JPH0815336B2 - Video signal processing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing device for restoring a high-definition television signal band-compressed by offset subsampling.

[0002]

2. Description of the Related Art The band of high-definition television signals is 20 MH
z or more, and the band is compressed by some method when transmitting using a satellite or the like. As an effective technique for significantly compressing the band of high-definition television signals, MUSE (Mu
The ltiple Sub-Nyquist Sampling Encoding system has been proposed (Ninomiya, et al. "High-definition Television Satellite 1-Channel Transmission System (MUSE)", Technical Report TE of the Television Society.
BS 95-2, pages 37-42).

This MUSE system performs offset sub-sampling between fields and frames as shown in FIG. 5, and transmits 1/4 sampling points of the original signal sampling points to complete 4 fields. A picture is transmitted, and the band of the original signal is compressed to 1/4. On the receiving side, sample points that have not been transmitted (non-sample points) are interpolated from the transmitted sample points to restore the original signal. For example, for a still image area, interpolation is performed using sample points of the current field and all three past fields. On the other hand, for the moving image area, interpolation is performed only at the sample points in the transmitted field. As described above, since the still image portion and the moving image portion have different interpolation methods, the receiving side detects the movement of the image and switches the interpolation method to restore the image.

By the processing on the transmitting side and the receiving side as described above, high-definition television broadcasting can be enjoyed at home. However, the above signal processing circuit (MUSE decoder)
Is very expensive and it will take a considerable amount of time for it to be popularized for home use. Therefore, there is a device that converts a high-definition television signal into an existing standard television signal by using a system conversion circuit in order to display it on a standard television which is now widely used in homes and to record and reproduce it on a VTR. Among them, a video signal processing circuit that performs interpolation processing to restore an image with a simple configuration has been proposed. As a conventional video signal processing device, for example, "EDUSE-compatible MUSE / NTSC
Converter ”Technical Report BC, Television Society of 1990
S90-3 pp. 13-18.

FIG. 6 is a block diagram of this conventional video signal processing apparatus. Reference numeral 101 is an input terminal for inputting a MUSE signal, and 102 is a sampling point in a field to a non-sampling point for restoring a band-compressed MUSE signal. Interpolation circuit 103 for interpolating, a frame memory 103, an adder 104 for averaging, a motion detection circuit 105, a mixer 106,
Reference numeral 107 is an output terminal for taking out a high-definition television signal from which aliasing distortion has been removed.

The MUSE signal input to the input terminal 101 is interpolated from sample points in the field to non-sample points in order to restore the band-compressed signal in the interpolation circuit 102. The signal interpolated in the field corresponding to the moving image processing of the MUSE decoder by the interpolation circuit 102 has a signal passing characteristic as shown in the frequency characteristic diagram of FIG. The high-definition component of the high-definition television signal due to the offset sub-sampling of the MUSE system as shown in the frequency characteristic diagram of b) is reproduced as aliasing distortion and the image quality deteriorates. Therefore, the interpolated signal is supplied to the frame memory 103, and the output signal of the interpolation circuit 102 and the output signal of the frame memory 103 are added by the adder 10
In 4, an averaging process is performed between frames to obtain a signal from which aliasing distortion caused by interframe offset subsampling is removed. However, in a moving image, if the averaging process is performed between frames, image quality deterioration such as a double image occurs. Therefore, the motion detection circuit 105 detects the motion of the image, and the adder 104
And the interpolating circuit 10
The signal which has been processed in the field and is mixed in accordance with the amount of motion detected by the mixer 106 and has no image quality deterioration even in a moving image, and aliasing distortion caused by inter-frame offset subsampling. The signal from which is removed is obtained at the output terminal 107.

[0007]

However, in the above-mentioned configuration, the adder 104 performs the averaging process between frames, so that the aliasing distortion caused by the inter-frame offset sub-sampling is removed.
Although the flicker component of Hz becomes invisible, the band-compressed MUSE signal further includes aliasing distortion due to the inter-field offset subsampling.
Since the high-frequency component of 2 MHz or more is reproduced while being folded back to the vertical high-frequency band, the vertical line portion of the image appears to have a jagged distortion, which causes a feeling of strangeness.

