JPS60206288A - Processor of pal color signal - Google Patents

Abstract

PURPOSE:To keep properly the inversion state of a PAL phase by comparing a selection output of a selecting means for introducing alternatively an output signal of a PAL phase inverting means and a chroma component of an input signal with a signal showing a normal PAL phase inversion state and by switching the selection state at the time of dissidence of said output and the signal. CONSTITUTION:A chroma input signal (b) and a signal (c) obtained by PAL phase inverting the signal (b) by means of a PAL phase invertor 1 are impressed to a switch 2. An output (k) is introduced as a corrected chroma signal and its phase is compared with that of a reference subcarrier in a PD (phase comparator) 3. The compared output (d) is extracted by a switch 4 only for a burst period and turns out to be a clock input of a D-FF (delayed flip-flop) 6 through a level comparator 5, while a signal level of a reference PAL pulse (g) is latched. The reference PAL pulse (g) denotes the normal PAL phase inversion state of a chroma signal and a binary level signal having one horizontal period. An output (h) of the D-FF6 and the pulse (g) becomes a clock input of an FF8, and a Q output (j) controls the switch 2.

Description

TECHNICAL FIELD The present invention relates to a PAL color video signal processing device, and more particularly to a PAL phase processing device for external synchronization in a PAL color video playback device.

BACKGROUND ART The color video signal Ep of the PAL system is expressed as Ep=Y+(B
-Y)mωst±(I(-Y)(2)ωst...
・・・・・・・・・ (Given to the next expression.Here,
Y indicates the luminance signal, B and R indicate the blue and red signals, and ωS
is the angular frequency of the color subcarrier (subcarrier) and is approximately 4.43 M)lz. The sign of equation (1) is l
This means phase inversion for each horizontal scanning line, and the It-Y component of the conveyed color signal is 18c1) from each other for every 1 horizontal scanning line.
A subcarrier signal of ±oosωst having a phase difference is AM-modulated and transmitted. Therefore, the color burst signal must also serve as information for inverting the phase of the demodulating subcarrier of the 1t-y component line by line on the receiver side. Therefore, as shown in the vector diagram in Figure 1, the color burst signal is ±1 around the 13-Y axis.
The phase is switched to the 35'th phase for each line and sent out as a phase-inverted signal ain (ω!t f 135°).

When using the AL color video signal for the purpose of externally synchronizing and synthesizing images, the following three points are essential.

(1) II (horizontal) - Vl vertical sync both external 1-1
- Synchronize to V sync.

(:2) Synchronize color burst to external reference subcarrier.

(3) P A L phase (color burst and (R, -
(meaning the phase of the signal Y-ωst) is maintained correctly.

In particular, regarding the PAL phase in item (3) above, when performing image composition etc., the color tone may become completely symmetrical (inverted) with respect to the B-Y axis. When a scan operation or a jump operation is performed in order to perform special playback in a disc player), the PAL phase inversion state changes at a certain point (such as at the time of a recording track jump).

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a PAL color signal processing device that always correctly maintains a PAL phase inversion state.

1) The AL color signal processing device according to the present invention includes a PA
The phase of the chroma component of the L format color video input signal is set to B-
YI'l! Convert P so that it is symmetrical with respect to 11I
an AL phase inversion means, a selection means for selectively deriving an output signal of the PAL phase inversion means and a chroma component of the input signal, a phase detection means for detecting a color burst phase of the selected output, It is characterized by comprising a control means for comparing a signal indicating a regular PAL phase inversion state for each horizontal scanning period of a component with a detection signal of the phase detection means and switching the selection state of the selection means when the two do not match. 0 Embodiment Below, an embodiment of the present invention will be explained using the drawings. is L) After receiving PAL phase inversion by AL phase inverter l, switch 2
It will be a one-person effort C. A reproduced chroma signal is directly applied to each input of this switch 2.

The corrected chroma signal is output from the switch 20, and the phase is compared with the reference subcarrier in the PD (phase comparator) 3. This comparison output d is extracted only during the burst period by the switch 4 and becomes the comparison output e of the level comparator 5. This comparator 5 output cuff FiD-F'F (delayed flip-flop') 6
The signal level of the reference PAL parnuda, which is the clock input of the data input, is latched. This reference PAL pulse g is a signal indicating the inverted state of the normal PAL position a of the chroma signal, and is a binary bell signal having l horizontal period. This L)-FF6(7)Q output and PA
The L pulse J is input to the AND gate 7, and the output of this gate becomes the clock input of F li" 8. This li
' The Q output of F8 controls switch 2.

