JPH06292194A - Video signal processing circuit - Google Patents

Abstract

PURPOSE:To provide a video signal processing circuit capable of setting input data in accordance with compressed picture quality. CONSTITUTION:This circuit is equipped with an A/D part 372 which performs the analog/digital conversion of a video signal, an image compression part 342 which compresses image data from the A/D part 372, a picture quality correction circuit 42 which adjusts the picture quality of the video signal to be imparted to the image compression part 342, and a picture quality correction control circuit 41 which controls by adjusting the picture quality of the video signal outputted from the picture quality correction circuit 42 along with the change of a compression parameter. Also, the video signal is supplied to the A/D part 372 after passing through the picture quality correction circuit 42. An appropriate video signal can be supplied to the image compression part 342 in accompanying with changing the compression quantity of the picture compression part 342 by changing the compression parameter to be imparted to the image compression part 342, and also, changing the picture quality of the video signal to be supplied to the image compression part 342 corresponding to the compression parameter at the picture quality correction circuit 42.

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 circuit used in a videophone or the like, and more particularly to a video signal for adjusting the image quality of a video signal input to an image compression section according to the degree of image compression. It relates to a processing circuit.

[0002]

2. Description of the Related Art Conventionally, a video signal processing circuit of this type has an analog / digital converter for analog / digital converting a video signal obtained from a television camera or the like, and image compression of image data from the analog / digital converter. It is known as a circuit that includes an image compression unit for changing the compression amount by changing the compression parameter given to the image compression unit. Such a video signal processing circuit is often used in, for example, a videophone. This video phone
As is well known, in addition to conventional telephones that perform only voice communication, it is also possible to communicate with self-portraits of callers and images of materials, etc., to spread the ISDN (Integrated Services Digital Communication Network). Accordingly, various types have been developed.

By the way, although the ISDN has a sufficiently wide band as compared with a general telephone line, the band is not wide enough to transmit a video signal in the occupied band of the signal. Therefore, conventionally, in the video telephone, by using the above-mentioned video signal processing circuit, the video signal to be transmitted is compressed to a band that can be transmitted by ISDN, and the compressed video signal is sent to ISDN. Then, in the above-mentioned video telephone, for example, when transmitting a still image or when it is desired to increase the transmission speed, the compression parameter and the like of the image compression unit may be changed.

[0004]

However, in the above-mentioned conventional video signal processing circuit, even if the compression parameter of the image compression unit is changed, the image quality of the video signal supplied to the compression unit is changed. Instead, since the video signal is given as it is, there is a drawback that the compression of the video signal is difficult and the data amount becomes large. Further, in the above-described conventional video signal processing circuit, when the image compression unit is block-on coding, there is a drawback in that the edges of the video are overemphasized and the video becomes blocky. on the other hand,
In the above video signal processing circuit, when the compression amount of the image compression unit is changed to reduce the amount of compression, it is conceivable that filtering corresponding to this is applied to the video signal and supplied to the image compression unit. However, there is a drawback that the image quality of the reproduced image becomes worse than the image quality set by the image compression unit because of too much filtering, or the filtering is not effective. Therefore, an object of the present invention is to provide a video signal processing circuit capable of forming an input image according to the compressed image quality.

[0005]

According to a first aspect of the present invention, an analog / digital converter for converting a video signal into an analog / digital signal is used.
A video signal processing circuit comprising a digital converter and an image compression unit for compressing image data from the analog / digital converter, wherein the compression amount is changed by changing a compression parameter given to the image compression unit. An image quality correction circuit that adjusts the image quality of a video signal supplied to the image compression unit, and an image quality correction control circuit that adjusts and controls the image quality of the video signal output from the image quality correction circuit when the compression parameter is changed. It is provided in a processing circuit to achieve the above object. According to a second aspect of the present invention, in the video signal processing circuit according to the first aspect, the image quality correction circuit includes:
The image quality of the video signal is adjusted in an analog manner, and the video signal with the adjusted image quality is applied to the input of the analog / digital converter. According to a third aspect of the present invention, in the video signal processing circuit according to the first aspect, the image quality correction circuit is arranged between the analog / digital converter and the image compression section, and digitally adjusts the image quality of the video signal. To be configured.
According to a fourth aspect of the present invention, in the video signal processing circuit according to the first aspect, the image quality correction circuit is arranged in the television camera and is configured to adjust the image quality of the video signal in an analog manner.

