JP3020544B2 - Scan conversion device for image signal - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scan conversion apparatus for an image signal, and is particularly suitable for converting an image signal of an interlace scan method into an image signal of a non-interlace scan method. The present invention relates to a scan conversion device.

[Conventional technology]

In order to display interlaced scanning image signals with high quality, scan conversion is performed by generating information on scanning lines missing in interlaced scanning by interpolation scanning, converting the information into a non-interlaced scanning signal sequence, and displaying it. Is performed.

In this scan conversion, so-called motion adaptive signal processing is performed in order to obtain a high-quality reproduced image from a still image to a moving image. That is, the interpolated scanning line information IP _S for the still image generated by the operation between the fields, the interpolated scanning line information IP _S suitable for the moving image generated by the operation of the field
_M is weighted by a motion coefficient k (0k1, k = 0 at rest) corresponding to the motion of the image, and finally the interpolated scanning line signal IP
IP = generates a _{(1-k) · IP S} + k · IP M, and the scan conversion to the signal series of the non-interlaced scanning scheme line summer using this signal as.

[Problems to be solved by the invention]

In the above prior art, the interpolation scanning line information IP suitable for a moving image is used.
_{Since M} is generated by the average value of the upper and lower scanning lines in the same field, there was a problem that the vertical resolution was reduced in the moving image mode.

An object of the present invention is to provide a scan conversion device for image signals that enables reproduction of an image with high vertical resolution even in a moving image mode.

It is another object of the present invention to provide a scan conversion apparatus for an image signal which changes a vertical resolution characteristic according to the movement of an image and matches the visual characteristic.

[Means for solving the problem]

To achieve the above object, the interpolated scanning line information IP _M for Video, less gain reduction at the vertical frequency characteristic midrange to high range region, and a characteristic that does not impair the time-frequency characteristic interpolation filter In this case, the generated signal is used.

Further, in order to achieve the other object, the tap coefficient of the interpolation filter is adaptively changed according to the motion of the image so that the image can be displayed with the vertical frequency characteristics more matched with the visual characteristics. Things.

[Action]

In the present invention, image information for a moving image corresponding to an interpolated scanning line indicated by a black circle is generated by a vertical interpolation filter from an interlaced scanning image signal indicated by a white circle in FIG.

This interpolation filter applies a vertical frequency characteristic F (ν) to an image signal of interlaced scanning of M scanning lines.
(Ν: direct frequency) is F (0) = 1, F (ν ₁ ) = 0
_{(Ν 1 = M / 2)} , composed of transversal filter having the characteristics of F (ν ₁ /2)=0.5. Accordingly, the following relationship is established between the tap coefficients a _i (i = 0, 1,..., L) of the interpolation filter.

a ₀ = 0.5 (1) a _2i = 0 (2) The contracting conditions of the equations (1) to (3) and the vertical frequency ν
= Α _m ν ₁ By defining the gain at the point of β _m as β _m ,
From an image signal of interlaced scanning, it is possible to constitute an interpolation filter for generating interpolated scanning line information IP _M for videos having various vertical frequency characteristic.

For example, setting α _m = 1/4 and β _m = 1 makes it possible to realize the interpolation filter circuit shown in FIG. Further, by adding a condition of α _m = 3/8 and β _m = 1, it is possible to realize this characteristic with an interpolation filter circuit as shown in FIG.

FIG. 4 shows the vertical frequency characteristics of these interpolation filter circuits. In the figure, the characteristics of interpolated scanning lines for moving images obtained by the prior art are shown by dotted lines. As is clear from the comparison of the characteristics of the two, according to the present invention, the signal obtained from the interpolation filter circuit having the characteristic of small gain reduction in the middle to high ranges of the vertical frequency is used as interpolation scanning line information for a moving image. In addition, it is possible to solve the problem of the vertical resolution in the moving image mode which is a problem in the related art.

