JP2003274215A - Signal generator circuit and video camera provided therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid such generation that not color appears on a monitor for receiving image signals or no color signals are recorded on a VCR. <P>SOLUTION: The video camera outputs image signals containing own luminance signals and chroma signals synchronized with luminance signals and chroma signals contained in video signals inputted from another video camera as external synchronizing signals. A comparator 64 calculates the ratio of a frequency corresponding to a horizontal synchronizing signal contained in the luminance signal of the image signal from the other video camera to the frequency of own subcarrier signal (chroma signal). If the calculated ratio is out of a specified range, a switch 44 is connected to a VCO control voltage 42 (a connection terminal 44b) to make a chroma system PLL open, thereby fixing the frequency of the subcarrier signal (chroma signal) to a rated frequency determined in the NTSC or PAL system, depending on the VCO control voltage 42. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal generating circuit, and more particularly to a horizontal synchronizing signal and a subcarrier respectively synchronized with a horizontal synchronizing signal of a luminance signal and a burst signal of a chroma signal included in an externally input video signal. The present invention relates to a signal generation circuit that generates a signal.

[0002]

2. Description of the Related Art When video signals of a plurality of video cameras are switched by a switcher and output to one monitor, it is necessary to prevent synchronization disturbance on the monitors at the time of switching. Therefore, in order to synchronize the video signal of the video camera with the video signal of another video camera, some video cameras have an external synchronization function for synchronizing with the video signal input from the outside.

The external synchronization function of the video camera generates a video signal in which the brightness signal and the chroma signal included in the video signal input from the outside are synchronized with the brightness signal and the chroma signal of the device.

First, a horizontal synchronizing signal is extracted from a luminance signal included in a video signal (external synchronizing signal) input from the outside, and a burst signal is extracted from a chroma signal also included in the video signal.

Then, a phase comparison is performed between the extracted horizontal synchronizing signal and the own horizontal synchronizing signal formed from an oscillation circuit that generates a clock that serves as a reference for the luminance signal of the video camera output signal. PLL (Phase Lock) that controls the oscillation frequency of the oscillation circuit that generates the reference clock
ed Loop). By doing so, the luminance signal of the own device is synchronized with the luminance signal included in the video signal of another video camera input from the outside.

The phase of the extracted burst signal is compared with that of the subcarrier signal (burst signal) of the own device, which is made from an oscillation circuit that generates a reference clock of the chroma signal of the video camera output signal, and the chroma of the own device is compared. A PLL that controls the oscillation frequency of an oscillation circuit that generates a clock that serves as a signal reference is configured. This synchronizes the own chroma signal with the chroma signal included in the video signal of another video camera input from the outside.

Two Ps, such as a luminance system and a chroma system, are provided.
By operating the LLs at the same time, it is possible to output a video signal that is synchronized with the brightness signal and the chroma signal, which are both included in the video signal input from the outside.

The above is the case where the external synchronization signal is a VBS (Video Burst SYNC) signal which is a video signal having a burst (VBS mode), but VS (Video SYNC) which is a video signal without a burst is used as the external synchronization signal. ) A signal may be input. Further, there may be a case where no external synchronizing signal is input.

When the video signal is a VS signal, only the luminance PLL is operated and the chroma frequency is adjusted to a standard frequency in advance.
An external synchronization operation is performed in synchronization with only the luminance signal (VS mode).

When the external synchronizing signal is not input, the self-oscillation operation is performed so that the frequency of the luminance signal and the frequency of the chroma signal have a constant ratio defined by the standard (INT.
mode).

[0011]

The ratio of the frequency of the horizontal synchronizing signal (luminance signal) of the video signal output from the video camera to the frequency of the subcarrier signal (chroma signal) is
It is determined by video signal standards such as NTSC (National Television System Committee) and PAL (Phase Alternation by Line). However, some of the actual video signals output from the video camera are out of the standard. If there is a video camera that outputs a video signal that is out of the standard, the video signals of other video cameras that are synchronized with this will also be out of the standard. If the video signal is largely out of the standard, the monitor that receives the output of this video signal is not colored, or V
There arises a problem that a color signal is not recorded in a CR (Video Cassette Recorder).