[0006]

According to the first aspect of the invention, the data input to the image compression section is adjusted in advance by the image quality correction circuit before being input. The image quality correction circuit outputs the image data input under the control of the image quality correction control circuit as a predetermined data amount. Therefore, when the image compression unit changes the image quality parameter, the image quality correction control circuit similarly changes the parameter of the image quality correction circuit so that the image compression unit supplies a necessary and sufficient amount of data. As a result, necessary and sufficient data is input to the image compression unit, and the image compression process is optimized. According to the second aspect of the invention, the image quality correction circuit can adjust the image quality of the video signal in an analog manner, and provides the image signal with the adjusted image quality to the input of the analog-digital converter. Can be done at. Since the image quality correction circuit according to the invention of claim 3 is capable of digitally adjusting the image quality of the video signal and provided between the analog / digital converter and the image compression unit, the data amount of the video signal can be digitally adjusted. And an appropriate amount of data can be given to the image compression unit. Since the image quality correction circuit according to the invention of claim 4 can adjust the image quality of the video signal in an analog manner and is provided in the television camera, it is not necessary to provide a special image quality correction circuit.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the video signal processing circuit of the present invention will be described in detail below with reference to FIGS. 1 to 4 are diagrams for explaining an example of a videophone to which the video signal processing circuit of the present invention is applied. First, the configuration of the videophone will be described with reference to FIGS. 1 and 2, and then the video signal processing circuit will be described with reference to FIGS. FIG. 1 is an explanatory diagram of an embodiment of a videophone of the present invention. In FIG. 1, the videophone 10 is connected to a communication line (not shown). This video phone 1
0 indicates a communication line (not shown) when the other party is called and, for example, the other party's videophone (not shown) goes off-hook.
It will be connected to the other party's videophone via the ISDN line network and communication line. The videophone also has the same components as the videophone 10 and can perform the same processing.

Next, the structure of the videophone 10 will be described in detail. The above-mentioned video telephone 10 includes a base portion 11, a handset 12 is arranged on the left side of the base portion 11, and a display support portion 13 is arranged on the right side. The handset 12 is for making a call, and includes a microphone and a speaker (not shown). A speaker 14 and various operation keys 1 are provided on the upper surface of the base portion 11.
5 are arranged. The operation keys 15 include a speaker volume knob 151 for adjusting the volume of the speaker 14,
A menu for displaying a menu such as a handset volume knob 152 for adjusting the volume of the handset 12, various function keys 153 associated with the telephone function, a ten-key 154 for dialing, a recording key 155 associated with the television function, a privacy key 156, and various mode settings. Various operation keys 15 such as a screen key 157 are arranged.

A camera 16 composed of, for example, a CCD is arranged on the front side of the upper portion of the display support 13 so as to photograph the speaker. Further, a display 17 for displaying an image is attached to the side surface of the display support 13 on the handset 12 side. On the display 17, the image of the other party transmitted from the videophone of the other party is displayed and the operation key 1
A menu screen is displayed according to various modes designated by the operation of 5, and the image captured by the camera 16 and transmitted to the other party is displayed after being combined with the image of the other party. Various displays such as displaying predetermined message texts and icons (pictograms) individually or in combination with images are performed. On the rear side surface of the base portion 11, a video tape recorder (VTR) not shown
A VTR connection terminal (not shown) for connecting the mouse and a socket for connecting the mouse 22 are arranged. A camera switching key 18 for switching between the VTR connected to the above-mentioned connection terminal and the camera 16 attached to the videophone 10 is arranged on the right side surface of the display support 13. Further, the communication line 3 is provided on the rear side surface of the base portion 11.
It also has a connection terminal for connecting.

