JPH07274131A - Still image processing circuit for muse decoder - Google Patents

Abstract

PURPOSE:To obtain the emphasis of a component only in the pass band of a still image signal without increasing a line memory. CONSTITUTION:The output signal of an inter-field insertion filter 3 in a still image system is inputted to an adder 26. The output signals of a line delay circuits 4-10 group in the inter-field insertion filter 3 are guided to a two-dimensional filter consisting of a vertical low pass filter 23 and a horizontal band pass filter 24, and the filter output is inputted to the adder 26 through a coefficient unit 25 as an emphasis signal. Thus, folded interruption is prevented from being emphasized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a still image processing circuit of a MUSE decoder for demodulating a band-compressed high-definition television signal into a broadband high-definition television signal. It is intended to improve.

[0002]

2. Description of the Related Art As a method of band-compressing a broadband high-definition television signal at a practical level for transmission, MUSE (Multiple Sub-Nyqist Sampling) for subsampling the original high-definition television signal in four fields Enc
oding) system (“A new transmission system for high-definition television-MU
SE- ", NHK Giken monthly report, Ninomiya, 27, No. 7, 1984).

FIG. 6 shows the configuration of a decoder for demodulating the band-compressed high-definition television signal (MUSE signal) into the original broadband high-definition television signal. The MUSE signal S1 input from the input terminal 36 becomes a signal S2 by first interpolating the signal of the current field and the signal of one frame (2 fields) before by the interframe interpolating circuit 37. This signal S2 is interpolated with the signal one field before by the next inter-field interpolation circuit 38 and becomes a signal S3 which is field interpolated using the data for four fields.
This signal S3 is an image signal for a still image. on the other hand,
The image signal S4 for the moving image is the field interpolation circuit 3
In step 9, the data is interpolated from the data of only one field. The still image signal S3 and the moving image signal S4 are mixed by the mixing circuit 41 at a ratio based on the amount of motion of the image detected by the motion detection circuit 40, and output as the high-definition television signal S5.

FIG. 7 shows an example of an inter-field interpolation circuit 38 for still picture processing used in the decoder circuit for the MUSE signal. In this figure, the two-dimensional filter for inter-field interpolation is composed of vertical 9-tap filters.

A signal (hereinafter referred to as a 0H signal) S11 in which the signal of the current field and the signal of the field two fields before, which are input from the input terminal 1, are interpolated between frames is used as the field memory 2
In, the signal S16 (hereinafter referred to as 0.5H signal) is obtained after being delayed by about 1 field period (563 line period). These signals S11 and S16 are input to the inter-field interpolation filter 3 in the next stage. The inter-field interpolation filter 3 band-limits the high frequency components in the diagonal direction of the image.

In the inter-field interpolation filter 3, 0
The H signal S11 is a signal (hereinafter referred to as a 1H signal) S1 delayed by one line period by one line delay circuits 4, 5, 6, and 7 which delay the input signal by approximately one line period.
2, 2 line period delayed signal (hereinafter 2H signal) S13, 3
A signal delayed by a line period (hereinafter, 3H signal) S14 and a signal delayed by a line period (hereinafter, 4H signal) S15 are provided.
Of these, the 0H signal S11 and the 4H signal S15 are the adder 1
The signal S20 (hereinafter 0H + 4H) is added by 1 and
Further, the 1H signal S12 and the 3H signal S14 are added by the adder 12 to be a signal S21 (hereinafter 1H + 3H).

Further, a 0.5H signal S16 is delayed by one line period by the one-line delay circuits 8, 9 and 10 for delaying the input signal by approximately one line period (hereinafter referred to as 1.5H signal) S17, two lines. A signal delayed by a period (hereinafter, 2.5H signal) S18 is a signal delayed by three lines (hereinafter, 3.5H signal) S19. Of these, 0.
The 5H signal S16 and the 3.5H signal S19 are added by the adder 13 to form a signal S22 (hereinafter 0.5H + 3.5H), and the 1.5H signal S17 and the 2.5H signal S18 are added by the adder 14. Signal S23 (hereinafter 1.5H + 2.
5H).

These signals S20, S21, S13, S
22 and S23 are horizontal filter groups 15, 16 and 1 of the next stage.
7, 18 and 19 and the output signal thereof is added by the adder 20.
Then, the signal is fully added to form a signal S29. Here, the horizontal filter groups 15, 16, 17, 18, 19 and the adder 20
Represents a two-dimensional filter circuit, and its output signal S29 is a signal in a two-dimensional frequency band as shown in FIG. 8A.

