JP2600446B2 - Video signal processing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television signal processing apparatus, and more particularly, to a video signal processing apparatus having a function of converting an interlaced scanning video signal into a sequential scanning signal.

MUSE system for transmitting a high definition television signal having a number of scanning lines of the prior art 1125 and band compressed signals approximately 8.1MH _z by multiple subsampling has been proposed. This method performs offset sub-sampling between fields, between frames, and between lines, as described in NHK Technical Research VOL39, No. 2, 1987 "Development of MUSE Method", so that the sub-sample phase goes around in four fields. It is a thing.

The television signal of the above-mentioned system is not limited to reception by a standard receiver designed for high-definition television, and it is desired that the television signal can be viewed by a receiver designed for NTSC,
For this purpose, a converter for converting the MUSE signal into 525 scanning line signals is required. For example, as shown in FIG. 6, this conversion apparatus can convert a 16: 9 aspect ratio signal of a high definition television signal into a range compatible with the current system having 525 scanning lines, that is, an aspect ratio of 4: 4. 3 selects 1050 areas, which is twice 525 lines, and finally converts them to 525 lines, or substantially increases the vertical and horizontal image display ranges of the received high definition television signal. The conversion of the number of scanning lines is performed without any loss. Further, it is effective to easily process the signal band-compressed by the MUSE system in order to manufacture this converter inexpensively. For this reason, as shown in FIG. After the MUSE signal supplied to the A / D converter is converted into a digital signal by the AD conversion circuit 2, the spatial filter 3
Performs low-pass filtering on the two-dimensional space in the vertical and horizontal directions, converts the signal specifications of the high-definition television to the specifications for the 525-system using the time axis conversion circuit 4, and further converts the signals into a DA conversion circuit The signal is encoded by a NTSC encoder 6 into a required composite NTSC signal, for example, and transmitted to a signal output terminal 10.

The image information of the high-definition television converted by the MUSE signal converter is supplied to, for example, a receiver as shown in FIG. This device converts a converted NTSC signal supplied through a signal input terminal 11 into a digital signal by an AD conversion circuit 21, and then demodulates the signal as a luminance signal / color difference signal or a GBR three primary color signal by an NTSC decoder 7, By converting the number of scanning lines to the image display device 9 via the DA conversion circuit 51, a double-density image is displayed.

The above-described configuration of the conversion apparatus shown in FIG. 7 adapts the basic scanning parameters, that is, the number of scanning lines, the image display range, the number of images per second, etc., to the current 525 receiving system for viewing in this system. Is converted.

Problems to be Solved by the Invention When receiving the above-described converted high-definition television broadcast signal, it is possible to obtain an image quality that can be practically used by an interlaced scanning type receiving device that is currently frequently used. However, there is a technical problem that the image quality is significantly degraded when the above-described apparatus shown in FIG. This is because, in the temporal direction caused by the inter-frame and inter-field offset subsampling, that is, in the aliasing component in the time-frequency domain, in particular, the aliasing of the offset sampling between the fields is determined by the sequential scan conversion processing as aliasing in a vertical one horizontal two-dimensional space. This is because it occurs on the screen.

Therefore, when converting a high-definition television signal, it is desirable to prevent a significant deterioration in image quality from occurring in any of these receiving apparatuses. A three-dimensional spatiotemporal signal processing circuit similar to that designed in the above is required, and as a result of an increase in the scale of the conversion device, there is an economical problem that it becomes expensive.

An object of the present invention is to substantially eliminate the image quality deterioration caused by the simple high-definition television signal conversion apparatus even if the transmission signal of the high-definition television signal conversion apparatus has aliasing components due to inter-field offset subsampling. An object of the present invention is to provide a video signal processing device.

Means for Solving the Problems A video signal processing apparatus according to the present invention comprises a scanning conversion circuit for converting an input television signal of an interlaced scanning method into a sequential scanning signal, and a two-dimensional horizontal-vertical signal output from the scanning variable circuit. And a spatial filter circuit for performing spatial filtering, wherein the spatial filter is configured to operate as a low-pass filter in at least a predetermined operation mode.