Furthermore, for moving images, the characteristics of the interpolation filter circuit are changed in accordance with the speed of the motion.For example, characteristic 2 is used for loose motion, and interpolation scanning line information of the conventional technology is used for severe motion. Therefore, scan conversion of the image signal can be realized in a form more matched with the visual characteristics.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. Image signal V _S of the interlaced scanning, moving image interpolation filter circuit 1, the still image interpolation signal generation circuit 2, the motion detection circuit 3, is input to the delay circuit 6.

Moving image interpolation filter circuit 1, the interpolation filter of the above-mentioned properties, to produce a suitable interpolation scanning line information IP _M on the moving image. Further, the still picture interpolation signal generating circuit 2, for example, prior to field scan lines, or the like mean of the signal of the scanning lines before and after the field, to generate an interpolated scanning line information IP _S suitable for still images.

The motion detection circuit 3 detects the motion of the image based on a difference signal between frames of the image signal, and calculates a motion coefficient k (0k1, still mode k = 0, moving image mode k =
1) is generated.

Coefficient load circuit 4, k with respect to interpolation scanning line information IP _M, performing the calculation of coefficients load 1-k with respect to interpolation scanning line information IP _S. The signals subjected to these coefficient weights are added by an adder circuit 5, and a signal IP of an interpolation scanning line necessary for non-interlaced scanning is obtained.
Generate

The signal V _M and the signal IP whose delay has been adjusted by the delay circuit 6
Is input to the time axis conversion circuit 7 and is compressed by half the time axis.
In addition, an image signal sequence V _S ′ converted into a desired non-interlaced scanning form by performing time series rearrangement is generated.

Next, a configuration example and characteristics of the interpolation filter circuit 1 for a moving image used in this embodiment will be described with reference to FIGS.

Moving image interpolation filter circuit shown in FIG. 2, to generate the same vertical respective two X _-1 in field, X ₀ and X _1, X ₂ of the image signals from the interpolation scanning line information IP _M interlaced This can be realized by a combination of a one-line delay circuit 8, a coefficient load circuit 4, and an adder circuit 5.

Coefficients a ₁ = 0.6036, a ₃ = −0.1036 are applied to the signal delayed by one line by the one-line delay circuit 8, respectively.
Generating a signal IP _M by adding.

On the other hand, the moving image interpolation filter circuit shown in FIG. 3 has three upper and lower X _-2 , X _-1 and X ₀ in the same field, and
X _1, X _2, and generates an interpolation scanning line information IP _M from the image signal of the interlaced scanning of X _3. In this case, the load factor is a ₁ = 0.6
036, a ₃ = −0.1974, a ₅ = 0.0938.

FIG. 4 shows the vertical frequency characteristics of these interpolation filter circuits. Conventional technology (upper and lower scanning lines in the same field)
X _0, compared to the characteristics of the average of the X _1), improves the characteristics of the midrange to high range area, higher-vertical resolution interpolation scanning line information IP
_M can be generated.

As described above, according to this embodiment, it is possible to generate a non-interlaced image signal having a high vertical resolution even for a moving image.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, the characteristics of the vertical resolution of the interpolated scanning line information corresponding to the moving image are changed according to the moving speed of the image, and a non-interlaced scanning image signal is generated in a form more consistent with the visual characteristics. It is.

The basic configuration of this embodiment is almost the same as that of FIG. 1, but the functions of the interpolation filter circuit 9 for moving images and the motion detection circuit 10 are slightly different. That is, the motion detecting circuit 10 in the image motion velocity information k _v (0k _v 1, motion k _v = 0 and Yutsukuri, fast motion k _v = 1) detection of newly added, also interpolation video the filter circuit 9 can be changed the Supporting connexion vertical frequency characteristic to the velocity information k _v.

A configuration example and characteristics of the interpolation filter circuit 9 for a moving image will be described with reference to FIGS. 6 and 7. FIG. Scan lines X _-2 , X _-1 , X _{0 of} three interlaced scans in the same field
And X _1, the image signals of X _2, X _3, the coefficient a ₁ = 0.5k _v +0.6
_{036 (1-k v),} a 3 = -0.1974 (1-k v), a 5 = 0.0938
(1-k _v) weighted with coefficients load circuit 4, respectively, to generate the interpolated scanning line information IP _M by adding them. Then, Yotsute to changing the velocity information k _v, to achieve a variety of vertical frequency characteristics in a range from the solid line as shown in Figure 7 to the dotted line.

