JP3144180B2 - 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 apparatus for compressing and expanding a digital video signal.

[0002]

2. Description of the Related Art In recent years, D1, D2 video tape recorders (hereinafter referred to as VT) for digitizing and recording / reproducing video signals.
Abbreviated as R. ) Has been developed. Also, video floppy capable of recording and reproducing digital still images and VTR capable of recording digital moving images have been developed as consumer equipment. Examples of development of consumer digital VTRs include the Journal of the Institute of Television Engineers of Japan (Vol. 45, No. 7, pp. 813-8).
19, 1991). This consumer digital VTR uses various methods to determine the degree of redundancy of the video signal,
The data amount is compressed to about 1/5 and recorded.

[0003] A conventional video signal processing apparatus will be described below. FIG. 6 is a block diagram of a conventional video signal processing device. FIG. 5 is an explanatory diagram of the video signal subjected to the orthogonal transformation in FIG.

In FIG. 6, reference numeral 61 denotes an input terminal to which a digitized video signal is input, and 62 denotes a luminance signal (hereinafter abbreviated as Y signal) input to the input terminal 61 and a color difference signal (RY signal). , BY signals) into blocks of 8 × 8 pixels, and 63 orthogonally transforms the signal for each block output from the blocker 62 to obtain orthogonal components (DC signal and AC component). An orthogonal transformer that outputs
Reference numeral 64 denotes a class discriminator that determines the class of the block from the 63 AC components output from the orthogonal transformer 63. 65 denotes a signal output from the orthogonal transformer 63 based on the class information output from the class discriminator 64. The quantized signal from the quantizer for quantization is output to an output terminal 66.

The operation of the conventional video signal processing device configured as described above will be described below.

The video signal input to the input terminal 61 (one frame is composed of 720 × 480 pixels of Y signal, RY and BY
The color difference signal of the signal is composed of 180 × 480 pixels, and each pixel has an 8-bit value. The blocking unit 62 blocks the input signal (Y signal, RY signal, BY signal) in units of 8 × 8 pixels. Each of the blocked signals is supplied to an orthogonal transformer 63, which orthogonally transforms the signal for each block, and outputs orthogonal components (a DC signal and an AC component). The orthogonal transformer 63 converts the result of the orthogonal transformation from a DC value with low horizontal and vertical frequency components to an AC value with high frequency (DC → AC1 → AC2 →... → A).
C63) to the classifier 64. FIG. 5 shows this state. Here, AC1 to AC5 are defined as area 0, AC
6 to AC20 are defined as area 1, AC21 to AC42 are defined as area 2, and AC43 to AC63 are defined as area 3. The class discriminator 64 discriminates the class of the signal in block units output from the orthogonal transformer 63 based on the rules described in (Table 1). For example, a block obtained by orthogonally transforming a Y signal and
If the maximum value of the AC signal in the block is 30, the class is determined to be 2.

[0007]

[Table 1]

When the class value is 3, the quantizer 65 shifts down the AC value in the block by one bit (1/2).
After that, the quantized data amount is estimated using a total of 30 blocks of 20 blocks for the Y signal, 5 blocks for the RY signal, and 5 blocks for the BY signal as one unit. Nine types of quantization are used in the quantizer 65, and the contents are shown in (Table 2). Quantization is performed by bit shifting the AC signal in each area.

[0009]

[Table 2]

Table 3 shows the relationship between the nine types of quantization numbers and the sixteen types of quantization steps Qno. The data amount estimation after the quantization is performed by using 16 types of quantization steps Qno.
Required every time.

[0011]

[Table 3]

When the quantization step Qno is 0, each block has a quantization value indicated by a new quantization step Qno 'obtained by adding an offset value (shown in Table 4) based on the class value of each block to the quantization step 0. Quantization is performed using the quantization number.

[0013]

[Table 4]

The quantizer 65 compares the number of accumulated code words obtained when the variable-length coding is performed on the quantized signal with a predetermined target value, and determines the maximum quantization step value Qn that does not exceed the target.
Perform quantization based on o. That is, the offset value of each block is added to this Qno (if the addition result is 15 or more, it is set to 15.), and the new quantization step Qno 'is performed.
Is quantized with a quantization number corresponding to.

[0015]

However, in the above configuration, when class determination is performed based on the maximum value of the AC component, a large class value is selected for a block including an edge portion of a character or the like appearing in an image, and a large class value is selected for an edge peripheral portion. It causes image quality degradation.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a video signal processing apparatus for reducing the deterioration of the image quality in the peripheral portion of an image edge.

[0017]

According to a first aspect of the present invention, there is provided the above-mentioned object.
Adjacent multiple of the input video signal to achieve
Into blocks by collecting sample values ofmeans
And blockingmeansThe signal for each block output from
Performs orthogonal transformation and outputs orthogonal components (DC signal and AC component)
Orthogonal transformationmeansAnd the orthogonal transformmeansBlocks supplied by
Level detection means for detecting a level value from a signal for each
Orthogonal transformationmeansOf DC signal for each block supplied from
Supplied from width value and level detection meansPer blockLebe
Classification to Calculate Class Value from Rule ValuemeansAnd the class size
AnothermeansQuantization step based on the class value output from
Orthogonal transformationmeansQuantizing the output signal ofmeansWhen
It has a configuration with.

Further, the second invention to achieve the above object, a blocking means constituting the block collects adjacent plurality of sample values of an input video signal, outputted from the blocking unit Orthogonally transforms the signal of each block,
Orthogonal transform hand for outputting a quadrature component (DC signal and an AC component)
A stage, a level detecting means for detecting the level value from the signal of each block supplied from the orthogonal transform unit, an edge detecting means for calculating the edge information from the signal of each block supplied from the orthogonal transform means <br/> And the block supplied from the orthogonal transformation means.
Supplied from DC signal amplitude value and edge detection means for each lock
Rank value from edge information for each block
And a rank value detection means, blanking supplied from the level detecting means
Supplied from level and rank value detection means for each lock
Class discrimination to find class value from rank value for each block
And means, an output signal of the orthogonal transform means in the quantization step based on the class value output from the class discrimination means has a structure with a quantization means for quantizing.

[0019]

[Action] The first invention by the configuration described above, the level value is larger supplied from the level detecting means, and when the amplitude value of the DC signal is large, the class discrimination means outputs a smaller class values, the quantization means Becomes larger.
As a result, the quantization error of the block including the edge is reduced, and the image quality deterioration around the edge of the image is also reduced.

According to the second aspect of the present invention, the level value supplied from the level detecting means is large and the rank value is high.
When the rank value supplied from the value detection unit is small , the class determination unit outputs a small class value, and the offset value in the quantization unit increases. As a result, the DC signal
Even if the width value is small, the quantization error of the block including the edge is reduced, and the image quality deterioration around the edge of the image is also reduced.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the video signal processing apparatus according to the present invention will be described below.

FIG. 1 is a block diagram of a video signal processing apparatus according to the first embodiment. In FIG. 1, reference numeral 11 denotes an input terminal to which a digitized video signal is input, and 12 denotes a luminance signal (hereinafter abbreviated as Y signal) input to the input terminal 11 and a color difference signal (RY signal, B- signal). A blocker 13 for blocking each of the Y signals) into a signal of 8 × 8 pixels, and 13 orthogonally transforms the signal of each block output from the blocker 12 and outputs orthogonal components (DC signal and AC component). An orthogonal transformer 14 is a level detecting means for calculating a sum of absolute values of AC signals excluding a DC signal from a signal for each block supplied from the orthogonal transformer 13, and 15 is a block for each block of the signal supplied from the orthogonal transformer 13. A class discriminator for obtaining a class value from the color information and the amplitude value of the DC signal and the sum of the absolute values of the AC components supplied from the level detecting means 14. A class discriminator 16 is based on the class value output from the class discriminator 15. In quantizer for quantizing the output signal of the orthogonal transformer 13 in the quantization step,
The quantized signal is output to the output terminal 17.

The operation of the video signal processing apparatus according to the first embodiment configured as described above will be described below.

The video signal input to the input terminal 11 (one frame is a Y signal of 720 × 480 pixels, RY and BY
Each of the color difference signals is composed of 180 × 480 pixels, and each pixel has an 8-bit value. The blocking unit 12 blocks the input signal (Y signal, RY signal, BY signal) in units of 8 × 8 pixels. Each of the blocked signals is supplied to an orthogonal transformer 13, and orthogonally transforms the signal of each block, and an orthogonal component (a DC signal and an AC component) is output. The level detector 14 calculates the sum of the absolute values of the AC signals excluding the DC signal from the signal supplied from the orthogonal transformer 13. The class discriminator 15 determines the class value based on the rule of (Table 5) from the amplitude value of the DC signal supplied from the orthogonal transformer 13 and the sum of the absolute values of the AC components supplied from the level detector 14. .

[0025]

[Table 5]

In order to improve the image quality of the edge portion of the image, the class value of a block having a large absolute value sum of the AC components may be reduced. However, in this method, the number of blocks with a small class value increases, and in an image with a large amount of information, even if the quantization is performed with the minimum quantization step value, the target value is exceeded, and a part of the information is lost. There is. Also, by increasing the number of blocks having small class values, the superiority of blocks having originally small class values, such as flat portions of an image, may be impaired and image quality may be degraded.

Therefore, in the first embodiment of the present invention, only when the sum of the absolute values of the AC components is large and the DC amplitude value is large, that is, only for the edge portion of the image which is bright and easily visible visually. By reducing the class value, the above problem can be solved and the image quality can be prevented from deteriorating.

The orthogonal transformer 13 converts the result of the orthogonal transformation from a DC value with low horizontal and vertical frequency components to an AC with high frequency.
Output to the quantizer 16 as a value (DC → AC1 → AC2 →... → AC63). FIG. 5 shows this state. Here, AC1 to AC5 are area 0, AC6 to AC20 are area 1, AC21 to AC42 are area 2, AC43 to A.
C63 is defined as area 3.

When the class value is 3, the quantizer 16 shifts down the AC value in the block by one bit (1/2).
After that, the quantized data amount is estimated using a total of 30 blocks of 20 blocks for the Y signal, 5 blocks for the RY signal, and 5 blocks for the BY signal as one unit. Nine types of quantization are used in the quantizer 16, and the contents are shown in (Table 2). Quantization is performed by bit shifting the AC signal in each area. In addition, 9 kinds of quantization numbers and 16
Table 3 shows the relationship between the types of quantization steps Qno.
The data amount after quantization is calculated using 16 types of quantization steps Q
It is determined every no. When the quantization step Qno is 0, each block is quantized with the quantization number indicated by the new quantization step Qno 'obtained by adding the offset value (see (Table 4)) based on the class value of each block to the quantization step 0. Perform the conversion. The quantizer 16 compares the cumulative number of codewords when the signal after the quantization is subjected to variable-length coding with a predetermined target value, and determines the maximum quantization step value Qn that does not exceed the target.
Perform quantization based on o. That is, the offset value of each block is added to this Qno (if the addition result is 15 or more, it is set to 15.), and the new quantization step Qno 'is performed.
Is quantized with a quantization number corresponding to.

Next, a description will be given of a second embodiment of the video signal processing apparatus according to the present invention. FIG. 2 is a block diagram of a video signal processing device according to the second embodiment. FIG. 3 is an explanatory diagram of an operation of edge detection, and FIG. 4 is an explanatory diagram of a rank for class determination.

In FIG. 2, reference numeral 21 denotes an input terminal to which a digitized video signal is input, and 22 denotes a luminance signal (hereinafter abbreviated as Y signal) input to the input terminal 21 and a color difference signal (RY signal). , BY signals) into blocks of 8 × 8 pixels, and 23 orthogonally transforms the block-by-block signal output from the blocker 22 to obtain orthogonal components (DC signal and AC component). An orthogonal transformer that outputs
24 is a level detecting means for calculating the sum of the absolute values of the AC signals excluding the DC signal from the signal for each block supplied from the orthogonal transformer 23, and 25 is the edge information of the signal for each block supplied from the orthogonal transformer 23. Edge detector for calculating, 2
6 is based on the color information for each block of the signal supplied from the orthogonal transformer 23, the amplitude value of the DC signal, the sum of the absolute values of the AC components supplied from the level detector 24, and the edge information supplied from the edge detector 25. A classifier 27 for obtaining a class value is a quantizer for quantizing an output signal of the orthogonal transformer 23 in a quantization step based on the class value output from the class discriminator 26, and the quantized signal is output. Terminal 2
8 is output.

The operation of the video signal processing apparatus according to the second embodiment configured as described above will be described below.

The video signal input to the input terminal 21 (one frame is composed of 720 × 480 pixels of Y signal, RY and BY
The color difference signal of the signal is composed of 180 × 480 pixels, and each pixel has an 8-bit value. The blocking unit 22 blocks the input signal (Y signal, RY signal, BY signal) in units of 8 × 8 pixels. Each of the blocked signals is supplied to an orthogonal transformer 23, which orthogonally transforms the signal of each block, and outputs orthogonal components (a DC signal and an AC component). The level detector 24 calculates the absolute value sum of the AC signal excluding the DC signal from the signal supplied from the orthogonal transformer 23. As shown in FIG. 3, the edge detector 25 sums the absolute values (hereinafter, side1) of the 7 pixels having the highest horizontal frequency except for the DC signal of the signal for each block of 8 × 8 pixels supplied from the orthogonal transformer 23. ) And the sum of the absolute values of the 7 orthogonal components having the highest vertical frequency (hereinafter referred to as “side2”) minus the absolute value sum of the remaining 49 orthogonal components (hereinafter referred to as etc). A value (hereinafter, referred to as edge) is output.

The class discriminator 26 determines a rank value based on the rule of FIG. 4 from the amplitude value of the DC signal supplied from the orthogonal transformer 23 and the edge information supplied from the edge detector 25. At the same time, the level value is determined from the sum of the absolute values of the AC components supplied from the level detecting means 24, and is determined from the combination of the rank value, the level value, and the color information (Table 6).
The class value is determined based on the rule described above.

[0035]

[Table 6]

In the first embodiment, the class value is reduced only when the sum of the absolute values of the AC components is large and the DC amplitude value is large, that is, only at the edges of the image and in the bright and visually conspicuous portions. Thus, the image quality deterioration of the edge portion is prevented. However, in the second embodiment, if there is an edge even in a block having a small DC component amplitude value, the image quality deterioration may be conspicuous. are doing. FIG. 3 shows a method of edge detection. Edge detection utilizes the fact that the value of the component with the highest vertical frequency or the component with the highest horizontal frequency after orthogonal transformation increases when there is an edge in the vertical or horizontal direction of the image.

As described above, when the edge information is large even if the DC amplitude value is small, the class value becomes small and the image quality can be prevented from deteriorating.

The orthogonal transformer 23 converts the result of the orthogonal transformation from a DC value with low horizontal and vertical frequency components to an AC with high frequency.
Output to the quantizer 27 as a value (DC → AC1 → AC2 →... → AC63). FIG. 5 shows this state. Here, AC1 to AC5 are area 0, AC6 to AC20 are area 1, AC21 to AC42 are area 2, AC43 to A.
C63 is defined as area 3.

When the class value is 3, the quantizer 27 shifts down the AC value in the block by one bit (1/2).
After that, the quantized data amount is estimated using a total of 30 blocks of 20 blocks for the Y signal, 5 blocks for the RY signal, and 5 blocks for the BY signal as one unit. Nine types of quantization are used in the quantizer 27, and the contents are shown in (Table 2). Quantization is performed by bit shifting the AC signal in each area. In addition, 9 kinds of quantization numbers and 16
Table 3 shows the relationship between the types of quantization steps Qno.
Estimation of the data amount after quantization is performed in 16 types of quantization steps Q
It is determined every no. When the quantization step Qno is 0, each block is quantized with the quantization number indicated by the new quantization step Qno 'obtained by adding the offset value (see (Table 4)) based on the class value of each block to the quantization step 0. Perform the conversion. The quantizer 27 compares the cumulative number of codewords when the variable-length coding is performed on the quantized signal with a predetermined target value, and determines the maximum quantization step value Qn that does not exceed the target.
Perform quantization based on o. That is, the offset value of each block is added to this Qno (if the addition result is 15 or more, it is set to 15.), and the new quantization step Qno 'is performed.
Is quantized with a quantization number corresponding to.

[0040]

As described above, according to the present invention, a block generator for forming a block by collecting a plurality of adjacent sample values of an input video signal, and a signal for each block output from the block generator are provided. An orthogonal transformer for orthogonally transforming and outputting orthogonal components (a DC signal and an AC component); a level detecting means for calculating a sum of absolute values of AC signals excluding a DC signal from a signal supplied from the orthogonal transformer; An edge detector that calculates edge information of a signal for each block supplied from the detector,
Color information and DC for each block supplied from the orthogonal transformer
A class discriminator that obtains a class value from the sum of the absolute value of the AC component supplied from the signal amplitude value and the level detecting means and the edge information supplied from the edge detector, and a class value output from the class discriminator. By providing a quantizer for quantizing the output signal of the orthogonal transformer in the quantization step, a small class value is selected for a block including an edge portion such as a character appearing in an image, and a quantization error is reduced. ,
It is possible to prevent the image quality from being deteriorated in the edge portion, and the practical effect is great.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a configuration of a video signal processing device according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of an operation of edge detection in the second embodiment.

