JPH034158B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to the reproduction of low frequency converted color signals recorded on a magnetic tape using a rotary head type VTR or the like.
A PS processing method (hereinafter referred to as "A track" and "B track") in which the phase of the low-frequency conversion color signal is shifted in the opposite direction by 90 degrees every 1H in the adjacent tracks (hereinafter referred to as "A track" and "B track") is used as a method for removing crosstalk from adjacent tracks. A color signal that separates a low-pass converted color signal recorded using a PI processing method (hereinafter referred to as the PI method) that inverts the phase of the B track with respect to the A track every 1H (hereinafter referred to as the PI method) into two color difference signals. It relates to a processing device.

Conventional configuration and its problems When recording and reproducing color video signals in a conventional rotary head type VTR, a modulated luminance signal that is FM modulated and a low-frequency converted color that is converted to a low-frequency carrier frequency fec are used. The signals are mixed and recorded on magnetic tape. In this case, since high-density recording is performed without intervening guard bands between adjacent tracks, the modulated luminance signal is
Inclined azimuth recording is performed, and the PS system or PI system is adopted for the low frequency conversion color signal so that a frequency interleave relationship is established between adjacent tracks. The low-pass converted color signal that has been subjected to PS processing or PI processing as described above has its shifted or inverted phase returned to its original state during playback, and is then converted to the original high carrier frequency fsc (3.58MHz in the NTSC system). It is necessary to convert the frequency, and the first method is to convert the low carrier frequency c that has undergone PS processing or PI processing in the circuit.
Create a signal of
By creating a signal with frequency sc + c and further multiplying this signal with frequency so + c and the low-pass conversion color signal in a multiplier circuit, the carrier frequency becomes sc + c.
There is a method to obtain a carrier color signal with −c=sc, but the second method is to obtain a low-frequency conversion color signal whose modulation axis is PS.
Alternatively, since it is considered to be a quadrature two-phase balanced modulation wave that has undergone PI processing, the low-pass conversion color signal is once demodulated into two color difference signals, and after demodulation, quadrature two-phase balanced modulation is performed using a carrier wave of the reference frequency sc. It is also possible to obtain a carrier color signal with a predetermined carrier frequency sc.

The first method described above is the most common conventional method, but requires two multiplication circuits and an accompanying bandpass filter to remove the upper sideband or lower sideband generated by multiplication. Each multiplication circuit is required, which has the disadvantage of increasing the circuit scale.In the second method, when directly restoring the low-frequency conversion color signal, a demodulation axis is created according to the PS method and PI method. A new circuit is required to demodulate the low frequency converted color signal based on the demodulation axis.

Purpose of the Invention The present invention solves the above-mentioned conventional drawbacks, and when the second method described above is adopted as a method for reproducing a low-frequency converted color signal, the present invention is capable of demodulating the low-frequency converted color signal using a relatively simple digital circuit. It is an object of the present invention to provide an inexpensive color signal processing device capable of creating an axis and digitally demodulating a low-frequency converted color signal.

Structure of the Invention In order to achieve the above object, the color signal processing device of the present invention performs phase shift or phase inversion processing and samples and holds a low frequency converted color signal using a clock having a frequency four times as high as the low frequency carrier frequency. and converting means for analog-to-digital conversion, and a sign-inverted pulse having the same frequency and phase synchronization as the low-frequency conversion burst and a frequency twice the sign-inverted pulse, based on the horizontal synchronizing pulse and the field discrimination signal from the clock. a pulse generating means for generating a color difference signal separation pulse having a color difference signal;
means for performing +/- sign inversion around the code of the value component; and processing means for separating the sign-inverted digital output into data units using the color difference signal separation pulse to obtain two systems of digital data. and is configured to obtain two color difference signal data from the low frequency converted color signal.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit block diagram of a color signal processing device that separates a low frequency converted color signal subjected to PS processing into two color difference signal data in an embodiment of the present invention;
FIG. 2 is a vector diagram of a low frequency conversion color signal supplied to the circuit of FIG. 1, and FIG. 3 is a waveform diagram of various signals in the circuit of FIG. 1.

