JPH08275154A - Image signal processing unit - Google Patents

Abstract

PURPOSE: To reduce distortion in a reproduced image of an image data signal coded in the unit of blocks. CONSTITUTION: A storage medium reproducing device 15 reproduces a storage medium recording an image data signal coded in the unit of blocks. Image data are separated from a bit stream BS obtained by a system multiplexer demultiplexer 21 and fed to a video decoder 22. The video decoder 22 generates a luminance signal Y and color difference signals Cb, Cr from the image data. The signals Y, Cb, Cr are given to a post-processing section 23, in which the signals are converted into three primary color data signals DRM, DGM, DBM being image data signals and written in a memory section 38. The signal written in the memory section 38 is read and a digital filter section 39 attenuates a high frequency component and the result is given to a D/A converter section 41, in which the signals are converted into analog three primary color signals RQ, GQ, BQ. The signals RQ, GQ, BQ are fed to a display device 16 to obtain a reproduced image without distortion at block borders.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal processing device. More specifically, the distortion of the reproduced image at the boundary between blocks is reduced by band-limiting the decoded signal of the image data signal compressed in block units with a filter to attenuate high frequency components.

[0002]

2. Description of the Related Art An MPEG (Moving Picture Experts Group) compression technique is known so that a video signal can be digitized and, for example, image data signals can be stored and transmitted at low cost. Here, an example of the configuration of the video signal encoding / decoding apparatus is shown in FIG.

The video signal is separated into a luminance signal Y and color difference signals Cb and Cr by a preprocessing unit 1 and supplied to an information source encoder 3 of a video encoder unit 2. The color difference signal Cb is a signal obtained by subtracting the luminance signal Y component from the blue primary color signal, and the color difference signal Cr is a signal obtained by subtracting the luminance signal Y component from the red primary color signal. In the information source encoder 3, arithmetic processing for compressing the data amount is performed on the supplied signal. The compressed data is supplied to the video signal multiplex encoder 4 and variable-length coded, and the data is converted into a hierarchical format.

The image data thus obtained is supplied to the system multiplex encoder 6 via the transmission buffer 5 for keeping the transmission data amount constant. The system multiplexing encoder 6 is supplied with audio data, user data, sync signals, etc. from an audio encoder, a data signal generator, etc. (not shown), and the image data, audio data, and user data are synchronized so as to be synchronized during reproduction. Data and the like are multiplexed to generate an MPEG type bit stream. This bit stream is recorded in the storage medium 7, for example.

When the bit stream recorded in the storage medium 7 is read out and supplied to the system demultiplexer 8, the system demultiplexer 8 synchronizes with the image data, audio data, and user data while synchronizing with the bit stream. Data etc. are separated. This image data is supplied to the reception buffer 10 of the video decoder unit 9. The image data supplied during the data decoding process is temporarily stored in the reception buffer 10.

The data stored in the reception buffer 10 is
It is sequentially read and supplied to the video signal multiplexing decoder 11 defined by MPEG. The video signal multiplex decoder 11 performs hierarchical structure decoding and variable length decoding on the supplied image data, and supplies the obtained data to the information source decoder 12. In the information source decoder 12, the data is expanded to generate the luminance signal Y and the color difference signals Cb and Cr, which are supplied to the post-processing unit 13.
In the post-processing unit 13, the luminance signal Y and the color difference signals Cb, Cr
The video signal is reproduced based on the.

The structure of image data is shown in FIG.
The luminance signal Y and the color difference signals Cb and Cr supplied to the information source encoder 3 of the video encoder unit 2 are, for example, the color difference signal C.
When one pixel of b and Cr is a signal of the 4: 2: 0 encoding system corresponding to four pixels of the luminance signal Y around it, as shown in FIG. 3A, four blocks of 8 pixels × 8 lines are provided. Luminance signal and the color difference signal Cb and the color difference signal Cr of one block of 8 pixels × 8 lines overlap to form one macroblock. The information source encoder 3 performs the encoding process for each macroblock on the macroblock signal thus configured, and the information source decoder 12 performs the decoding process for each macroblock. As shown in FIG. 3B, one screen of the NTSC system has 352 effective pixels in the horizontal scanning direction and 240 lines in the vertical scanning direction, and 16 pixels × 16 lines is one macroblock. The screen has 22 (horizontal scanning direction) × 15 (vertical scanning direction) macroblocks.

