JPH01185092A - Video signal processor - Google Patents

Abstract

PURPOSE:To decrease a picture quality deterioration by delaying a luminance signal to the delay of the deformation time of a color signal to be necessarily generated since a color comb line filter is used. CONSTITUTION:In a route to pass only the luminance signal, a delaying element 2, for concrete example, a line memory, a CCD, etc., is inserted, and the luminance signal is delayed by 1H relatively to the color signal only at the time of recording, or the luminance signal is delayed by 1H to the color signal only at the time of reproducing. Since the luminance signal is delayed by 1H period at the time of recording and reproducing in passing through a delaying circuit in such a way, the change time of the color signal and the change time of the luminance signal are made to relatively coincide. Thus, the change of color components and the timing dislocation of the change time of luminance components generated due to a color comb line filter 4 in the processes of recording and reproducing can be corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal processing device having a comb filter in a color signal processing system. The present invention relates to a video signal processing device having a function of preventing signal degradation.

[Conventional technology]

Conventionally, in the color signal processing of home VTRs, the phase inverted method (hereinafter referred to as the PI method) has been used, as described in the document r NHK Home Video Technology (Japan Broadcasting Corporation W) J, pages 87 to 91. Color crosstalk from adjacent tracks has been removed by a combination of a phase shift method (hereinafter abbreviated as PS method) and a color comb filter.

FIG. 7 shows an example of the circuit configuration of a color comb filter. In the figure, 18 is an IH delay element, 19 is a subtracter, and 20
is an attenuator. However, IH represents a horizontal scanning period. Changes in the signal waveform at each point in Figure 7 are shown in Figure 8.
As shown in the figure. The operation of the color comb filter shown in FIG. 7 will be explained using FIG. 8. f□(t), is the input color signal. This is expressed as the following equation.

f, (t) =A□sin (+)Cj””” (1)
However, ωC is the angular frequency of the input color signal, and A is a constant representing the amplitude of the input color signal.

L(t) indicates the output after fl(t) passes through the IH delay element 18, and when f(1) has a correlation for each IH, it is expressed by the following equation.

f2(t) = A, sinωc(t-r) = A1(si
nωct cosωCt-cosωctsinωCτ)
......(2) However, τ represents the delay time by 18, that is, τ
=LH. f, (t) is calculated by the subtracter 19 as f□(1
) minus f2(t). Therefore, f3(t)=f□(t)-L(t)=A, sinωct-A, (sinωct cosω
at-cosωct sinωCτ) ・・・・・・
It is expressed as (3). By the way, the color signal angular frequency ω
C (= I H) is for the purpose of interleaving the frequency spectra of the luminance signal and color signal.

Selected for a particular relationship. In the NTSC system, there is the following relationship: R=flat×÷・°・ωCτ=455π (4). If we substitute equation (4) into equation (3).

f, (t) = A15inωct - A1(sin
ωct cos(455c)-cosωct 5in(
455π) = 2 A15inωct - (5). Furthermore, the output obtained by attenuating f3(t) to 1/2 the amplitude by the 7-tensioner 20 is f4(t). That is, it is expressed by the following equation.

-Top f4(t) f3(t) =A, sinωct ・--(6) The waveforms in FIG. 8 represent these relationships.

That is, if the input color signal fl(t) has a correlation for each IH, f4(t)=f1(t)... (7) A relationship is established.

Next, consider a case where the input color signals have no correlation for each IH. At this time, the output f, (t) of the LH delay element 18 is expressed by the following equation.

L(t) = A2 sin ωc (t-τ) = A 2 (sin (1) Ct cos ωat
−cosωct sinωct) ・・・・・・ (
8) However, ', -1i-Az. If calculations are made in the same manner, the output f4(t) of the attenuator 20 can be expressed as shown in the following equation.

f4(t) =A, sinωct+A25inωct=
= + sxn (1) at ·-, (9) Equation (7) and Equation (8) mean the following. Input signal f! (t)
If there is a correlation with the pre-IH signal, the comb filter output f,(t) in FIG. 7 has the same amplitude as the input signal. On the other hand, when the input signal f(1) has no correlation with the signal before IH, the amplitude of the output f4(t) is the input signal f, (
The average value of the amplitude A1 of signal L(t) before IH and the amplitude A2 of signal L(t) before IH.

FIG. 5 is a block diagram showing an example of a video signal processing system of a home VTR, and FIG. 5(A) shows a signal processing system during recording,
FIG. 5(B) shows the signal processing system during reproduction.

