JPH0226438B2 - - Google Patents

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproduction device for a carrier color signal, and more particularly to a reproduction device that performs backward de-emphasis on the vertical spatial frequency of a carrier color signal reproduced from a magnetic recording medium. BACKGROUND TECHNOLOGY In a recording and reproducing apparatus such as a VTR, a luminance signal and a carrier color signal are separated from a color video signal to be recorded and reproduced, each is subjected to predetermined signal processing, and then both signals are multiplexed and recorded. In the case of reproduction, noise has conventionally been reduced using line correlation for the carrier color signal as well as for the luminance signal. In other words, since the reproduced carrier color signal usually has line correlation, but most of the noise mixed in the reproduced carrier color signal has no line correlation, the input/output reproduced carrier color of the 1H delay circuit By mixing the signals to extract noise that has no line correlation and mixing this noise with the reproduced carrier color signal through a limiter, it is possible to extract a reduced reproduced carrier color signal in which the noise is canceled out. Problems to be Solved by the Invention However, the conventional recording/reproducing apparatus having the above-mentioned noise reduction circuit inputs and reproduces signal components having no line correlation as well as noise for reproduced carrier color signals having no line correlation. Since it is subtracted from the carrier color signal, there is a problem in that the vertical spatial frequency characteristics (vertical resolution) deteriorate. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a carrier color signal reproducing apparatus that solves the above-mentioned problems by imparting non-linear characteristics to the vertical spatial frequency of the reproduced carrier color signal. Means for Solving the Problems The carrier color signal reproducing device of the present invention compares the high frequency component of the vertical spatial frequency of the reproduced carrier color signal with the low frequency component, and This provides a non-linear characteristic that relatively attenuates the level, and also performs backward de-emphasis. Function: The vertical spatial frequency of the reproduced carrier color signal is given non-linear de-emphasis characteristics that vary depending on the amplitude. As a result, the reproduced carrier color signal is not given a backward de-emphasis characteristic when there is no line correlation, and the stronger the line correlation is, the greater the backward de-emphasis characteristic is given to it. Embodiment FIG. 1 is a block system diagram showing an embodiment of the apparatus of the present invention together with a recording system. In the figure, a color video signal of standard television system (NTSC system or PAL system) that enters input terminal 1 is supplied to low-pass filter 2, where the luminance signal is separated, and then supplied to band filter 3. The carrier color signal is then separated into waves. The luminance signal is supplied to the recording luminance signal processing circuit 4 through the delay circuit 53, where it undergoes predetermined signal processing such as frequency modulation (FM). On the other hand, the carrier color signal is transmitted to the pre-emphasis circuit 54.
1 horizontal scanning period (1H) appearing vertically on the screen, as will be explained in detail later herein.
