JPH0548676B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention reproduces a pair of component color signals and luminance signals separately recorded simultaneously on adjacent tracks and converts them into a predetermined video signal. The present invention relates to a playback device.

Background technology and its problems A pair of component color signals, for example a pair of color difference signals R-Y, B-Y, are compressed in time axis to 1/2.
These compressed color difference signals are arranged alternately within the horizontal period,
In a recording/reproducing apparatus which separately and synchronously records the composite compressed color difference signal and luminance signal on adjacent tracks and reproduces them, signal processing as shown in FIG. 1 is performed during reproduction.

FIG. 1 shows an example of a reproduction device for color signals in particular. A composite compressed color difference signal recorded on a magnetic tape 1 is reproduced by a head Hc, and the reproduced composite compressed color difference signal is transmitted to an FM modulator 2. The demodulated signal is then supplied to a time axis expander 3 consisting of a CCD or the like that also serves as a time axis correction, where it is corrected and a pair of color difference signals R whose time axes are expanded are generated.
-Y, B-Y are output.

The pair of color difference signals R-Y and B-Y are converted by the encoder 4 into a carrier color signal with 3.58MHz as a subcarrier, and this is supplied to the comb filter device 20 at the subsequent stage and included in the carrier color signal. The noise components that are generated are removed. The output is combined with a reproduced luminance signal Y in an adder 5 to form a well-known signal Sv.

Now, if the playback device 10 is configured in this way,
The time axis expander 3 is required for two channels, R-Y system and B-Y system, but in this case, the input and output level characteristics of each channel generally do not match, and therefore the pair of color difference signals after time axis expansion is There will be a level difference between them.

Furthermore, if the carrier color signal is supplied to the comb filter device 20, the passing frequency will be high and the frequency characteristics will become a problem. If you also apply, e.g.
When using it as a PAL playback device,
The comb filter device 20 requires a delay element for two horizontal periods (H), and therefore cannot be used in common.

Moreover, by providing a 2H delay element, the vertical resolution is significantly degraded.

On the other hand, when the comb filter device 20 is provided between the FM demodulator 2 and the time axis expander 3 as shown in FIG.
Although the drawbacks caused by providing 0 at the final stage are eliminated, the mismatch in output levels caused by passing through the time base expander 3 is unavoidable.

OBJECTS OF THE INVENTION Accordingly, the present invention eliminates the output level difference between a pair of component color signals caused by time axis expansion processing, and also makes it possible to share a comb filter device.

Summary of the Invention Therefore, the present invention provides a video signal consisting of a luminance signal and a component color signal whose time axis is compressed to 1/2 so that a pair of color difference signals exists within one horizontal scanning time. In a reproducing apparatus that reproduces the video signal from a recording medium in which the luminance signal and the component color signal are separately recorded on adjacent tracks, a demodulator 2 that demodulates the component color signal; A time axis expander 3 consisting of a CCD that doubles the time axis of a pair of color difference signals of demodulated component color signals, and a comb filter to which the pair of color difference signals obtained from this time axis expander 3 are supplied. 2
1, 22 and a correlator 27 that takes line correlations between the input and output signals of the comb filters 21 and 22; a modulator 4 that modulates the output signal of the comb filter circuit 20; The reproduction apparatus is characterized in that it includes an adder 5 for adding the carrier color signal obtained from the modulator 4 and the reproduced luminance signal.

Embodiment Next, an example of the present invention will be described with reference to FIG. 3 and subsequent figures. However, in the example below, the pair of component color signals is a pair of color difference signals R-Y, B-
This is the case when Y is used.

In this invention, as shown in FIG. 3, a comb filter device 20 is provided between the time axis expander 3 and the encoder 4.

In this way, even if the output levels of the pair of color difference signals R-Y and B-Y deviate due to the time axis expander 3, they are averaged by the later-stage comb filter device 20, which will be described later, so that the output level The difference can be suppressed.

Furthermore, since the color difference signals R-Y and B-Y before being modulated are supplied to the comb filter device 20, the signals to be recorded on the magnetic tape 1 are NTSC.
Comb filter device 20 for both PAL and PAL methods
can be used in common. That is, this comb filter device 20 only needs to be provided with a 1H delay element.

This also makes it possible to improve vertical resolution degradation.

Furthermore, since the signal to be processed by the comb filter device 20 is a baseband component color signal, the passband is narrow and the frequency characteristics are good.

By the way, a special filter device is used as the comb filter device 20 used in the above-described reproduction device 10. In other words, in the conventional comb filter device consisting of a 1H delay element, an adder, and a subtracter, the leading edge of the input color difference signal (front edge of the image)
It is well known that the color level decreases and color shift occurs at the trailing edge (back edge of the image).

Comb filter device 20 used in this invention
improves the color level drop and color shift at the leading and trailing edges of the input color difference signal to the extent that they are completely undetectable visually, and in areas with line correlation, the S/N improvement achieved by the conventional comb filter is improved. It is constructed so that sufficient effects can be obtained.

FIG. 4 is a basic block diagram of this comb filter device 20, and FIG. 5 is a schematic waveform diagram showing the operation of FIG. 4.