The present invention solves the above problems and is capable of removing not only aliasing distortion caused by inter-frame offset subsampling but also aliasing distortion caused by uncomfortable inter-field offset subsampling. An object is to provide a processing device.

[0009]

In order to achieve the above object, the present invention inputs a high-definition television signal band-compressed by offset sub-sampling, and samples in a field to restore the sub-sampled signal. Interpolation means for interpolating non-sampled points from points, first and second field memories cascaded for storing the interpolated signal, output of the interpolation means and first field memory First adder for averaging inter-fields from the output of the above, a second adder for averaging inter-frames from the output of the interpolating means and the output of the second field memory, and input / output of two field memories From the output of the first adder and the output of the correlation adder, the field difference and the frame difference are detected from the output, and the switching signal is output according to the magnitude of the difference. Signal switching device for switching the output of the adder, motion detecting device for detecting the motion of the image from the output of the interpolating device and the output of the second field memory, and the output of the signal switching device according to the detected motion. A mixer is provided for mixing the outputs of the interpolating means.

A high-definition television signal band-compressed by offset subsampling is input, and first and second cascaded field memories for storing the input television signal and two field memories are connected. First, second and third interpolation means for interpolating non-sampled points from sampled points in the field to recover the sub-sampled signals from the input and output, and the output of the first interpolation means and A first adder for averaging inter-fields from the output of the second interpolating means, and a second adder for averaging inter-frames from the outputs of the first and third interpolating means And a correlation discriminator that detects a field difference and a frame difference from the outputs of the three interpolators and outputs a switching signal according to the magnitude of the difference, and an output of the first adder by the output of the correlation discriminator. From a signal switcher for switching the output of the second adder, the output of the first interpolating means and the output signal of the third interpolating means, or from the input of the first field memory and the output of the second field memory. It comprises a motion detecting means for detecting the motion of an image and a mixer for mixing the output of the signal switching device and the output of the first interpolation means according to the detected motion.

[0011]

According to the present invention, the television signal interpolated in the field is supplied to the two field memories by the above-mentioned structure, and the aliasing distortion caused by the inter-field offset sub-sampling is removed by taking an average between the fields. Switching between a signal and a signal from which aliasing distortion caused by inter-frame offset sub-sampling is removed by averaging inter-frames, by discriminating which distortion is larger based on the magnitude relationship between the inter-field difference and the inter-frame difference. Thus, aliasing distortion caused by not only interframe but also interfield offset subsampling can be removed. Further, by detecting the motion of the image and performing the averaging process between the fields or frames and the intra-field averaging process, it is possible to prevent the deterioration of the image quality such as the occurrence of a double image in the moving image. it can.

Further, the capacity of the field memory can be reduced by providing the field memory so as to store the signal before the interpolation processing.

[0013]

(Embodiment 1) FIG. 1 is a block diagram of a video signal processing apparatus according to a first embodiment of the present invention. In FIG. 1, 11 is an input terminal for inputting a MUSE signal, 12 is an interpolation circuit for interpolating a non-sample point from a sample point in the field to restore a band-compressed MUSE signal, 13, 1
4 is a field memory, 15 and 16 are adders for performing averaging processing, 17 is a field difference detection circuit for detecting aliasing distortion due to inter-field offset subsampling, and 18 is a frame difference for detecting aliasing distortion due to inter-frame offset subsampling. A detection circuit, 19 is a correlation determination circuit that determines which of the field and frame folding distortion is larger, 20 is a signal switcher, and 2
Reference numeral 1 is a motion detection circuit, 22 is a mixer, and 23 is an output terminal for taking out a high-definition television signal restored and having aliasing distortion removed.