The progressive scanning conversion circuit described above converts an interlaced scanning input television signal having N scanning lines and M images per second into a progressive scanning image signal having N scanning lines and M images per second. In the conversion, the moving part and the still part of the image in the input television signal are detected, and for the still image part, the interpolation scanning line is formed using the signal of the field adjacent to the processing field. The spatial filter has a plurality of signal processing modes and performs required signal processing on a sequentially scan-converted video signal. Number of scanning lines obtained by converting television signals
When processing 525 interlaced scanning television signals, aliasing components due to inter-field sub-sampling included in the input television signal are removed by controlling to operate as a two-dimensional low-pass filter. It is characterized by doing.

Embodiments The present invention will be described below in detail with reference to the drawings. FIG. 1 shows a video signal processing device according to an embodiment of the present invention. In the figure, the interlaced scanning television signal supplied to the signal input terminal 110 is converted into a digital video signal by the AD conversion circuit 210, and then converted by the progressive scanning conversion circuit 800 into a progressive scanning signal.

For example, a case where the input television signal is a standard signal according to the known NTSC system, that is, a case where the input television signal is a television signal produced using an NTSC camera and a television signal having a scanning parameter equivalent thereto is described. Then, this progressive scan conversion circuit 800 has 525 scan lines.
Book, field frequency 59.94 (H _Z ), frame frequency 29.
97 signal (H _Z), i.e. the horizontal scanning frequency 15.734 (K
H _Z horizontal scanning frequency input signals) is 31.468 (KH _Z) 525 scanning lines, the sent is converted into progressive scanning signal having a frame frequency of 59.94 (H _Z). Input television signal is NTSC
Encoded in a luminance signal (hereinafter abbreviated as Y signal)
And a carrier chrominance signal (hereinafter abbreviated as C signal) are frequency-multiplexed, the progressive scan conversion circuit uses a Y / C
A Y / C separation circuit for separation and an NTSC color decoder for demodulating the separated C signal and returning it to a color difference signal are arranged, and these Y signal and color difference signal are sequentially subjected to scan conversion processing. Be composed.

The spatial filter 810 filters the video signal supplied from the progressive scan conversion circuit 800 in a two-dimensional space of one vertical and one horizontal. The input television signal is a standard NTSC signal, that is, a Y signal. When the C signal and the C signal are accurately frequency-interleaved with a 1/2 line offset, the input signal discriminating circuit 820 controls the spatial filter 810 to substantially maintain the wideband transmission characteristics.
This is because the Y signal and the C signal supplied from the sequential scan conversion circuit 800 are not band-limited and the DA converter 5
Send to 1.

On the other hand, when the input television signal is a non-standard signal, for example, when a high-definition television signal based on the MUSE system is converted into a 525-line system that does not completely satisfy the NTSC standard by a converter having a simple configuration. In the case where the frequency interleaving relationship between the Y signal and the C signal is not maintained, the input signal discrimination circuit 820 sets the spatial filter 810 to have a two-dimensional vertical-horizontal spatial frequency characteristic as shown in FIG. After being controlled so as to have characteristics and removing the oblique high-frequency signal component from the signal sent from the sequential scan conversion circuit 800, the DA conversion circuit 51
As a video signal which has been sequentially scan-converted. The second figure, the vertical axis represents the vertical spatial frequency [nu (present), the horizontal axis represents the horizontal spatial frequency mu (MH _Z), the band for the signal component in the vertical and horizontal respectively only with the input television signal No limiting effect is given, and a signal passing characteristic is set to remove or suppress only the high-frequency signal component in the oblique direction on the screen. This can be obtained, for example, by cascading a vertical reduction filter and a horizontal reduction filter. The vertical spatial frequency 525/2 (lines) indicates the highest frequency in the vertical direction that can be reproduced without distortion in a video signal of 525 (lines) sequentially converted into scanning lines, and the horizontal spatial frequency μ ₁ indicates that the highest frequency of the Y signal of the NTSC video signal is about 4
(MH _Z), thus about twice the 8MH _Z of the maximum frequency, which is because the both doubled vertical and horizontal sampling frequency by interlacing.

