JPS60132494A - Processor of pal carrier chrominance signal - Google Patents

Abstract

PURPOSE:To correct turbulence of continuity of inversion at every horizontal section of a red color different signal of an RAL signal by switching a frequency converting signal without the use of a glass delay line. CONSTITUTION:A signal sent from a frequency convertor circuit 14 is supplied to a BPF41 for extracting signal having frequency of fSC+fL and a BPF42 for extracting a signal having a frequency of fSC-fL. An output of the BPF41 and that of the BPF42 are supplied to one end of an input terminal of a switch circuit 45 through a phase correction circuit 43 and the other end of the input terminal of the switch circuit 45 through a phase correction circuit 44, respectively. The switch circuit 45 is switched by an output signal of a sequence detection circuit 30, and the switched signal is supplied to a frequency convertion circuit 5 as a frequency converting signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color signal processing device for a PALIBI color signal which is frequency-converted to the lower frequency side of an FM-modulated luminance signal and recorded.

BACKGROUND TECHNOLOGY AND PROBLEMS In the case of popular home VTRs and so-called 8mm video VTRs that are integrated with a camera, the luminance signal is FM modulated to a relatively high band when recording color video signals. The carrier color signal is frequency-converted to the lower frequency side and recorded.

By the way, when recording and reproducing PAL video signals using this VTR, it must be noted that one modulated color signal of the PAL carrier color signal is inverted every horizontal section. That is, as shown in Figure 1, the carrier color signal of a PAL color video signal is expressed as F+=(Es-Ey)+j(EREy) in every other horizontal section, and in every other horizontal section, In the horizontal interval, F−= (Es
Ey) j (ER-Ey),
The phase of the modulation signal of the red color difference signal is inverted every horizontal interval, and correspondingly, a burst signal B+ whose phase is advanced by 135 degrees with respect to the B-Y axis is inserted for the signal F0. A burst signal B- whose phase is delayed by 135 degrees with respect to the B-Y axis is inserted into the signal F-.

In performing color demodulation of this PAL system color video signal, when the color video signal reproduced from the VTR is supplied to the television receiver, the following steps are performed as described above.
The phase of the modulated signal of the red color difference signal in one modulated color signal section must be correctly inverted for each horizontal interval.

When playing back a VTR, the continuity of the inversion of the modulated color signal is taken into account without any problem, but when playing back in high speed or slow motion, the rotating head scans across multiple tracks. In this case, this l
The continuity of the reversal for each water half interval may be lost.

That is, FIG. 2 shows an example of a trunk pattern of a β format VTR compatible with PAL color video signals, in which every other track is TAX.

1゛A2...For example, the track recorded by one of the two rotary heads HA is TBl, T
B2...indicates the tracks recorded by the rotary head HB whose azimuth angle is different from that of the other head HA, and arrows (1a) and (1b) in the figure indicate the recorded conveyance color signals. The phase of the burst signal in each horizontal interval (1H) is shown. Note that the actually recorded signals are recorded on tracks TA1 and TA2, for example, in order to eliminate crosstalk of carrier color signals between adjacent tracks.
..., the carrier color signal is recorded with the phase of the subcarrier inverted for each horizontal section, and in the remaining trunks TBI, TB2, ..., the subcarrier is recorded with the same phase. Therefore, it does not indicate the phase of the burst signal on the actual recording pattern, but during playback.
Truck TA1. This is a case in which the phase is restored for TA2....

By the way, in this tape pattern, since the horizontal alignment is 1H, the color alignment of the PAL color video signal is not taken.

Therefore, when the RAD HA rotates and scans the locus shown by the broken line in FIG. 2 in the 1 ili speed playback mode, the playback signal is extracted from track T A l to track T at point a in the same figure, for example. Jump to A2. Looking at the phase of the burst signal in the reproduced signal obtained by this high-speed reproduction, as shown in FIG. burst signal sequence) is reversed. therefore,
If an attempt is made to reproduce the video by supplying such a PAL color video signal to a monitor receiver, correct colors will not be reproduced on the screen.