As described above, according to the present embodiment, it is possible to generate a non-interlaced scanning image signal in a form that matches the visual characteristics even for a moving image.

Next, an embodiment of the motion detection circuits 3 and 10 will be described with reference to FIG. This is achieved with a configuration similar to that used in many of the prior art.

The one-frame difference signal extraction circuit 11 performs a difference operation between the interlaced scanning image signal V _S and a signal delayed by one frame to extract a difference signal component FD between one frame. This signal is subjected to an absolute value quantization process in an absolute value quantization circuit 12 to generate a quantized signal QFD. Next, the three-dimensional smoothing circuit 13 applies a horizontal
A smoothing process is performed in a three-dimensional region of vertical and time to remove noise components and reduce omission of motion detection, thereby generating a signal ▼. Then, the motion information generating circuit 14
Then, a motion coefficient k and speed information _kv are generated according to the level of the signal ▼.

Another embodiment of the motion detection circuits 3 and 10 will be described with reference to FIG. In this embodiment, a pattern portion of an image is extracted as one object region, and a motion is detected for each object region.

The object region extraction circuit 15 detects an image pattern portion from a high frequency component of the image signal, and detects one continuous image pattern portion.
The object region signal OB is generated by performing a smoothing process to obtain the number of regions.

On the other hand, the one-frame difference signal extraction circuit 11 detects the one-frame difference signal component FD as described above.

The moving object region extraction circuit 16 extracts a moving object region from the signals OB and FD as a moving object region signal MOB. That is, when the difference signal component FD for one frame exists in the area of the object area signal OB, the object area is determined to be a moving object and is extracted as a moving object area.

The motion information extraction circuit 17 includes a difference signal QFD between one frame, which has been subjected to absolute value quantization by the absolute value quantization circuit 12, and a moving object region signal.
Generate motion information QFD 'using MOB. For example, in the moving object area, the maximum value of the signal QFD included in this area is used.
Extract as FD '.

This signal is converted by a two-dimensional smoothing circuit 18 into two horizontal and vertical signals.
By performing a smoothing process in the dimensional area, a signal ▲ ▼ for reducing detection omission of motion is generated. Then, the motion information generating circuit 14, in response to the signal ▲ ▼ level, generating a motion coefficient k, and velocity information k _v.

In the present embodiment, since the motion is focused on the object area, it is possible to detect the motion with higher detection accuracy than the motion detection shown in FIG.

Next, another embodiment of the present invention will be described with reference to FIG. In many cases, the image signal is subjected to gamma correction for compensating for the gamma characteristic of the picture tube. In this embodiment, non-interlaced scan conversion with higher accuracy is performed on this type of image signal. It is suitable for.

The gamma-corrected image signal is subjected to an inverse gamma operation in an inverse Gaman circuit 19 to obtain a linear image signal sequence V (1 /
Γ). And, from this linear image signal,
Video interpolation filter circuit 20, Still image interpolation signal generation circuit 2
, The interpolated scanning line information IP _M for moving image and still image, respectively.
To generate the IP _S. Then, these signals are weighted by the motion coefficient k obtained from the motion detection circuit 21, and the two are added by the addition circuit 5 to obtain an interpolation scanning line signal in a linear system.
Generate IP (1 / Γ).

This signal is subjected to a gamma correction operation in the gamma correction circuit 22 to be converted into a gamma corrected interpolated scanning line signal IP. This signal and the signal V _M delayed adjusted by the delay circuit end 23 1/2 compression of the time axis in the time axis converter circuit 7, and row operations Narabikae chronological connexion, an image signal of the non-interlaced scanning Generate.

In this embodiment, the video interpolation filter circuit 20 includes:
The one shown in FIG. 2, FIG. 3, or FIG. 6 can be used. 8 and 9 can be applied to the motion detection circuit 21.