The two-dimensional low-pass characteristic shown in FIG. 2 is an example of the characteristic of the spatial filter 810 when a non-standard signal is input, but is not necessarily limited to this characteristic in practicing the present invention. It is not necessary, and it can be realized from the viewpoints of the video signal bandwidth, circuit scale, and production cost of the input television signal.

The above-described AD conversion circuit 210 and DA conversion circuit 51 are for converting an analog input television signal into a digital signal, performing the above-described signal processing, and then supplying the digital signal to the display device 9 adapted to the analog signal. However, they are not indispensable for practicing the present invention, and can be appropriately selected.

Next, another embodiment of the present invention will be described with reference to FIG. In the figure, a signal input terminal 111 is coupled to an input of an AD converter 211, and the output of the AD converter 211 is Y / C
It is coupled to the input of separation circuit 812. This Y / C separation circuit
812 separates the Y signal and the C signal by separating the inter-line correlation or the inter-frame correlation when the NTSC composite signal is supplied to the signal input terminal 111 or by combining them, and outputs the Y signal to the conductor 813 and the conductor The C signal is sent to 814. In the above case, the signal selection circuit 213 selects the terminal b to which the conductor 814 is connected, that is, the broken line side, as shown in the figure, and the C signal demodulation circuit 214 sends out color difference signals, for example, I and Q signals. C signal scan conversion circuit to which the color difference signal is supplied
215 converts interlaced scanning signals into sequential scanning signals by signal processing within a field or between fields, and
The signal spatial filter 216 removes the high-frequency signal component in the oblique direction and supplies it to the inverse matrix circuit 817.

The Y signal sent out to the above-mentioned conductor 813 is sequentially converted from an interlaced scanning signal into a scanning signal by a Y signal scanning conversion circuit 815, and after removing a diagonal high frequency signal component by a Y signal spatial filter 816, The signal is supplied to the above-described inverse matrix circuit 817, is converted into three primary color signals of GBR by inverse matrix processing with the color difference signal, and is further supplied to the display device 9 via the DA conversion circuit 510. The signal input terminal 112 and the AD conversion circuit 212 are for separating and coupling the Y signal and the C signal,
In this case, the above-described signal selection circuit 213 selects the C signal sent from the AD conversion circuit 212 as shown on the a side, that is, as indicated by the solid line, and supplies it to the C signal demodulation circuit 214. When this separation and coupling is performed, the YC separation circuit 812 substantially stops the inter-line correlation or inter-frame correlation processing, and
The signal from 211 can be supplied to the Y signal scan conversion circuit 815 as it is.

FIG. 4 shows a configuration example of a spatial filter arranged according to the present invention. A signal selection circuit 8162 for selecting an input and an output of the filter is provided, and a C signal spatial filter 216 is a C signal constituting a low-pass filter in a vertical and horizontal two-dimensional space like the Y signal. 2D LPF2161
And signal selection circuit for selecting input and output of this filter
2162.

These signal selection circuits 8162 and 2162 are controlled by the input signal discrimination circuit 820, and when the input signal is a standard signal, both select the a side so as not to give a substantial band limiting effect. If the input signal is a non-standard signal, the b side is selected and both the Y signal and the C signal are controlled so as to perform a two-dimensional low-pass filtering process. The inverse matrix circuit 817 obtains three primary color signals of GBR. It is configured as follows. Therefore, for a so-called quasi-NTSC signal obtained by converting a high-definition television signal obtained by performing band compression using a field offset sub-sample such as a MUSE signal or in which the frequency interleaving relationship between the Y signal and the C signal is not accurately maintained. Only 2D LPF after progressive scan conversion
Since processing is performed, optimal signal processing can be performed on each signal.

