal period earlier,
Since the dropout processing timing signal is supplied to the output processing circuit so as to perform a so-called dropout processing, the minimum gray replacement processing can be performed to make the projected image easy to view. Further, the average pulse width detection circuit 17 latches the average pulse width detection signal at the rising edge of the GH signal to obtain a third guard band signal, which is supplied to the mixed guard band signal generation circuit 20. Even if the rising edge of the reproduced horizontal synchronizing signal is cut off during the search operation, optimal gray replacement can be performed using the third guard band signal, and the rising edge of the GH signal is guarded during the high-speed search operation. To achieve the best possible gray replacement and prevent the so-called image disorder from occurring, and to display very high quality images.

It should be noted that the present invention is not limited to the above-described embodiment, and may take various other configurations without departing from the gist of the present invention.

[0042]

According to the present invention described above, the dropout detection signal is used as the pulse width detection signal from the pulse width detection means.
By latching the signal, a signal indicating a phase shift of the reproduction synchronization signal is obtained. For example, when applied to a time axis correction device of a video signal reproduction device, the reproduction horizontal synchronization signal Even if the rising edge is cut off, optimal gray replacement can be performed by a signal indicating this phase shift, and at the time of high-speed search operation, the rising edge of the GH signal is guarded to perform optimal gray replacement. Thus, there is an advantage that an extremely high quality image can be displayed without causing so-called image disorder.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a phase shift detection circuit according to the present invention.

FIG. 2 is a timing chart for explaining one embodiment of a signal processing circuit of the video signal reproducing apparatus of the present invention.

FIG. 3 is a timing chart for explaining one embodiment of the phase shift detection circuit of the present invention.

FIG. 4 is a timing chart for explaining one embodiment of the phase shift detection circuit of the present invention.

FIG. 5 is a block diagram showing a specific example of a mix guard band signal generation circuit for explaining a phase shift detection circuit of the present invention.

FIG. 6 is a timing chart for explaining a phase shift detection circuit according to the present invention;

FIG. 7 is a block diagram showing a specific example of an average pulse width detection circuit for explaining the phase shift detection circuit of the present invention.

FIG. 8 is a timing chart for explaining a phase shift detection circuit according to the present invention;

FIG. 9 is a block diagram showing an example of a time axis correction device to which the phase shift detection circuit of the present invention is applied.

FIG. 10 is an explanatory diagram showing a timing at the time of writing.

FIG. 11 is an explanatory diagram showing an image projection state.

FIG. 12 is a timing chart showing dropout processing and gray replacement processing after reading.

FIG. 13 is an explanatory diagram showing an image projection state.

FIG. 14 is an explanatory diagram showing a video record location of the beta cam system.

FIG. 15 is a timing chart showing a conventional guard band detection and gray replacement.

FIG. 16 is an enlarged view of a part of the video record location of the beta cam system.

FIG. 17 is an explanatory diagram showing image bending at the time of a forward operation.

FIG. 18 is an explanatory diagram showing image bending during a reverse operation.

[Explanation of symbols]

 4 Divider circuit 5 Horizontal cycle count circuit 6 Dropout stretch circuit 7 Gate circuit 8 Timing generator 9 Average horizontal cycle data latch circuit 10 Average horizontal cycle detection circuit 11 Average cycle detection signal generation circuit 12 Gate circuit 13 Average cycle detection circuit 17 Average Pulse width detection circuit 18 Phase detection circuit 20 Mix guard band signal generation circuit

Claims (1)

(57) [Claims] 1. A dropout of a reproduction synchronization signal is detected.
Dropout that outputs a dropout detection signal
Detection means, and a pulse width detection means for generating a pulse width detection signal by detecting the horizontal sync pulse width of the reproduction synchronization signal, a pulse width detection signal from said pulse width detecting means, said de
A phase shift detection circuit, wherein a signal indicating a phase shift of the reproduction synchronization signal is obtained by latching a dropout detection signal .