JPH0662344A - Scanning line number converter - Google Patents

Abstract

PURPOSE:To convert the number of scanning lines without deteriorating resolution for the still picture of a MUSE signal. CONSTITUTION:A MUSE/NTSC converter is provided with a first vertical low-pass filter 11 which executes vertical filtering processing in a field to the MUSE signal so as to convert the number of scanning lines and a second vertical low-pass filter 12 which executes inter-field vertical filtering processing to the MUSE signal so as to convert the number of scanning lines. A mixing circuit 13 selects the output of the first vertical low-pass filter 11 for the movement area of the MUSE signal based on a movement detecting signal (k) and generates and outputs the signal for NTSC based on the outputs of the first and second low-pass filters 11 and 12 for the still area. The number of taps of the filter is substantially increased concerning the still area so that resolution is improved.

Description

Detailed Description of the Invention

[0001]

This invention relates to MUSE / NTSC
The present invention relates to a scanning line number conversion device used in a converter or the like and converting the number of scanning lines from 1125 to 525, for example.

[0002]

2. Description of the Related Art In recent years, MUSE (multiple sub-Nyquists ampling encodin) has been developed for high-definition satellite broadcasting.
Various MUSE / NTSC converters have been developed to make it possible to receive a television signal based on the g) system by a television receiver for the NTSC system, which is the current standard system. To convert MUSE signal to NTSC signal, MU
It is necessary to reproduce the SE signal into an image of 1125 lines at the high-definition scan rate and further convert the number of scanning lines from 1125 to 525. Known scanning line number conversion devices of this type include a two-line → one-line system, a five-line → two-line system, and a three-line → one-line system. It is also used as a vertical low-pass filter for removing aliasing distortion.

FIG. 6 shows the configuration of a conventional scanning line number converting apparatus. The conversion device is composed of a vertical low-pass filter that performs an intra-field operation. In this apparatus, the signals delayed by 1 line and 2 lines by the 1-line delay circuits 1 and 2 and the signal of the current line are appropriately weighted by the multipliers 3, 4 and 5, respectively, and then added by the adder 6. By doing so, the number of scanning lines is converted.

[0004]

However, in the above-mentioned conventional scanning line number conversion device, since the intra-field processing is the basic, the number of taps of the filter is limited,
The pass band characteristic of the filter becomes a gradual characteristic, for example, as shown in FIG. Therefore, although the moving image area is acceptable, the resolution of the still area is conspicuously deteriorated.

The present invention has been made in order to solve such a problem, and an object thereof is to provide a scanning line number conversion device capable of preventing deterioration of resolution of a still image.

[0006]

In the scanning line number converting apparatus according to the present invention, a first video signal based on the first scanning line number and a second video image based on the second scanning line number are provided. In a scanning line conversion device for converting into a signal, a first vertical filter for converting the number of scanning lines by applying vertical filtering processing within a field to the first video signal, and a field interval for the first video signal. Second vertical filter for converting the number of scanning lines by performing the vertical filtering process of No. 2 and the second video signal based on the output of the first vertical filter for the motion area of the first video signal. And outputs the first image signal to the still region of the first video signal.
And a second video signal generating means for generating and outputting the second video signal based on the output of the second vertical filter.

[0007]

According to the present invention, for the moving area of the first video signal, the second video signal is generated using the output of the first vertical filter based on the intra-field operation.
In addition, for the still region of the first video signal, not only the output of the first vertical filter but also the output of the second vertical filter based on the inter-field arithmetic processing is used to perform the second
Is generated. Therefore, since the number of taps of the filter is increased in the static region, the pass band characteristic of the filter can be made steep, which prevents deterioration of resolution. In addition, since the inter-field correlation is high in the static area, no problem occurs due to inter-field arithmetic processing. On the other hand, with respect to the motion area, the deterioration of resolution is not so noticeable from the beginning, so there is no problem.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an M according to an embodiment of the present invention.
3 is a block diagram showing the configuration of a scanning line number conversion circuit 10 in a USE / NTSC converter. FIG.