In Fig. 1, 1 is an input terminal to which a low-band conversion color signal q is input, 2 is an input terminal to which a clock b having four times the low-band conversion carrier frequency is input, and 3 is a logic input terminal for A track and B track. A terminal 4 is inputted with a field discrimination signal i whose values H and L are inverted, and a terminal 4 is inputted with a horizontal synchronizing pulse h. First, the low frequency conversion color signal q input from input terminal 1 is A/
The D converter 5 performs analog-to-digital conversion at the timing of the clock b input from the input terminal 2. As shown in Fig. 2, the low-pass conversion color signal q has a RY component o and a B-Y component p of the color difference signal having a vectorial phase of 90°, and the clock b is, for example, a horizontal synchronizing pulse h and From low frequency conversion burst
It is created by a PLL circuit, and the clock is set such that in a steady state, AD conversion output data c becomes repeating data of color difference signal components p, o, -po, as shown in the timing diagram of FIG. Next, the converted AD conversion output data c is subjected to sign inversion by the sign inversion circuit 6 only for the data portions -p and -o according to the timing of the sign inversion pulse f.
The AD conversion data k is repeated data of p and o. The sign-inverted pulse f is generated by the clock b and the frequency divider 9.
Create 4-phase pulses shifted by 1 clock using the shift register 10 from the frequency divided by 4,
This can be obtained by switching and outputting this every 1H using the data selector 13. sign inversion pulse f
To switch, a signal j is created by latching the field discrimination signal i in the flip-flop 11 at the falling edge of the horizontal synchronization pulse h, and the up-down operation of the up-down counter 12 that counts the horizontal synchronization pulse h is switched by the signal j. This is done using the outputs Q _A and Q _B of the up-down counter 12. With the above circuit configuration, the sign-inverted pulse f advances in phase by one clock b every 1H when the field discrimination signal i is a logic value H, and by 1 clock every 1H when the field discrimination signal i has a logic value L. This results in a delay of 1 minute, and sign inversion along the sampling demodulation axis is performed. For example, if the code of the DC component of AD conversion output data C is 8-bit digital data "10000000", the sign inversion is 1 of all the inverted outputs of output data C = "01111111".
The complement of +1 = "10000000". Also,
If the code of the DC component is located between "10000000" and "01111111", it is possible to simply invert the data. To explain a more detailed example, inverting the sign of data means, for example, inverting the maximum value of digital data, ``11111111'' when C is 8 bits, to make it the minimum value of ``00000000''. , If the DC component is not located between "10000000" and "10000000", invert the digital data as in the case of the one's complement described above, and then add the complement corresponding to the digital value of the DC component. The sign is reversed by . Further, the sign-inverted pulse f is subjected to an exclusive OR with a signal delayed by one clock of the clock b by the flip-flop 14 and an exclusive OR circuit 15. The output of the exclusive OR circuit 15 is latched by the flip-flop 16 to be used as the O-order hold of the two color difference signal data d ₁ and d ₂ and the color difference signal separation pulses g ₁ and g ₂ . The AD converted data k that has passed through the sign inversion circuit 6 is latched by the latch circuits 7a and 7b based on the color difference signal separation pulses g ₁ and g ₂ , respectively, and the two color difference signal data d ₁ and
d Separated into ₂ . Since these color difference signal data d ₁ and d ₂ have a portion with the other color difference signal data due to timing, they are finally transferred to the flip-flops 8a and 8b.
A latch is further applied to obtain color difference signal data e ₁ and e ₂ separated into usable color difference signal components p or o.

In the waveforms of each part of FIG. 3, the timing of the low frequency conversion burst period at a certain point in time (1H) of the above-mentioned color signal processing circuit and the timing of the burst period in the next horizontal period (2H) are shown. ,
The low frequency carrier frequency c of the low frequency converted color signal q is determined to be an integral multiple of 1/2 of the horizontal synchronization frequency _H , and the low frequency converted color signal q is determined by PS processing in the 1st and 2nd H.
90° phase shifted, low frequency conversion burst r
The phase of is also shifted in the same way. In addition, the two color difference signal data e ₁ and e ₂ have a frequency that is twice the low carrier frequency fc.
Since it is obtained with 2fc, one color difference signal data is the 1st H based on the horizontal synchronizing pulse h.
The sampling point has a 180° phase shift with the 2nd H,
Assume that the data is discontinuous. Therefore, in the circuit of this embodiment, interpolation is performed using an O-order hold filter that interpolates the data of the previous sampling point as intermediate data of the sampling point, and each color difference signal data is continuous and output of data per 1H. It is assumed that the timing is aligned, making subsequent processing easier.