In this embodiment, since the interpolation scanning line signal is generated in the linear signal sequence, it is possible to prevent various kinds of deterioration due to the non-linearity of the image signal due to the gamma correction.
For this reason, scan conversion to non-interlaced scanning with higher accuracy can be realized.

On the other hand, recently, a display having a linear characteristic such as a flat display is often used for display. An embodiment of the present invention suitable for this type of linear display system will be described with reference to FIG.

The gamma-corrected image signal is subjected to inverse gamma scanning by an inverse gamma circuit 19 to obtain a linear system image signal V (1 / Γ).
Convert to For this image signal V (1 / Γ),
As in the embodiment of FIG. 10, a linear interpolation scanning line signal IP (1 /
Γ) is generated. This signal and the linear image signal V _ML whose delay has been adjusted by the delay circuit 23 are
Performs / 2 compression and time-series rearrangement operations to generate a non-interlaced image signal of a linear signal sequence.

〔The invention's effect〕

According to the present invention, it is possible to perform scan conversion to a non-interlaced image signal with a small decrease in vertical resolution even for a moving image. is there.

In addition, since scan conversion to non-interlaced scanning can be performed in a form that matches the moving image with the visual characteristics, it is effective in improving the quality of the image.

It is clear that the present invention can be applied to various types of image signals, such as a luminance signal, a color difference signal, and three primary color signals.

Further, the present invention can be applied to scan conversion of an image signal having various numbers of scanning lines, for example, an interlaced scanning signal such as NTSC, PAL, SECAM, or HDTV of the current television system into a non-interlaced scanning signal. It is also clear.

[Brief description of the drawings]

FIG. 1 is an overall block diagram of an embodiment of the present invention, and FIG.
FIGS. 3 and 3 are block diagrams of an embodiment of a moving image interpolation filter circuit according to the present invention, FIG. 4 is a frequency characteristic diagram of the above filter, and FIG. FIG. 6 is a block diagram of an embodiment of a moving picture interpolation filter circuit used in the embodiment of FIG. 5, and FIG.
8 and 9 are block diagrams of an embodiment of a motion detecting circuit, and FIGS. 10 and 11 are general blocks of an embodiment of the present invention for a gamma-corrected image signal. It is a block diagram. 1 ... Moving-film interpolation filter circuit 2 ... Still image interpolation signal generation circuit 3 ... Motion detection circuit 4 ... Coefficient load circuit
5 ... addition circuit, 6 ... delay circuit, 7 ... time axis conversion circuit, 8 ... 1 line delay circuit, 9 ... moving image interpolation filter circuit, 10 ... motion detection circuit, 11 ... 1 frame Difference signal extraction circuit, 12 ... absolute value quantization circuit, 13 ... three-dimensional smoothing circuit, 14 ... motion information generation circuit, 15 ... object area extraction circuit, 16 ... moving object area extraction circuit, 17: a motion information extraction circuit, 18: a two-dimensional smoothing circuit, 19: an inverse gamma circuit, 20: a video interpolation filter circuit, 21: a motion detection circuit, 22: a gamma correction circuit, 23 ... Delay circuit.

Claims (2)

(57) [Claims] A first means for generating first interpolated search line information corresponding to a still image and second interpolated scan line information corresponding to a moving image from an interlaced scanning image signal; A second means for detecting more movement, and changing a ratio of the mixed addition of the first interpolation scanning line information and the second interpolation scanning line information in accordance with a result of the movement detection by the second means. And a fourth means for generating a non-interlaced scanning image signal sequence by compressing a time axis of the image signal and the interpolation scanning line signal and rearranging the time sequence. In the image signal scan conversion apparatus for performing scan conversion from interlaced scan to non-interlaced scan, the first means may convert the second interpolated scan line information into at least N (N3 ) Of the scan line Generated by a linear combination calculation of the image signal, and scan conversion apparatus for an image signal, characterized in that to change the coefficient values of the linear combination calculated in accordance with the speed of motion detected by the second means. 2. The apparatus according to claim 1, wherein said image signal is an image signal obtained by converting a gamma-corrected image signal into a linear signal series by inverse gamma scanning.