Explaining the mutual relation and operation of each of the above-mentioned components, the MUSE signal input to the input terminal 11 is unsampled from the sampling points in the field in order to restore the band-compressed signal in the interpolation circuit 12. Point interpolation is performed. The interpolated signal is then cascaded to
The output signals of the interpolating circuit 12 and the field memory 13 are supplied to the individual field memories 13 and 14, and the adder 15 performs inter-field averaging processing to cause aliasing distortion due to inter-field offset subsampling. The signal is obtained by removing the signal. On the other hand, the interpolation circuit 12
And the output signal of the field memory 14 are subjected to averaging processing between frames by an adder 16 to obtain a signal from which aliasing distortion due to interframe offset subsampling is removed. The input / output signals of the two field memories 13 and 14 are the field difference detection circuit 1
7 and the frame difference detection circuit 18 to detect the aliasing distortion due to the inter-field offset sub-sampling and the aliasing distortion due to the inter-frame offset sub-sampling, and which of the aliasing distortion between the field and the frame is larger in the correlation determining circuit 19? Signal switching unit 20 is controlled so as to pass the signal from which the stronger aliasing distortion has been removed, and the signal and the adder from which the aliasing distortion due to the inter-field offset subsampling output from the adder 15 has been removed. The signal output from 16 from which the aliasing distortion due to the inter-frame offset subsampling is removed is switched.

Further, the motion detecting circuit 21 detects the motion of the image from the input signal of the field memory 13 and the output signal of the field memory 14, and performs an averaging process between the fields or frames output from the signal switch 20. And the signal output from the field interpolation circuit 12 which has been subjected to the intra-field processing.
In step 2, since the mixing process is performed according to the amount of motion detected by the motion detection circuit 21, image quality deterioration (2
A signal in which the aliasing distortion is almost removed without any occurrence of a double image is obtained at the output terminal 23.

As described above, according to the first embodiment,
After the field interpolation corresponding to the moving image processing of the MUSE decoder is performed in the interpolation circuit 12, the aliasing distortion occurring in the still image is added using the output signal of the interpolation circuit 12 and the output signal of the field memory 13. A signal from which aliasing distortion caused by inter-field offset sub-sampling is removed is obtained by performing inter-field averaging in the regenerator 15, and the output signal of the interpolation circuit 12 and the output signal of the field memory 14 are used. By performing averaging processing between frames in the adder 16, a signal in which aliasing distortion caused by inter-frame offset subsampling is removed can be obtained. These two signals are the fields for detecting the absolute value of the inter-field difference from the adjacent three field signals as shown in FIG. 2 in order to detect the situation of the aliasing distortion between the field and the frame from the adjacent three field signals. By providing the difference detection circuit 17, the frame difference detection circuit 18 that detects the absolute value of the inter-frame difference, and the correlation determination circuit 19 that compares the two differences and detects the magnitude relationship between them, as shown in FIG. The signal switching unit 20 switches and outputs a signal obtained by processing a signal having a stronger aliasing distortion according to the magnitude of the aliasing distortion between fields and the aliasing distortion between frames that is a flicker component of 15 Hz. As a result, the signal switch 20 obtains a signal from which aliasing distortion due to field and interframe offset subsampling is removed.

(Second Embodiment) FIG. 4 is a block diagram of a video signal processing apparatus according to a second embodiment of the present invention. In FIG. 4, 31 is an input terminal for inputting a MUSE signal, 3
Reference numerals 2, 33 are field memories, 34, 35, 36 are interpolation circuits for interpolating non-sample points from sample points in the field to restore the band-compressed MUSE signal, and 37, 38 are additions for performing averaging processing. , 39 is a field difference detection circuit for detecting aliasing distortion due to inter-field offset subsampling, 40 is a frame difference detection circuit for detecting aliasing distortion due to inter-frame offset subsampling, and 41 is either the field or frame aliasing distortion. Correlation determination circuit for determining whether or not, 42 is a signal switcher, 43 is a motion detection circuit, 44 is a mixer, 4
Reference numeral 5 is an output terminal for taking out a high-definition television signal that has been restored and has the aliasing distortion removed.

