JPH07154519A - Method for picture signal conversion and still picture transmitter - Google Patents

Abstract

PURPOSE:To receive color still picture data by a facsimile terminal equipment by forming a facsimile signal comprising plural white and black dots from a television picture signal. CONSTITUTION:Color still picture data are written in a picture memory 5 as a luminance signal Y and a color difference signal C via an NTSC decoder 4 by using a memory controller 7, compressed and stored in a RAM 22. When an opposite terminal equipment has no required function, a CPU 20 of a sender side reads out picture data from the RAM 22 according to a program stored in a ROM 21 and applies expansion processing to the data and writes picture elements of the signals C, Y to the picture memory 5, converts the signal Y into a white and black dot pattern with the number of dots in response to the picture quality and applies MH compression to facsimile signals by one line and sends the compressed signal to a telephone line L via a moden 35 and a NCU 36. A reception signal is fetched by the RAM 22 at a receiver side, expanded and decoded and stored in the memory 5 and uses an NTSC encode circuit 8 to convert the signal into an NTSC color video signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of converting an image signal of a standard color television system such as the NTSC system into a facsimile signal and a method of inverse conversion thereof, and further,
The present invention relates to an apparatus for transmitting the above still image information by using the former method when the other party is a facsimile terminal when transmitting standard still picture color still image information through an analog telephone line.

[0002]

2. Description of the Related Art There is known a videophone which transmits a still image using a public line. In this system, a video camera is attached to a videophone device, a video signal of a still image taken by the video camera is converted into a signal in a voice band, and the signal is transmitted through a public line.

In this videophone device, a monochrome still image is processed by an amplitude-phase modulation system (TTC of still image videophone).
(Abbreviated name of the Telegraph and Telephone Technical Committee) Standard method). On the other hand, a color still image of a standard color television system such as the NTSC system is converted into a TTC standard system videophone signal in a facsimile modem and transmitted (see, for example, Japanese Patent Laid-Open No. 2-246486). There is also a method in which a color still image signal is separated into a luminance signal and a color difference signal, converted into a digital signal, data-compressed and transmitted in a voice band, and then transmitted through a public line (for example, Japanese Patent Laid-Open No. 3-103). No. 124186).

[0004]

By the way, in the case of the above-mentioned conventional video telephone apparatus, a signal transmitted by the amplitude-phase modulation method requires a dedicated decoder for demodulating the signal, and the data is compressed. Also for the transmitted color still image signal, it is necessary to decompress the compressed data and obtain the original color still image signal from the decoded luminance signal and color difference signal.

Therefore, in order to transmit and receive a still image, generally, a dedicated video telephone apparatus equipped with a modulation and demodulation circuit or a data compression encoder and a decompression decoder must be provided on both the transmitting side and the receiving side. The still image signal could not be delivered.

By the way, recently, facsimile machines have become widespread. An object of the present invention is to enable transmission / reception of a still image by an image signal of a standard color television system even if a counterpart device is this widely used facsimile apparatus. .

[0007]

In order to solve the above problems, the present invention provides a method for converting a color still image signal into a facsimile signal. It also provides a method of converting a facsimile signal into a still image signal.

That is, the former conversion method according to the present invention is a method for converting an image signal of a standard color television system into a facsimile signal for forming a facsimile image composed of a plurality of black and white dots, which is the standard color television. The luminance level of each luminance signal sample is detected by sampling the luminance signal of the image signal of the method, and one row in the horizontal direction of the facsimile image is set to 1 of the luminance signal.
In addition to being associated with a line, a plurality of horizontal black and white dots of the facsimile image are associated with one of the luminance signal samples, and the luminance signal samples are dealt with according to the luminance level of each luminance signal sample. The facsimile signal is formed by determining whether each of the plurality of black and white dots is "white" or "black".

In the latter conversion method of the present invention, one line in the horizontal direction of the facsimile image is made to correspond to one line of the luminance signal, and black and white dots in the horizontal direction of the facsimile image are appropriately thinned to obtain each line. The dots are made to correspond to one of the luminance signal samples of the image signal of the standard color television system and written in the image memory, and the black and white dot data is converted from the image memory into the image signal of the standard standard color television system. It is characterized in that the image signal of the standard color television system is encoded from the luminance signal in synchronization with the readout.

[0010]

When the conversion method according to the present invention having the above-mentioned structure is used, a facsimile signal composed of black and white dot data can be formed from a color image signal of a standard color television system. Therefore, this signal is compressed for facsimile such as MH compression. It becomes possible to encode and transmit it via a public telephone line.