The signal flow in FIG. 5 will be briefly explained below.

The input video signal includes a luminance signal distributed in a frequency band from DC component to approximately 5 MHz, and approximately 3.58 MHz ± 500K.
It consists of a composite signal mixed with a color signal distributed in the IIz frequency band. During recording, a luminance signal of approximately 3 MHz or less is extracted by the LPFI and sent to the FM modulator 3.
The signal is then FM modulated and then input to the recording amplifier 8. On the other hand, the color signals extracted by the color comb filter 4 and the BPF 5 are transferred to the frequency converter 6 and the LPF 7.
After being converted into a low frequency band, the signal is input to the recording amplifier 8.

FMI! superimposed in recording amplifier 8! The ill1 degree signal and the low frequency conversion color signal are sent to the magnetic head 10 via the rotary transformer 9 and recorded on the magnetic tape 11. During reproduction, signals recorded on the magnetic tape 11 are detected by the magnetic head 10, transmitted to the reproduction preamplifier 12 via the rotary transformer 9, and amplified. The amplified signal is transmitted to HPF13 on the one hand, and LPF7 on the other hand.
will be communicated to. Luminance FM extracted by HPF13
The signal is demodulated by the FM demodulator 14, band-limited by the LPFI, and then input to the mixer 16.

The low frequency converted color signal extracted by the LPF 7 is reconverted to a high frequency signal by the frequency converter 15 and BrF3. The color signal converted into seven bands of 3.58 MHz±500 passes through a color comb filter 4 to remove crosstalk from adjacent tracks, and then is input to a mixer 16. The brightness signal and the color signal are superimposed in the mixer 16 and output as a composite signal.

FIG. 6 is a diagram showing the timing of the luminance signal and color signal in the signal processing system of FIG. 5. In FIG. 5, (A) is the original signal color component, (B) is the original signal luminance component, (C) is the recorded signal color component, (D) is the recorded signal luminance component, (E) is the reproduced signal color component, ( F) represents the reproduced signal luminance component, respectively.

As shown in the original signals (A) and (B), the signals of both the color component and the luminance component change after time t□. That is, the boundaries of signal changes are all at time t0. On the other hand, in the recording signal color component (C), when the signal level before time t□ is set to 1, a color component with a level of 0.5 has shifted into the IH period immediately after time t4. This is the color comb filter 4 in Fig. 5(A).
This is because the signal level becomes the average value with the signal level before IH in the portions where there is no correlation for each LH. The principle is as described above. Similarly, during reproduction, the color components pass through the color comb filter 4 shown in FIG. 5(B), resulting in a waveform as shown in FIG. 6(E). At time t, a color component with a level of 0.75 is shifted in the IH period immediately after the surface, and a color component with a level of 0.25 is shifted in the next IH period.

In FIG. 6(E), the central time when the level of the reproduced color signal changes from 1 to 0 is t3. The time at which the reproduced luminance signal changes in FIG. 6(F) is t□, and compared to this, the time at which the color signal (E) changes is delayed by IH. In fact, on the playback screen, only the color components appear to bleed downward by 16 minutes, resulting in deterioration in image quality.

[Problem to be solved by the invention]

In the above conventional technology, the change time of the color component is delayed by passing through the color comb filter. Specifically, the central time of change is delayed by 0.5H by passing through the color comb filter once. This has not been taken into consideration, and there has been a problem in that the change time of the color component is delayed relative to the luminance component in the output after recording and reproduction, resulting in deterioration of image quality.

The object of the invention arises due to the color comb filter in the process of recording and reproduction. The purpose is to correct the timing difference between the change in color component and the time of change in luminance component.

[Means to solve the problem]

The above purpose is to insert a delay element such as a line memory or CCD in a path through which only the luminance signal passes, and to delay the luminance signal by IH relative to the color signal only during recording, or only during reproduction. This is achieved by delaying the luminance signal by IH relative to the color signal.