FIG. 3 is a timing chart showing the operation of the blocks in FIG.
(k) is the corresponding waveform. Note that (α) indicates the horizontal scanning section number.

As shown in FIG. 3 ((1), (1)), the case where the PAL phase inversion state of the input chroma signal is reversed from the s+1th line will be explained.

Assume that the input chroma signal initially matches the reference PAL pulse, but the PAL phase is reversed at the i+1th line. Up to the n-th line, FF8 is at a low level, and switch 2 is tilted toward the contact side indicated by the white circle in FIG. Therefore, the operation at line n 0 is +(R
-Y) (shown with diagonal lines in Figure 3), - at line n-1
(RY), a chroma signal having a phase of +(R, -Y) on the n line is input to the PD 3 and compared with the reference length carrier to obtain the output signal shown in (d). switch 4
In addition, the output of the comparator 5 extracted only during the burst period contains a pulse that becomes high level only during the burst period of the tL-2 line and the n line, as shown in (7), and this signal σ) The reference PAL pulse (
y) is D −1” F 6 party output (
h) □ n 2 + n l * Since this D-1i' P 6 time is at a low level, AN
The D gate 7 output is at a low level regardless of the reference L) AL pulse. That is, FF8 is not triggered at all and its output 0 remains at a low level. That is, in this case, switch 2 remains as shown.
If the PAL phase state of the input chroma signal is reversed from the z+1st line after scanning or the like, the PAL phase of the input chroma signal is n lines.

n+1 line, n+2 line, n+3 line...
・Then, respectively +(It-Y) and +(1(,-Y)
, -(1(, -Y).

+(R-Y), and the order is disturbed O, that is, the phase of +(R-Y) is at the z+1st line, so the comparator 5
A pulse that becomes high level during the burst period is outputted to the output σ), which latches the reference PAL pulse (). At this time, since the reference PAL node is at a low level, D-FF6
Q output (gradient) becomes high level.As a result, one of the inputs of AND gate 7 becomes high level, so the reference PAL
The pulse directly becomes the trigger of FF8 (see timing chart). With the rise of this trigger, FF8 is inverted and its Q output changes from low level to high level. As a result, switch 2 is now switched to the black circle contact side. P of
The AL phase inverter force is selected (see timing chart).

Therefore, from the (n+2)th line, a corrected chroma signal having an I'AL phase that matches the reference PAL pulse is obtained. That is, immediately after detecting a mismatch on line n+1,
This means that corrections are being made.

This operation continues until the PAL phases match (D-FF6 Q
(until the output reaches a low level), so even if an error occurs due to noise or the like, the PAL chroma phase correction is quick and accurate because the determinations are made one after another.

FIG. 4 is a diagram of another embodiment of the present invention.
Parts equivalent to those in FIG. 2 are indicated by the same reference numerals, and other blocks are the same as in FIG. 2. In this example, P
The output of D3 is sampled by a sample-and-hold circuit consisting of a switch 4° capacitor 9 and a buffer lO, and this sampling pulse is applied to the gate of an AND gate II which receives the reference burst gate signal and the reference I) AL pulse as input. This is the output. The output of the comparator 5 directly becomes the power of the two-man AND gate 701.

Even in such an M configuration, the same signal as (7) in FIG. 3 is obtained at the output 0) of FF8, and the same effect as in the example in FIG. 2 is achieved.

Effects As described above, according to the present invention, the chroma correction output of the PAL system is always observed and the PAL phase is determined.
Even if the PAL phase inversion state is reversed, correction is made immediately. In addition, even if the judgment is incorrect due to noise, etc., the correction operation will be performed until the PAL phases match.
Accurate PAL phase correction becomes possible.

[Brief explanation of drawings]

FIG. 1 is a diagram showing l) AL phase states, FIG. 2 is a block diagram of an embodiment of the present invention, FIG. 3 is a timing chart of the device of FIG. 2, and FIG. 4 is a diagram showing another embodiment of the present invention. FIG. 3 is a partial block diagram of an example. - Explanation of symbols of main parts 1...PAL phase inverter 2...Switch 3...I'D' 6.8...I
i'F Applicant Pioneer Co., Ltd. Agent Patent Attorney Motobuta Hizumura

Claims (1)

[Claims] PAL phase inversion means for converting the phase of chroma component 1 of a PAL color video input signal so that it is symmetrical with respect to the BY axis; and an output signal of the PAL phase inversion means and a chroma component of the input signal. selection means for alternatively deriving the color burst phase of the selected output; phase detection means for detecting the color burst phase of the selected output; 1. A PAL color signal processing apparatus, comprising control means for comparing the detection signal of the phase detection means and switching the selection state of the selection means when the two do not match.