The relationship and operation of each constituent element of this embodiment will be described. The MUSE signal input to the input terminal 31 is stored in the cascade-connected two-field memories 32 and 33, and the interpolation circuits 34, 35 and 36. In, the band-compressed signals of three adjacent fields are interpolated from sample points in the field to non-sample points. Next, the output signal of the interpolating circuit 34 and the output signal of the interpolating circuit 35 are subjected to averaging processing between fields by the adder 37 to obtain a signal from which aliasing distortion due to interfield offset subsampling is removed. can get. On the other hand, the output signal of the interpolating circuit 34 and the output signal of the interpolating circuit 36 are subjected to averaging processing between frames by an adder 38 to obtain a signal from which aliasing distortion caused by interframe offset subsampling is removed. To be In addition, the interpolated signals of the adjacent three fields output from the interpolating circuits 34, 35 and 36 are the field difference detecting circuit 39 and the frame difference detecting circuit 4.
0, the aliasing distortion due to the inter-field offset subsampling and the aliasing distortion due to the inter-frame offset subsampling are detected, and the correlation discrimination circuit 41 is detected.
Which is larger than the inter-frame offset distortion between the field and the frame, the signal from which the inter-field offset subsampling-induced aliasing distortion is output from the adder 37 and the inter-frame offset output from the adder 38 are determined. The signal switch 42 is controlled so that the signal from which the aliasing distortion caused by subsampling is removed and the signal from which the aliasing distortion is stronger is removed.

Further, the motion detecting circuit 43 detects the motion of the image from the output signal of the interpolating circuit 34 and the output signal of the interpolating circuit 36, and averages the fields or frames output from the signal switching circuit 42. In the moving image, the processed signal and the signal output from the interpolation circuit 35 which has been processed in the field are mixed according to the amount of motion detected by the motion detection circuit 43. Also, a signal in which the aliasing distortion is almost removed without image quality deterioration (such as occurrence of double image) is obtained at the output terminal 45.

As described above, according to the second embodiment,
By providing a field memory for obtaining signals between three adjacent fields so as to store a television signal before being interpolated, aliasing distortion caused by inter-field and inter-frame offset sub-sampling of the MUSE system is almost eliminated. It can be completely removed and the field memory capacity can be cut in half.

In the first embodiment, the field difference detection circuit 17 uses all the signals of the three adjacent fields, but it may detect the difference between the preceding and succeeding fields. Also, the motion detection circuit 21
Detects the motion of an image from a signal between 1 frames, but it is also possible to derive a signal between 1 frames and detect the motion from a signal between 2 frames. In the second embodiment as well, the motion detection circuit 43 is interpolated 1
Although the motion of the image is detected from the signal between the frames, the motion of the image may be detected from the signal between the frames before being subjected to the interpolation process, and the same as in the first embodiment. It goes without saying that the motion may be detected from the signal between the two frames.

[0022]

As is apparent from the above embodiments, according to the present invention, non-sample points are interpolated from sample points in a field to restore a high-definition television signal band-compressed by offset subsampling. Interpolation means, first and second field memories cascaded to store the interpolated signal, and interfield averaging from the output of the interpolation means and the output of the first field memory A field difference and a frame difference are detected from the input and output of the first adder, the output of the interpolating means and the output of the second field memory, and the average of the frames. , A correlation discriminating means for outputting a switching signal according to the magnitude of the difference, and a signal switching circuit for switching the output of the first adder and the output of the second adder by the output of the correlation discriminating means. An output device, an output of the interpolating device and a motion detecting device for detecting the motion of the image from the output of the second field memory, and an output of the signal switching device and an output of the interpolating device according to the detected motion. Since a mixer is provided, the image quality does not deteriorate even in moving images with a simple configuration, and not only aliasing distortion caused by inter-frame offset subsampling, but also aliasing distortion caused by interfield offset subsampling with a sense of discomfort A video signal processing device for removal can be provided.