This signal S29 is sent to the enhancer 33 of the next stage.
Entered in. In this enhancer 33, a horizontal BPF (band pass filter) 34 is used to convert the signal S29 from the signal S29 shown in FIG.
A signal S30 having a band as shown in (B) is extracted, multiplied by K in a coefficient unit 35, and added to an original signal S2 in an adder 36.
As shown in FIG. 8 (C), the signal S3 in which the horizontal middle-high range is boosted in the horizontal mid-high range is added to the signal S3.
1 is obtained. Here, the coefficient unit 35 may have a fixed coefficient, or may have the above K variable by an external control. Further, the coefficient unit 35 may be based on the non-linear characteristic so that the noise component is not unnecessarily emphasized.

[0010]

As described above, M
In the USE signal decoder circuit, in the configuration in which the signal passed through the inter-field interpolation filter is horizontally emphasized,
Folding interference that occurs when the cutoff area of the inter-field interpolation filter is not sufficiently dropped because the inter-field interpolation filter is also subjected to enhancement processing.
There is a problem that image quality is deteriorated due to emphasis.

Therefore, an object of the present invention is to provide a still picture processing circuit of a MUSE decoder which can enhance a still picture signal without emphasizing folding interference in the decoder of the MUSE signal.

[0012]

According to the present invention, an MUSE signal is input and interfield interpolating means for performing interfield interpolating processing is used in cascade connection between the interfield interpolating means. Means for performing filtering processing in the vertical and horizontal directions using the output signals of the plurality of one horizontal period delay means, and adding the obtained signals to the output signal of the inter-field interpolation means as an enhancement compensation signal. Prepare

[0013]

By the above means, enhancement can be obtained only for the components within the pass band of the inter-field interpolation filter, and it is possible to prevent deterioration of image quality such as emphasizing folding interference. Further, by using the line memory output inside the inter-field interpolation filter, it is possible to suppress an increase in hardware scale.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention. The same parts as those of the conventional inter-field interpolation circuit 3 shown in FIG. 7 are designated by the same reference numerals. Therefore, the configuration of different parts will be described.

In this embodiment, the signals S20, S21, S
13, S22 and S23 are further input to the vertical low pass filter (vertical LPF) 23. And this vertical L
Output signal S41 filtered by PF23
The (vertical low-frequency component) is subjected to horizontal filtering processing by the horizontal band pass filter (horizontal BPF) 24 to become a signal S42, multiplied by k in the coefficient unit 35 at the next stage, and input to the adder 26. (Signal S43). The adder 26 outputs the signal S43 from the coefficient unit 35 and the signal S from the previous adder 20.
29 is added to obtain the output signal S.

Here, as the signal S43, in the vertical direction,
Since the two-dimensional filtering processing in the horizontal direction is performed, the component of the area A1 as shown in FIG. 4A is obtained. As a result, after the output signal S29 of the inter-field interpolation filter 3 and the compensation signal S43 from the enhancer 41 are added, an output having the characteristic shown in FIG. 4B is obtained. As can be seen from this characteristic, it is possible to enhance the image without the enhancer emphasizing the aliasing interference in which the inter-field interpolation filter 3 cannot sufficiently drop the cutoff area as in the conventional case. .

The present invention is not limited to the above embodiment. FIG. 2 shows a second embodiment of the present invention. First
The same parts as those in the above embodiment are designated by the same reference numerals. The difference from the first embodiment is that the vertical low pass filter 23 of the first embodiment is a vertical band pass filter (vertical BPF) 43.
To the horizontal bandpass filter 2 of the first embodiment.
4 is replaced with a horizontal low pass filter (horizontal LPF) 44. The output of this two-dimensional filter is multiplied by the coefficient in the coefficient unit 45 and output as the compensation signal S43. Output signal S5 of the two-dimensional filter in this embodiment
2 and the output signal S53 of the coefficient unit 45 are the components of the area A2 as shown in FIG. As a result, the output signal S29 of the inter-field interpolation filter 3 and the enhancer 41
After the compensation signal S53 is added by
An output having the characteristics shown in is obtained. This characteristic also prevents the enhancer from emphasizing the aliasing interference that has not been able to sufficiently drop the cutoff region by the interfield interpolation filter 3.

FIG. 3 further shows a third embodiment of the present invention. The same parts as those in the first and second embodiments are designated by the same reference numerals. In the case of this embodiment, the two-dimensional filters shown in FIGS. 1 and 2 are connected in parallel, and the output signal S thereof is output.
43 and S53 are combined by the adder 46 to obtain the compensation signal S
54. According to this embodiment, the components of the areas A1 and A2 as shown in FIG. 5 can be emphasized. Also in this embodiment, the enhancer does not emphasize the aliasing interference that the inter-field interpolation filter 3 has not sufficiently dropped the cutoff region.