As shown in FIG. 4, in this comb filter device 20, an input signal (R-Y or B-Y color difference signal) (FIG. 5A) is sent to a 1H delay line 21 and a subtracter 22.
An input signal S _C with an improved S/N ratio as shown in FIG. 5C is obtained. This signal is given to a correlator 27 and correlated with the input signal S _A. This correlator 27 has an AND function, and its output is the signal shown in FIG. 5D.
S _D (= S _A × S _C ). Therefore, since the output of the correlator 27 does not contain anything that is not present in the input signal S _A ,
As shown in FIG. 5D, no extra signal appears at the trailing edge X _B of the input signal. As a result, color blur in the vertical direction of the screen can be eliminated.

Furthermore, in this embodiment, the principle shown in FIG. 4 is improved, and the correlator 27 is configured so that the color level drop at the leading edge X _F of the input signal shown in FIG. 5D is corrected. . That is, as shown in the waveform diagram D in FIG. ₆ , at the leading edge X _F , the output signal S _B (FIG. 6B) of the 1H delay line 1 is For those that do not exist (S _A1 in the figure), correlator 2
It is output as is as the output S _D of 7 (Fig. 6D).
Also, signals with line correlation in both S _A and S _B are extracted as the output of the comb filter (S _D = S _C ). _In addition, in _the trailing edge portion _{of the} signal
= S _A × S _C ). As a result, a signal is obtained which is substantially the same as the input signal S _A , but whose S/N ratio has been improved by the comb filter.

Next, FIG. 7 is a block diagram of a circuit of a filter and correlator for removing noise showing an embodiment of the present invention, and FIG. 8 is a waveform diagram showing its operation.

First, to explain along the lines of Fig. 8, as in Fig. 6, the input S _A (in this example, the signal S _b delayed by τ)
By subtracting the 1H delayed signal Sc (FIG. 8B) from (FIG. 8A), the comb filter signal _Sc is obtained. At this time, noise components or distortion components (indicated by circles in FIG. 8) that have no line correlation and are included in the input signal S _A are attenuated.

The reproduced signal of the input signal S _A is distorted in one direction of the amplitude axis by a nonlinear portion of the electromagnetic conversion system of the magnetic tape 1/magnetic head H _C.
If the input signal is recorded in 1H alternating inversion, distortion components appear in opposite phases in alternating lines. Therefore, the distortion components of the signal processed by the comb filter are canceled by averaging.

Next, the logical product S _A ×S _C of the input Sb and the comb filter output S _C is taken to form a signal that does not cause color shift at the trailing edge as shown in FIG. 8D. Please input
If the swing width of S _A is set larger than S _C ,
The output of the comb filter is taken out as is except at the trailing edge. Also, at the leading edge, the level is 1/2 (−
6dB), an input signal S _A1 appears with the distortion component attenuated to 1/2.

Next, the logical sum (S _A + S _B ) of S _A and S _B is taken,
As shown in FIG. 8E, signals with line correlation and distortion or noise without line correlation are extracted. Furthermore, the logical product (S _A ×S _{c) of} this signal S _E and the input signal S _A is taken, and as shown in FIG. Also, signals that cause color shift at the trailing edge of the input signal S _A are removed.

As a final process _{, the} logical sum (S _D +
S _F ) is taken and level correction is performed at the leading edge to obtain the output signal S _G of FIG. 8G.

Comparing the output signal S _G and the input signal S _A , the first line of the input signal is the input itself, the middle part is the output after noise removal processing by the comb filter, and the next line after the input signal is finished. There is no extra signal on the line. Therefore, the problems of color level deterioration at the vertical leading edge of the image and color bleeding at the trailing edge, which are drawbacks of conventional comb filter devices, are both eliminated.

Next, the block circuit diagram of the embodiment shown in FIG. 7 will be explained. Note that the symbols S _A to S _G in FIG. 7 correspond to the waveform diagrams in FIG. 8. The input signal passes through an amplifier 30 and is applied to series τ delay lines 31 and 32.
τ is a minute delay time, and the input Sa and the outputs Sb and Sc of each delay line 31 and 32 are used to remove phase distortion. The output Sb of the delay line 31 is treated as a main line output and processed by a comb filter consisting of a 1H delay line 21, a subtracter 22, and an adder 23.
Comb filter output S _C , S _E and the above input signal
Sa to Sc are processed by correlators 35 to 42, and the calculations (product and sum) explained in FIG. 8 are performed.

Since each correlator performs calculations on only one of the upper and lower halves of the waveform of the input signal to be processed, two systems of correlators are provided to process the upper and lower halves of the waveform.

FIG. 9A and FIG. 10A show each correlator 35 to 42.
9B and 10B show the corresponding operating waveforms. Figure 9A and 1
As shown in Figure 0A, the correlator is constructed by commonly connecting the emitters and collectors of a pair of NPN or PNP transistors, and the output Sz of the product x or sum + of the inputs Sx and Sy is connected to the common emitter resistance RE.
taken from.