Further, since the facsimile signal can be converted into the image signal of the standard color television system,
Facsimile images can be displayed as still images on standard television receivers with video signal input terminals.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image conversion method according to the present invention will be described below with reference to the drawings together with a still image transmission apparatus to which the image conversion method is applied.

FIG. 1 is a block diagram of an embodiment of a still image transmission apparatus according to the present invention. Reference numeral 1 is an input terminal for an NTSC standard color television system color video signal. The input color video signal supplied to the input terminal 1 is, for example, a color video signal of an image photographed by a popular camera integrated VTR, a reproduction color video signal from the VTR section, a laser disc player, a CD- NTSC color video signals from various sources are possible, such as color video signals from a ROM player.

Reference numeral 2 is a reference NTSC signal generation circuit. The reference NTSC video signal from this generation circuit 2 is
It includes horizontal and vertical sync signals as well as burst signals as color sync signals. This reference NTSC video signal is
As will be described later, the received facsimile signal
It is used to obtain the NTSC image signal in synchronization with the reference NTSC video signal when forming the C format image signal.

Reference numeral 3 is an input switching circuit, which is a reference NTS from the color video signal and generation circuit 2 through the input terminal 1.
Any one of the C video signals is selected and used as its output. The input switching circuit 3 is switched by a switching control signal from a system controller 23, which will be described later, and selects a signal from the input terminal 1 at the time of transmission and a reference NTSC video signal from the generation circuit 2 at the time of reception.

Reference numeral 4 is an NTSC decoding circuit. This N
A schematic block diagram of the TSC decoding circuit 4 is shown in FIG. In the NTSC decoding circuit 4, in order to digitally process the NTSC color video signal from the input switching circuit 3, the NTSC decoder 41 decodes the luminance signal, the red color difference signal and the blue color difference signal from the input color video signal.

Then, the luminance signal and the color difference signals of red and blue are respectively converted into A / D converters 42, 43, 44.
A / D conversion at 8 bits / pixel
The digital luminance signal Y and the digital color difference signals Cr and Cb are converted. In this example, the luminance sample Y is 512 samples per line, but the color difference signals Cr, Cb
Are alternately output from the multiplexer 45 as a dot-sequential signal, and each sample has 256 samples. Therefore, each digital pixel sample is a 16-bit digital signal including a set of the luminance signal sample Y and the red color difference signal Cr, or a set of the luminance signal sample Y and the blue color difference signal Cb.

An image memory 5 has one digital pixel sample (Y, Cr or a set of Y, Cb).
Frames are stored. In this example, the number of display pixel samples in one frame is horizontal × vertical = 512 (pixels) × 480 (lines).

Reference numeral 6 denotes a sync separation circuit, which is an input switching circuit 3
The horizontal and vertical sync signals are separated from the video signal from. The separated synchronization signal is used for timing control when writing and reading the image data in the image memory 5.

Reference numeral 7 denotes a memory controller, which is controlled by the system controller 23 and controls reading / writing of the image memory 5. This memory controller 7
Also performs write or read address generation in synchronization with the sync signal from the sync signal separation circuit 6. One frame of data stored in the image memory 5 constitutes one still image, and the same frame of data is repeatedly read from the image memory 5 to display a still image on the monitor screen. The image memory 5 may be written with a black and white video signal obtained by converting the facsimile image signal, as described later.

Reference numeral 8 is an NTSC encoding circuit. Figure 3
A block diagram of the outline of the NTSC encoding circuit 8 is shown in FIG. In the encoding circuit 8, first, the luminance signal Y which is the lower 8 bits of the 16-bit digital pixel sample read from the image memory 5 is latched by the latch circuit 8.
Latch 1 and high 8 of digital pixel samples
Among the bit color difference signals, the red color difference signal Cr is latched by the latch circuit 82, or the blue color difference signal Cb is latched by the latch circuit 83 for synchronization. In this case, in the synchronized state, the color difference signal samples Cr and Cb are such that the same sample is continuous every two pixels.

The luminance signal Y and the color difference signals Cr and Cb thus latched are respectively converted into A / D converters 84, 85 and 8 respectively.
Convert to analog signal at 6. Then, the analog luminance signal and the color difference signal thus obtained are supplied to the NTSC encoder 87 to form an NTSC color video signal. As described above, since one frame of data is repeatedly read from the image memory 5 to the NTSC encoding circuit 8, the output signal from the NTSC encoding circuit 8 is a color still image signal.