The above has explained the case where a PAL video signal is recorded and played back using a Beta system VTR, but horizontal alignment or
H or 2 H, color alignment is not taken and a similar problem occurs.

Therefore, a carrier color signal processing device as shown in FIG. 4 was proposed.

That is, this example is for an 8 mm video, and in every other track during recording, the carrier color signal has one subcarrier.
The subcarriers are recorded with a shift of 90° for each horizontal section, and in the remaining every other track, the subcarriers are recorded with the same phase.

In Fig. 4, the signals reproduced by the two rotary heads are supplied to the reproduction amplifier (2) through the input terminal (1), and the output of this amplifier (2) is sent to the bypass filter (3).
A luminance signal subjected to the FM conversion is extracted through the FM converter, and is FM demodulated and output.

Further, the output of the amplifier (2) is supplied to a low-pass filter (4) to extract a low-pass converted carrier color signal, which is supplied to a frequency conversion circuit (5). On the other hand, a variable frequency oscillator (11) is provided that generates a signal with a frequency equal to the low subcarrier frequency fL of the carrier color signal that has been low-pass converted, and the frequency fL from the variable frequency oscillator (11) is provided.
The signal is supplied to a phase control circuit (12), subjected to phase control as described below, and then supplied to a frequency conversion circuit (14).

On the other hand, the sub-III transmission frequency f of the original l) A L method
1le (-4,43M Ilz) reference oscillator (15
) is supplied to this frequency conversion circuit (14), from which the oscillation signals from the frequencies f , , c+ f 1 . signal and frequency rsc-rt.

signal is obtained. Then, these are passed through a band pass filter (16), and only a signal of "ζ frequency rsc+fL" is extracted, and this is supplied to a frequency conversion circuit (5) as a frequency conversion signal.

In this frequency conversion circuit (5), the frequency r sc
The low-pass conversion subcarrier frequency rt is subtracted from the signal of +fL, but the subcarrier frequency r 5c-
A signal returned to 4.43 MHz is obtained, which is extracted through a bandpass filter (6).

In this case, the phase of the subcarrier wave, which was phase shifted during recording, is restored by changing the phase of the frequency conversion signal in the frequency conversion circuit (5) by the phase control circuit (12). Zunawaji, phase control circuit (12)
'ζ control signal is supplied through terminal (13) to 'C1
Only when reproducing from a track in which a carrier color signal is recorded with a phase shift of 90" for each horizontal section, an operation is performed to shift the phase of the signal from the variable frequency oscillator (11) by 90" for each horizontal section. , whereby the phase of the subcarrier is restored. Although the output of the bandpass filter (6) still contains crosstalk components from adjacent trunks, this is due to the C-shaped comb filter (9) consisting of a delay circuit (7) and a subtraction circuit (8) in two horizontal sections. ), and a crosstalk-free carrier color signal is derived at the output terminal αψ.

In this case, the variable frequency oscillator (11) is
A so that its output has a constant relationship with the reproduced signal.
PC can be connected. That is, a part of the signal passing through the comb filter (9) is supplied to the burst gate circuit (17) to extract a burst signal, which is then sent to the phase comparator circuit (17).
8) and is phase-compared with the signal of frequency rsc from the reference oscillator (15), and the comparison error voltage is supplied to the variable frequency oscillator (11) through the low-pass filter (19) to generate its oscillation. The frequency is now controlled.

In this signal processing device, the sequence of burst signals as described above is corrected as follows.

That is, a switch circuit (21) is provided between the comb filter (9) and the output terminal aω, and the output signal of the comb filter is connected to one input terminal of the switch circuit (21). A signal is supplied through a delay circuit (22) that is delayed by λ (wavelength of the subcarrier), and the output signal of the comb filter (9) is supplied as is to the other input terminal.

Further, the signal passed through the comb filter (9) is supplied to the burst signal sequence detection circuit (3o), and when the sequence is correct, the switch circuit (21) maintains the same switching state, and the sequence is reversed. When it happens,
Signal through comb filter (9) and delay circuit (22)
The switching state with the delayed signal is inverted. In this way, the burst signal sequence whose inversion continuity has been lost will be restored to its original state.