Therefore, the main object of the present invention is to prevent the monitor from being colored or the color signal not being recorded in the VCR even if the video signal input as the external synchronizing signal is out of the standard. , To provide a video camera at low cost.

[0013]

SUMMARY OF THE INVENTION The present invention provides a second horizontal synchronizing signal and a subcarrier signal which are respectively synchronized with a first horizontal synchronizing signal of a luminance signal and a burst signal of a chroma signal included in a video signal input from the outside. In the signal generating circuit to be generated, a determining means for determining whether the frequency of the first horizontal synchronizing signal and the frequency of the subcarrier signal satisfy a predetermined relationship, and the frequency of the subcarrier signal when it is determined that the predetermined relationship is not satisfied. Is provided with a first fixing means for fixing to a first predetermined frequency.

[0014]

According to the present invention, the discriminating means is provided in the signal generating circuit for generating the second horizontal synchronizing signal and the subcarrier signal which are respectively synchronized with the first horizontal synchronizing signal and the burst signal input from the outside of another video camera or the like. ,
Whether the frequency of the first horizontal synchronizing signal and the frequency of the subcarrier signal input from the outside satisfy a predetermined relationship, for example, if the ratio of the frequency of the first horizontal synchronizing signal and the frequency of the subcarrier signal is within a predetermined range. Determine if there is. When the determining unit determines that the frequency of the first horizontal synchronizing signal and the frequency of the subcarrier signal do not satisfy the predetermined relationship, the first fixing unit determines the frequency of the subcarrier signal to the first fixed frequency (NTSC standard or The frequency is fixed to the PAL standard). Therefore, even if the frequency of the burst signal input from the outside such as another video camera is largely out of the standard, the signal generation circuit (including the video camera) includes a normal subcarrier signal conforming to the standard. The video signal is output.

[0015]

According to the present invention, even if the burst signal input from the outside is out of the standard, the video signal including the subcarrier signal (chroma signal) of the frequency defined in the standard is output. The monitor that receives this video signal is not colored, and the VCR does not record the color signal.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the detailed description of the following embodiments made with reference to the drawings.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a signal generation circuit 10 of a video camera of this embodiment comprises a sync separation circuit 12 and a BPF.
(Band Pass Filter) 32 is included. A video signal (composite signal) from another video camera is input to the sync separation circuit 12 and the BPF 32 as an external sync signal.

The sync separation circuit 12 separates the horizontal sync signal from the luminance signal included in the video signal to obtain an LPF (Low
The LPF 14 shapes the horizontal synchronizing signal and supplies it to the phase comparator 16.

The phase comparator 16, the LPF 18, the frequency controller 24, the oscillator circuit 26 and the frequency divider 28 are connected in series, and the output of the frequency divider 28 is fed back to the phase comparator 16 to form a luminance system PLL. To do.

The phase comparator 16 compares the phase of the horizontal synchronizing signal with the feedback signal (horizontal synchronizing signal) obtained from the frequency divider 28, and outputs the phase difference to the LPF 18 as a pulsed phase difference signal. . The LPF 18 removes the AC component of the phase difference signal and uses it as a control voltage for the frequency controller 24. The frequency controller 24 controls the oscillation circuit 26 to control the LP
The oscillation circuit 26 outputs a signal having a frequency corresponding to the control voltage given from F18. Then, the frequency divider 28 divides the frequency of the signal obtained from the oscillation circuit 26 by a predetermined ratio (which will be described later in detail) to generate a horizontal synchronizing signal synchronized with the horizontal synchronizing signal included in the external synchronizing signal. . Further, the frequency divider 28 feeds back the frequency-divided signal (horizontal synchronizing signal) to the phase comparator 16.

As a result, the signal (clock) obtained from the oscillation circuit 26 becomes the reference of the luminance signal of the video camera, and the signal obtained from the frequency divider 28 is the video signal (external input) of another video camera. It is synchronized with the horizontal sync signal.