An output switching circuit 9 selectively takes out either the signal from the input switching circuit 2 or the signal from the NTSC encoding circuit 8 and outputs it to the output terminal 10. The output terminal 10 is connected to, for example, a video input terminal of an NTSC television receiver, and a color still image is displayed on its screen.

Reference numeral 11 is a data compression / expansion circuit. As will be described later, this circuit 11 functions as a data compression circuit when transmitting a color still image signal, and as a data decompression circuit when receiving compressed color still image data. In this example, the JPEG method is used as the data compression method for the color still image data. The compression rate is fixed at 1/20, for example.

Reference numeral 20 is a CPU. Further, reference numeral 21 is a program ROM, and a processing program for transmission and reception is stored in this ROM 21.
Executed by.

A printer 32 is connected to the CPU 20 via a printer interface 31, and an image scanner 34 is connected to the CPU 20 via an image scanner interface 33. The still image in the image memory 5 can be printed on the recording paper by the printer 32. Further, an image signal obtained by scanning a paper document by the image scanner 34 is input to this device. This image signal can be transmitted as a facsimile signal, or can be converted into a still image signal of a standard television system by an image conversion method described later and can be monitored by the television receiver.

In this example, the printer 32 and the image scanner 34 are provided in the apparatus, but the apparatus may be provided with an interface and a connector for the printer and the image scanner.
In that case, the user can expand the function of the system simply by connecting the printer 32 or the image scanner 34 to the connector as required.

By connecting the printer 32 and the image scanner 34, the apparatus shown in FIG. 1 can be made to function as a general facsimile apparatus.

A main RAM 22 has a capacity of, for example, 1.5 Mbytes and stores compressed video data. The main RAM 22 also stores image data transmitted as a facsimile signal.

Reference numeral 23 is a system controller, which is a CPU 2
Performs system control around 0, timing control, address decoding, JPEG interface, etc. Reference numeral 24 is a RAM that functions as a work area when performing JPEG compression / decompression.

To the system controller 23, a dip switch (Dip, SW) as an input key and other key switches (SW) are connected, and a light emitting diode LED for display is connected. The image quality mode, which will be described later, and the vertical gradation mode of the facsimile are set by the input operation using the key switch.

Reference numeral 35 is a G3 facsimile modem.
The apparatus of this example allocates still image digital data to an HDLC frame according to a facsimile procedure and manually transmits it. Then, as will be described later, when the still image information is transmitted, the CPU 20 is controlled by the program of the ROM 21.
Recognizes whether the transmission partner device is a device capable of receiving and decoding the still image data compressed by the device of this example, or a facsimile device, and the partner device compresses the compressed image data. If it is a device capable of decoding, the compressed still image data is transmitted via the facsimile modem 35 in accordance with a facsimile procedure. When the counterpart device is a facsimile machine, the still image signal is converted into a facsimile signal, compression-coded for facsimile, and transmitted via the modem 35, as described later. As the compression encoding method in this case, for example, the MH method is adopted.

Reference numeral 36 is an NCU (network control unit), to which a telephone line L is connected and a telephone 37 is connected. The NCU 36 has a telephone / modem switching function, a ring back tone detection function, and a call end pulse detection function.

In the case of this example, there are a plurality of image qualities when transmitting color still image information by the switch connected to the system controller 23. In this example, "fine mode", "standard mode" and "high speed mode". The three modes can be selected.

In the fine mode, one frame of image data is composed of all the pixels (512 × 480) of the display pixel samples in the image memory 5. In the standard mode, one frame of image data is thinned to 1/2 the number of pixels in the horizontal direction with respect to the display pixel sample of the image memory 5, and the number of lines is thinned to 1/2 in the vertical direction. It is configured by a number (256 × 240). In the high-speed mode, the image data of one frame is thinned out to 1/4 of the number of pixels in the horizontal direction with respect to the display pixel sample of the image memory 5, and the number of lines is set to 1 in the vertical direction.
The number of pixel samples is thinned to / 4 (128 × 120).

NTSC in standard mode and high speed mode
The thinning process performed on the signal from the decoding circuit 4 may be performed when the image data is read from the image memory 5 or may be performed when the image data is written. However, if it is performed at the time of writing, the image memory 5 is set to 1 in the standard mode.
In the 1/4 area divided into / 2, 1/4 in high-speed mode
Image data for one frame can be written in the 1/16 area divided into
Each of the four or 16 still images can be divided and displayed.