After pre-emphasis is performed for each signal component at an interval, and a pre-emphasis characteristic is given in which the level of the high-frequency component of the vertical spatial frequency is relatively enhanced compared to the low-frequency component, the signal is sent to the recording conveyance color signal processing circuit 6. Here, it is converted into a predetermined signal form suitable for magnetic recording and reproduction, such as frequency conversion to a low frequency band. The delay circuit 53 described above is a circuit for delaying the luminance signal by the time delay caused by the pre-emphasis circuit 54 and aligning the time with the pre-emphasized carrier color signal, and the delay circuit 55 described later is a de-emphasis circuit. This is a circuit for delaying the reproduced luminance signal by the time delay caused by 56 and adjusting the time with the de-emphasized reproduced carrier color signal. The pre-emphasis circuit 54 is a backward-type pre-emphasis circuit or a combination of a backward-type and a forward-type pre-emphasis circuit, which outputs a high-frequency component of vertical spatial frequency with a relatively enhanced level compared to a low-frequency component. On the other hand, a de-emphasis circuit 56, which will be described later, has a characteristic of outputting the high-frequency components of the vertical spatial frequency of the reproduced carrier color signal with the level attenuated relatively compared to the low-frequency components, and is complementary to the pre-emphasis circuit 54. This is a de-emphasis circuit that has a spatial frequency versus level characteristic in the vertical direction, and is of a backward type or a combination of a backward type and a forward type. Here, the forward type is an input signal that is obtained by weighting and adding input information temporally past the output time, and a signal that is obtained by weighting the output information at the output time. On the other hand, the backward type is a type of circuit that weights temporally future input information and adds and synthesizes the main signal at the time of output. The luminance signal and the carrier chrominance signal which are respectively converted into predetermined signal formats and taken out by the recording luminance signal processing circuit 4 and the recording carrier chrominance signal processing circuit 6 are supplied to the recording amplifier 7, where they are mixed and amplified, respectively. Thereafter, the data is recorded on the magnetic tape 9 by the rotary recording head 8. The reproducing apparatus of this embodiment is an apparatus for reproducing the carrier color signal recorded as described above, in which the reproducing rotary head 10 reproduces the already recorded signal on the magnetic tape 9, and the reproduced signal is passed through the preamplifier 11. It is supplied to a high-pass filter 12 and a low-pass filter 13, respectively. For example, an FM luminance signal is separated by a high-pass filter 12 and demodulated into a luminance signal of the original band by a reproduced luminance signal processing circuit 14. On the other hand, the carrier color signal that has been low-pass converted and recorded by the low-pass filter 13 is separated from the reproduced signal, and this carrier color signal is supplied to the reproduced carrier color signal processing circuit 15, where the original signal is It is returned to the form and becomes a reproduced transport color signal. The reproduced carrier chrominance signal is supplied to a de-emphasis circuit 56, where the vertical spatial frequency component has a characteristic in which the level of the high-frequency component in the vertical direction is relatively attenuated compared to the low-frequency component. It is given a characteristic complementary to the frequency vs. level characteristic. Therefore, from the de-emphasis circuit 56, the pre-emphasized reproduced carrier color signal is restored to its original waveform before being pre-emphasized and is taken out and supplied to the mixing circuit 17 where it is delayed from the reproduced luminance signal processing circuit 14. It is mixed with the reproduced luminance signal obtained through the circuit 55. As a result, a reproduced color video signal with reduced noise components is taken out from the mixing circuit 17 to the output terminal 18. Here, in this embodiment, since the spatial frequency versus level characteristic in the vertical direction of the screen is de-emphasized by the de-emphasis circuit 56, the S/N ratio of the reproduced carrier color signal can be improved.
Further, since the vertical spatial frequency versus level characteristic degraded by the de-emphasis circuit 56 is emphasized and recorded by the pre-emphasis circuit 54 provided in the recording system in advance, the S/N ratio is improved at the output terminal 18. A reproduced color video signal with no deterioration in spatial frequency versus level characteristics in the vertical direction is extracted. Next, each embodiment of the de-emphasis circuit 56 will be described. Figure 2 shows the de-emphasis circuit 5.
6 shows a block system diagram of the first embodiment of No. 6. In the figure, the reproduced carrier color signal input to the input terminal 60 is
n delay circuits 61 ₁ to 61 connected in cascade
On the other hand, the coefficient (-1) is supplied to the adder circuit 64 through the coefficient circuit 62 ₁ of ⁿ ·ln and the phase adjuster 63 ₁ , respectively. The reproduced carrier color signals outputted from the delay circuits 61 ₁ to 61 _o-1 , each having a delay time of, for example, 1H, are sent to the coefficient circuits 62 ₂ to 62 _o and the phase adjusters 63 ₂ to 63 _o.
are supplied to the adder circuit 64 through each of them. Further, the reproduced carrier color signal extracted after being delayed by nH from the delay circuit 61 _o at the final stage is multiplied by a positive coefficient lo by the coefficient circuit 62 _o+1 and then supplied to the addition circuit 64. is supplied to Each output reproduced carrier color signal of coefficient circuits 62 ₁ to 62 _o is the output reproduced carrier color signal (main signal) of coefficient circuit 62 _o+1.