In the above example, the inter-field interpolation filter 3 is explained as a vertical 9-tap filter.
Even if the number of vertical taps changes, the idea of the present invention is effective. The present invention can be applied even if the internal configuration of the inter-field interpolation filter 3 is changed. Vertical LPF2
Although 3 and the vertical BPF 43 are set as a 9-tap filter, for example, only the signals S16, S21, S22 are configured to be guided to the vertical LPF 23 and / or the vertical BPF 43, and these filters are configured as a 5-tap filter. May be.

[0020]

As described above, according to the present invention,
The output signal of the inter-field interpolation filter and the output signal of the line delay circuit group of this inter-field interpolation filter are combined with the output of a two-dimensional filter for filtering in the vertical direction and further filtering in the horizontal direction. It is possible to enhance the component of only the pass band of the still image signal without increasing the line memory.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention.

FIG. 4 is an explanatory view of bandpass characteristics shown for explaining the operation of the circuit of the present invention.

FIG. 5 is an explanatory view of bandpass characteristics, which is also shown for explaining the operation of the circuit of the present invention.

FIG. 6 is an explanatory diagram of a MUSE decoder.

FIG. 7 is a diagram showing a conventional still image processing circuit.

FIG. 8 is a band pass characteristic explanatory diagram showing the operation of the circuit of FIG. 7 for explaining the operation.

[Explanation of symbols]

2 ... Field memory, 3 ... Inter-field interpolation filter, 4-10 ... 1 line delay circuit, 11-14, 20,
26, 46 ... Adder, 15-19 ... Horizontal filter, 2
3, 43 ... Vertical low pass filter, 24, 44 ... Horizontal filter, 25, 45 ... Coefficient unit.

Claims (8)

[Claims] 1. An inter-field interpolating means for receiving an MUSE signal and performing inter-field interpolating processing, and a plurality of one horizontal period delay means used in cascade connection in the inter-field interpolating means. Performs vertical and horizontal filtering using the output signal,
A still picture processing circuit of a MUSE decoder, comprising: a means for adding the obtained signal to the output signal of the inter-field interpolation means as a compensation signal for enhancement. 2. Field memory means for guiding an input signal, and n (n = 0,
1, 2, 3, ..., Each of which delays the input signal by about 1 horizontal period, and the first to n-th delay means and the m output signals of the field memory means are connected in cascade (m = m). , 2, 3, ..., Each delays the input signal by approximately one horizontal period, the (n + 1) th
To (n + m) th delay means, the input signal, the output signal of the field memory means,
And an output signal of the delay means of the first to (n + m) th delay means, or a linear combination signal thereof is introduced,
Filtering means for inter-field interpolation, which band-limits a high frequency component in an oblique direction of an image, the input signal, an output signal of the field memory means,
And vertical filter means for guiding the output signal of the delay means of the first to (n + m) th delay means, or at least one of the linear combination signals thereof, for performing band limitation in the vertical direction of the image, and the vertical filter means. An output signal of the filter means is introduced, a coefficient multiplier means for multiplying this signal by a constant, an output signal of the filter means for inter-field interpolation,
A still image processing circuit of a MUSE decoder, comprising: first linear combination means for adding the output signal of the coefficient unit means. 3. The output signal of the vertical filter means, when being guided to the coefficient multiplier means, is guided through horizontal filter means for band-limiting the horizontal direction of the image. Still picture processing circuit of MUSE decoder. 4. The vertical filter means and the coefficient multiplier means form a unit circuit, and K unit circuits (K = 2, 3, 3).
4) are connected in parallel, and the output signals of the unit circuits are added by the second linear combining means, and the first linear combining means outputs the output of the second linear combining means and the inter-field interpolation. 3. The MUS according to claim 2, wherein the output signal of the filter means of is added.
Still picture processing circuit of E decoder. 5. At least one of said unit circuits, when the output signal of its vertical filter means is led to its coefficient multiplier means, is led through horizontal filter means for band-limiting the horizontal direction of the image. The still picture processing circuit of the MUSE decoder according to claim 4. 6. The still picture processing circuit of a MUSE decoder according to claim 2, wherein said vertical filter means is a two-dimensional filter means for band-limiting the vertical and horizontal directions of the image. 7. The MUS according to claim 2 or 4, wherein the coefficient unit has a non-linear input / output characteristic.
Still picture processing circuit of E decoder. 8. The still image processing circuit of the MUSE decoder according to claim 2, wherein the coefficient unit has variable input / output characteristics.