The RAM 22 can store the compressed data of a plurality of still images, and can store the compressed data of 30 still images when the image quality is in the fine mode, for example.

Further, in this example, as the vertical gradation mode of the facsimile image, two modes, a normal mode and a fine mode, can be set by a key switch connected to the system controller 23. In the case of this example, when A4 size recording paper is assumed, the normal mode is horizontal direction × vertical direction = 1728 (dots) × 1144 (lines), and the fine mode is also horizontal direction × vertical direction = It is set to 1728 (dots) × 2288 (lines). Also, the dot density in the vertical direction is double that in the normal mode. For example, in normal mode, 3.85.
1 line / mm, and in fine mode, it is 7.71 line / mm.

The signal processing operation in the still image transmission apparatus having the above hardware configuration will be described below.

[Preparation (standby) state] In this preparation state, an incoming call is waited for through the telephone line L, and the NTSC color video signal from the input terminal 1 is passed through the input switching circuit 3 and the output switching circuit 9. The desired color still image can be taken in while supplying the monitor image connected to the output terminal 10 and monitoring the reproduced image.

That is, when a desired image is found on the screen of the monitor receiver, the still image capturing switch connected to the system controller 23 is operated. Then, under the control of the memory controller 7, the color still image data of one frame immediately after the timing when the capture switch is operated is stored in the image memory 5.
That is, the luminance signal data Y and the color difference signal data C of the one frame decoded by the NTSC decoding circuit 4
r and Cb are written.

Then, the memory controller 7 repeatedly reads out the color still image data from the image memory 5, supplies it to the NTSC encoding circuit 8, and switches the output switching circuit 9 to the NTSC encoding circuit 8 side. Therefore, the color still image captured in the image memory 5 is displayed on the screen of the monitor receiver.

When the user wants to save the color still image, he operates the save key. Then, the memory controller 7 reads the color still image data from the image memory 5 and sends it to the compression / expansion circuit 11. compression/
The decompression circuit 11 performs the JPEG compression processing of the color still image data under the control of the system controller 23. And the compressed color still image is in RAM
It is stored in 22.

As described above, the color still image to be transmitted can be stored in the RAM 22 in advance. Even if you do not store the color still image you want to send, you can send it by performing the same operation as above while checking it on the screen of the monitor and operating the send key instead of the save key. Is also possible. Even in that case, the RAM 22 temporarily stores the compressed image data.

[Description of Transmission] A program for transmission is stored in the ROM 21 and executed by the CPU 20. In the present invention, at the time of this transmission, it is recognized whether the transmission partner device is a corresponding terminal device having the same function as the device of the example of FIG. 1 or a general facsimile device, and the transmission signal form corresponding to each is recognized. And send it.

FIG. 4 is a schematic flow chart of the operation at the time of transmission of the apparatus of this example, and FIG. 5 is a diagram showing a sequence at the time of transmission.

That is, the transmitting side (calling terminal) performs a calling operation in step 101, and sends a calling tone CNG to the other side (called terminal), as shown in FIG. In response to this, the other party is connected to the line and then sends the called terminal identification signal CED to the transmitting party. Thus, the sender confirms the other party's response in step 102.

Then, in step 103, the digital identification signal DIS continuously sent from the other party is received. When the partner device is a terminal having a function outside the CCITT standard receiving function, the non-standard terminal identification signal NSF is also received. The signal DIS indicates that the other device is CCI.
The signal NSF is a signal sent when the terminal has a receiving function of the TT standard, and the signal NSF is sent to identify the function when the partner device also has a function outside the range of the receiving function of the CCITT standard. Is coming. This non-standard terminal identification signal NSF includes a member code, and it is identified from this member code whether the receiving side terminal has the function of FIG.

From the above, the transmitting side performs the step 10
In step 4, the other device receives the signal DIS and then the signal NSF.
It is determined whether or not the terminal is a corresponding terminal having the same function as the apparatus of FIG. Then, the transmitting side sends these signals DIS and N
The digital command signal DCS or the non-standard function setting signal NSS is transmitted to the function selected from the functions of the receiving side partner device indicated by SF. Then, after waiting for the reception preparation confirmation signal CFR from the partner device, the process proceeds to the next step 105 or step 106. Each control signal in the above sequence is transmitted in the form of an HDLC frame.