On the right side surface of the display support portion 13, a photographing condition switching key 19 for switching photographing conditions such as an aperture according to the brightness of a room photographed by the camera 16,
A color adjustment knob 20 for adjusting the colors (RGB) of the image displayed on the display 17, and a cap 21.
Are arranged at predetermined positions. Cap 2
Reference numeral 1 is for covering a screw (not shown) for fixing the display 17 to the display support 13. In addition, the display 17 is the cap 2
It is attached by a biasing force in the direction of the display support 13 by a spring so as to be vertically rotatable about the center of 1. A mouse 22 is connected to the videophone 10.

FIG. 2 shows a schematic configuration of the above-mentioned answering machine videophone. As shown in FIG. 2, the video phone 10 includes a central processing unit 31. The central processing unit 31 is a well-known CPU (Central Proc
essing unit) 311, ROM (read only memory) storing various programs and data for realizing communication and remote control functions, and RAM (random memory) as working memory storing various data.
An access memory) is provided as a memory 312. In this RAM, for example, a telephone number of a person who can receive an incoming call in a incoming call restriction mode that restricts incoming calls other than a designated caller, which is set by operating the function keys 153 and the numeric keypad 154, a speed dial, and Various data such as various flags indicating states such as standby, outgoing call, incoming call, and communication are stored.

The central processing unit 31 also includes a chip set 313 as a communication interface, and a key controller 314 for controlling instruction signals input from various keys of the operation keys 15. The mouse 22
Is connected to the circuit of the operation key 15 via the socket S, and the position information is displayed on the operation key 15 and the key controller 3.
It can be given to the CPU 311 via 14. The central processing unit 31 is connected to the communication control unit 3 via a bus line (ISA bus) 32 such as a data bus.
3 and the image processing unit 34 are connected. In addition, via the ISA bus 32, a personal computer,
CAD (Computer Aided Design), DTP (desk
It can be connected to various information processing devices such as top publishing.

The communication control unit 33 has an ISDN connection terminal 33.
1 and is connected to the ISDN line. The communication control unit 33 controls transmission and reception of data such as communication control signals, voice data, and image data. The image processing unit 34 reproduces the compressed image data transmitted from the videophone of the other party via the communication control unit 33, the image reproducing unit 341, the camera 16 and the VTR.
The communication control unit 33 includes an image compression unit 342 that compresses the image data supplied from the communication unit 26. The videophone 10 further includes a D / A (digital / analog) converter 37 connected to the image processor 34,
An image composition section 36 connected to the D / A conversion section 37,
The image composition unit 36 and the image composition control unit 35 connected to the communication control unit 33 are provided.

The audio control unit 38 includes a handset 12, a speaker 14, voice input / output terminals 25a and 25c of a VTR connection terminal 25, and a chip set 313.
Are connected. This audio control unit 38
, Audio switching, hold tone, DTMF (dual tone)
multiplex frequency) and the volume of the speaker 14 and the handset 12 are adjusted. The D / A converter 37 is a video signal (NTSC; national televisio) obtained by image-synthesizing the image data reproduced by the image reproducing unit 341 of the image processing unit 34 into a digital signal by the image combining unit 36.
D / A that converts the N system committee) into an analog signal
Part 371 and A for converting analog signals into digital signals
The / D section 372 is provided. The digital image data converted by the A / D unit 372 is supplied to the image compression unit 342 of the image processing unit 34 via the image synthesis unit 36.

When the image synthesizing unit 36 does not perform image synthesizing, the image data reproduced by the image reproducing unit 341 of the image processing unit 34 is simply passed through and the D / A conversion unit 37 performs the D / A conversion.
The image data from the A / D unit 372 of the D / A conversion unit 37 can be supplied to the unit 371 and the image compression unit 342 of the image processing unit 34. In addition, the image composition unit 36
When combining images, the image data from the image reproduction unit 341 of the image processing unit 34 and the A of the D / A conversion unit 37
The image data from the / D unit 372 is digitally processed, and the digital signal obtained by the image synthesis is processed by the D / A converter unit 37.
The display can be switched between the parent screen and the child screen while being given to the section 371. This image composition unit 36
Are controlled by control signals from the image composition control unit 35 and the central processing unit 31. The audio control unit 38 includes a voice input / output terminal 2 of the handset 12, speaker 14, and VTR connection terminal 25.
5a, 25c and the chip set 313 are connected. The audio control unit 38 switches between audio switching, hold tone, and DTMF (dual tone multiplex freq).
uency), the volume of the speaker 14 and the handset 12 are adjusted.