The input MUSE signal is, for example, a signal obtained by removing a phase shift due to inter-line offset subsampling by a horizontal filter, and is supplied to a first vertical lowpass filter 11 and a second vertical lowpass filter 12. The input signal supplied to the first vertical low-pass filter 11 is sequentially input to the 1-line delay circuits 21 and 22 and delayed by 1 line and 2 lines, respectively.
The input signal, the signal delayed by one line, and the signal delayed by two lines are respectively multiplied by the multiplier 2
3, 24, 25 are weighted by the coefficients a ₁ , a ₂ , a ₃ and added by the adder 26. On the other hand, the input signal supplied to the second vertical low-pass filter 12 is sequentially input to the 1-field delay circuit 31 and the 1-line delay circuit 32, and delayed by 1 field and 1 field + 1 line, respectively. The signal delayed by 1 field, the signal delayed by 1 line by the 1-line delay circuit 21, and the signal delayed by 1 field + 1 line are respectively multiplied by coefficients b ₂ , Weighting is performed by b ₁ and b ₃ , and the sum is added by the adder 36. The outputs A and B of these vertical low-pass filters 11 and 12 are supplied to the mixing circuit 13. The mixing circuit 13 combines the outputs A and B according to the motion detection signal k separately generated from the MUSE signal, and outputs an output signal obtained by converting the number of scanning lines.

Next, the operation of the scanning line number conversion circuit 10 thus constructed will be described. When the MUSE signal is input to the first vertical low-pass filter 11, the signal is multiplied by the coefficient a ₁ , the signal one line before is multiplied by the coefficient a ₂ , and the signal two lines before is multiplied by the coefficient a _3. Has been
These are added. The signals used for the calculation here have a spatial positional relationship as shown by "O" in FIG.
The target pixel is a pixel that is multiplied by the coefficient a _2, and the level of the target pixel is determined using upper and lower pixels in the same field. The coefficients a ₁ , a ₂ and a ₃ can be arbitrarily set according to the filter characteristics to be set, for example, 1/4, 1/2,
It is set to 1/4 etc. Further, in the two-to-one system, the center of gravity of the coefficient may be changed for each field.

On the other hand, when the MUSE signal is input to the second vertical low pass filter 12, the signal one line before the signal is multiplied by the coefficient b _{1 and} the signal one field before is multiplied by the coefficient b _2. The signal one field + 1 line before is multiplied by the coefficient b ₃ , and these are added. The signals used for the calculation here have a spatial positional relationship as shown by "Δ" in FIG. The target pixel is a pixel that is multiplied by the coefficient b _1, and the level of the target pixel is determined using the pixels above and below the previous field. The coefficients b ₁ , b ₂ and b ₃ can be arbitrarily determined like the coefficients a _{1 to} a ₃ .

The signal A output from the first vertical low pass filter 11 and the signal B output from the second vertical low pass filter 12 can be expressed by the following equation 1.

[0013]

## EQU1 ## A = a ₁ + a ₂ z ^-H + a ₃ z ^-2H B = b ₁ + b ₂ z ^-f + b ₃ z ^-fH

Here, z ^-H represents one line delay and z ^-f represents one field delay. The mixing circuit 13 mixes these signals A and B as shown in the following Expression 2.

[0015]

## EQU2 ## X = kA + (1-k) (A + B) / 2

Here, k is a motion detection signal, and 0≤k≤1.
, And k≈0 for still images and k≈1 for moving images. Therefore, the signals output from the mixing circuit 13 are represented by the following Expression 3 depending on the image situation.

[0017]

## EQU00003 ## Still image (k.apprxeq.0) X.apprxeq. (A + B) / 2 Moving image (k.apprxeq.1) X.apprxeq.A Slightly moving image (k.apprxeq.0.5) X.apprxeq. (3/4) A + (1
/ 4) B

As is clear from the above, in the moving image,
Only the output signal A of the vertical low pass filter 11 is selected as the conversion signal. In this case, since the number of taps is the same as the conventional one, the pass band characteristic of the filter is as shown in FIG. 3A, and the resolution in the high frequency range is deteriorated, but in this case, since it is a moving image, the deterioration is almost noticeable. Absent. Further, in the still image, the output signals A of the vertical low-pass filters 11 and 12,
Since B is included in the same ratio, the number of taps of the filter is substantially doubled as compared with the former, and the pass band characteristic of the filter also has a steep characteristic as shown in FIG. can do. Therefore, the resolution in the high frequency band is improved and the image quality is improved.