FIG. 5 shows an example of the sequence detection circuit (30).

That is, the signal passed through the comb filter (9) is supplied to the phase detection circuit (32) via the burst gate circuit (31,) (which may also be used as the burst gate circuit (17)). On the other hand, the frequency f sc = 4, 43 MHz
The signal from the reference oscillator (33) is sent to the switch circuit (3
4) is supplied to one input terminal, and the phase is inverted and supplied to the other input terminal. Then, this switch circuit (34) switches between one input terminal and the other every horizontal interval by a signal that inverts the state of l'lJl'OJ at the time of the horizontal synchronizing signal HD from the flip-flop circuit (36). This switch circuit (3
The output of 4) is supplied to the phase detection circuit (32).

The phase of the signal from the reference oscillator (33) coincides with the -(R-Y) axis, for example, as shown in Figure 6, and therefore the phase of the output signal from the switch circuit (34) is 3B. Therefore, when the sequence of the burst signal is correct, as shown in FIG. 3C, a positive output signal is obtained from the phase detection circuit (32) at the time of the burst signal, and the aforementioned If the "C sequence is reversed at point a," the phase detection circuit (3
2) An output signal of negative polarity can be obtained. The output DS of the phase detection circuit (32) thus obtained is supplied to the level comparison circuit (38) via the low-pass filter (37), and compared with the reference voltage ER. When the output of (32) is low, that is, when a negative detection output is obtained, a signal that rises to I' l J is obtained from this comparator circuit (38), and this rise of "1" causes the flip-flop circuit (39 ) is reversed. Then, the output signal sw obtained from this flip-flop circuit (39) is supplied as a switching control signal to the switch circuit (21).

Therefore, from the time when the sequence of burst signals is reversed, the switch circuit (2I), for example, switches to the delay circuit (22).
As a result, the situation where the sequence is reversed is corrected.

In addition, in this switching state, when the sequence detecting circuit (30) again detects a reversal of the sequence, the switch circuit (21) returns to the switching state shown in the figure, and the sequence is made difficult to stop.

In other words, each time the sequence is reversed, the switch circuit (21
) is reversed.

Incidentally, in the carrier color signal processing apparatus shown in FIG. 4, an IH-1 delay circuit (22) is used to compensate for the reversal of the burst signal sequence. However, this delay circuit (22) generally uses a glass delay line, and has the disadvantage that it is very expensive, has a large size, and requires a large mounting area when incorporated into an actual device.

Purpose of the Invention In view of the above points, the present invention uses a glass delay line, which has conventionally caused inconvenience, in controlling disturbances in the continuity of inversion for each horizontal section of the modulation signal of the red color difference signal of the PAL signal. The purpose of this invention is to provide something that can correct this continuity disturbance without causing any problems.

SUMMARY OF THE INVENTION This invention relates to processing of a carrier color signal of a playback signal from a VTR in which a PAL color video signal is recorded by a so-called low-pass conversion method, and one of the signals is changed by crystal speed playback or the like. When the continuity of inversion for each horizontal interval of modulation color 4#1 becomes reversed from a certain point, in order to correct it, the signal for frequency conversion is set at the same level as the low subcarrier frequency IL. This is done by switching between the sum signal and the difference signal of the subcarrier--transmission frequency fsc.For this reason, there is no need to use a glass delay line, which reduces cost and This is very effective in terms of implementation.

Embodiment FIG. 7 shows an example of the apparatus of the present invention, taking an 8 mm video camera as an example. The same parts as in the example of FIG.

In this example, the signal from the frequency conversion circuit (14) is supplied to a bandpass filter (41) for extracting a signal with frequency fsc+fL, and also with frequencies rs, -
A bandpass filter (4
2). and bandpass filter (41)
The output of the bandpass filter (42) is supplied to one input terminal of the °ζ switch circuit (45) via the phase correction circuit (43), and the output of the bandpass filter (42) is supplied to the switch circuit (45) via the phase correction circuit (44). is supplied to the other input end of the . This switch circuit (45) is connected to the sequence detection circuit (3).
0), and the switched signal is supplied to the frequency conversion circuit (5) as a frequency conversion signal.