A switch 22 whose connection destination is switched by a synchronous mode setting circuit 58 is arranged between the LPF 18 and the frequency controller 24. The switch 22 includes three connection terminals. LP when the switch 22 is connected to the connection terminal 22a or the connection terminal 22b
The F18 and the frequency controller 24 are connected to connect to the PL of the luminance system.
L is constructed. When the switch 22 is connected to the connection terminal 22c, a VCO (Voltage Controlled Oscilla)
tor) The control voltage 20 is connected to the frequency controller 24.
In this case, the frequency controller 24 controls the oscillation circuit 2 based on the constant voltage (DC voltage) given from the VCO control voltage 20.
Control 6 Depending on this, NTSC standard or P
The oscillation circuit 26 is caused to oscillate at the frequency of the luminance signal defined in the AL standard. Therefore, the horizontal synchronization signal of the video camera is not synchronized with the horizontal synchronization signal included in the video signal of another video camera that is externally input.

On the other hand, the BPF 32 extracts the chroma signal from the video signal and supplies it to the phase detector 33. The phase detector 33 detects the phase of the burst signal from the output of the sync separation circuit 12, extracts only the burst signal from the output of the BPF 32, and supplies it to the phase comparator 38.

The phase comparator 38, the LPF 40, the frequency controller 46, the oscillator circuit 48 and the frequency divider 50 are connected in series, and the output of the frequency divider 50 is fed back to the phase comparator 38 to form a chroma system PLL. To do.

The phase comparator 38 compares the phase of the burst signal output from the phase detector 33 with the feedback signal (subcarrier signal) obtained from the frequency divider 50, and determines the phase difference as a pulse-like phase difference. The signal is output to the LPF 40. The LPF 40 removes the AC component of the phase difference signal and uses it as a control voltage for the frequency controller 46. Frequency controller 4
Reference numeral 6 controls the oscillation circuit 48 so that the oscillation circuit 48 outputs a signal having a frequency corresponding to the control voltage given from the LPF 40. Then, the frequency divider 50 divides the frequency of the signal obtained from the oscillation circuit 48 at a predetermined ratio (details will be described later) to generate a subcarrier signal. Also, the frequency divider 50
Feeds back the divided signal to the phase comparator 38.

As a result, the signal (clock) obtained from the oscillation circuit 48 becomes the reference of the chroma signal (burst signal) of the video camera, and the signal obtained from the frequency divider 50 is the video signal of another video camera ( External input) burst signal.

A switch 44 whose connection destination is switched by a synchronous mode setting circuit 58 is arranged between the LPF 40 and the frequency oscillator 46. The switch 44 includes three connection terminals. When the switch 44 is connected to the connection terminal 44a, the frequency controller 46 has the LPF4
0 is connected to form a chroma PLL. When the switch 44 is connected to the connection terminal 44b, the frequency controller 4
A VCO control voltage 42 is connected to 6. In this case, the frequency controller 46 controls the oscillation circuit 48 based on the constant voltage provided from the VCO control voltage 42,
The oscillation circuit 48 is oscillated at the frequency of the chroma signal defined in the NTSC standard or the PAL standard. Therefore, the chroma signal of the video camera is not synchronized with the chroma signal (burst signal) included in the video signal of the other externally input video camera.

When the switch 44 is connected to the connection terminal 44c, the LPF 36 is connected to the frequency controller 46, and the phase comparator 34, LPF 36, frequency controller 46,
The oscillator circuit 48 and the frequency divider 50 configure a PLL that uses the output of the frequency divider 30 and the output of the frequency divider 50 as inputs to the phase comparator 34. In this PLL, the output of the frequency divider 30 is synchronized with the output of the frequency divider 30. As described above, the ratio between the frequency of the horizontal synchronizing signal and the frequency of the subcarrier signal is fixed by the standard.

Therefore, the switch 22 is connected to the connection terminal 22c so that the frequency divider 28 is connected to the NTSC standard or PAL.
When the horizontal synchronizing signal of the frequency according to the standard is output, the frequency divider 30 frequency-divides the output of the oscillation circuit 26 and outputs the subcarrier signal of the frequency according to the NTSC standard or the PAL standard. Then, the output of the frequency divider 30 and the frequency divider 5
The output of the frequency divider 50 is synchronized with the output (subcarrier signal) of the frequency divider 30 by the PLL having the output of 0 as the input.