[0008]

By the way, the reproduced image shown in FIG. 4A, which is generated based on the video signal from the post-processing unit 13 after the processing is performed in the unit of macroblock, is the same as that shown in FIG.
As shown in FIG. 4B in which a part of the reproduced image shown in FIG.
Image distortion may be noticeable at the boundary of macroblocks. Further, when the reproduced image is displayed on a display device having a spatial resolution better than that of the television device, the distortion of the image at the boundary portion of the macroblock becomes more remarkable.

Therefore, the present invention provides an image signal processing apparatus capable of reducing distortion of a reproduced image of an image data signal encoded in block units.

[0010]

An image signal processing apparatus according to the present invention includes a decoder means for decoding a compressed image data signal coded in block units, and an image data signal decoded by the decoding means. Filter means for attenuating high frequency components.

[0011]

According to the present invention, since the high frequency component of the image data signal decoded by the decoder means is attenuated by the filter means, it is possible to attenuate the high frequency component of the image data signal at the block boundary. Becomes

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an image signal processing apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 shows an image signal processing device as a personal computer (hereinafter referred to as “personal computer”).
The above shows the configuration when it is provided.

In FIG. 1, a storage medium reproducing device 15 is shown.
Then, the bit stream BS of the MPEG system, for example, recorded in the storage medium 7 shown in FIG. 2 is read. This bit stream BS is supplied to the system demultiplexer 21 of the decoder unit 20 which is the decoder means. In the system demultiplexer 21, the bit stream B
The image data is separated from S and supplied to the video decoder 22.

The video decoder 22 corresponds to the video decoder section 9 in FIG. 2, and generates a luminance signal Y and color difference signals Cb and Cr from the supplied image data. The luminance signal Y and the color difference signals Cb and Cr are supplied to the post-processing unit 23. In the post-processing unit 23, the luminance signal Y and the color difference signal C
Three primary color data signals D which are image data signals from b and Cr
RM, DGM, and DBM are generated and supplied to the signal selection unit 37 of the capture substrate unit 30 described later. Further, the post-processing unit 23 sends the three primary color data signals DRM, DGM, DB to the signal generation unit 36 of the capture substrate unit 30 described later.
The M sync signal SYM is supplied.

The television reception signal RF is converted into an image signal SV by a TV signal processing section 31 having a TV tuner of the capture board section 30. This image signal SV is Y / C
The separation unit 32 separates the luminance signal Y and the carrier color signal C.
The luminance signal Y is supplied to the sync separation unit 33 and the RGB decoder unit 3
4 is supplied. Further, the carrier color signal C is supplied to the RGB decoder unit 34. The RGB decoder section 34 generates three primary color signals RT, GT, BT which are analog signals based on the luminance signal Y and the carrier color signal C, and the A / D conversion section 35.
Is supplied to.

The sync separator 33 separates the sync signal SYT from the luminance signal Y. The synchronization signal SYT is supplied to the signal generator 36. The signal generator 36 has, for example, a PLL circuit and the like, and the write control signal WC and the synchronization signal SYC supplied to the display device 16 are based on a reference signal generated in synchronization with the synchronization signal SYT or the synchronization signal SYM. Is generated. The synchronizing signal SYC is a signal synchronized with the synchronizing signal SYT or the synchronizing signal SYM.
The write control signal WC is supplied to the A / D conversion section 35 and the memory section 38 which is a memory means. In addition, the synchronization signal SY
C is supplied to the signal selection unit 42 and the PC signal processing unit 51 of the mother board unit 50.

