JPH0323779A - Filter circuit - Google Patents

Abstract

PURPOSE:To process a luminance signal with one delay circuit only and to simplify the constitution by applying vertical pre-emphasis processing or vertical de-emphasis processing to a luminance signal, suppressing a signal component of a chroma band, and applying the vertical de-emphasis processing when required. CONSTITUTION:Comb line filter circuits 4, 5 and chroma signal band attenuation filter circuits 32, 34, 36 are provided, which suppress the signal component of the chroma band as to a luminance signal SYIN(SDEM) based on the output signal SYEN of the comb line filter circuits 4, 5. Moreover, based on the output signal SYEN of the comb line filter circuits 4, 5, noise reduction filter circuits 6, 7, 8 emphasizing or suppressing the luminance signal SYIN(SDEM) are provided. Thus, the luminance signal SYIN is processed by one delay circuit only and the constitution of the signal processing circuit is simplified more of the share of processing.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a filter circuit, and is suitable for application to, for example, a video tape recorder.

B. Summary of the Invention The present invention provides a filter circuit that performs vertical pre-emphasis processing or vertical de-emphasis processing on a luminance signal based on the output signal of a comb filter circuit, while suppressing the signal strength of the chroma band. Accordingly, the configuration of the signal processing circuit can be simplified.

C. Prior Art Conventionally, some videotape recorders have been designed to provide higher quality playback video than when recording and playing back standard television broadcasts. It is designed to be able to input and output signals separated into luminance signals and chroma signals. Furthermore, in this type of video table recorder, a luminance signal and a chroma signal are combined to create a video signal, and the video signal is output together with the luminance signal and chroma signal. Is it now possible to monitor the recording and playback status even on television devices that are not equipped with it? It is. Furthermore, crosstalk between adjacent horizontal scanning lines is improved by applying pre-emphasis processing and de-emphasis processing using vertical correlation to the luminance signal. That is, as shown in FIGS. 4 and 5, in the recording signal processing circuit 1, the XY filter circuit 2 receives the luminance signal sy+N, suppresses the signal intensity of the chroma band in a comb-like shape, and sends it to the adder circuit 3. Output.

The adder circuit 3 adds the chroma signal SCIN to the luminance signal SXV output from the XY filter circuit 2, and thereby synthesizes the chroma signal SCIN and the luminance signal SWIN to create a signal that is compatible with a normal video signal. video signal S
,. ■Outputs. On the other hand, the delay circuit 4 is configured to receive the brightness signal SYIN and output a delayed brightness signal SVD delayed by one horizontal scanning period with respect to the current brightness signal SvIN. The subtraction circuit 5 extracts the delayed luminance signal SV from the luminance signal SV+8.
D is subtracted, which results in the sixth ? As shown in FIG. 2, the signal strength of a portion where there is little correlation between adjacent horizontal scanning lines (that is, a portion where the signal level of the luminance signal changes in the vertical direction) is extracted.

Here f. represents the frequency of the horizontal scan line. The amplifier circuit 6 receives the output signal Svt. 4
, the small amplitude part is emphasized and output. As a result, for portions where the signal level of the luminance signal changes in the vertical direction, the portions where the change is small are emphasized. The adder circuit 8 receives the output signal of the amplifier circuit 6 and the delayed luminance signal S.
As shown in FIG. (referred to as luminance signal)S
■It is designed to get 8. The waste wave number modulation circuit 9 receives the luminance signal S FILM that has been subjected to vertical bias processing, adds its differential waveform, performs normal bias processing, and then frequency modulates and outputs the signal. On the other hand, the low frequency conversion circuit 11 converts the chroma signal S CI
N is received, frequency-converted, and then added to the frequency-modulated luminance signal via an adder circuit 12. In this way, the output signals of the adder circuit 12 are sequentially recorded on the magnetic tape 15 via the magnetic head l6, and at this time, the recording state can be checked by monitoring the video signal SC (INF). ．In contrast, as shown in Figure 8,
During reproduction, the reproduced signal SIIF obtained via the magnetic head 16 is band-limited by a low-pass filter circuit 17 and a high-pass filter circuit 18, and is separated into a chroma signal component and a luminance signal component.

One frequency conversion circuit is configured to convert the signal component of the chroma signal to the original chroma band, contrary to the low frequency conversion circuit 1l, thereby obtaining a reproduced chroma signal scout.

On the other hand, the demodulation circuit 20 is configured to demodulate the frequency-modulated luminance signal and then output it to the vertical de-emphasis circuit 21 .

The vertical de-emphasis circuit 21 receives the luminance signal S Ill! output from the demodulation circuit 20 . After extracting the signal intensity of the portion with little correlation between adjacent horizontal scanning lines from M, this is amplified by a nonlinear amplifier circuit, and, contrary to vertical pre-emphasis processing, the original luminance signal S! It is designed to be subtracted from 1121.

As a result, as shown in FIG. 9, it is possible to suppress the signal components emphasized by the vertical re-emphasis processing, and it is possible to reduce crosstalk between relatively adjacent horizontal scanning lines. Emphasis circuit 21
The luminance signal S VOIJT output from the chroma signal S
,. By monitoring the uT with a monitor device, it is possible to obtain a reproduced video with a higher resolution than that of standard television broadcasting.

On the other hand, the YX filter circuit 22 is configured to be the same circuit as the YX filter circuit 2 of the recording signal processing circuit 1. ? After correcting the frequency characteristics of the luminance signal syo2 through the YX filter circuit 22, the adding circuit 23 outputs the chroma signal S,. By adding it to u7, as in the case of the recording signal processing circuit 1, a video signal SCO■ which is compatible with a normal video signal is output. D Problems to be Solved by the Invention Incidentally, in this type of YX filter circuits 2 and 22, in order to suppress signal components in the chroma band in a comb-like shape, a delay circuit whose delay time is one horizontal scanning period is used. There is a need. Therefore, two delay circuits are required in each of the recording signal processing circuit and the reproduction signal processing circuit, which causes problems in that the structure of the signal processing circuit becomes complicated and the size increases. The present invention has been made in consideration of the above points, and aims to propose a filter circuit with a simple structure that can reduce the size of the signal processing circuit. ? Means for Solving the Problems In order to solve the problems, in the first invention, comb filter circuits 4 and 5;
Based on the output signal sveN of the luminance signal SV. H
Regarding (SD■), color signal band attenuation filter circuits 32, 34, 36 (36,
42, 43) and the output signals S'fEH of the comb filter circuits 4, 5, the luminance signal SYIN CSo
noise reduction filter circuits 6, 7, 8 (7, 46, 47) that emphasize or suppress the noise.

Furthermore, in the second invention, a comb filter circuit 4,
5 is a delay circuit 4 that delays the luminance signal Sv'N (S++tx) by one horizontal scanning period;
the color signal band attenuation filter circuit 32;
, 34, 36 (36, 42, 43) are the output signals Sv! of the subtraction circuit 5''. A bandpass filter circuit 32 (42) which receives the signal S.N and limits the band in the chroma band, and an output signal S.N of the bandpass filter circuit 32 (?2). PF (S■■)
and a signal synthesis circuit 36 for synthesizing the luminance signal SvIN (Set) or the output signal S0 of the delay circuit 4, and noise reduction filter circuits 6, 7, 8 (7, 46
, 47) are the output signal STEN of the reduction circuit 4 and the luminance signal Sy+H (S■.) or the output signal s of the delay circuit 4.
yo and signal synthesis circuits 8 and 47. ? The color signal band attenuation filter circuits 32, 34, 36 (36
, 42, 43) to suppress signal components in the chroma band, and noise reduction filter circuits 6, 7, 8 (7
, 46, 47) to emphasize or suppress the luminance signal S7■ (SotM), the comb filter circuits 4 and 5 can be used in common to simplify the overall structure. G example? An embodiment of the present invention will be described in detail with reference to the drawings below. (G1) First Embodiment In FIG. 1, in which parts corresponding to those in FIG. , the video signal SC
Synthesize ONF. In other words, the bandpass filter circuit 3
2 is designed to extract the signal strength of the chroma band from the output signal Sv■ (Fig. 6) of the subtraction circuit 5 whose signal level changes in the shape of a comb. It is designed to obtain an output signal SIFF whose spectrum is distributed in the shape of a comb like the signal. The subtraction circuit 36 is configured to subtract the output signal SIFF amplified by the amplifier circuit 34 from the delayed luminance signal S0,
As a result, a luminance signal S8y in which the signal level in the chroma band is suppressed in a comb-like manner is obtained. Thus, through the subtraction circuit 36, the XY filter? The output signal Sxv (FIGS. 4 and 5) of path 2 can be obtained. Therefore, based on the output signal Sv■ of the comb filter circuit composed of the delay circuit 4 and the subtraction circuit 5, the luminance signal SI
By performing vertical pre-emphasis processing on N and suppressing the signal strength of the chroma band, the luminance signal SV+U can be processed with only one delay circuit, and the signal processing circuit can be simplified accordingly. Thus, in this embodiment, the delay circuit 4 and the subtraction circuit 5 constitute comb filter circuits, whereas the bandpass filter circuit 32, the amplifier circuit 34, and the subtraction circuit 36 operate based on the output signal SvtH of the comb filter circuit. hand,
Regarding the luminance signal SvIN, a color signal band and attenuation filter circuit is constructed to suppress the signal strength of the chroma band. On the other hand, the low-pass filter circuit 7, the amplifier circuit 6, and the adder circuit 8 receive the output signal Sv■ of the comb filter circuit.
Based on this, we construct a noise reduction filter circuit that emphasizes the luminance signal Svrw. According to the above structure, the output signal S of the comb filter circuit
,. By performing vertical pre-emphasis processing on the luminance signal SWIM and suppressing the signal component in the chroma band, the luminance signal SvI,l can be generated with only one delay circuit.
The structure of the signal processing circuit can be simplified accordingly.

? G2〉Second Embodiment In FIG. 3, in which parts corresponding to those in FIG. Based on this, a video signal S CONF is synthesized.

That is, the luminance signal output from the demodulation circuit 20 is 30%.
is applied to a comb-shaped filter circuit composed of a delay circuit 4 and a subtraction circuit 5, and a luminance signal 3 of 11% whose signal level changes in the shape of a comb is produced. Bandpass filter circuit 4
2 has a frequency characteristic that combines the characteristics of both the lohas filter circuit 7 and the bandpass filter circuit 32 (FIG. 1), and ? In addition to extracting the signal component in the chroma band from the frequency signal S VKH, the signal component in the low frequency band is extracted by attenuating it by a predetermined level compared to the signal component in the chroma band. On the other hand, the amplifier circuit 43 has a characteristic opposite to that of the amplifier circuit 6, and is configured to emphasize and amplify the large amplitude portion, and its output signal is subtracted from the delayed luminance signal sve by the subtraction circuit 36. .

Therefore, via the amplifier circuit 43, it is possible to obtain a luminance signal SIPF+, which is the sum of the signal intensity that has been emphasized through vertical re-emphasis processing and the signal intensity of the chroma band. Therefore, by subtracting the luminance signals S■ and ■ from the delayed luminance signal SYD, it is possible to obtain a luminance signal in which the chroma band is suppressed after being subjected to vertical de-emphasis processing. Thus, by adding the luminance signal to the chroma signal S course via the adding circuit 23, the video signal S
,. , can be synthesized. On the other hand, the amplifier circuit 46, like the amplifier circuit 43, is configured to emphasize and amplify the large amplitude portion, thereby obtaining an emphasized signal component through vertical pre-emphasis processing. On the other hand, the subtraction circuit 47 outputs the delayed luminance signal syo.
The output signal of the amplifier circuit 46 is subtracted from
In this manner, the vertically de-emphasized luminance signal S your can be obtained via the subtraction circuit 47 .

Thus, in this embodiment, the bandpass filter circuit 42, the amplifier circuit 43, and the subtraction circuit 36 constitute a color signal band attenuation filter circuit, whereas the lowpass filter circuit 7, the amplifier circuit 46, and the subtraction circuit 47 constitute a noise signal band attenuation filter circuit. A reduction filter circuit is constructed.

According to the above structure, the output signal 3 of the comb filter circuit
Based on 0H, the luminance signals sy+,l are subjected to vertical de-emphasis processing, while the other side is subjected to vertical de-emphasis processing and the signal components of the chroma band are suppressed, thereby processing the reproduced signal SIF with only one delay circuit. As a result, the structure of the signal processing circuit can be simplified accordingly. ? G3) Other Embodiments In the above-described embodiment, the output signal S Y! of the comb filter circuit. We have described the case where the luminance signal SVIM is subjected to vertical emphasis processing or vertical de-emphasis processing by adding or subtracting the delayed luminance signal based on N'), and the video signal SCO is synthesized. , the present invention may alternatively perform addition/subtraction processing on the luminance signal S_INs_SDtH with respect to the output signal S_ of the band-limited comb filter circuit. Further, in the above-described embodiment, a case has been described in which the amplifier circuits 6, 43, and 46 having nonlinear input/output characteristics emphasize and amplify the small amplitude and large amplitude portions, respectively, but the present invention is not limited to this. , an amplifier circuit with linear input/output characteristics may be used. Further, in the above-described embodiment, the case where the low-pass filter circuit 7 is used to limit the band when performing the vertical re-emphasis processing and the vertical de-emphasis processing is described, but the present invention is not limited to this. When performing vertical pre-emphasis processing and vertical de-emphasis processing, the low-pass filter circuit 7 may be omitted.

Incidentally, in this case, the bandpass filter circuit 42 only needs to extract signal components in the chroma band. Furthermore, in the above-described embodiment, the output signal S l! of the comb filter circuit is applied to an NTSC video table recorder. Although the case has been described in which the signal strength of the chroma band centered on frequencies 3 and 58 (MHz) is extracted from N, the present invention is not limited to this. For example, when applied to a PAL video table recorder, the frequency 4.43
All you have to do is extract the signal strength of the chroma band centered on (MHz). Furthermore, in the above-described embodiment, a case was described in which the recording signal processing circuit and the reproduction signal processing circuit were constructed separately, but the present invention is not limited to this, and a part of the comb filter circuit etc. may be used in common. You can. In this way, the overall structure can be further simplified. Further, in the above-described embodiments, the present invention was applied to a video table recorder, but the present invention is not limited to this, but can be widely applied to filter circuits of various video equipment. H Effects of the Invention As described above, according to the present invention, the luminance signal is subjected to vertical pre-emphasis processing or vertical de-emphasis processing based on the output signal of the comb filter circuit, while the signal components in the chroma band are suppressed. In addition, by performing vertical de-emphasis processing as necessary, the luminance signal can be processed with only one delay circuit, and the structure of the signal processing circuit can be simplified accordingly.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a recording signal processing circuit according to an embodiment of the present invention, FIG. 2 is a characteristic curve diagram for explaining its operation, FIG. 3 is a block diagram showing a reproduction signal processing circuit, and FIG. 4 5 is a block diagram showing a conventional recording signal processing circuit.
Figures 8 to 7 are characteristic curve diagrams for explaining the operation.
The figure is a block diagram showing the reproduced signal processing circuit, and FIG. 9 is a characteristic curve diagram for explaining its operation.

Claims (2)

[Claims] (1) a comb-shaped filter circuit; and a chrominance band attenuation filter circuit that suppresses signal components in the chroma band for the luminance signal based on the output signal of the comb-shaped filter circuit; and a noise reduction filter circuit that emphasizes or suppresses a luminance signal based on the noise reduction filter circuit. (2) The comb filter circuit includes a delay circuit that delays the luminance signal by one horizontal scanning period, and a subtraction circuit that subtracts the output signal of the delay circuit from the luminance signal, and the chrominance signal band attenuation filter circuit. a bandpass filter circuit that receives the output signal of the subtraction circuit and limits the band in the chroma band; and a signal synthesis circuit that synthesizes the output signal of the bandpass filter circuit and the luminance signal or the output signal of the delay circuit. Claims characterized in that the noise reduction filter circuit includes a signal synthesis circuit that synthesizes the output signal of the subtraction circuit and the luminance signal or the output signal of the delay circuit. The filter circuit according to item 1.