In the above explanation, we have described the case where a low-pass converted color signal q that has been subjected to PS processing is separated into two color difference signal data e ₁ and e ₂ , but when dealing with a low-pass converted color signal that has been subjected to PI processing For example, as shown in FIG. 4, the shift register 10 in FIG. Replaced with one frequency divider and one flip-flop
An AND circuit 19 is added that inhibits the horizontal synchronizing pulse h entering the clock input of the flip-flop 18, which creates a frequency-divided wave of the horizontal synchronizing pulse h when the output signal j of No. 1 has a logical value L, and the sign is inverted by the field discrimination signal i. Invert the pulse f every 1H,
By operating it so that it is output continuously as it is, color difference signal data e ₁ , similar to that in PS processing
e ₂ is obtained. Note that 20 is a data selector. In addition, in PI processing, the low carrier frequency is set to an odd multiple of 1/4 of the horizontal synchronization frequency _H.
As in the case of PS processing, when the horizontal synchronization pulse h is used as a reference, the sampling points are at the 1st and 2nd H.
Since there is a 180° phase shift and the sampling becomes discontinuous, interpolation of the data in the middle of the sampling point is performed using O-order hold, and the sampling frequency s of the color difference signal data is continuous at four times the low frequency carrier frequency c. And the data is converted to an integral multiple of _H. In addition, the above description deals with the case of a low-frequency conversion color signal with a 1H correlation, such as when recording and reproducing the carrier color signal PS of the NTSC system and the PI system, but when there is a 2H correlation, such as with the PAL system, the above As is clear from the explanation, the sampling frequency of each color difference signal data after interpolating the data between the sampling points is four times the low carrier frequency and an odd multiple of H/2, and the sampling frequency of each color difference signal data after interpolating the data between the sampling points is four times the low carrier frequency and an odd multiple of _H /2. Output timing can be aligned.

To obtain a carrier color signal of carrier frequency sc using the color signal processing circuit configured as above, D/A
A converter converts the two color difference signal data into analog values and then performs quadrature two-phase balanced modulation, or a digital color encoder converts the obtained color difference signal data into carrier color signal data, and then
One method is to perform A conversion and obtain a carrier color signal.
The crosstalk component of the analog signal obtained by D/A conversion of color difference signal data or the obtained carrier color signal is shifted by 1/2 of the horizontal synchronization frequency with respect to the original signal, so it can be removed by a comb filter, and the PS
The effects of treatment and PI treatment are not lost.

Effects of the Invention As explained above, according to the present invention, low-frequency conversion color signals that have become discontinuous due to PS processing or PI processing are Since it can be converted into a continuous digital color difference signal without losing the stroke removal effect of processing and PU processing, subsequent signal processing can be simplified.Furthermore, since analog frequency conversion is not used, color signal processing can be easily digitized, making it possible to integrate circuits and reduce costs.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram of a color signal processing device according to an embodiment of the present invention, FIG. 2 is a vector diagram of a low-frequency conversion color signal, and FIG. 3 is a signal waveform diagram of each part of the circuit shown in FIG. FIG. 4 is a circuit block diagram of a color signal processing device in another embodiment of the present invention. 5... A/D converter, 6... Sign inversion circuit, 7a,
7b...Latch circuit, 8a, 8b, 11, 14, 1
6, 18...Flip-flop, 9...Frequency divider, 10
... Shift register, 12... Up-down counter, 13, 20... Data selector, 15... Exclusive OR circuit, 17... Inverter, 19... AND circuit.

Claims (1)

[Scope of Claims] 1. Conversion means for sample-holding and analog-to-digital conversion of a low frequency converted color signal that has been subjected to phase shift or phase inversion processing using a clock having a frequency four times as high as the low frequency carrier frequency; Pulse creation means for creating a sign inversion pulse having the same frequency and phase synchronization as the low frequency conversion burst and a color difference signal separation pulse having twice the frequency of the sign inversion pulse based on the horizontal synchronization pulse and field discrimination signal from the clock. means for inverting the sign of the DC value component of the digital output from the converting means by using the sign inversion pulse; A color signal processing device comprising processing means for separating each data to obtain two systems of digital data, and obtaining two color difference signal data from the low frequency converted color signal. 2. The low frequency conversion color signal is subjected to phase shift processing, and the pulse generating means creates four-phase pulses having frequencies equal to the low frequency carrier frequency from a clock having a frequency four times as high as the low frequency carrier frequency. 2. The color signal processing device according to claim 1, wherein the four-phase pulses are sequentially switched every horizontal period to obtain a sign-inverted pulse. 3. The low frequency conversion color signal is subjected to phase inversion processing, and the pulse generation means uses 4 of the low frequency carrier frequency.
Two pulses, one with the same frequency as the low carrier frequency and the other with the inverted pulse, are created from a clock with twice the frequency, and the clock consisting of these two pulses is switched every 1H to create a sign-inverted pulse. A color signal data device according to claim 1, which is configured to obtain a color signal.