By the way, the output of the LPF 14 is the detector 52.
The output of the phase detector 33 is given to the detector 54. Then, the external synchronization signal determination circuit 56 determines whether the external synchronization signal includes both the luminance signal (horizontal synchronization signal) and the chroma signal (burst signal) based on the outputs of the detector 52 and the detector 54 (external synchronization signal VBS signal), a luminance signal is included in the external synchronization signal and a chroma signal is not included (the external synchronization signal is a VS signal), or whether the external synchronization signal does not exist. Further, the synchronization mode setting circuit 58 determines the operation mode based on the determination result of the external synchronization signal determination circuit 56, and switches the connection destination of the switch 22 and the switch 44.

That is, when the external synchronization signal is VBS, the synchronization mode setting circuit 58 connects the switch 22 to the connection terminal 22a and the switch 44 to the connection terminal 44a in order to set the VBS mode. By doing so, both the luminance PLL and the chroma PLL function, and both the luminance signal and the chroma signal are synchronized with the luminance signal and the chroma signal included in the external synchronization signal.

When the external synchronizing signal is the VS signal (not including the chroma signal), the synchronizing mode setting circuit 58 outputs V
In order to set the S mode, connect the switch 22 to the connection terminal 22
The switch 44 is connected to the connection terminal 44b. By doing so, only the PLL of the brightness system functions and the brightness signal is synchronized with the brightness signal included in the external synchronization signal. And chroma signal is NTSC standard or PA
The frequency is adjusted to the frequency defined by the L standard.

Further, when there is no external sync signal, the sync mode setting circuit 58 connects the switch 22 to the connection terminal 22c and the switch 44 to the connection terminal 44c in order to set the INT mode. By doing so, the frequency of the luminance system oscillation circuit 26 and the chroma system oscillation circuit 48
The self-oscillation operation is performed so that the frequency and the frequency have a constant ratio defined by the NTSC standard or the PAL standard.

By the way, the ratio of the frequency of the horizontal synchronizing signal (luminance signal) and the frequency of the subcarrier signal (chroma signal) included in the video signal output from the video camera is
It is determined by the video signal standards such as NTSC and PAL. However, some video signals output from the video camera are out of the standard. If there is a video camera that outputs a video signal that is out of the standard, the video signals of other video cameras that are synchronized with this will also be out of the standard. If the video signal largely deviates from the standard, problems occur such that the monitor receiving the video signal does not have colors or the VCR does not record the color signal.

Therefore, in the signal generating circuit 10 of this embodiment, the frequency of the horizontal synchronizing signal of the video signal input from the outside and the frequency of the subcarrier signal generated by the signal generating circuit 10 (actually, the frequency divider 50). Is the frequency of the output from the oscillating circuit 48 before it is divided into the frequency of the subcarrier signal, because the higher the frequency, the easier it is to compare with the horizontal synchronizing signal. When the ratio deviates from the standard by 60 ppm or more, that is, when the ratio deviates greatly from the standard, the switches 22 and 44 are switched to the VS mode. By this,
Only the luminance signal is synchronized with the luminance signal included in the external synchronization signal, and the chroma signal becomes a signal having a frequency defined by the standard.

Specifically, the frequency of the output of the LPF 14 is counted by the counter 60, and the frequency of the output of the oscillator circuit 48 is counted by the counter 62. Then, the comparator 64
Is based on the count value of the counter 60 and the count value of the counter 62.
The ratio with the frequency of the output of 8 is calculated, and the ratio is compared with the ratio defined in the standard to calculate how much it deviates from the standard. Then, the calculation result is given to the synchronous mode setting circuit 58. The synchronous mode setting circuit 58 switches the mode of the switch 22 and the switch 44 according to the calculation result.

The operation of the synchronous mode setting circuit 58 will be described with reference to the flowchart of FIG. First, first step S1
Switch 22 and switch 4 in the initial state in
4 is set to the VBS mode (connected to the connection terminals 22a and 44a). Then, in step S3, it is determined whether or not the calculation result is ± 60 ppm or more, that is, whether the ratio of the frequency of the horizontal synchronizing signal and the frequency of the output of the oscillation circuit 48 deviates from the standard by ± 60 ppm or more. If there is a deviation of ± 60 ppm or more, step S
5, the switch 22 and the switch 44 are set to the VS mode (connected to the connection terminals 22b and 44b).

On the other hand, in step S3, ± 60 pp
If it is determined that the difference is not more than m, step S7
In, it is determined whether the calculation result is ± 50 ppm or less. Then, if it is ± 50 ppm or less, the switch 22 and the switch 44 are set to the VBS mode in step S9. If it is determined in step S7 that it is not less than ± 50 ppm, step S
9 is skipped and the current mode is retained.

As described above, according to the video camera including the signal generating circuit 10 of this embodiment, the ratio between the frequency of the horizontal synchronizing signal and the frequency of the subcarrier (the frequency of the output of the oscillation circuit 48) is higher than the standard. If there is a large deviation, by setting the VS mode, only the luminance signal can be synchronized with the luminance signal of the external synchronizing signal, and the chroma signal can have the frequency defined in the standard. Therefore,
Even when the chroma signal included in the external synchronization signal is largely out of the standard, the video camera including the signal generation circuit 10 adversely affects other video cameras, the monitor is not colored, and the VCR is colored. A signal is output that is not recorded or is not recorded.

When the ratio between the frequency of the horizontal synchronizing signal and the frequency of the subcarrier deviates greatly from the standard, the VS mode is not set, but the INT mode (switch 22 is connected to the connection terminal 22c is connected. , Switch 4
4 is connected to the connection terminal 44c). By doing so, not only the chroma signal but also the luminance signal can have the frequency defined in the standard.
Therefore, even when the luminance signal included in the external synchronization signal is largely out of the standard, the luminance signal and the chroma signal having normal frequencies can be output.

Since the VS mode and the INT mode are the functions provided in the conventional video camera, the video camera provided with the signal generating circuit 10 of this embodiment does not need to add a new circuit and can be realized at a low cost. You can

As shown in FIG. 3A, the video output of the video camera 102 is used as a reference, and another video camera 10
There is a video camera system in which the output signals of 4, 106 and 108 are synchronized, and the output signals of each video camera are selected by a switcher 110 and output to a monitor 112. Here, it is assumed that the video camera 102 is a video camera with a color / monochrome switching function that stops the chroma oscillation circuit in the monochrome mode.

In this case, when the black-and-white mode is changed to the color mode, the chrominance-type oscillation circuit is not stable for several seconds, so that the ratio between the luminance-type frequency and the chrominance-type frequency of the video camera 102 is not stable. Therefore, if the video cameras 104, 106 and 108 are conventional video cameras, the frequency of the chroma system is not stable, a signal having an abnormality in the chroma system signal is output, and the monitor 112 is not colored. Occurs.

However, in the case of a video camera equipped with the signal generation circuit 10 of this embodiment, a chroma signal having a frequency specified in the standard is output while the chroma system oscillation circuit of the video camera 102 is not stable. The problem that the monitor 112 is not colored does not occur.

Further, as shown in FIG. 3B, the video output of the video camera 122 is synchronized with the video camera 124, and the video output of the video camera 124 is synchronized with the video camera 12.
There is a video camera system in which 6 are synchronized, the output signal of each video camera is selected by the switcher 128 and output to the monitor 130. Here, it is assumed that the video camera 122 is a video camera with a color / monochrome switching function that stops the chroma oscillation circuit in the monochrome mode.