The principle by which the subcarrier is inverted with respect to the BY axis each time the frequency conversion signal is switched will be explained below.

Now, if the angular frequency of the low-band subcarrier is ωl, the angular frequency of the original subcarrier is ω2, and the phase of the reproduced carrier color signal is θ, then when a signal of ω2 + ω1 is used as the frequency conversion signal, The output of the frequency conversion circuit (5) (or the output of the bandpass filter (6)) is as follows.

ω2+ω1-(ω1+θ)→ω2-θ Next, when the signal ω2-ω1 is used as the frequency conversion signal, ω2-ω1+(ω1+θ)→ω2+θ, and in the reproduced carrier color signal, θ-0 is changed to B- Considering the Y axis, by switching this frequency conversion signal, the phase of the signal obtained by frequency conversion is inverted with respect to the BY axis.

By the way, when the frequency conversion signal is switched in this way, the following problems arise.

First, the first problem is a change in the phase lock point of the APC loop. That is, the APC circuit works so that the two input signals of the phase comparator circuit (18) have a phase difference of 90'', but for the reasons described later, this lock point is set to one of the input signals shown in FIG. When the reference phase of the signal from the oscillator (15) is 0°, the phase of the other input signal is 9°.
There are two cases: a case where the phase point A is delayed by 0° and a case where the phase point B is advanced by 90''.

That is, for example, if there is a phase error Δθ in the low-pass conversion carrier color signal, when the frequency is converted by ω2 + ω as a frequency conversion signal, ω2 + ω1 - (ω1 + Δθ) - = 5ω2 - Δθ Also, as a frequency conversion signal ω2 In the case of conversion by −ω5, ω2−ω1+(ω1+Δθ)→ω2+Δθ, and the phase error becomes an opposite phase.

The APC circuit works to eliminate phase errors in the output, so if the output of the variable frequency oscillator (11) becomes ω1 + Δθ, the frequency conversion circuit (5)
The phase error disappears as follows: θ)-(ω1+Δθ)→ω2 or (ω2-ω1-Δθ)+(ω1+Δθ)→ω2. That is, a variable frequency oscillator (1
In 1), the oscillation output is corrected in the same direction regardless of the switching of the switch (45), and therefore the output of the phase comparison circuit (18) in °C is also in the same direction. If the frequency conversion signal is changed manually by switching the switch (45) in this phase comparison II (1B), the phase error direction will be in the opposite direction, so the phase comparison circuit (
In 18), the switching of the switch circuit (45) results in having two lock points, point A and point B, and the lock phase changes by 180°, that is, is reversed.

This will not cause any problems unless processing such as ζ phase detection is performed in the subsequent circuit when handling the terminal 01 signal. Since the circuit uses a phase detection method, it is inconvenient that the phase of the signal obtained at this output terminal (ll) is inverted.Therefore, in this example, the burst key I-circuit (17) and Phase comparison circuit (18
) A switch circuit (16) is provided between the burst gate circuit (17), and the burst signal from the burst gate circuit (17) is supplied as is to one input end of the switch circuit (46), and is also supplied via a phase inversion circuit (47). ζThe switch circuit (46) is switched by the output SW of the sequence detection circuit V&(30) in synchronization with the switching of the switch circuit (45), and the lock point is set to one. be made to be.

The circuit for this phase inversion processing is a comb filter (
9) and the burst gate circuit (17) and the output terminal aω, or it may be provided in the signal path supplied from the oscillator (15) to the phase comparator circuit (18). Furthermore, it may be provided between the phase comparator circuit (18) and the iJ variable frequency oscillator (11).

The next problem is the bandpass filter (6) (41
) This is the phase jump at the time of switching due to the phase shift in (42).