The coefficient circuit 6
Among 2 ₁ to 62 _o , the coefficient circuit to which the reproduced delayed carrier color signal is supplied whose delay time difference relative to the main signal is an odd multiple of 1H is selected to have a negative coefficient value, and is an even multiple of 1H. The coefficient circuits to which the delayed reproduction carrier color signal is supplied are each selected for positive coefficient values. Furthermore, the phase adjusters 63 ₁ to 63 _o adjust the phases so that they are completely in phase or completely opposite to the main signal, respectively. A signal having a waveform as if the spatial frequency components of the input reproduced carrier color signal in the vertical direction of the screen were integrated is taken out from the adder circuit 64, and this signal is supplied to a non-linear circuit 65. The nonlinear circuit 65 is, for example, an amplitude limiter that limits the amplitude of an input signal to a constant value, and input signals with an amplitude smaller than this constant value are passed through with the same amplitude, and input signals with an amplitude larger than this constant value are passed through. The input signal is configured to be output after being limited to this constant value. The signal taken out from the non-linear circuit 65 is supplied to an adder circuit 66, where it is added to the nH delayed reproduction carrier color signal multiplied by a positive coefficient _L1 by a coefficient circuit 67, and then output to an output terminal 68. Ru. The signal output to this output terminal 68 is reproduced with a de-emphasis characteristic in which the high-frequency component of the spatial frequency in the vertical direction of the screen of the input reproduced carrier color signal is relatively attenuated in level compared to the low-frequency component. This is a carrier color signal, and is a reproduced carrier color signal to which a non-linear de-emphasis characteristic is given, in which the amount of de-emphasis decreases as the amplitude increases. This embodiment is a backward type de-emphasis circuit which obtains a de-emphasized reproduced carrier color signal by weighting and adding and combining temporally future reproduced carrier color signals with respect to the main signal at the output point. It is also an output weighted type and an acyclic type. Next, FIG. 3 shows the second part of the de-emphasis circuit 56.
A block system diagram of an example is shown. In the figure, the same components as those in FIG. 2 are denoted by the same reference numerals, and the explanation thereof will be omitted. The reproduced carrier color signal that has entered the input terminal 60 is supplied as a main signal to the delay circuit 72 ₁ through a coefficient circuit 70 ₁ that multiplies it by a negative coefficient −lo.
In addition, coefficient circuits 70 ₂ , 70 ₃ , ..., 70 _o +1 for multiplying by coefficients _{l 1 ,} -l 2 , ..., (-1) ⁿ⁺ _{1 lo} and a phase adjuster 7
1 ₁ , 71 ₂ ,..., 71 _o through the adder circuit 73 ₁ ,
73 ₂ ,..., 73 _o . Each output signal of delay circuits 72 ₁ to 72 _o having a delay time of 1H is supplied to adder circuits 73 ₁ to 73 _o , respectively. As a result, a carrier color signal having a waveform as if vertical spatial frequency components of the input reproduced carrier color signal were integrated is taken out from the adder circuit _73o , and is passed through the adder circuit through a nonlinear circuit 74 having the same configuration as the nonlinear circuit 65. 75. The adder circuit 75 receives the reproduced carrier color input through a coefficient circuit 76 and a phase adjuster 77, which multiply the reproduced carrier color signal delayed by nH and taken out from the final stage delay circuit _61o by a positive coefficient _L1 . The signal and the output signal of the non-linear circuit 74 are added and combined to generate a reproduced carrier color signal to which the non-linear de-emphasis characteristic has been added, and this is output to the output terminal 68. This embodiment is an input weighted backward de-emphasis circuit. Incidentally, the delay circuits 61 ₁ to 61 _o in FIG. 3 can also be constituted by one delay circuit having a delay time of nH (the same applies to FIG. 2). Next, FIG. 4 shows the third section of the de-emphasis circuit 56.