In the A / D converter 35, the write control signal WC
The respective signals of the three primary color signals RT, GT, BT are converted into digital three primary color data signals DRT, DGT, DBT based on the above, and are supplied to the signal selection unit 37.

In the signal selection section 37, the selection signal S supplied from the PC signal processing section 51 of the mother board section 50 which will be described later.
Based on E, one of the three primary color data signals DRM, DGM, DBM or the three primary color data signals DRT, DGT, DBT is selected, and the memory section 3 as a memory means is selected.
8 is supplied.

The three primary color data signals written in the memory section 38 are read out based on the read control signal RC supplied from the PC signal processing section 51, and the three primary color data signals DR are read.
N, DGN, and DBN are supplied to the digital filter unit 39 and the image data signal conversion unit 40 which are filter means.

In the digital filter unit 39, the three primary color data signals DRN, DGN, DB based on the read control signal RC.
Band limitation of N is performed and high frequency components are attenuated. The band-limited signals are the three primary color data signals DRQ, DGQ,
It is supplied to the D / A converter 41 as DBQ. In the D / A converter 41, the three primary color data signals DRQ, DGQ, DBQ are analog three primary color signals RQ, based on the read control signal RC.
Converted to GQ and BQ. These three primary color signals RQ, GQ, BQ
Is supplied to the signal selection unit 42.

In the image data signal conversion section 40, a pixel data signal TD is generated from the three primary color data signals DRN, DGN, DBN and supplied to the PC signal processing section 51 of the mother board section 50.

The PC signal processing unit 51 generates a new pixel data signal GD in which a television image is captured in the computer image based on the pixel data of the computer image and the pixel data signal TD supplied from the image data signal conversion unit 40. Is generated. The pixel data signal GD is supplied to the color palette ROM section 52. In the PC signal processing unit 51, the synchronization signal S supplied to the display device 16 is also used.
YP is generated and the signal selection unit 4 of the capture substrate unit 30 is generated.
2 and the selection signal SE for switching the image displayed on the screen of the display device 16 is generated and supplied to the signal generator 36, the signal selector 37, and the signal selector 42. Further, the read control signal RC is generated based on the synchronization signal SYC and supplied to the memory section 38, the digital filter section 39 and the D / A conversion section 41.

In the color palette ROM section 52, the pixel data signal GD is converted into the three primary color data signals DRP, DGP, DBP.
Is converted to. These three primary color data signals DRP, DGP, D
BP is converted into three primary color signals RP, GP, BP synchronized with the synchronization signal SYP by the D / A converter 53, and then supplied to the signal selector 42 of the capture substrate unit 30.

The display device 16 is connected to the signal selection section 42, and the three primary color signals and the synchronization signal supplied based on the selection signal SE supplied to the signal selection section 42 are selected, and the selected signal is selected. Is the display device 16
And the image is displayed.

Next, the operation will be described. When an image based on the signals recorded in the storage medium is displayed on the screen of the display device 16, the signal selection unit 37 receives the three primary color data supplied from the post-processing unit 23 by the selection signal SE from the PC signal processing unit 51. Signals DRM, DGM,
DBM is selected. The signal generator 36 also generates the write control signal WC and the sync signal SYC based on the reference signal generated in synchronization with the sync signal SYM.

The three primary color data signals DRM, DGM, DBM selected by the signal selection unit 37 are written in the memory unit 38 based on the write control signal WC. Further, the data written in the memory section 38 is read by the read control signal RC generated by the PC signal processing section 51 based on the synchronization signal SYC, and the band is limited by the digital filter section 39. This band-limited signal is further D / A
The converter 41 converts the analog three primary color signals RQ, GQ, BQ and supplies them to the signal selector 42. Signal selection unit 42
Then, based on the selection signal SE, the three primary color signals RQ, GQ, BQ
And the synchronizing signal SYNC are selected and supplied to the display device 16.

As described above, the three primary color data signals, which are signals obtained by decoding the recording signals of the storage medium, are band-limited by the digital filter unit 39, converted into analog signals, and supplied to the display device 16, so that the space is reduced. Even with the display device 16 having a good resolution, the distortion of the image at the boundary portion of the macroblock is reduced, and a good display image can be obtained.

When the selection signal SE selects the three primary color data signals DRT, DGT, DBT supplied from the A / D converter 35 in the signal selector 37, the signal generator 36 synchronizes with the synchronization signal SYT. Then, the write control signal WC and the synchronizing signal SYC are generated based on the reference signal thus generated, and the three primary color data signals DRT, DGT, DBT are written in the memory section 38 based on the write control signal WC. Further, the data written in the memory section 38 is read by the PC signal processing section 51 by the read control signal RC generated based on the synchronization signal SYC, and is also converted into the pixel data signal TD by the image data signal conversion section 40. It is supplied to the PC signal processing unit 51.

Therefore, the PC signal processing unit 51 generates a new pixel data signal GD in which the television image is captured in the computer image, and the color palette ROM unit 2 is generated.
After being converted into the three primary color signals RP, GP and BP in 6 and then selected by the signal selecting section 42 and supplied to the display device 16, the synchronizing signal SYP is also supplied to the display device 16 so that it is displayed on the screen of the display device 16. Computer images with captured television images can be displayed.

By the way, in the above embodiment, the post-processing section 23
Three primary color data signals DRM, DGM, DBM supplied from
Is stored in the memory unit 38 of the capture substrate unit 30, but the memory unit is not limited to the memory unit 38 of the capture substrate unit 30, and needless to say, an image memory of a personal computer or the like may be used. is there. Further, by storing the three primary color data signals DRM, DGM, DBM in the memory unit,
By sequentially reading this signal and supplying it to the digital filter section 39, the band limitation processing of the signal can be surely performed, but the three primary color data signals DRM, DGM, and DBM can be obtained without using the memory section.
Even if the signal is supplied to 9, the band of the signal can be limited. Also, the three primary color data signals DRM, DGM, DBM are MPE
The signal is not limited to the signal generated from the signal obtained by decoding the G system bit stream BS.

[0031]

According to the present invention, since the high frequency component of the image data signal is attenuated at the boundary of the blocks, for example, when an image based on this image data signal is displayed on a display device having a good spatial resolution. Even in this case, it is possible to reduce image distortion at the block boundary.

Further, since the image data signal decoded by the decoder means is stored in the memory means and the stored image data signals are sequentially read out and supplied to the filter means, the high frequency component of the image data signal. The attenuation process can be performed more reliably.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of an image signal processing device according to the present invention.

FIG. 2 is a diagram showing a configuration of a video signal encoding / decoding device.

FIG. 3 is a diagram showing a structure of image data.

FIG. 4 is a diagram showing an example of a reproduced image.

[Explanation of symbols]

 7 Storage Media 15 Storage Media Playback Device 16 Display Device 20 Decoder Unit 21 System Demultiplexer 22 Video Decoder 23 Post Processing Unit 36 Signal Generation Unit 37 Signal Selection Unit 38 Memory Unit 39 Digital Filter Unit 41 D / A Conversion Unit 42 Signal Selection Department

Claims (3)

[Claims] 1. A decoder means for decoding a compressed image data signal encoded in block units, and a filter means for attenuating a high frequency component of the image data signal decoded by the decoder means. Image signal processing device. 2. A memory means for storing the image data signal decoded by the decoder means, wherein the image data signal decoded by the decoder means is stored in the memory means and stored in the memory means. The image signal processing apparatus according to claim 1, wherein the image data signals thus generated are sequentially read and supplied to the filter means. 3. The image signal processing apparatus according to claim 1, wherein the compressed image data signal is an MPEG bit stream.