When configured with NPN transistors as shown in Figure 9A, the output level is the part where the input Sx and Sy levels are high, so as shown in Figure 9B, the upper half of the waveform is the logical sum Sx + Sy, and the lower half is the logical product Sx. ×
The output Sz of Sy is obtained.

In addition, when configured with PNP transistors as shown in Figure 10A, the part where the input Sx and Sy levels are low becomes the output level, so as shown in Figure 10B, the upper half of the waveform is the logical sum Sx+Sy, and the lower half is the logical sum. The output Sz of Sx×Sy is obtained.

Each of the correlators 35 to 42 shown in FIG. 7 is constructed by combining the basic circuits shown in FIG. 9A or FIG. 10A. In FIG. 7, correlators 37 and 38 are supplied with inputs Sa and outputs Sb and Sc of γ delay circuits 31 and 32, and a logical sum Sa+Sb+Sc is formed in the lower half and upper half of the signals, respectively. This processing is performed as a preprocessing to remove phase distortion, but in this explanation, the sum Sa + Sb + Sc or the product Sa・
Sb and Sc are treated as being practically equivalent to the input signal in FIG. 8A. Output S _A of correlators 37 and 38
are given to correlators 41 and 42, respectively, and subtracter 22
The comb filter output S _C obtained from (Figure 8C)
and is ANDed to form the output S _D =S _A ×S _C (FIG. 8D).

On the other hand, the output of the 1H delay line 21 of the comb filter (FIG. 9B) and the main line signal Sb (=S _A ) are sent to the adder 2.
3 to form the signal shown in FIG. 8E. This signal S _E and the signals Sa, Sb, and Sc are given to multipliers 35 and 36, and in the upper and lower halves of the signals, Sa・Sb・Sc×S _E , that is, S _A
The signal shown in Figure 8F after the AND operation of ×S _E is performed.
_SF is formed. This signal S _F and multipliers 41 and 42
The outputs S _D are given to correlators 39 and 40, respectively,
A logical OR operation of S _D +S _F is performed on each of the upper and lower halves of the signal to form the output S _G shown in FIG. 8G.

The processed signal is sent to the lower slice circuit 43
and the adder 4 through the upper slice circuit 44, respectively.
5 and taken out via a low-pass filter 46 for removing high frequency components.

When using the above-described comb filter device 20, a pair of transistors can be used by first constructing it as shown in FIGS. 9A and 10A.
Therefore, the balance between the base-emitter voltage of the transistor is improved, and the input level can be eliminated without adjustment. Further, since the pair of color difference signals has a horizontal blanking period, by pedestally clamping this horizontal blanking level, the DC level of the signal input to the correlator is stabilized. In this case, although not shown, a clamp circuit may be provided before the correlators 35 to 38.

Note that the video signals that can be handled by this playback device 10 may be of the SECAM format in addition to those described above.

Effects of the Invention As explained above, according to the present invention, since comb processing can be performed in a low frequency region, the frequency characteristics of the comb filter device 20 are improved, and its configuration (clock system, number of bits, etc.) is improved. In addition to being simple, it is possible to eliminate the level difference between a pair of color difference signals caused by time axis expansion processing, and
Since the comb filter device can be shared, the configuration can be simplified. Further, since the comb filter device uses a 1H delay element as shown in FIG. 7, there is no deterioration in vertical resolution.

Since the adder 23 can perform simple addition, it can also be configured as a resistance addition type (using the same resistance). In this case, the output level after the addition is
Since the output level matches the output level of No. 2, there is no need to adjust both.

[Brief explanation of the drawing]

Figures 1 and 2 are system diagrams of conventional playback devices;
FIG. 3 is a system diagram showing one line of the reproducing device according to the present invention, FIG. 4 is a block diagram showing the principle of the comb filter device, FIGS. 5 and 6 are waveform diagrams showing the operation of FIG. 4, and FIG. The figure is a block diagram showing an embodiment of the comb filter device, FIG. 8 is a waveform diagram showing the operation of FIG. 7, and FIGS. 9A and 10A are circuits showing the basic configuration of the correlator used in FIG. 7, respectively. Figures 9B and 10B are Figures 9A and 10, respectively.
FIG. 3 is a waveform diagram illustrating the operation of FIG. 10 is a reproduction device, 20 is a comb filter device,
2 is an FM demodulator, 3 is a time axis expander, and 4 is an encoder.

Claims (1)

[Claims] 1. A video signal consisting of a luminance signal and a component color signal whose time axis is compressed to 1/2 so that a pair of color difference signals exists within one horizontal scanning time is used as the luminance signal. and a component color signal are recorded separately on adjacent tracks, the reproducing device for reproducing the video signal includes: a demodulator for demodulating the component color signal; and a component demodulated by the demodulator. Double the time axis of a pair of color difference signals
A comb filter circuit consisting of a time axis expander made of a CCD, a comb filter to which a pair of color difference signals obtained from the time axis expander is supplied, and a correlator that takes line correlation between the input and output signals of the comb filter. A reproducing device comprising: a modulator that modulates the output signal of the comb filter circuit; and an adder that adds the carrier color signal obtained from the modulator and the reproduced luminance signal.