The amplifier 39 includes an amplifier (AMP) 391,
The video input / output terminals 25b and 25 of the VTR connection terminal 25 are provided with an AMP 392 and a changeover switch section 393.
d, D / A converter 37, camera 16 and display 1
It is connected to 7. Here, the AMP 392 is an analog video signal or VTR captured by the camera 16.
The analog video signal supplied from the VTR 26 via the connection terminal 25b is amplified. The selection of both video signals is determined by the connection state of the changeover switch unit 393 by the changeover operation of the camera changeover key 18 in FIG. The AMP 391 is the D of the D / A converter 37.
The analog video signal from the / A unit 371 is amplified and supplied to the display 17. The display 17
Display the supplied video signal in color.

Further, the central processing unit 31 takes in position information from the mouse 22, forms position display data based on the position information, transmits the position display data by including it in the transmission data, and transmits the image via the chip set 313. It is given to the synthesizing unit 36. As a result, the image composition unit 36 can display the cursor based on the position information from the mouse 22 on the parent screen.
The other party's videophone can display a cursor on the display screen. Further, the central processing unit 31 of the videophone of its own station can form position display data based on the position data sent from the other party and supply it to the image synthesizing unit 36. Thereby, the cursor of the other party can also be displayed on the display 17.
In addition, the image synthesizing unit 36 can change the display area of the small screen based on the control signal from the central processing unit 31. An image quality correction control circuit 41 is connected to the ISA bus 32. The image quality correction control circuit 41 can control the image quality of an image quality correction circuit (not shown) in the camera 16 according to a compression parameter. ing. The camera 16 can adjust the image quality of the video signal in an analog manner, and can change the image quality of the output signal according to the image quality adjustment control signal from the image quality correction control circuit 41. Further, the video signal processing circuit includes the image processing unit 3 described above.
4, the image compression unit 342, the A / D unit 372 of the D / A conversion unit 37, the camera 16, and the image quality correction control circuit 41.

FIG. 3 shows a circuit configuration in the image processing section 34. As shown in FIG. 3, the image reproducing unit 341 of the image processing unit 34 includes a first-in first-out FIFO memory 3 in which image data supplied from the ISA bus 32 is stored.
41a, a Huffman decoding unit 341b for Huffman decoding the image data of the FIFO memory 341a, and a block memory 341c for storing the decoded image data.
And a playback unit 341d that reads out image data stored in the block memory 341c and plays back image data compressed by motion compensation interframe prediction, DCT, or the like. A frame buffer may be arranged instead of the FIFO memory 341a, and the image data supplied from the ISA bus 32 may be stored in this frame buffer.

The block memory 341c has an area for two frames, alternately stores the Huffman-decoded image data, and the area not storing the image data (the area of the previous frame). The image data is read from the area (where the image data is stored) and the image is reproduced. Then, when the recording key 155 (FIG. 1) is pressed, the compressed image data before reproduction stored in the block memory 341c is supplied to the central processing unit 31 via the ISA bus 32 and stored in the memory 312. RAM
It is designed to be stored in.

On the other hand, the image compression section 342 has a setting parameter storage section 342a in which parameters for setting image quality are stored, and a block memory 342b in which digital image data supplied from the D / A conversion section 37 is stored.
A compression unit 342c that compresses the image data stored in the block memory 342b by motion compensation inter-frame prediction, DCT, etc., a Huffman encoding unit 342d that further Huffman-encodes the compressed image data, and a buffer memory 342e. It has and. The setting parameter storage unit 342a is connected to the central processing unit 31 via the ISA bus 32, and stores each parameter designated by the caller or the other party's speaker when the caller specifies the image quality. , Is automatically set and changed by an instruction from the central processing unit 31.