FIG. 4 is an explanatory diagram of a rank for class determination in the second embodiment.

FIG. 5 is an explanatory diagram of an orthogonally transformed video signal.

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

[Explanation of symbols]

 11, 21 Input terminal 12, 22 Blocking device 13, 23 Orthogonal transformer 14, 24 Level detecting means 15, 26 Class discriminator 16, 27 Quantizer 17, 28 Output terminal 25 Edge detector

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N 1/41-1/419 H04N ^7/ 24-7/68 H04N 11/00-11/22

Claims (6)

(57) [Claims] 1. A blocking means for collecting a plurality of adjacent sample values of an input video signal to form a block, and orthogonally transforming a signal for each block output from the blocking means to obtain an orthogonal component ( and orthogonal transform means for outputting a DC signal and an AC component), a level detecting means for detecting the level value from the signal of each block supplied from the orthogonal transform unit, a DC signal of each block supplied from the orthogonal transform means And the block supplied from the level detecting means.
And class discrimination means from the level values determined class value for each, to have a quantization means for quantizing the output signal of the orthogonal transform unit in the quantization step based on the class value output from the class discrimination means Characteristic video signal processing device. 2. Blocking means for collecting a plurality of adjacent sample values of an input video signal to form a block, and orthogonally transforming a signal for each block output from the blocking means to obtain an orthogonal component ( and orthogonal transform means for outputting a DC signal and an AC component), a level detecting means for detecting the level value from the signal of each block supplied from the orthogonal transform means, from the signal of each block supplied from the orthogonal transform means Edge detection means for calculating edge information, and a DC signal for each block supplied from the orthogonal transformation means
And the block supplied from the edge detecting means.
Rank value detection method that detects the rank value from each edge information
A stage, a level value for each block supplied from the level detection means, and a level value for each block supplied from the rank value detection means.
And class determination means for determining a class value from rank value, and characterized by having a quantization means for quantizing an output signal of the orthogonal transform unit in the quantization step based on the class value output from the class discrimination means Video signal processing device. Wherein the level detecting means, orthogonally converted AC
3. The video signal processing apparatus according to claim 1 , wherein a level value is obtained for each block from a sum of absolute values of the AC signal as a component . 4. An edge detecting means for each of the orthogonally transformed blocks, the orthogonal component having the highest horizontal frequency and the orthogonal component having the highest vertical frequency excluding the DC signal of the signal in the block.
The value obtained by subtracting the sum of absolute values of the remaining orthogonal components from the sum of absolute values is
3. The video signal processing device according to claim 2, wherein the edge information is obtained based on whether or not the value is equal to or greater than a predetermined value. 5. A plurality of adjacent video signals of an input video signal.
A block forming step of collecting sample values to form a block, and a signal for each block output from the block forming step.
Performs orthogonal transformation and outputs orthogonal components (DC signal and AC component)
Orthogonal transformation step, and from the signal for each block supplied from the orthogonal transformation step,
A level detection step of detecting a level value, and a DC signal for each block supplied from the orthogonal transformation step
And the block supplied from the level detection step
A class discriminating step of obtaining a class value from each level value, based on the class value output from the class discriminating step.
Quantize the output signal of the orthogonal transformation step in the quantization step
Video signal processing, comprising:
Method. 6. A plurality of adjacent video signals of an input video signal
A blocking step of collecting sample values to form a block; The signal for each block output from the blocking step is
Performs orthogonal transformation and outputs orthogonal components (DC signal and AC component)
Orthogonal transformation step, From the signal for each block supplied from the orthogonal transformation step
A level detection step of detecting a level value; From the signal for each block supplied from the orthogonal transformation step
An edge detection step of calculating edge information; DC signal for each block supplied from the orthogonal transformation step
And the block supplied from the edge detection step
Rank value detector that detects the rank value from each edge information
About The level for each block supplied from the level detection step
Value and each block supplied from the rank value detection step.
A class determination step of obtaining a class value from the rank value; Based on the class value output from the class determination step
Quantize the output signal of the orthogonal transformation step in the quantization step
Video signal processing, comprising:
Method.