A block system diagram of an example is shown. In the figure, the same components as those in FIG. 3 are given the same reference numbers, and their explanations will be omitted. Like the second embodiment shown in FIG. 3, this embodiment is an input weighted, backward type de-emphasis circuit, but differs from the second embodiment in the location where the main signal is obtained. In FIG. 4, the reproduced carrier color signal taken out after being delayed by a total of nH from the delay circuit _61o is supplied to coefficient circuits 81 and 76, respectively, multiplied by a negative coefficient -Lo by the coefficient circuit 81, and then added. It is supplied to circuit 80 as a main signal. The adder circuit 80 adds and synthesizes the signal from the adder circuit 73 _o and the above-mentioned main signal, outputs a signal with a waveform in which vertical spatial frequency components are integrated, and passes it through the non-linear circuit 74 to the adder circuit. Supply to 75. Next, FIG. 5 shows the fourth section of the de-emphasis circuit 56.
A block system diagram of an example is shown. In the figure, the same components as those in FIG. 2 are denoted by the same reference numerals, and the explanation thereof will be omitted. However, in reality, each coefficient (-1) ⁿ of the coefficient circuits 62 ₁ to 62 _o+1 and 86 ₁ to 86 _o in FIG.
ln~-l ₁ , lo and the coefficient circuit 62 ₁ ~ shown in FIG.
Each coefficient (-1) ⁿ l _o to -l ₁ and Lo of 62 _o+1 are different values from each other. This embodiment is an output-weighted de-emphasis circuit that is a combination of a forward type and a backward type, and is an acyclic de-emphasis circuit. For example, each delay circuit 85 ₁ has a delay time of 1H.
~85 _o , coefficient circuits 86 ₁ ~86 _o to which their output reproduced carrier color signals are supplied, and a phase adjuster 87
₁ to _87o constitute a forward type de-emphasis circuit section together with the adder circuit 88. The adder circuit 88 receives the main signal taken out from the coefficient circuit 62 _o+1 and the phase adjusters 63 ₁ to 6 which are temporally future input information for this main signal.
3 each reproduced carrier color signal from _o and a phase adjuster 8 which is temporally past input information with respect to the main signal.
By adding and combining the reproduced carrier color signals of 7 ₁ to 87 _o , respectively, a waveform is created as if the vertical spatial frequency components of the input reproduced carrier color signal were integrated (in this embodiment, forward type and backward type , the signal is integrated before and after the edge), and this signal is output to the adder circuit 90 through a non-linear circuit 89 having the same configuration as the non-linear circuit 65. The adder circuit 90 adds a coefficient _L1 to the reproduced carrier color signal taken out from the delay circuit _61o .
a reproduced carrier color signal from a coefficient circuit 91 for multiplying by
The signals from the non-linear circuit 89 are added and combined, and a de-emphasized reproduced carrier color signal is outputted to the output terminal 68. According to this embodiment, smear is reduced by the non-linear circuit 89 (some remains), but since it is distributed above and below the line, the S/
If the N improvement level is sufficient, the smear will become less noticeable,
On the other hand, if the same amount of smear as before is sufficient, a larger S/N improvement can be obtained. Next, a fifth embodiment of the pre-emphasis circuit 56 will be described with reference to FIG. In the figure, the same components as those in FIG. 2 are denoted by the same reference numerals, and their explanations will be omitted. In FIG. 6, the reproduced carrier color signal input to the input terminal 20 and restored to its original band is supplied to a subtraction circuit 21 and an addition circuit 93, respectively. The reproduced carrier color signal outputted from the subtraction circuit 21 is supplied to a 1H delay circuit 23, where it is delayed by one horizontal scanning period, and then converted into a coefficient K ₁ (for example, 0.87) by a coefficient circuit 24.
The signal is multiplied by , and then supplied to the phase adjuster 25 . The phase adjuster 25 is an unnecessary circuit if an accurate 1H delay time can be obtained by the 1H delay circuit 23. However, the delay time actually obtained by the 1H delay circuit 23 is not exactly 1H, and in this case, the output signal of the coefficient circuit 24 is supplied to the subtraction circuit 21 without performing phase adjustment, and the output signal is subtracted from the input reproduced carrier color signal. When this operation is performed, the coefficient K ₁ is equivalently reduced, so that the required de-emphasis characteristic cannot be obtained. Therefore, by adjusting the phase of the output signal of the coefficient circuit 24 using the phase adjuster 25 so that it becomes the same as the phase of the reproduced carrier color signal delayed by 1H, the desired de-emphasis characteristic can be obtained. The subtraction circuit 21 performs a subtraction operation of subtracting the output signal of the phase adjuster 25 from the reproduced carrier color signal from the input terminal 20. Here, as is well known, the color subcarrier frequency of the carrier color signal in the NTSC system is 227.5 times the horizontal scanning frequency, and due to the fraction of 0.5, the color subcarrier has a phase of 0.5 period at the beginning and end of 1H. In other words, they differ by 180°. Therefore, phase adjuster 2
The extracted carrier color signal delayed by exactly 1H from input terminal 20 has an opposite phase relationship with the reproduced carrier color signal input from input terminal 20, and is outputted from subtraction circuit 21 by 1H earlier. A reproduced carrier color signal that is substantially added to the reproduced carrier color signal of is extracted. The reproduced carrier color signal output from the subtraction circuit 21 is supplied to a 1H delay circuit 23, and is also supplied to a coefficient circuit 26, where it is multiplied by a coefficient K ₂ (for example, 0.13), and then passed through a phase adjuster 27 to an addition circuit. 93. The adder circuit 22 subtracts the reproduced carrier color signal from the input terminal 20 with the signal from the phase adjuster 27 whose level is so high that there is no line correlation, and the reproduced carrier color signal from the input terminal 20 has a phase difference. The signal from the adjuster 27 is added and combined by the adder circuit 93 to form a reproduced carrier color signal imparted with a linear de-emphasis characteristic, which is then supplied to the delay circuit 61 ₁ and the coefficient circuit 62 ₁ , respectively. In this example, the fifth
Like the de-emphasis circuit shown in the figure, this is an output-weighted de-emphasis circuit that combines a backward type and a forward type, but the basic components of a cyclic de-emphasis circuit are used as the forward type, as shown in Figure 5. different. This embodiment can also obtain the same non-linear de-emphasis characteristic as in FIG. 5, and the same effect as in FIG. 5 can be obtained. In FIG. 6, the connection order of the cyclic de-emphasis circuit section and the backward de-emphasis circuit section may be reversed. The relationship between the types of the embodiments of the de-emphasis circuit in the apparatus of the present invention described above and the drawing numbers showing the embodiments corresponding to the types is summarized as shown in the following table.

[Table] Although the de-emphasis circuits in the blank sections in the above table are not shown, these circuits are also included in the device of the present invention. For example, it is possible to configure an output weighted de-emphasis circuit consisting of a combination of an acyclic type and a cyclic type. Note that the present invention is not limited to the above embodiments; for example, although the phase adjuster is provided on the output side of the coefficient circuit in all the embodiments, it may also be provided on the input side of the coefficient circuit, and the phase adjuster may be provided on the input side of the coefficient circuit. Circuit 61 ₁ ~ 61 _o , 7
The delay times of 2 ₁ to 72 _o , 85 ₁ and 85 _o may be any delay time as long as it is a natural number multiple of 1H. However, in this case, the coefficient circuits 62 ₁ to 62 _o , 70 ₂ to 70 _o+1 , 86 ₁ to
The sign of each coefficient of _86o must be selected so as to have a predetermined phase relationship with the main signal. In addition, the de-emphasis circuit has been described for the case where the reproduced carrier color signal, which has been separated from the reproduced signal and returned to its original band, is used as an input signal.
The input signal may be a carrier color signal that has been low-band-converted before being returned to the original band.
In this case, since de-emphasis is performed on the carrier color signal that has been low-band converted and has a color subcarrier frequency of 629kHz, for example, the carrier color signal in the original band (in the case of the NTSC system, the color subcarrier frequency is 3.58kHz) is de-emphasized. This eliminates the need for a phase adjuster for adjusting the phases of two input signals in the adder/subtractor circuit, which is required when de-emphasis is performed for MHz).
This is because a delay circuit is provided in the de-emphasis circuit, and the delay circuit usually has a slight error from the predetermined delay time. The phase change in the output signal of the color subcarrier frequency is e.g.
This is because the color subcarrier frequency is much lower when inputting a low frequency converted carrier color signal of, for example, 629kHz than when inputting a carrier color signal of 3.58MHz.
Furthermore, as a result, waveform restorability can be more improved when de-emphasis is applied to the low-pass converted carrier color signal than when de-emphasis is applied to the carrier color signal. Furthermore, although the above embodiment has been described with reference to the case where NTSC carrier color signals are de-emphasized, the present invention can also be applied to PAL carrier color signals. However, in this case, in the carrier color signal of the PAL system, the phase of the color subcarrier of one of the two color difference signals is inverted every 1H, so the delay circuits 23, 61 ₁ to 61 _o , 72
₁ to 72 _o and 85 ₁ to 85 _o are each configured to have a delay time that is a natural number times 2H. Also PAL
Since the phase of the carrier color signal in this system is reversed by a delay of 2H or an odd multiple thereof, the n used for each coefficient in the coefficient circuit means that the coefficient circuit has a delay time difference of 2nH with respect to the main signal. This will show that there is. Also, non-linear circuits 65, 74, 8
9 is not limited to an amplitude limiter. Effects of the Invention As described above, according to the present invention, at least backward de-emphasis and non-linear de-emphasis are performed on the vertical spatial frequency of the reproduced carrier color signal during reproduction.
Less deterioration in vertical resolution, S/S of reproduced carrier color signal
The N ratio can be improved, and the de-emphasis amount is made smaller when there is no correlation in the vertical direction of the reproduced carrier color signals. Even through a de-emphasis circuit, the original signal waveform can be reproduced with almost no practical problems, and when de-emphasis is performed in a combination of backward and forward types, smear is not noticeable when the S/N improvement is the same as before. If the same amount of smear is required, the S/N ratio can be improved compared to the conventional method.

[Brief explanation of drawings]

FIG. 1 is a block system diagram showing an embodiment of the apparatus of the present invention together with a recording system, and FIGS. 2 to 6 are block system diagrams showing respective embodiments of the de-emphasis circuit in the block system shown in FIG. 1. . 56... Day emphasis circuit, 20, 60...
...Reproduction carrier color signal input terminal, 23...1H delay circuit, 65, 74, 89...Non-linear circuit, 61 ₁ ~
61 _o , 72 ₁ to 72 _o , 85 ₁ to 85 _o ... delay circuit.

Claims (1)

[Scope of Claims] 1. A carrier color signal reproducing device that obtains a reproduced carrier color signal in the original signal form from a reproduced signal reproduced from a recording medium on which the carrier color signal is converted into a predetermined signal format and recorded, performing at least vertical backward de-emphasis on the reproduced carrier color signal, comparing the high frequency component of the vertical spatial frequency of the reproduced carrier color signal to the reduced component; 1. A reproducing device for a carrier color signal, comprising a de-emphasis circuit that provides a non-linear characteristic that relatively attenuates the level according to the amplitude.