FIG. 4 is a block diagram showing a concrete example of the video signal processing circuit. The configuration shown in FIG. 4 shows a connection state of elements that execute signal processing.
Has a built-in image quality correction circuit (not shown) so that the image quality can be processed in an analog state. The image quality correction circuit of the camera 16 is controlled by the image quality control signal from the image quality correction control circuit 41. The video signal obtained by the camera 16 is processed by an image quality correction circuit (not shown) and then input to the A / D unit 372. A
The signal digitized by the / D section 372 is the image processing section 3
4 has been input to the image compression unit 342. The image compression unit 342 is configured to perform image compression according to the compression parameter given from the ISA bus 32. Although it is shown in FIG. 4 in this way, in reality, as shown in FIG. 2, the signal output from the camera 16 is transmitted via the changeover switch unit 393 of the amplification unit 39 and the amplifier (AMP) 392. It is adapted to be input to the A / D section 372 of the / A conversion section 37. Also, the A / D unit 372 of the D / A conversion unit 37
The signal digitized in (1) is input to the image compression section 342 of the image processing section 34 via the image synthesizing section 36, but since it is not directly related as an element of this embodiment,
These are omitted in the description.

The operation of the videophone configured as described above will be described with reference to FIGS. 1 to 4. First, the normal operation of the videophone will be briefly described. (1) Main operation First, the main operation will be described. That is, the CPU 311
Each state FG (flag) of the memory 312 is detected, each process is performed, and in the process, the predetermined state FG is changed to shift to the next process or the previous process.
That is, normally, by repeating the waiting process,
The outgoing call or the incoming call is monitored, and when the outgoing call or the incoming call is detected, a predetermined FG is changed, and then the process shifts to the corresponding process. In the outgoing call and incoming call processing, when normal processing is performed, the processing shifts to in-communication processing. Then, when the in-communication process ends, or when a specific operation or the like is performed in the incoming or outgoing call process, the process returns to the waiting process and the outgoing or incoming call is monitored again. That is, when the video telephone 10 is installed, the ISD
The N board (communication control unit 33), the image processing board (image processing unit 34), the keyboard (operation keys 15), and the image combining unit 36 are initialized and various memory areas are initialized. When the operator of the videophone processes the operation keys such as the function keys 153 and the numeric keypad 154, the CPU 311 shifts to DI / O processing and outputs control signals to each board and status signals from each board. Accept the supply of.

Then, the CPU 311 accesses the flag storage area of the RAM 312 in the memory 312, confirms whether any of the flags is in the ON state, executes the process corresponding to the flag in the ON state, and goes to a predetermined portion. The instruction signal of is output. That is, the CPU 311 shifts to the standby process when the standby FG is ON, shifts to the outgoing process when the outgoing FG is ON, and shifts to the incoming process when the incoming FG is ON, When the communication FG is ON, the process moves to the communication process.

(2) Image Data Communication Operation Next, the image data transmission / reception operation during communication processing will be briefly described. The video signal of the self-portrait photographed by the camera 16 or the video supplied from the VTR 26 is
After being amplified by the AMP 392, it is supplied to the D / A conversion unit 37. Here, the analog video signal is input to the A / D unit 37.
After being converted into digital image data in 2, the image data is simply passed through the image synthesizing unit 36 and supplied to the image processing unit 34. The image data supplied to the image processing unit 34 is stored in the image compression unit 34.
In step 2, motion-compensated inter-frame prediction and image compression by DCT or the like are performed. The compressed image data is further Huffman encoded by the image compression unit 342 and sequentially stored in the buffer memory in the image compression unit 342. The image data stored in this buffer memory is stored in the ISA bus 3
2 is taken into the central processing unit 31 and further ISA
It is transmitted from the communication control unit 33 to the ISDN line via the bus 32.