For example, assume that there is a phase shift of Cθ1 in the bandpass filter (6). Now, assuming that the bandpass filter (41) is selected by the switch circuit (45), the AP
In order that the output signal of the band pass filter (6) becomes ω2 by the C circuit, °ζ in the frequency conversion circuit (5) is changed to (ω2+ω1-01)-ω1→ω2-01 and in the frequency conversion circuit (14). "ζ is ω2+(ω1-01)
The output of the frequency oscillator (11) becomes ω1-θ1.

At this time, when switching to the band pass filter (42),
In the frequency conversion circuit (14), ω2-(ω1-0
1) ω2-ω1→-θ1 On the other hand, frequency conversion circuit (5)
The smell ζ is (ω2-ω1+01)+ω11?6ω2+
01, and θ1 at the output of the bandpass filter (6)
A phase change of ω2+201 occurs in response to the phase shift of ω2+201.

Therefore, when switching the bandpass filters (41) (42), the output of the frequency oscillator (11) is ω1+
As can be seen by considering that the APC is locked at θ1, switching causes a phase jump of 2θ, l, which is similar to a skew. Bandpass filters (41) and (42)
) phase shift θ2. Regarding θ3, °ζ similarly causes a phase jump when switching the 'ζ switch circuit (45).

Therefore, in this example, phase correction circuits (43) and (44) are provided on the output side of the bandpass filters (41) and (42).
For example, the phase correction circuit (43) performs phase correction of 2θ1-θ2, and the phase correction circuit (44) performs phase correction of −03.

The phase correction circuit (43) may perform a phase correction of -02, and the phase correction circuit (44) may perform a phase correction of -2θ1-θ3.

Furthermore, band pass filters (61, (41)).

A phase correction circuit is provided on the output side of (42), and each phase shift amount -θ1. −θ2. It may be configured to perform phase correction of −θ3.

As described above, according to the present invention, PA can be achieved by simply switching the frequency conversion signal without using a glass delay line.
If the continuity of inversion for each horizontal section of the red color difference signal of the L signal is reversed, it becomes possible to correct it, which is advantageous for non-electronics in terms of cost and implementation. .

[Brief explanation of drawings]

Figure 1 is a diagram for explaining the PAL signal, Figure 2 is a diagram showing the state in which the sequence of burst signals is reversed, and Figure 3 is a diagram for explaining the PAL signal.
4 is a block diagram of an example of a conventional PAL signal processing device, FIG. 5 is a block diagram of an example of its essential parts, FIG. 6 is a diagram for explanation, and FIG. FIG. 7 is a block diagram of an example of the device of this invention, and FIG. 8 is a diagram for explaining the same. (5) is a frequency conversion circuit for converting a low-pass conversion carrier color signal into a 9 carrier color signal, (14) is a frequency conversion circuit for obtaining a frequency conversion signal, and (15) is the original subcarrier frequency. oscillator, (41) and (42) are band pass filters for extracting the sum and difference signals of the low subcarrier frequency and the subcarrier frequency, respectively, (45) is a switch circuit for switching the same, (30) is a burst signal sequence detection circuit.

Claims (1)

[Claims] The frequency is converted to the lower frequency side of the FM-modulated luminance signal.
When reproducing the recorded PAL color carrier color signal,
a circuit for detecting that the continuity of inversion for each horizontal section of the burst signal has been reversed; and a frequency conversion circuit for converting the low-pass converted carrier color signal to one with nine subcarrier frequencies. , when the low frequency conversion subcarrier frequency is f L and the original subcarrier frequency is f 8C, the frequency f gc+f is used as the frequency conversion signal of the frequency conversion circuit.
and a circuit that forms two signals, a signal with a frequency of L and a signal with a frequency of f8cmfL, and when it is detected by the output of the detection circuit that the continuity of inversion for each horizontal section of the burst signal is reversed, the above-mentioned A processing device for a PAL III color sending signal, which is configured to switch between a signal with a frequency fsc+fL and a signal with a frequency fBc-fL as a frequency conversion signal.