Although a known method such as taking a difference between two frames can be used as the motion detecting method, in this case, there is a problem that a memory for two frames must be used. Therefore, for example, the motion detection circuit 40 as shown in FIG. 4 may detect the motion. That is, MU
Since the SE signal is subjected to inter-frame offset sub-sampling, the pixel phase is shifted by 180 ° between frames. Therefore, the vertical averaging circuit 42 and the horizontal averaging circuit 43 interpolate pixels in the vertical and horizontal directions. Then, the subtracters 44 and 45 calculate the differences between the pixels interpolated in the vertical and horizontal directions and the target pixel one frame before which is delayed by the one-frame delay circuit 46, respectively. Then, the absolute value calculation circuits 49 and 50 calculate the absolute values, the minimum value is selected by the minimum value selection circuit 51 in order to prevent erroneous detection, and then the motion signal is stretched in the vertical and horizontal directions by the non-linear processing circuit 52. The motion detection signal k is obtained. In addition,
Here, the low-pass filters 41 and 48 are filters for removing aliasing distortion included in 4 MHz or more of the MUSE signal.

FIG. 5 is an overall block diagram including the scanning line conversion circuit 10 and the motion detection circuit 40. The motion detection signal k, which is the output of the motion detection circuit 40, is a still image signal C that has passed through the 1-frame delay circuit 61 and the interframe interpolation circuit 62, and a moving image signal that has passed through the field interpolation circuit 63. It is supplied to the mixing circuit 64 which mixes with D. The mixing circuit 64 uses the motion detection signal k to output the output X ′ shown in the following Expression 4.

[0021]

## EQU00004 ## X '= kC + (1-k) D

Further, the motion detection signal k is supplied to the scanning line number conversion circuit 10 through the delay circuit 65 for adjusting to the delay of the vertical filtering process in the scanning line number conversion circuit 10 of this embodiment. Has become. Thereby, the phase of the motion detection signal k and the phase of the target pixel can be matched.

The present invention is not limited to the above-described embodiment, and the structure of the first and second vertical filters, the number of taps, and the like depend on the conversion system of the number of scanning lines. Various modifications can be implemented without departing from the above.

[0024]

As described above, according to the present invention,
For the motion area of the first video signal, the output of the first vertical filter based on the intra-field operation is used to generate the second video signal.
For the still region of the first video signal, the first vertical filter output and the second vertical filter output based on the inter-field arithmetic processing are used to generate a second video signal. Since the second video signal is generated, it is possible to improve the resolution for the still region.

[Brief description of drawings]

FIG. 1 is a MUSE / NTSC according to an embodiment of the present invention.
It is a block diagram of a scanning line number conversion circuit in a converter.

FIG. 2 is a diagram showing a spatial positional relationship of pixels used for calculation in the same circuit.

FIG. 3 is a diagram showing respective pass band characteristics of a still image and a moving image of the same circuit.

FIG. 4 is a block diagram showing an example of a motion detection circuit applied to the same circuit.

FIG. 5 is an overall block diagram including the motion detection circuit and the scanning line number conversion circuit.

FIG. 6 is a block diagram of a scanning line number conversion circuit in a conventional MUSE / NTSC converter.

[Explanation of symbols]

1, 2, 21, 22, 32, 47, 61, 62 ... 1 line delay circuit, 3-5, 23-25, 33-35 ... Multiplier, 6, 26, 36, 63, 65 ... Adder, 10 ... scanning line number conversion circuit, 11 ... first vertical low-pass filter, 1
2 ... 2nd vertical low pass filter, 13, 64 ... Mixing circuit, 31 ... 1 field delay circuit, 40 ... Motion detection circuit, 41, 48 ... Low pass filter, 44, 45 ... Subtractor, 49, 50 ... Absolute value calculation Circuits, 51 ... Minimum value selection circuit, 52 ... Non-linear processing circuit, 61 ... 1 frame delay circuit, 62 ... Interframe interpolation circuit, 63 ... Field interpolation circuit, 65 ... Delay circuit.

Claims (1)

[Claims] 1. A scanning line conversion device for converting a first video signal based on a first scanning line number into a second video signal based on a second scanning line number, wherein: A first vertical filter for converting the number of scanning lines by performing vertical filtering processing in the field on the signal, and a second vertical filter for performing vertical filtering processing between fields on the first video signal to convert the scanning line number For the vertical filter and the moving area of the first video signal, the second video signal is generated and output based on the output of the first vertical filter, and the second video signal is output to the still area of the first video signal. On the other hand, based on the outputs of the first and second vertical filters, the second vertical filter is used.
And a second video signal generating means for generating and outputting the video signal of 1.