In this case, the video camera 122 is in the monochrome mode, and the video camera 124 and the video camera 126 are in the black and white mode.
Is operating in color mode, the video camera 122
Outputs a VS signal, the video camera 124
It becomes a mode. At this time, if the video camera 124 is a conventional one, the chroma signal of the video signal output from the video camera 124 has a frequency adjusted in advance at the time of factory shipment, and the luminance signal has a frequency synchronized with the luminance signal of the video camera 122. Becomes Therefore, the ratio between the luminance signal and the chroma signal is not the ratio defined in the standard.
Further, although the video camera 126 is in the VBS mode, the external synchronizing signal, that is, the output of the video camera 124 may not have the ratio defined by the standard, and the external synchronizing operation is performed based on such an abnormal external synchronizing signal. The output of the video camera 126 is as described above, and the switcher 128 and the monitor 130 which receive the video signal from the video camera 126.
May malfunction.

However, if the video camera 126 is a video camera equipped with the signal generation circuit 10 of this embodiment, the chroma signal has a frequency defined by the standard, so that the switcher 128 and the monitor which receive the video signal of the video camera 126. There is no fear that the 130 will malfunction.

The standard value will be described below. NTS
In the case of the C standard, the frequency of the oscillation circuit 26 is 286
It is 36.360 KHz. And the frequency divider 28 is 1 /
Divided to 1820, the output is 15.734264KH
z, the frequency divider 30 divides the frequency by 1/8, and the output is 3
579.545 KHz. The frequency of the oscillation circuit 48 is 14318.180. And the frequency divider 5
0 is divided into 1/4 and the output is 3579.545KH
z.

The standard frequency fH of the synchronizing signal (luminance signal) input to the counter 60 is 15.734264K.
The standard frequency 4 fsc of the oscillation circuit 48 input to the counter 62 is 14318.180 KHz.
Is. Therefore, the ratio of both standards is 4 fsc /
fH is 910.

In the case of the PAL standard, first, the frequency of the oscillation circuit 26 is 28375.000 KHz. And
The frequency divider 28 divides the frequency by 1/1816, and its output is 15.
625 KHz, the frequency divider 30 divides by 5/32,
Its output is 433.61875 KHz. Also,
The frequency of the oscillator circuit 48 is 17734.475 KHz. Then, the frequency divider 50 divides the frequency by 1/4, and the output is 433.61875 KHz.

The standard frequency fH of the synchronizing signal (luminance signal) input to the counter 60 is 15.625 KHz, and the standard frequency 4fsc of the oscillation circuit 48 input to the counter 62 is 17734.475 KHz. is there. Therefore, the ratio of both standards is 4 fsc / fH
Is 1135.

The embodiment described above can be modified in various ways. For example, the counter 60 is LPF1.
Although the frequency of the signal output by the frequency divider 4 is counted, the counter 60 may instead count the frequency of the signal output by the frequency divider 28, as shown in FIG.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of a synchronous mode setting circuit.

FIG. 3A and FIG. 3B are schematic views for explaining the problems solved by the present invention.

FIG. 4 is a block diagram showing the overall configuration of another embodiment of the present invention.

[Explanation of symbols]

10 ... Synchronous circuit 20 ... VCO control voltage 22… Switch 24… Frequency controller 26 ... Oscillation circuit 28 ... Divider 30 ... Divider 42 ... VCO control voltage 44 ... switch 46 ... Frequency controller 48 ... Oscillation circuit 50 ... Divider 58 ... Synchronous mode setting circuit 60 ... Counter 62 ... Counter 64 ... comparator

Claims (3)

[Claims] 1. A signal generating circuit for generating a second horizontal synchronizing signal and a subcarrier signal which are respectively synchronized with a first horizontal synchronizing signal of a luminance signal and a burst signal of a chroma signal included in a video signal input from the outside. Discriminating means for discriminating whether or not the frequency of the first horizontal synchronizing signal and the frequency of the subcarrier signal satisfy a predetermined relationship, and the frequency of the subcarrier signal is determined to be a first predetermined value when it is determined that the predetermined relationship is not satisfied. A signal generating circuit comprising first fixing means for fixing the frequency. 2. The signal generating circuit according to claim 1, further comprising second fixing means for fixing the frequency of the second horizontal synchronizing signal to a second predetermined frequency when it is determined that the predetermined relationship is not satisfied. 3. A video camera comprising the signal generating circuit according to claim 1.