JPH05227514A - Sub-band dividing filter and sub-band synthesizing filter - Google Patents

Abstract

PURPOSE:To constitutes a circuit which sub-band divides or synthesizes video signals with low speed logical elements. CONSTITUTION:In a sub-band dividing filter which horizontally and then vertically sub-band divides the video signals, a parallel processing is executed by each horizontal sample, and the video signals are rearranged by a rearranging means 2 so that the parallel processing can be executed by each vertical line. In a sub-band synthesizing filter which vertically and then horizontally sub-band synthesizes the video signals, the parallel processing is executed by each vertical line, and the video signals are rearranged by a rearranging means 7 so that the parallel processing can be executed by each horizontal sample. Therefore, the sub-band dividing filter and the sub-band synthesizing filter can be constituted of the low speed logical elements by introducing the parallel processing and rearranging means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a subband division filter and a subband synthesis filter used when digitally encoding a video signal for transmission or recording.

[0002]

2. Description of the Related Art In recent years, televisions have been actively improved in image quality. As one of them, research and development of high-definition television are remarkable (for example, the literature “Literature Special Issue on High-Definition Television”, Journal of the Television Society, Vol. 36, No. 10).
Issue, 1982). However, since a high-definition television image signal has a large amount of image information as compared with a current television system, a high-efficiency encoding technique is indispensable for efficient transmission or recording.

One of the effective high-efficiency coding systems for high-definition television is the sub-band coding system (for example, the document "Sub-band Extrapolation Predictive Coding System", National Conference of Television Society). Shu, pp.457-458,
1989). The subband coding method is defined by J. D. Quadrature Mirror Filter (hereinafter referred to as QMF) proposed by Johnston
Etc. (For example, the document "A Filter Family Designed for Youth in Quadrature Mirror Filter Banks"("A Filter Family for Use
in QuadratureFilter Banks "in Proc. 1
980 ICASSP, pp. 291 to 294), the video signal is divided into a plurality of different frequency bands, and encoding and quantization suitable for each frequency band are performed. The sub-band division filter is a filter that divides the plurality of different frequency bands, and the sub-band synthesis filter is a filter that synthesizes a plurality of different frequency bands.

An example of the above-described conventional sub-band division filter and sub-band synthesis filter for video signals will be described with reference to the drawings. FIG. 7 shows a block diagram of a conventional subband division filter and subband synthesis filter.

In the block diagram of the sub-band division filter of (A) of FIG. 7, 200 is an input terminal for a video signal, 210 is a horizontal division filter for dividing in the horizontal direction of the spatial frequency region of an image, and 211 and 212 are. Switches for downsampling at a period 2T that is twice the sampling period T of the input video signal, 220 and 230 are vertical division filters for dividing in the vertical direction, 221, 222, 231,
Reference numeral 232 denotes a switch for down-sampling at a period 2T _H that is twice the period T _H of one horizontal line, 201, 202, 20.
Reference numerals 3 and 204 are output terminals for the divided video signals.

In the block diagram of the sub-band synthesis filter of (B) of FIG. 7, 301, 302, 303, 3
Reference numeral 04 designates input terminals for the divided video signals, 310 and 320.
Is a vertical synthesizing filter for synthesizing in the vertical direction of the spatial frequency domain of the image, 311, 312, 321, 322 are periods T _H
A switch for up-sampling at 330, a horizontal synthesis filter 330 for horizontally synthesizing, 331, 332 a period T
A switch for up-sampling at, and 300 is an output terminal for a combined video signal.

The conventional sub-band division filter and sub-band synthesis filter configured as described above will be described below.
The operation will be described with reference to (FIG. 7), (FIG. 8) and (FIG. 9). First, a conventional subband division filter will be described with reference to (A) of FIG.

The video signal applied to the input terminal 200 is
First, the horizontal division filter 210 divides the image into two bands in the horizontal direction of the spatial frequency domain. That is, the horizontal low-frequency component of the image (hereinafter referred to as the L component)
And a high frequency component (hereinafter, referred to as H component), and is down-sampled by the switches 211 and 212. After that, the L component and the H component are divided into two bands in the vertical direction of the spatial frequency domain of the image by the vertical division filters 220 and 230, respectively, and the switches 221 and 2 are provided.
After being downsampled at 22, 231, 232,
It becomes the LL component, the LH component, the HL component, and the HH component, which are output to the output terminals 201, 202, 203, and 204, respectively.