[Effect]

In general, in home VTRs, in color signal processing, the signal is passed through a color comb filter both during recording and during playback. At this time, the change time of the color signal is 1
During the recording and reproducing process, the luminance signal is delayed by IH. In the method used this time, the luminance signal is passed through a delay circuit and delayed by an IH period during recording and playback, so the change time of the color signal and the change time of the luminance signal are relatively coincident, and the timing difference is corrected. Ru. Furthermore, by selecting the delay time of the delay element in integer multiples of IH, even when compatible with other VTRs to which the present invention is not applied, the timing difference between the color signal and the brightness signal can be reduced by an integer multiple of IH. It is possible to maintain compatibility because it only occurs in this form.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a block diagram showing an example of a VTR signal processing system to which the present invention is applied, and an IH delay element 2 is additionally inserted compared to FIG. 5, which is a block diagram of the conventional example described above. They are completely equivalent. Delay element 2 is 0-5M)
It is an element for IH delaying a luminance signal having a band of Iz, and specific examples include line memory and COD. Descriptions of other components and signal flows are the same as those shown in FIG. 5, and will therefore be omitted. FIG. 2 is a diagram showing the timing of the luminance signal and color signal in the signal processing system of FIG. 1, and each waveform (A)
The meanings of ~(F) are the same as those in FIG. 6, so the explanation will be omitted. In Figure 1 (A), by inserting the IH delay element 2 into the luminance signal processing system during recording, the second
The change time of the luminance signal at the time of recording in Figure (D) is a time delayed by IH with respect to the original signal (B), that is, time t. Since no particular delay element is inserted during reproduction, the change time of the reproduced luminance signal is also t3. Therefore, in the recording/reproduction output, the change time of the color signal and the change time of the luminance signal are relatively coincident.

Next, another embodiment of the present invention will be described with reference to FIGS. 3 and 4. FIG. 3 is a block diagram showing an example of a VTR signal processing system to which the present invention is applied, and an IH delay element 17 is additionally inserted compared to FIG. 5, which is a block diagram of the conventional example described above. They are completely equivalent. As with the delay element 2, specific examples of the delay element 17 include a line memory and a CCD. Descriptions of other components and signal flows are the same as those shown in FIG. 5, and will therefore be omitted. FIG. 4 shows the signal processing system in FIG. 3.

6 is a diagram showing the timing of a luminance signal and a color signal, and the meanings of each waveform (A) to (F) are the same as those in FIG. 6, so a description thereof will be omitted. In FIG. 3(B), by inserting the LH delay element 17 into the luminance signal processing system during reproduction, the change time of the reproduced luminance signal in FIG. 4(F) is different from that of the original signal (B) and the recorded signal. The time is delayed by IH with respect to (D), that is, time t3. Therefore, in the recording/reproduction output, the change time of the color signal and the change time of the luminance signal are relatively coincident.

〔Effect of the invention〕

According to the present invention, with respect to the delay in the change time of the color signal that inevitably occurs due to the use of a color comb filter, the change time of the color signal and the brightness signal in the recording and reproduction output is delayed by means of delaying the brightness signal. Since they can be made to match relatively, it has the effect of reducing image quality deterioration caused by a timing shift between the color signal and the luminance signal.

[Brief explanation of the drawing]

FIG. 1 is a signal processing block diagram of an embodiment of the present invention, and FIG.
The figure is a signal waveform diagram in the processing system of Figure 1, Figure 3 is a signal processing block diagram of another embodiment of the present invention, and Figure 4 is a signal waveform diagram of the processing system of Figure 3.
Figure 5 is a signal waveform diagram in the processing system shown in Figure 5. Figure 5 is a signal processing block diagram of the conventional example. Figure 6 is a signal waveform diagram in the processing system shown in Figure 5. Figure 7 is a block diagram showing the configuration of the color comb filter. , FIG. 8 is a waveform diagram of the signal processed by the color comb filter. l...LPF, 2...IH delay element, 3...FM
Modulator, 4... Color comb filter, 5... BP
F, 6...Frequency converter, 7...LPF, 8...
Recording amplifier, 9... Rotary transformer, 10...
Magnetic head, 11... Magnetic tape, 12... Reproduction preamplifier, 13... HPF, 14... FM demodulator,
15... Frequency converter, 16... Mixer, 17...
・IH delay element, 18... IH delay element, 19...
Subtractor, 20...attenuator. 7, - No. l ro 7 /j J 4 Kototsu 2nd 51!

Claims (1)

[Claims] 1. During recording and/or playback, in a video signal processing device that includes a comb filter as a component in the color signal processing system, the luminance signal is processed for approximately one horizontal scanning period relative to the color signal. A video signal processing device comprising: a delay circuit having a delay function; and means for operating the delay function only during recording and not during playback, or means for operating the delay function only during playback and not during recording.