On the other hand, the image data from the other party's videophone received by the communication control unit 33 is supplied to the central processing unit 31 via the ISA bus 32. Since this image data has been compressed by the other party's videophone, it is sequentially supplied to the image reproducing unit 341 for reproduction by a method opposite to that compressed by the image compressing unit 342. Image reproduction unit 341
After being decoded by Huffman decoding, the image data supplied to is stored in the memory in the image reproducing unit 341 in frame units. The data stored in this memory is supplied to the D / A converter 37 after being reproduced by IDCT or the like. The digital image data supplied to the D / A conversion unit 37 is converted into an analog video signal by the D / A unit 371, and the display 1 is transmitted via the AMP 391 of the amplification unit 39.
7 and is displayed on the display 17. The videophone operates as described above to communicate image data.

(3) Operation of this embodiment It is assumed that the compression parameter of the image compression unit 34 is changed in order to attach importance to the communication speed or to transmit a still image or the like. Then, the central processing unit 31 gives the compression parameter to the image compression unit 34 via the ISA bus 32. The image compression unit 34 stores the compression parameter in the setting parameter storage unit 342a. As a result, the compression unit 342c changes the compression amount. Further, the compression parameter is sent to the image quality correction control circuit 41 via the ISA bus 32.
Given to. The image quality correction control circuit 41 stores the compression parameter, forms an image quality correction control signal according to the compression parameter, and supplies it to the image quality correction circuit in the camera 16.

Thus, the image quality correction circuit in the camera 16 outputs a signal of a predetermined image quality corresponding to the amount of compression by controlling the change of the luminance signal component of the input video signal. The video signal from the camera 16 is A /
The data is digitized by the D unit 372 and input to the image compression unit 342. Then, a signal having a predetermined image quality corresponding to the amount of compression is supplied to the compression unit 342c of the image compression unit 342. In this embodiment, since the image quality of the video signal supplied to the compression unit 342c and the amount of compression by the compression unit 342c are adjusted, the intra-frame correlation reduces the amount of smooth data and the inter-frame correlation. Similarly, the amount of data is reduced because it becomes dull. In addition, in this embodiment, since the edges of the image are blurred, the glock key is improved.

FIG. 5 is a block diagram showing a second embodiment of the video signal processing circuit. The second configuration example shown here is
Instead of providing an image quality correction control circuit in the camera 16 as shown in FIG. 1 or 4, the A / D of the D / A converter 37 is not provided.
The feature is that the image quality correction circuit 42 is provided before the input of the section 372. The image quality correction circuit 42 includes an image quality correction control circuit 41.
A predetermined image quality is obtained by the image quality correction control signal from. Then, the video signal input to the image quality correction circuit 42 becomes a signal according to the image quality correction control signal and is input to the A / D unit 372. The second embodiment has the same effect as the embodiment shown in FIGS. 1 and 4, and
In the embodiment of FIG. 4, only the video signal from the camera 16 can be adjusted to the compression parameter, but in this embodiment, the input video signal may be the video signal of the camera 16 or the VTR 26.

FIG. 6 is a block diagram showing a third embodiment of the video signal processing circuit. In the third embodiment, the image quality correction circuit 42a is capable of digitally adjusting the image quality of the video signal, and the image quality correction circuit 42a is provided between the A / D unit 372 and the image compression unit 342. is there. Also,
The image quality correction circuit 42a is characterized in that a parameter from the compression parameter storage unit 342a of the image compression unit 342 is input as an image quality correction control signal. Here, it is assumed that the compression parameter of the image compression unit 34 is changed. Then, the central processing unit 31 sets the compression parameter to IS.
It is given to the image compression unit 342 via the A bus 32. The image compression unit 342 stores the compression parameter in the setting parameter storage unit 342a. Thereby, the compression unit 342
c varies the amount of compression. Further, the compression parameter is
It is given to the image quality correction circuit 42a as an image quality correction control signal.

As a result, the image quality correction circuit 42a controls the change of the luminance signal component of the input video signal,
A signal with a predetermined image quality corresponding to the amount of compression is output. The video signal from the camera 16 or VTR 26 is A
The image quality correction circuit 42a is digitized by the / D unit 372.
Entered in. Then, the image quality correction circuit 42a produces a signal having a predetermined image quality corresponding to the compression amount. The output signal from the image quality correction circuit 42a is supplied to the compression unit 3 of the image compression unit 342.
42c is supplied. In the third embodiment, the compression unit 342
Since the image quality of the video signal supplied to c and the amount of compression by the compression unit 342c are adjusted, the intra-frame correlation becomes sharp and the amount of data decreases, and the inter-frame correlation becomes sharp. Similarly, the amount of data is reduced. In addition, in this embodiment, since the edges of the image are blurred, the blockiness is improved.

In the first and second embodiments described above, the image quality correction control circuit 41 is described as an independent circuit, but the present invention is not limited to this configuration, and other configurations are possible. It is also possible to do so. For example, the function of the image quality correction control circuit 41 can be realized by the central processing unit 31. In this case, the programs and data required to realize the functions are stored in the memory 312.

[0032]

As described above, according to the first aspect of the invention, the image quality correction circuit capable of adjusting the image quality of the video signal supplied to the image compression unit, and the image quality correction circuit output when the compression parameter is changed. The image quality correction control circuit that adjusts and controls the image quality of the video signal to be adjusted, and the image quality of the video signal supplied to the image compression unit and the amount of compression by the image compression unit are adjusted, so that intra-frame correlation can be achieved. Similarly, the amount of data decreases, and the correlation between frames becomes sharper, so that the amount of data also decreases. According to the first aspect of the invention, since the edges of the image are blurred, the blockiness is improved. According to the second aspect of the invention, since the video signal whose image quality is adjusted by the image quality correction circuit is given to the input of the analog-digital converter, it is possible to adjust the image quality of all the video signals. According to the third aspect of the present invention, the image quality of the video signal can be digitally adjusted by the image quality correction circuit, so that the data amount can be adjusted more accurately. According to the fourth aspect of the invention, since the image quality correction circuit in the television camera is used, the number of parts is reduced.

[Brief description of drawings]

FIG. 1 is an external configuration diagram of a videophone to which an embodiment of the present invention is applied.

FIG. 2 is a circuit configuration diagram of the videophone of the above.

FIG. 3 is a block diagram showing a circuit configuration of an image processing unit of the videophone.

FIG. 4 is a block diagram showing a first embodiment of the same.

FIG. 5 is a block diagram showing a second embodiment of the same.

FIG. 6 is a block diagram showing a third embodiment of the same.

[Explanation of symbols]

 10 Video Phone 11 Base Part 12 Handset 13 Display Support 14 Speaker 15 Operation Key 16 Camera 17 Display 18 Camera Switch Key 31 Central Processing Section 311 CPU 312 Memory 32 ISA Bus 33 Communication Control Section 34 Image Processing Section 35 Image Synthesis Control Section 36 Image synthesizer 37 D / A converter 38 Audio controller 39 Amplifier 41 Image quality correction control circuit 42 Image quality correction circuit 42a Image quality correction circuit 342 Image compression unit 372 A / D unit

Claims (4)

[Claims] 1. An analog / digital converter for converting a video signal into an analog / digital signal, and an image compression section for image-compressing image data from the analog / digital converter, wherein a compression parameter given to the image compression section is changed. In the video signal processing circuit for changing the compression amount, the image quality correction circuit for adjusting the image quality of the video signal given to the image compression unit, and the video signal output from the image quality correction circuit according to the change of the compression parameter. And an image quality correction control circuit for adjusting and controlling the image quality of the image signal processing circuit. 2. The image quality correction circuit is configured to adjust the image quality of a video signal in an analog manner, and to apply the video signal having the adjusted image quality to an input of an analog-digital converter. 1. The video signal processing circuit according to 1. 3. The image quality correction circuit is arranged between an analog / digital converter and an image compression unit, and is configured to digitally adjust the image quality of a video signal. Video signal processing circuit. 4. The video signal processing circuit according to claim 1, wherein the image quality correction circuit is arranged in a television camera and is configured to adjust the image quality of the video signal in an analog manner.