The above-described Y signal spatial filter 816 may be configured as shown in FIG. 5. In this case, the output of the subtraction circuit 8163 that performs the difference processing between the input and the output of the Y signal two-dimensional LPF has two outputs.
A dimensional high-frequency signal component is obtained. The signal selection circuit 8162 outputs the two-dimensional high-frequency signal component to one terminal a and the other terminal b.
The side is equivalently grounded, and the control signal supplied via the conductor 8201 selects the a side for a standard signal and the b side for a non-standard signal. This signal selection circuit 8162
Selects the a side, the two-dimensional high-frequency signal component transmitted from the subtraction circuit 8163 is combined with the Y signal two-dimensional LPF by the addition circuit 8165 amplified by the amplification circuit 8164, and then transmitted to the conductor 8166. You. Therefore, in this case, the two-dimensional high-frequency signal component is enhanced, so that the sharpness of the standard signal is improved.

Also, when the signal selection circuit 8162 selects the b side, that is, for the non-standard signal, the input of the amplification circuit 8164 becomes no signal, so that the addition circuit 8165 is effectively a Y signal two-dimensional LPF 816.
Only the signal from 1 is sent out on conductor 8166. Therefore, for non-standard signals, it is possible to remove the undesired image quality degradation caused by the field offset sub-sample as in the case of FIG. 4, and to provide the advantage of improving the image quality for standard signals as described above. it can.

Effect of the Invention As described above, the present invention, when converting an interlaced scanning signal into a sequential scanning signal, arranges a spatial filter that receives the signal after the progressive scanning conversion as input and provides a two-dimensional low-pass characteristic for a non-standard signal. By removing or suppressing the two-dimensional high-frequency signal component as a spatial filter having,
The standard signal is subjected to broadband processing or two-dimensional high-frequency signal enhancement processing. By adding a small-scale circuit, it is optimal according to the state of the input television signal supplied to this signal processing device. Since the signal processing described above can be performed, a high-quality image can be reproduced without impairing the economical efficiency.

In the above description, the configuration in which the progressive scan conversion and the spatial filter are separately arranged has been described. However, these can be integrated as a circuit configuration, and the determination of the input television signal is also performed. It is needless to say that the present invention is not limited to the configuration of the example, and various modifications are possible in practicing the present invention.

[Brief description of the drawings]

1 is a block diagram of a video signal processing apparatus according to an embodiment of the present invention, FIG. 2 is a characteristic diagram of a spatial filter suitable for implementing the present invention, and FIGS. 3 and 4 are other embodiments of the present invention. , FIG. 5 is a partial specific configuration diagram, FIG. 6 is a diagram showing an example of converting a high-definition television signal into a current standard television signal, FIG. 7 is a known configuration diagram of a conversion device for converting a MUSE high definition television signal into an NTSC signal, and FIG. 8 is a configuration diagram showing a video signal processing device in a conventional example of the present invention. 110: signal input terminal, 210: AD conversion circuit, 800: sequential scanning conversion circuit, 810: spatial filter, 51: DA conversion circuit, 9: image display device, 820: input signal discrimination circuit.

Claims (5)

(57) [Claims] 1. An apparatus for converting an input television signal of an interlaced scanning system into an output television signal of a progressive scanning system by performing an interpolation process between fields, wherein a vertical-horizontal conversion is performed on a video signal obtained by progressive scanning conversion. And a spatial filter that effectively performs signal processing in a two-dimensional space. The spatial filter is used to convert a two-dimensional signal to a non-standard signal obtained by converting an input television signal from a high-definition television signal. A video signal processing device characterized as being a low-pass filter. 2. The signal processing characteristic of a spatial filter is determined by determining whether an input television signal is a standard signal or a non-standard signal of a predetermined color television system. The video signal processing device according to the above. 3. An input television signal having 1125 scanning lines.
2. The video signal processing apparatus according to claim 1, wherein the spatial filter is a two-dimensional low-pass filter when the MUSE type HDTV signal is a non-standard signal obtained by converting the number of scanning lines into 525 lines. 4. The video signal processing apparatus according to claim 2, wherein when the input television signal is a standard television signal according to the NTSC system, the spatial filter has substantially wideband transmission characteristics. 5. The video signal processing device according to claim 4, wherein the spatial filter enhances the two-dimensional high-frequency signal.