A conceptual diagram of the divided bands is shown in FIG. In FIG. 8, the horizontal axis is the horizontal frequency of the spatial frequency region of the image, the vertical axis is the vertical frequency, and the video signal is divided into four regions on this plane. That is, a low-frequency component in the horizontal direction and a low-frequency component in the vertical direction (hereinafter referred to as LL component), and a low-frequency component in the horizontal direction and a high-frequency component in the vertical direction (hereinafter referred to as LH component), In the horizontal high range,
And the low-frequency component in the vertical direction (hereinafter referred to as the HL component)
And a high-frequency component in the horizontal direction and a high-frequency component in the vertical direction (hereinafter referred to as HH component).

A video signal divided into bands as described above is shown in FIG. In FIG. 9, 600 is a video field, and 601 is a subband-divided video signal that is output to the output terminals 201, 202, 203, and 204 of the subband-division filter in (A) of FIG. is there.
The video signal input to the input terminal 200 of the sub-band division filter includes all the pixels at the lattice points (FIG. 9),
The video signals output to the output terminals 201, 202, 203, and 204 are downsampled in the horizontal direction and halved in the horizontal direction, and downsampled in the vertical direction and halved in the vertical direction. There is.

Next, a conventional subband synthesis filter will be described with reference to FIG. 7B. The LL component, LH component, HL component, and HH component of the band-divided video signal are input terminals 301, 302, 303, 304, respectively.
Given to. The LL component and the LH component are switched by the switch 31.
After being up-sampled at 1 and 312, they are combined in the vertical direction of the spatial frequency domain of the image by the vertical combining filter 310 to obtain the L component. HL component and HH component are
After being up-sampled by the switches 321, 322, they are combined by the vertical combining filter 320 to obtain the H component. Next, the L component and the H component are switched to the switch 331,
After being up-sampled in 332, the horizontal synthesizing filter 330 synthesizes them in the horizontal direction, and the synthesized video signal is obtained at the output terminal 300.

[0012]

However, in the above-mentioned conventional configuration, the divided filter performs down-sampling after filtering, and the synthesis filter up-samples before filtering. You will need it. The horizontal division filter 210 has to finish the filtering operation for all input samples by the time the next sample is input, and similarly, the vertical division filters 220, 23.
0 is down-sampled after the horizontal division filter 210, and with respect to the video signal having a sample number of ½, the filtering operation needs to be completed before the next sample is input. That is, in the sub-band division filter, the filtering operation required for horizontal division must be completed within the sampling period of the input video signal, and even the filtering operation required for vertical division must be completed within twice the sampling period. Need to be completed. Similarly, in the sub-band synthesis filter, the vertical synthesis needs to be completed within twice the sampling period, and the horizontal synthesis needs to be completed within the sampling period.

Particularly, in the sub-band division filter and the sub-band synthesis filter for the high definition television video signal, the sampling cycle is short, and therefore each filtering operation requires very high-speed signal processing. Therefore, in order to realize this high-speed signal processing, it is generally necessary to use a high-speed logic element that is not suitable for being integrated into an IC because it consumes a large amount of power, and the reduction of circuits using this high-speed logic element has been a problem. ..

In view of the above problems, the present invention provides a sub-band division filter and a sub-band synthesis filter which realize the same signal processing by a low-speed signal processing circuit without using a circuit for high-speed signal processing. Is.

[0015]

In order to solve the above-mentioned problems, the sub-band division filter of the present invention employs n (n ≧ 2) sample points in the horizontal direction of a video signal as a processing unit for the spatial frequency of an image. A first band-splitting filter that divides into a plurality of frequency bands in the horizontal direction of the area and outputs n sample points in parallel for each frequency band, and m (m ≧ 2) video signals
A second band-splitting filter that divides the sample line of the above into a plurality of frequency bands in the vertical direction of the spatial frequency domain of the image, and rearrangement that rearranges n sample points in the horizontal direction into m sample lines. Means are provided.

The sub-band synthesis filter of the present invention receives as input a video signal divided into a plurality of frequency bands in the spatial frequency domain of an image, and processes m (m ≧ 2) sample lines of the video signal as a processing unit. As a first band synthesizing filter for synthesizing bands in the vertical direction of the spatial frequency domain of the image, and n (n ≧ 2) sample points in the horizontal direction of the video signal are input in parallel, and the n sample points are input. A second band synthesizing filter for synthesizing the band in the horizontal direction of the spatial frequency domain of the image as a processing unit, and a rearranging means for rearranging m sample lines into n sample points in the horizontal direction are provided.

[0017]

With the above construction, in the sub-band division filter of the present invention, the video signal outputted from the band division filter for band-dividing the image in the horizontal direction to the rearrangement means has a half rate for downsampling. In addition to this, this band division filter outputs n filtering results in the horizontal direction of the image in parallel, so that the original 2
The rate is 1 / n. That is, every 2nT which is 2n times the sampling period T of the video signal. Then, for the horizontal n video signals of the image that are input in parallel to the rearrangement unit at time intervals of 2nT, the vertical m video signals of the image are output in parallel at time intervals of 2mT, and the band in the vertical direction of the image is output. It is input to the band division filter for division.

Similarly, in the sub-band synthesizing filter of the present invention, the video signals output from the band synthesizing filter for synthesizing bands in the vertical direction of the image to the rearranging means are m video signals in the vertical direction of the image. , Are output in parallel every 2 mT. The video signals input to the rearrangement unit are output in parallel in the horizontal direction of the image every 2nT, and are input to a band synthesis filter that performs band synthesis in the horizontal direction of the image.

As described above, the processing time of the video signal is time 2
With each nT or 2mT, a parallel processing filtering algorithm can be adopted, and a subband division filter or subband synthesis filter can be realized by a low-speed signal processing circuit.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A subband division filter and a subband synthesis filter according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of the subband division filter and the subband synthesis filter of this embodiment.

In the block diagram of the sub-band division filter of (A) of FIG. 1, 10 is an input terminal of a video signal,
1 is a horizontal division filter, 2 is a rearrangement means for video signals,
Reference numerals 3 and 4 denote vertical division filters, and reference numerals 11, 12, 13, and 14 denote output terminals for divided video signals. In the block diagram of the sub-band synthesis filter of (B) of FIG. 1, reference numerals 21, 22, 23, and 24 are input terminals for encoded video signals, 5 and 6 are vertical synthesis filters, and 7 is an arrangement of video signals. Alternate means, 8 is a horizontal synthesis filter, and 20 is an output terminal of the synthesized video signal.

With respect to the sub-band division filter and sub-band synthesis filter of the present embodiment configured as described above,
The operation will be described below with reference to (FIG. 1), (FIG. 2), (FIG. 3), (FIG. 4), (FIG. 5) and (FIG. 6). First, the sub-band division filter (A) in FIG. 1 will be described.

First, the video signal supplied to the input terminal 10 is first divided into two bands in the horizontal direction of the spatial frequency region of the image by the horizontal division filter 1, and the L component and H
The ingredients are obtained. Here, in order to explain the configuration of the horizontal division filter 1, the algorithm will be described using equations. The video signal is x, and the number of taps N of the horizontal division filter used for horizontal filtering is N = 4N '(N' = 1, 2, 3, ...
,), The filter coefficient is h ₀ , h ₁ , ..., H _N−1 , and the number of horizontal pixels P in the coding region of the image is P = 4P ′ (P ′ = 1, 2, 3,
..), the outputs L and H of the low-pass filter and the high-pass filter are the following (Equation 1) and (Equation 2), respectively, in consideration of the characteristics of the FIR filter.

[0024]

[Equation 1]

[0025]

[Equation 2]

Here, the subscript j represents a pixel number in the horizontal direction, and j = 0, 1, ..., P / 2-1. The number of pixels is halved due to downsampling. When (Equation 1) and (Equation 2) are each decomposed into two terms, the following (Equation 3) and (Equation 4) are obtained.

[0027]

[Equation 3]

[0028]

[Equation 4]

Next, (equation 3) and (equation 4) are replaced by j =
2j '(j' = 0, 1, ..., P / 4-1), that is, even-numbered samples (hereinafter referred to as even-numbered samples), and j = 2j '+ 1, that is, odd-numbered samples (hereinafter referred to as even-numbered samples) , An odd sample) and divided into four terms, the following (Equation 5), (Equation 6), (Equation 7), and (Equation 8) are obtained.

[0030]

[Equation 5]

[0031]

[Equation 6]

[0032]

[Equation 7]

[0033]

[Equation 8]

That is, in (Equation 5), (Equation 6), (Equation 7), (Equation 8), different product sum terms of eight terms appear, and each product sum term is of the (N / 4) term. It is the addition result.

Four consecutive video signals x are used to calculate L and H of even samples, and four video signals shifted by two pixels from them are used to calculate L and H of odd samples. The filtering result is obtained by the product-sum calculation with and.
Considering that both components for 2 samples after 2: 1 down-sampling are obtained, the calculation of the different 8 terms necessary for the calculation of the L component and the H component is performed in 8 processing units. When calculating independently with the (filter), the product-sum calculation of each (N / 4) term should be completed within 4T. Here, the time T is the sampling period of the input video signal.

The above (Equation 5), (Equation 6), (Equation 7),
FIG. 2 shows a block diagram of an example of a circuit that realizes the filtering of (Equation 8). In FIG. 2, 30 is a video signal input terminal, 40 is a shift register, 41, 4
2, 43, 44, 45, 46, 47 and 48 are switches that simultaneously open and close with a cycle of 4T, 49, 50, 51, 52 and 5
3, 54, 55, 56 are filters, 57, 58, 59,
60, 61, 62, 63, 64 are arithmetic units, 31, 32,
33 and 34 are output terminals for the divided video signals.

The video signals applied to the input terminal 30 are successively input to the shift register 40 and the shift register 4
For the output of 0, the values of the past 6 pixels are obtained. This is because the filtering results L and H of even samples are calculated using the oldest four pixels, and the odd sample L and H are calculated using the newer four pixels. The values of these 6 pixels are the switches 41, 42, 43, 4
4, 45, 46, 47, 48 downsampled 4: 1 and filters 49, 50, 51, 52, 5
3, 54, 55, 56. Here, the filter 49 is in the first term of (Equation 5), the filter 50 is in the second term of (Equation 6), the filter 51 is in the third term of (Equation 5), and the filter 52 is in the (Equation 6). The fourth term, the filter 53 is the first term of (Equation 7), the filter 54 is the second term of (Equation 8), the filter 55 is the third term of (Equation 7), and the filter 56.
Corresponds to the fourth term of (Equation 8).

Next, the results of the filters 49 and 51 are the arithmetic unit 57, the results of the filters 50 and 52 are the arithmetic unit 58, the results of the filters 53 and 55 are the arithmetic unit 59, and the results of the filters 54 and 56. Are added by the arithmetic unit 60. Also,
The results of the arithmetic units 57 and 58 are added by the arithmetic unit 61, which becomes a low-frequency output (hereinafter referred to as Les) of even samples in the horizontal direction. The results of the arithmetic units 57 and 58 are subtracted by the arithmetic unit 62, which becomes a high-frequency output of even samples in the horizontal direction (hereinafter referred to as Hes).

Similarly, the results of the arithmetic units 59 and 60 are added by the arithmetic unit 63, which becomes a low-frequency output of odd-numbered samples in the horizontal direction (hereinafter referred to as Los). Calculator 59, 60
Is subtracted by the arithmetic unit 64, and this becomes a high-frequency output (hereinafter referred to as Hos) of odd-numbered samples in the horizontal direction. The above calculators 57, 58, 59, 60, 61, 62, 6
The processing by 3 and 64 corresponds to the calculation of the product-sum terms of (Equation 5), (Equation 6), (Equation 7), and (Equation 8). As described above, Les and Los are obtained as the L component and Hes and Hos are obtained as the H component.

Next, returning to (A) of FIG. 1, the description of the sub-band division filter will be continued. Horizontal division filter 1
The L component and the H component obtained by the above are rearranged by the rearranging means 2 so that the vertical filtering can be easily performed later. The operation of the sorting means 2
This will be described with reference to FIG.

In FIG. 4, 100 is a video field. The rearranging means 2 alternately outputs a pair of horizontal filtering results of even-numbered samples and odd-numbered samples, (Les, Los), which are obtained simultaneously as a horizontal time series, in pairs of two lines of Les and Los. Rearrange as you want. For example, in (FIG. 4), when the horizontal filtering result of the 2k-th line is expressed by the subscript 2k, (L _{2k, 0} , L _{2k, 1} ), (L _{2k, 2} , L _{2k, 3} ),
... (L _{2k, P / 2-4} , L _{2k, P / 2-3} ), (L _{2k, P / 2-2} ,
L _{2k, P / 2-1} ), (L _{2k + 1,0} , L _{2k + 1,1} ), ...
..., the _{(L 2k + 1, P /} 2-2, L 2k + 1, P / 2-1) Result pair of filtering input during the time 2T _H so on,
(L _{2k, 0} , L _{2k + 1,0} ), (L _{2k, 1} , L _{2k + 1,1} ), ...
・, (L _{2k, P / 2-2} , L _{2k + 1, P / 2-2} ), (L _{2k, P / 2-1} , L
_{2k + 1, P / 2-1} ) and output for 2T _H.
Although the L component has been described above, the same applies to the H component, and the pairs (Hes, Hos) are rearranged so that pairs of Hes and pairs of Hos for two lines are alternately output. After that, the even line L _{2k, i} (i = 0,1, ..., P / 2-1) of the low-pass filtering result after the rearrangement is Lel,
The odd line L _{2 k + 1, i} is written as Lol. Similarly, the even line of the high-pass filtering result is written as Hel, and the odd line is written as Hol.

As described above, the video signal input by the pair of the even sample and the odd sample of each band is output by the pair of the even line and the odd line. Since the input video data is raster-scanned, the vertical filter changes the video data to be filtered every 2T unlike the horizontal filter. However, by rearranging the video data described above, the video data to be filtered changes every 4T.

Returning to (A) of FIG. 1 again, the description of the subband division filter will be continued. The L component and the H component rearranged by the rearrangement unit 2 are divided into two bands in the vertical direction of the spatial frequency domain of the image by the vertical division filters 3 and 4, respectively, and the LL component, the LH component,
HL component and HH component are obtained. Here, in order to explain the configuration of the vertical division filters 3 and 4, a filtering algorithm will be described using equations. The video signal is x, the number M of taps of the vertical division filter used in the vertical filtering process is M = 2M ′ (M ′ = 1, 2, 3, ...) And the filter coefficients are h ′ ₀ , h ′ ₁ ,. ., H ' _M-1 , the vertical pixel number Q in the image coding area is Q = 2Q' (Q '= 1,
2, 3, ...), the outputs L and H of the low-pass filter and the high-pass filter are (Equation 9) and (Equation 10), respectively, in consideration of the properties of the FIR filter.

[0044]

[Equation 9]

[0045]

[Equation 10]

Here, the subscript j represents a pixel number in the vertical direction, and j = 0, 1, ..., Q / 2−1. The number of pixels is halved due to downsampling. When QMF is used for the vertical division filter, the symmetry of the filter coefficient of QMF, that is,

[0047]

[Equation 11]

From the above, by decomposing (Equation 9) and (Equation 10),

[0049]

[Equation 12]

[0050]

[Equation 13]

It becomes That is, (Equation 12) and (Equation 1)
In 3), the product-sum calculation of each M / 2 term appears.
Although the term of the sum of the video signals appears in (Equation 12) and the difference of the video signals appears in (Equation 13), these two video signals x are always pairs of even lines and odd lines.

FIG. 5 shows a block diagram of an example of a circuit that realizes the above-described (Equation 12) and (Equation 13) filtering. In FIG. 5, reference numerals 150 and 151 denote video signal input terminals, and 160, 161, 162, 163 and 16 respectively.
4,165,166,167,168,169, the delay element of time 2T _H, 180,181,182,183,
184, 185, 186, 187, 188, 189 are multipliers, 170, 171, 172, 173, 174, 17
5, 176, 177, 178, 179 are arithmetic units, 19
0, 191, 192, 193, 194, 195, 19
6, 197 are adders, and 152, 153 are output terminals of the filter.

The video signals of the even line Lol and the odd line Lel are applied to the input terminal 150 and the input terminal 151, respectively, and the delay elements 160, 161, 162 and 16 are supplied.
3, 164, 165, 166, 167, 168, 169
The value of the past (M-1) line obtained by
70, 171, 172, 173, 174 add, and arithmetic units 175, 176, 177, 178, 179 subtract. This addition or subtraction corresponds to addition or subtraction between the video signals of (Equation 12) and (Equation 13), respectively. The pair of values to be added or subtracted is the current line and the oldest line, and 1 The previous line, the second oldest line, and so on.

The above arithmetic units 170, 171, 172, 1
The results obtained at 73, 174 are the multipliers 180, 18
They are multiplied by 1, 182, 183, 184, and the results are all added by the arithmetic units 190, 191, 192, 193, and output to the output terminal 152 as the result of the low pass filter.

On the other hand, computing units 175, 176, 177, 1
The results obtained at 78 and 179 are the multipliers 185 and 18
6, 187, 188, 189, and the results are all added by the arithmetic units 194, 195, 196, 197, and output to the output terminal 153 as the result of the high pass filter. As described above, the low frequency component and the high frequency component in the vertical direction are obtained.

Returning to FIG. 1A, the description of the subband division filter will be continued. The low-frequency video signal obtained by the vertical division filter 3 corresponds to the LL component, and the high-frequency signal corresponds to the LH component. The high-frequency video signal obtained by the vertical division filter 4 corresponds to the LH component, and the high-frequency component corresponds to the HH component.
These LL component, LH component, HL component, and HH component are output to output terminals 11, 12, 13, and 14, respectively.

Next, the subband synthesis filter of (B) of FIG. 1 will be described. First, the input terminal 21,
The LL component and LH component of the video signal respectively given to 22 are input to the vertical synthesis filter 5, and an even line Lel and an odd line Lol of the L component are obtained. Further, the HL component and the HH component respectively given to the input terminals 23 and 24 are inputted to the vertical synthesizing filter 6, and the even line Hel and the odd line Hol of the H component are obtained.

Here, in order to explain the configuration of the vertical division filters 5 and 6, the filtering algorithm will be described using equations. Since the synthesis of the L component and the synthesis of the H component are the same procedure, only the L component, that is, the vertical synthesis filter 5 will be described below. Generally, the same coefficients as those used in the vertical division filter are used for the low-pass filter and the high-pass filter used for the vertical synthesis filter. Therefore, the video signal is x, and the tap number M of the vertical synthesis filter used in the vertical filtering process is M = 2M ′ (M ′ =
1, 2, 3, ...), and filter coefficients are h ′ ₀ , h ′ ₁ , ...
., H ' _M-1 , the vertical pixel number Q of the coded area of the image is Q
= 2Q '(Q' = 1, 2, 3, ...).

The result L of the filtering by the low-pass filter is that when U is the LL component and V is the LH component, the result is even line (Lel) and odd line (Lel) respectively.

[0060]

[Equation 14]

[0061]

[Equation 15]

It becomes Here, the subscript j of L = 2n, 2n
+1 represents the pixel number in the vertical direction, and j = 0, 1, ...
, Q / 2−1, and element 0 on the right side is the value inserted during upsampling.

From (Equation 14) and (Equation 15),

[0064]

[Equation 16]

[0065]

[Equation 17]

It becomes Similarly, the result H of the filtering by the high-pass filter is as follows for even line (Hel) and odd line (Hol), respectively.

[0067]

[Equation 18]

[0068]

[Formula 19]

It becomes Therefore, the reference "Application of Quadrature Mirror Filters" (see Application of Quadrature Mirror Filters)
s To Split Band Voice CodingSchemes ", in Pro
c. 1977 ICASSP, pp. 191-195)
Than,

[0070]

[Equation 20]

[0071]

[Equation 21]

There is the following relationship. Here, x is a synthesized video signal, the subscripts j = 2n, 2n + 1 of x represent pixel numbers in the vertical direction, and j = 0, 1, ..., Q-1.

From (Equation 20) and (Equation 21), a video signal can be obtained by doubling the right side of each. That is,
The values of the even and odd lines of the video signal are obtained from the sum and difference of the filtering results L and H. Above (Equation 2
FIG. 6 shows a block diagram of an example of a circuit that realizes the filtering of 0) and (Equation 21). In (Fig. 6),
700 and 701 are video signal input terminals, and 710 and 71.
1, 712, 713, 714, 715, 716 is time 2
T _H delay elements, 720, 721, 722, 723, 7
24, 725, 726, 727 are arithmetic units, 730, 73
1, 732, 733, 734, 735, 736, 73
7, 750, 751 are multipliers, 740, 741, 74
2, 743, 744, 745 are adders, 702, 703
Is the output terminal of the filter.

The input terminals 700 and 701 are each provided with LL.
Component, LH component are input, and these and delay element 710,
The value of the past (M-1) line obtained by 711, 712, 713, 714, 715, and 716 is the arithmetic unit 72.
In 0, 721, 722, and 723, addition and operation unit 724,
Subtraction is made at 725, 726 and 727. This addition or subtraction corresponds to the addition or subtraction of the components (U and V) of (Equation 20) and (Equation 21), respectively. The pair of values to be added or subtracted is the current line or the previous one. The lines are ... and so on.

The results obtained by the arithmetic units 720, 721, 722, 723 are the multipliers 730, 731, 732, 73.
3 and the result is the adder 740, 741, 74
All are added at 2, and the multiplier 750 performs double multiplication, and the low band Lel of the even line is output to the output terminal 703. On the other hand, computing units 724, 725, 726, 727
The result obtained by the above is the multipliers 734, 735, 736, 7
37, and the result is the adder 743, 744, 7
All of them are added at 45, multiplied by 2 at the multiplier 751, and the low band Lol of the odd line is output to the output terminal 702. As described above, synthesis in the vertical direction is performed and Lel and Lol of the L component are obtained, but with the same configuration, Hel and Hol of the H component are also obtained.

L obtained by the vertical synthesis filters 5 and 6
The rearrangement means 7 rearranges the video signals of the component and the H component so that the horizontal filtering can be performed later.
The operation of the rearrangement means 7 is just opposite to that of the rearrangement means 5, and will be described with reference to FIG.

In the rearrangement means 7, a pair (Lel, Lol) of video signals for two lines of an even line and an odd line in the vertical direction which are simultaneously obtained as a result of vertical filtering are
Rearrangement is performed so that a pair of even and odd samples (Les, Los), which is a time series in the horizontal direction, can be obtained at the same time. For example, in (FIG. 5), (L _{2k, 0} , L _{2k + 1,0} ),
(L _{2k, 1} , L _{2k + 1,1} ), ..., (L
_{2k, P / 2-2} , L _{2k + 1, P / 2-2} ), (L _{2k, P / 2-1} , L
_{2k + 1, P / 2-1)} so on, a video signal to be inputted during the time _{2T H, (L 2k, 0} , L 2k, 1), (L 2k, 2, L
_{2k, 3} ), ..., (L _{2k, P / 2-4} , L _{2k, P / 2-3} ),
(L _{2k, P / 2-2} , L _{2k, P / 2-1} ), (L _{2k + 1,0} ,
L _{2k + 1,1} ), ..., (L _{2k + 1, P / 2-2} , L
_{2k + 1, P / 2-1} ) and output for 2T _H.
Although the L component has been described above, the same applies to the H component, which is rearranged so that the pair (Hel, Hol) to the pair (Hes, Hos) can be obtained at the same time.

Returning to FIG. 2 again, the description of the subband synthesis filter will be continued. The L component and the H component rearranged by the rearranging means 7 are combined in the horizontal direction of the spatial frequency region of the image by the horizontal combining filter 8, and the combined video signal is output to the output terminal 20. Here, in order to explain the configuration of the horizontal synthesis filter 8, the algorithm will be described using mathematical expressions. Generally, the same filter as that used for horizontal division is used for the horizontal synthesis filter.

Therefore, the video signal is x, and the number N of taps of the horizontal synthesis filter used in the horizontal filtering process is N =
4N ′ (N ′ = 1,2,3, ...), filter coefficient,
_Let h ₀ , h ₁ , ..., H _N−1 , and the number of horizontal pixels P in the image coding region be P = 4P ′ (P ′ = 1, 2, 3, ...). Result of filtering by low pass filter L
Is

[0080]

[Equation 22]

[0081]

[Equation 23]

[0082]

[Equation 24]

[0083]

[Equation 25]

It becomes Here, element 0 is a value inserted at the time of upsampling. Similarly, the filtering result H by the high-pass filter is

[0085]

[Equation 26]

[0086]

[Equation 27]

[0087]

[Equation 28]

[0088]

[Equation 29]

It becomes Therefore,

[0090]

[Equation 30]

[0091]

[Equation 31]

[0092]

[Equation 32]

[0093]

[Expression 33]

It becomes Here, (Equation 30), (Equation 3)
1), (Equation 32), and (Equation 33) are equal to their left sides, as in the case of the vertical synthesis filter.

From the sum and difference of the L component and the H component, four continuous time-series decoded video signals can be obtained. Here, (Equation 30), (Equation 31), (Equation 32), (Equation 33)
, Appearing in addition and subtraction in the product sum terms of eight different terms at
The pixel numbers of the component (U) and the H component (V) are the same, and each is a continuous four components. Here, considering that the video data for 4 samples after the upsampling of 1: 4 is obtained, the calculation of 8 different items necessary for the calculation of the video data for 4 samples is performed by 8 processings. When calculating independently by the unit (filter), the sum of products calculation of the (N / 4) terms should be completed within 4T. Here, the time T is the sampling period of the output video signal.

The above (Equation 30), (Equation 31), (Equation 3)
2) and (FIG. 3) are block diagrams of an example of a circuit that realizes the filtering of (Equation 33). In (Fig. 3),
70, 71, 72 and 73 are video signal input terminals, 79,
80, 81 are delay elements at time T, 82, 83, 84, 8
5, 86, 87, 88, 89 are filters, 75, 7
6, 77, 78, 90, 91, 92, 93 are arithmetic units, 9
Reference numeral 4 is a shift register, and 74 is an output terminal for a decoded video signal.

The video signals Les and Hes supplied to the input terminals 70 and 71 are added and subtracted by the calculators 75 and 76, respectively, and the video signals Los and Hos supplied to the input terminals 72 and 73 are calculated in the calculator 77 and Addition and subtraction are performed at 78. The outputs of the calculators 75, 76, 77, 78 are filtered by the filters 82, 83, 84, 8 together with their values and the values delayed by the time T by the delay elements 79, 80, 81.
5,86,87,88,89. here,
The first term of (Equation 30) is the filter 82, the second term is the filter 86, the first term of (Equation 31) is the filter 88, and the second term is
The term is the filter 84, and the first term of (Equation 32) is the filter 8
7, the second term corresponds to the filter 83, the first term of (Equation 33) corresponds to the filter 85, and the second term corresponds to the filter 89.

Next, the results of the filters 82 and 86 are the arithmetic unit 90, the results of the filters 84 and 88 are the arithmetic unit 91, the results of the filters 83 and 87 are the arithmetic unit 92, and the filter 8
The results of Nos. 5 and 89 are respectively added by the arithmetic unit 93 and doubled. This adder 90, 91, 92, 93
The process according to (Equation 30), (Equation 31), (Equation 32)
This corresponds to the calculation between the sum-of-products terms of (Expression 33). The results of the arithmetic units 90, 91, 92 and 93 are input to the shift register 94 and output from the output terminal 74 in this order. In this way, the decoded video signal is obtained.