In addition, first and second cascaded field memories for storing high-definition television signals band-compressed by offset subsampling, and 2
First, second and third interpolation means for interpolating non-sampled points from sampled points in the field to recover the sub-sampled signals from the inputs and outputs of one field memory,
A first adder that averages between fields from the output of the first interpolation means and the output of the second interpolation means, and the frame from the output of the first interpolation means and the output of the third interpolation means. The second adder for averaging the two, the correlation determining means for detecting the field difference and the frame difference from the outputs of the three interpolating means, and outputting the switching signal according to the magnitude of the difference, and the correlation determining means From a signal switcher for switching the output of the first adder and the output of the second adder according to the output, the output of the first interpolation means and the output of the third interpolation means, or of the first field memory. A motion detecting means for detecting the motion of the image from the input and the output of the second field memory, and a mixer for mixing the output of the signal switching device and the output of the first interpolation means according to the detected motion are provided. Therefore, the image quality does not deteriorate even in moving images, Can provide a video signal processing apparatus can be reduced also memory capacity is possible aliasing also removed due to inter-frame and inter-field offset subsampling with. Its practical effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram of a video signal processing device according to a first embodiment of the present invention.

FIG. 2 is a detailed block diagram of a circuit for detecting a situation of aliasing distortion between a field and a frame in the embodiment.

FIG. 3 is a characteristic diagram for explaining an operation for discriminating folding distortion in the example.

FIG. 4 is a block diagram of a video signal processing device according to a second embodiment of the present invention.

FIG. 5 is a principle diagram for explaining a band compression method by MUSE offset subsampling.

FIG. 6 is a block diagram of a conventional video signal processing device.

FIG. 7 is a frequency characteristic diagram for explaining the occurrence of aliasing distortion caused by MUSE offset subsampling in field interpolation processing.

[Explanation of symbols]

 12, 34, 35, 36 ... Field interpolation circuit 13, 14, 32, 33 ... Field memory 15, 16, 37, 38 ... Adder 17, 39 ... Field difference detection circuit 18 , 40 ... Frame difference detection circuit 19, 41 ... Correlation determination circuit 20, 42 ... Signal switcher 21, 43 ... Motion detection circuit 22, 44 ... Mixer

Claims (5)

[Claims] 1. Interpolation means for inputting a high-definition television signal band-compressed by offset sub-sampling and interpolating non-sampled points from sampled points in a field to restore the sub-sampled signal, First and second field memories cascaded to store the interpolated signal, and a first inter-field average from the output of the interpolation means and the output of the first field memory. An adder, a second adder for taking an average between frames from the output of the interpolation means and the output of the second field memory, and a field difference and a frame from the input and output of the first and second field memories. Correlation determining means for detecting a difference and outputting a switching signal according to the magnitude of the difference, and output of the first adder and second addition by the output of the correlation determining means. Video signal processing apparatus provided with a signal switching unit for switching the output of. 2. Motion detection means for detecting the motion of an image from the output of the interpolation means and the output of the second field memory,
The video signal processing device according to claim 1, further comprising a mixer that mixes the output of the signal switching unit and the output of the interpolation unit according to the detected motion. 3. A first and a second cascade connected for inputting a high-definition television signal band-compressed by offset subsampling and storing the input television signal.
Field memory, and first, second and third interpolating non-sampled points from sampled points in the field to restore signals subsampled from the input and output signals of the first and second field memories. Interpolation means, a first adder for taking an average between fields from the output of the first interpolation means and the output of the second interpolation means, the output of the first interpolation means and the A second adder that averages the frames from the output of the third interpolating means, and a field difference and a frame difference are detected from the outputs of the first, second and third interpolating means, and the magnitude of the difference is detected. Correlation determining means for outputting a switching signal in accordance with the degree of
Video signal processing device comprising a signal switcher for switching between the output of the adder and the output of the second adder. 4. A motion detecting means for detecting a motion of an image from the output of the first interpolating means and the output of the third interpolating means, and the signal switching according to the motion detected by the motion detecting means. 4. The video signal processing device according to claim 3, further comprising a mixer for mixing the output of the mixer and the output of the first interpolation means. 5. A first field memory input and the second field memory
A motion detection circuit for detecting the motion of the image from the output of the field memory, and a mixer for mixing the output of the signal switcher with the output of the first interpolation means in accordance with the motion detected by the motion detection means. The video signal processing device according to claim 3, further comprising: