JPH0783494B2 - Video tape recorder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a video tape recorder commonly used in the PAL system and the SECAM system.

[Outline of Invention]

The present invention focuses on the fact that the modulation format of the carrier color signal is different between the PAL system and the SECAM system, and the system is based on the output of the phase comparator used for APC during the frequency conversion of the carrier color signal of the PAL system. This is a video tape recorder for both PAL and SECAM, which can reduce the cost by simplifying the configuration of the discrimination circuit by obtaining the discrimination output.

[Conventional technology]

First, referring to FIGS. 3 and 4, the conventional PAL-S
A video tape recorder (hereinafter abbreviated as VTR) commonly used for ECAM will be described.

Fig. 3 shows an example of the configuration of a conventional VTR playback system commonly used for PAL-SECAM.

In FIG. 3, the reproduction RF signal from the reproduction magnetic head (1) is supplied to the luminance signal-color signal (Y / C) separation circuit (3) via the reproduction amplifier (2), and the FM luminance signal Y It is separated into _FM and low-frequency conversion carrier color signal C _l (carrier frequency f _l ). The FM luminance signal Y _FM is demodulated by the demodulator (4) into the luminance signal Y, which is led to the output terminal (6) via the adder (5). The low-frequency conversion carrier color signal C _l is supplied to the first frequency converter (11) of the color signal processing circuit (10), and the horizontal synchronization signal separated from the luminance signal Y by the synchronization separation circuit (7) is generated. , Via the delay circuit (8) to the burst sampling circuit (13) of the color signal processing circuit (10).

In the color signal processing circuit (10), the first frequency converter (11) outputs the second frequency converter (12) (frequency fs).
c ± f _l ) is supplied, and the low-frequency conversion carrier color signal C _l is
It is returned to the original carrier color signal C (frequency fsc). The carrier color signal C is supplied to the burst sampling circuit (13), and the color burst signal transmitted together with the carrier color signal C is sampled by the burst flag from the delay circuit (8). This burst signal is phase-compared with the output of the crystal oscillator (15) in the phase comparator (14) composed of a multiplier, and the output of the phase comparator (14) is connected to one fixed contact of the switch (16) ( 16p), the movable contact (16c) and the low pass filter (17), the voltage controlled oscillator (VCO) (1
8) Supplied to. The other fixed contact (1
6s) is grounded via a capacitor. The frequency of the output of the VCO (18) is stepped down to f _l by the 1/8 frequency divider (19) and supplied to the second frequency converter (12), where the crystal oscillator (15) is mixed with the output, is converted to the frequency of fsc ± f _l, it is supplied to the first frequency converter (11).
Thereby, in the state where the movable contact (16c) of the switch (16) is connected to one fixed contact (16p), an automatic phase control (APC) loop is formed, and the carrier color signal C is transferred to the crystal oscillator (15). The time axis fluctuation during VTR playback is eliminated in phase synchronization with the output.

The carrier color signal C output from the color signal processing circuit (10) is directly supplied to one fixed contact (21p) of the switch (21), and the sideband is attenuated at a predetermined rate. It is supplied to the other fixed contact (21s) through the filter (22), and the output of the movable contact (21c) is supplied to the adder (5).

(30) is a system discrimination circuit, which is a color signal processing circuit (10)
The outputs of the burst sampling circuit (13) and the crystal oscillator (15) are supplied to the multiplier (31) of the system discrimination circuit (30),
The output of the multiplier (31) is supplied to the wave detector (33) via the bandpass filter (32), and the output of the wave detector (33) is passed through an integrating circuit represented by a capacitor (34) and then a comparator. (3
5) is supplied to and compared with a predetermined voltage Er.

If the carrier color signal C is of SECAM type, the comparator (3
Switch (16) and (21) according to the discrimination output of 5)
Is switched from the initial connection state opposite to that shown in the figure to the connection state shown in the figure.

The operation of the discrimination circuit (30) is as follows.

As is well known, the PAL subcarrier frequency fsc is constant at 4.43 MHz in all horizontal scanning periods, while S
In ECAM system, 4.40625MHz fscr for each horizontal scanning period,
Alternately switched to 4.2500MHz fscb.

Therefore, when the carrier color signal C is of the PAL system, the output of the multiplier (31) is
The sum and difference components of the frequency of the input signal, that is, 2fsc
It becomes the component and the DC component.

On the other hand, when the carrier color signal C is of the SECAM system, a difference component signal of fd = fsc−fscb≈180 KHz is generated at the output of the multiplier (31) every other horizontal scanning period. The difference component signal separated by the bandpass filter (32) whose center frequency is set equal to fd is double-wave rectified in the detector (33), and the output of the detector (33) alternates every horizontal scanning period. "Hi" and "L
The detected output is integrated by the integrator circuit (34) and compared with a predetermined voltage Er in the comparator (35). When the output of the integrator circuit (34) reaches Er, the comparator Controlled by the output of (35), switches (16) and (2
1) is switched to the connection state shown in the figure, and the carrier color signal C from the color signal processing circuit (10) is supplied to the adder (5) through the bell filter which is available in SECAM system, and the luminance signal Y is supplied.
Is added to obtain a composite video signal. In this case, the APC loop of the color signal processing circuit (10) is opened and put into a non-operating state. However, as is well known, in the SECAM system, since the color signal is a frequency modulation wave, the phase synchronization of the sub-carrier wave does not occur. It is unnecessary.

FIG. 4 shows the structure of a conventional VTR recording system commonly used for PAL-SECAM.

In Fig. 4, the composite video signal from the input terminal (41) is
The luminance signal Y and the carrier color signal C are separated by being supplied to the Y / C separation circuit (42). The luminance signal Y is a frequency modulator (4
3) and becomes an FM luminance signal Y _FM , which is supplied to the recording magnetic head (46) via the adder (44) and the recording amplifier (45). The carrier color signal C is directly supplied to one fixed contact (51p) of the switch (51), and the sideband is amplified at a predetermined rate. It is supplied to the other fixed contact (51s) through the bell filter (52), which has a characteristic opposite to that of the bell filter (22) described above, and the output of the movable contact (51c) is fed to the color signal processing circuit (60). The frequency converter (61) and the burst sampling circuit (62) are commonly supplied. The horizontal sync signal separated from the luminance signal Y by the sync separation circuit (47) is supplied to the burst sampling circuit (62) through the delay circuit (48).

In the color signal processing circuit (60), the first frequency converter (61) outputs the second frequency converter (63) output (frequency fs).
c ± f _l ) is supplied, and the carrier color signal C is converted into a low-frequency conversion carrier color signal C _l (frequency f _l ). In the burst sampling circuit (62), the color burst signal transmitted together with the carrier color signal C is sampled by the burst flag from the delay circuit (48). This burst signal is phase-compared with the output of the crystal oscillator (65) in the phase comparator (64) composed of a multiplier, and the output of the phase comparator (64) is connected to one fixed contact ( 66p), the movable contact (66c), and the low-pass filter (67), and is supplied to the crystal oscillator (65). In this case, the crystal oscillator (65) becomes a voltage controlled crystal oscillator (VCXO), the frequency of which follows the color subcarrier frequency of the input signal. The other fixed contact (66s) of the switch (66) is grounded via a capacitor. The horizontal sync signal from the sync separation circuit (47) is supplied to the second phase comparator (71) and the VCO (7
The output of 2) is supplied via the 1 / N frequency divider (73), and the output of this phase comparator (71) is supplied to the VCO (72).
The output of (72) is phase-synchronized with the horizontal sync signal. This VC
The frequency of the output of O (72) is 1/8 by the frequency divider (74).
It is stepped down to f _l and supplied to the second frequency converter (63), where it is mixed with the output of the crystal oscillator (65) and fsc
The frequency is converted to ± f _l and supplied to the first frequency converter (61). As a result, an APC loop is formed in the state where the movable contact (66c) of the switch (66) is connected to one fixed contact (66p), and the second frequency converter (6
The output of 3) is phase-synchronized with the color subcarrier in the input signal and also with the horizontal sync signal in the input signal.

The respective outputs of the burst sampling circuit (62) and the crystal oscillator (65) are supplied to the multiplier (31) of the system discrimination circuit (30). When the SECAM type composite video signal is supplied to the terminal (41), the switches (51) and (66) are connected by the output of the comparator (35) in the same manner as described above, in the initial connection opposite to that shown in the drawing. The state is switched to the connection state shown.

[Problems to be solved by the invention]

In the conventional VTR shared with PAL-SECAM as shown in FIGS. 3 and 4, the phase comparator for APC of the PAL system carrier color signal is provided in the color signal processing circuit (10) or (60). (14)
Alternatively, together with (64), a multiplier (31) dedicated to system discrimination
Are used, the structure is complicated, and the manufacturing cost is increased.

In view of this point, an object of the present invention is to enable PAL-SEC that can perform method discrimination with a simple configuration and reduce manufacturing cost.
It is in the place of providing a VTR shared by AM.

[Means for solving problems]

The present invention compares a phase of a color burst signal frequency and a reference frequency with a color signal processing circuit (10) for separating a luminance signal and a carrier color signal from a reproduction RF signal and extracting a color burst signal from the carrier color signal. Then, the automatic phase control loop (14), (15), (12), which controls to synchronize the phases,
(16), (17), (18), (19) and bandpass filter (3
2), a detector (33), an integrator circuit (34) and a comparator (35) for comparing with a predetermined voltage. The automatic phase control loops (14), (15), (12), (16), (17), (18),
A single PAL-SECAM discrimination circuit (32), (3) that obtains a PAL-SECAM discrimination signal from the output of the phase comparator (14) in (19).
3), (34), (35) and the PAL-SECAM discrimination signal based on the automatic phase control loops (14), (15), (12), (1
First switch (16) for selecting whether to make 6), (17), (18), (19) closed loop or open state
And a second switch (21) for selecting whether to add the carrier color signal to the luminance signal as it is or to add the carrier color signal to the luminance signal after the sidebands are attenuated at a predetermined ratio. When the PAL-SECAM discrimination signal discriminates the PAL system, the first switch (1
6) Automatic phase control loop (14), (15), (1
2), (16), (17), (18), (19) are closed loops, and automatic phase control loops (14), (15), (12), (1
When frequency conversion is performed using 6), (17), (18), and (19), the carrier color signal is added to the luminance signal as it is, and when the PAL-SECAM determination signal determines the SECAM method, SECAM The automatic phase control loops (14), (15), (1
2), (16), (17), (18), (19) as an open loop, automatic phase control loop (14), (15), (12), (1
6), (17), (18), and (19) are deactivated, frequency conversion is performed, and sidebands are attenuated at a predetermined ratio with respect to the carrier color signal before adding to the luminance signal. It is a video tape recorder commonly used for PAL-SECAM.

[Action]

According to the present invention, a multiplier for system determination is not required, and the configuration is simplified.

[Embodiment] An embodiment of the video tape recorder according to the present invention will be described below with reference to FIG.

The configuration of one embodiment of the present invention is shown in FIG. In FIG. 1, parts corresponding to those in FIG. 3 are designated by the same reference numerals, and redundant description will be omitted.

In FIG. 1, the outputs of the burst sampling circuit (13) and the crystal oscillator (15) are supplied to the phase comparator (14), and the output of the phase comparator (14) is connected to one fixed contact ( 16p) and the bandpass filter (32) of the system discrimination circuit (30D). This system discrimination circuit (30
D) is constructed by removing the multiplier (31) from the system discrimination circuit (30) of FIG. The remaining structure of this embodiment is the same as that of the conventional example shown in FIG.

The operation of this embodiment is as follows.

When the carrier color signal C is of the PAL type, the output of the phase comparator (14), which is a multiplier, is the 2fsc component and the DC component, and does not include the fd component. This DC component is supplied to the VCO (18) via the switch (16) and the low pass filter (17), and an APC loop is formed in the color signal processing circuit (10). In this case, no discrimination output is obtained from the discrimination circuit (30D).

When the carrier color signal C is of the SECAM system, the output of the phase comparator (14) has a difference of fd≈180 KHz every other horizontal scanning period, like the multiplier (31) shown in FIG. A component signal is generated. This difference component signal is separated by the bandpass filter (32) of the system discrimination circuit (30D) and controlled by the discrimination output of the comparator (35) in the same manner as described above, and the switches (16) and (21) are shown in the figure. Switch to the connected state.

According to this embodiment, since the difference component signal of the frequency fd peculiar to the SECAM system is obtained from the output of the phase comparator (14) for APC in the color signal processing circuit (10), the system discrimination circuit The structure of (30D) is simplified and the cost is reduced.

Next, another embodiment of the video tape recorder according to the present invention will be described with reference to FIG.

The configuration of another embodiment of the present invention is shown in FIG. In FIG. 2, parts corresponding to those in FIGS. 1 and 4 are designated by the same reference numerals, and duplicate description will be omitted.

In FIG. 2, the outputs of the burst sampling circuit (62) and the crystal oscillator (65) are supplied to the phase comparator (64), and the output of the phase comparator (64) is one fixed contact ( 66p) and the bandpass filter (32) of the system discrimination circuit (30D). The remaining structure of this embodiment is the same as that of the conventional example shown in FIG.

The operation of this embodiment is as follows.

When the carrier color signal C is of the PCL type, the output of the phase comparator (64), which is a multiplier, is the 2fsc component and the DC component, and does not include the fd component. This DC component is supplied to the crystal oscillator (VCXO) (65) via the switch (66) and the low pass filter (67), and an APC loop is formed in the color signal processing circuit (60). In this case, the discrimination circuit (30D)
No discriminant output can be obtained from.

When the carrier color signal C is of the SECAM system, the output of the phase comparator (64) has a difference of ft≈180 KHz at every 1 horizontal scanning period, like the multiplier (31) shown in FIG. A component signal is generated. This difference component signal is separated by the bandpass filter (32) of the system discrimination circuit (30D) and controlled by the discrimination output of the comparator (35) in the same manner as described above, and the switches (51) and (66) are illustrated. Switch to the connected state.

According to this embodiment, since the difference component signal of the frequency fd peculiar to the SECAM system is obtained from the output of the phase comparator (64) for APC in the color signal processing circuit (60), the system discrimination circuit The structure of (30D) is simplified and the cost is reduced.

〔The invention's effect〕

As described above in detail, according to the present invention, from the output of the phase comparator for APC in the color signal processing circuit, the 1
Since the difference component signal (frequency fd) is obtained at every horizontal scanning period, the structure of the system discriminating circuit is simplified and the cost is reduced, so that the PAL-SECAM common video tape recorder can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing the construction of an embodiment of a video tape recorder according to the present invention, FIG. 2 is a block diagram showing the construction of another embodiment of the present invention, and FIG. 3 is a construction of a conventional video tape recorder. FIG. 4 is a block diagram showing an example, and FIG. 4 is a block diagram showing another configuration example of a conventional video tape recorder. (10), (60) are color signal processing circuits, (11), (12),
(61) and (63) are frequency converters, (14) and (64) are phase comparators, and (30D) is a system discrimination circuit.

Claims (1)

[Claims] 1. A color signal processing circuit for separating a luminance signal and a carrier color signal from a reproduced RF signal and extracting a color burst signal from the carrier color signal, and a phase of a frequency of the color burst signal and a reference frequency. The output of the phase comparator in the automatic phase control loop consists of an automatic phase control loop that controls the phase to be synchronized, a bandpass filter, a detector, an integrator circuit, and a comparator that compares the voltage with a predetermined voltage. PAL-SECAM discrimination signal from a single PA
An L-SECAM discriminating circuit, a first switch for selecting whether the automatic phase control loop is closed loop or open based on the PAL-SECAM discriminating signal, and the carrier color signal as it is Add it to the luminance signal,
Or a second switch for selecting whether to add the carrier color signal to the luminance signal after attenuating the sideband at a predetermined ratio, and when the PAL-SECAM determination signal determines the PAL system , PAL
For the carrier color signal of the system, the automatic phase control loop is closed by the first switch, frequency conversion is performed using the automatic phase control loop, and the carrier color signal is added to the luminance signal as it is. When the PAL-SECAM discrimination signal discriminates the SECAM method, S
With respect to the carrier color signal of the ECAM system, the automatic phase control loop is opened by the first switch, the automatic phase control loop is deactivated, and frequency conversion is performed. A video tape recorder commonly used for PAL-SECAM, wherein sidebands are attenuated at a predetermined ratio and then added to the luminance signal.