As described above, by processing the horizontal processing in two parallels and the vertical processing in two parallels, the video data can be processed every 4T. It should be noted that although the two processes in the horizontal direction and the vertical direction are performed in parallel as described above, they may be performed in two or more.

[0100]

As described above, the sub-band division filter according to the present invention divides the number of sampling points in the horizontal direction of the image into the processing units, and performs n filtering results for each frequency band in the horizontal direction of the image. In parallel with each other, a vertical band division filter of an image in which m sample points in the vertical direction of the image are used as a processing unit, and n sample points in the horizontal direction of the image are m in the vertical direction. By providing the rearranging means for rearranging the sample points, the processing time of the video signal becomes every 2 nT or 2 mT of time, and by adopting the parallel processing filtering algorithm,
The sub-band division filter can be realized by a low-speed signal processing circuit.

The sub-band synthesizing filter of the present invention uses a band synthesizing filter for synthesizing bands in the vertical direction by using m sample points in the vertical direction of the image as a processing unit, and n sample points in the horizontal direction of the image. As a processing unit, a band synthesizing filter for synthesizing a band in the horizontal direction and a rearrangement unit for rearranging m sample points in the vertical direction of the image into n sample points in the horizontal direction are provided, and thus the processing time of the video signal is improved. But time 2
Every nT or every 2mT, and by adopting the parallel processing filtering algorithm, the subband synthesis filter can be realized by a low-speed signal processing circuit.

[Brief description of drawings]

FIG. 1A is a block diagram showing a subband division filter according to an embodiment of the present invention. FIG. 1B is a block diagram showing a subband synthesis filter according to an embodiment of the present invention.

FIG. 2 is a block diagram showing details of a horizontal division filter in FIG. 1;

FIG. 3 is a block diagram showing details of a horizontal synthesis filter in FIG. 1;

FIG. 4 is an explanatory diagram of the operation of the sorting means in FIG.

FIG. 5 is a block diagram showing details of a vertical division filter in FIG. 1;

FIG. 6 is a block diagram showing details of a vertical synthesis filter in FIG. 1;

FIG. 7A is a block diagram showing a configuration of a conventional subband division filter. FIG. 7B is a block diagram showing a configuration of a conventional subband synthesis filter.

FIG. 8 is a schematic diagram showing frequency division of a conventional subband division filter.

FIG. 9 is a schematic diagram of a video signal output from a conventional subband division filter.

[Explanation of symbols]

 1 horizontal division filter 2 rearrangement means 3 vertical division filter 4 vertical division filter 5 vertical synthesis filter 6 vertical synthesis filter 7 rearrangement means 8 horizontal synthesis filter 10 input terminal 11 output terminal 12 output terminal 13 output terminal 14 output terminal 20 output terminal 21 input terminal 22 input terminal 23 input terminal 24 input terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazushige Irie 1-6, Uchisaiwai-cho, Chiyoda-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation (72) Inventor Ryozo Kishimoto 1-1-1, Uchisaiwai-cho, Chiyoda-ku, Tokyo No. 6 Nippon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A video signal as an input, and the video signal is divided into a plurality of frequency bands in the horizontal direction of a spatial frequency region of an image using n (n ≧ 2) sample points in the horizontal direction of the video signal as a processing unit. A first band dividing unit that divides and outputs n sample points in parallel for each frequency band, and m (m ≧ 2) sample lines of the video signal as a processing unit Second band dividing means for dividing the spatial frequency domain into a plurality of frequency bands in the vertical direction, and n in the horizontal direction.
Reordering means for reordering the sample points into m sample lines, the output of the first band dividing means is connected to the input of the reordering means, and the output of the reordering means is the second And a sub-band division filter connected to the input of the band division means. 2. A video signal divided into a plurality of frequency bands in the spatial frequency domain of an image is input, and m of the video signal is input.
A first band synthesizing means for synthesizing the video signal in the vertical direction of the spatial frequency domain of the image using (m ≧ 2) sample lines as a processing unit, and n (n ≧ 2) in the horizontal direction of the video signal. ) Are input in parallel, and a second band synthesizing means for synthesizing the video signal in the horizontal direction of the spatial frequency region of the image using the n sample points as a processing unit, and m sample lines. A rearrangement unit for rearranging to n sample points in the horizontal direction is provided, the output of the first band synthesis unit is connected to the input of the rearrangement unit, and the output of the rearrangement unit is the second band. A subband synthesis filter, characterized in that it is connected to the input of a synthesis means.