If the partner device is a compatible terminal, the process proceeds to step 105 to send the compressed color still image data to the telephone line L via the modem 35 and the NCU 36, and to the partner device. This compressed image data is
As shown in FIG. 6, it is allocated to a 64-byte information field in the HDLC frame and transmitted. As is well known, the FCS (frame check sequence) next to this information field is a sequence for error control, and a 16-bit CRC code is inserted.

If the partner device is a facsimile terminal that is not a compatible terminal, the process proceeds to step 106, where the NTSC color still image signal is converted into a monochrome dot facsimile signal and the facsimile signal is obtained, as described below. Is compressed by the MH system, and the modem 35 and the NCU 36
To the telephone line L via. The facsimile signal is
Unlike the control signal, it is not configured as an HDLC frame,
It is sent as a bit sequence.

When the transmission of the still image information is completed, a procedure end signal EOP indicating it is transmitted to the other party, a message confirmation signal MCF from the other party is waited for, and a line disconnection command signal DCN is transmitted to the other party. . This is the end of the transmission procedure.

N in Step 106 of "Conversion Method from NTSC Color Still Image Signal to Facsimile Signal"
A method of converting a TSC color still image signal into a facsimile signal will be described next.

As described above, in this example, the display pixel sample of the color still image is as shown in FIG.
512 pixels × 480 lines, while the number of black and white dots in a facsimile image is 1728 ×, as shown in FIG.
It is 1144 or 1728 x 2288.

In this conversion method, basically, only the luminance signal sample Y of the NTSC color still image signal is converted into the facsimile signal, and the lines of the NTSC color still image correspond to the horizontal rows of the facsimile image. Let Corresponds to one luminance signal sample Y that realizes the vertical gradation function and one or more black and white dots in the horizontal direction of the facsimile image, depending on how many lines of the NTSC color still image correspond to the lines of the facsimile image. Let Set the level of the luminance signal sample Y to the corresponding multiple black and white dots in the horizontal direction,
The feature is that the horizontal gradation function is realized depending on how to correspond.

1. <Horizontal gradation function> First, the horizontal gradation function will be described. From above,
The luminance signal sample Y of one line is expressed by 1728 dots in one line of the facsimile image. However, since the number of pixels per line of the still image differs depending on the image quality mode, one pixel is displayed depending on the image quality mode. The number of black and white dots corresponding to the luminance signal sample Y of is different.

That is, as shown in the table of FIG. 9, in the fine mode, since the number of pixels in one line is 512, one luminance signal sample can correspond to three black and white dots, and the standard mode Then, the number of pixels in one line is 256
Therefore, one luminance signal sample can correspond to six black and white dots. In the high-speed mode, since the number of pixels in one line is 128, one luminance signal sample can be used as 12 black and white dots. Can be adapted to. Figure 1
FIG. 0 shows an example of a conversion table for converting a luminance signal of a still image into a facsimile image.

In this case, since the luminance signal sample is an 8-bit digital signal, the luminance signal level is
There is a level range from 0 to 255. In this example,
As shown in FIG. 10, the luminance signal level range is divided into four, and the level ranges L0, L1, L
2 and L3. Then, the gradation mode is set in three ways of "light", "normal", and "dark", and the respective division partition positions of the level ranges L0, L1, L2, L3 are made different according to each gradation mode.

Then, each level range L0, L1, L2,
An appropriate dot pattern (bit pattern) is set for a plurality of black and white dots corresponding to one luminance sample in association with each of L3. Each bit pattern shown in FIG. 10 is an example thereof.

2. <Vertical gradation function> This is a conversion function of the vertical dot density for the vertical scanning line of the color video image and the facsimile image. That is, the number of vertical pixels (number of lines) of the color video image
Is a function of changing the number of dots (= number of lines) in the vertical direction of the facsimile image.

As described above, the vertical gradation density of the facsimile image has the normal mode and the fine mode.
The vertical gradation rate is as shown in the table of FIG. 11 in combination with the image quality mode of the color video image. That is,
The n-times gradation (n = 1, 2, 4, 8) means that one line of the video image corresponds to n lines of the facsimile image.

FIG. 12A shows an example of a facsimile signal when a video image captured as a fine mode image (the number of lines is 480) is converted into a three-dot horizontal gradation facsimile image. FIG. 12B shows a vertical gradation of the normal mode of the facsimile signal, which is exactly the same as FIG. 12A. Further, FIG. 12C is similar to FIG. 12A.
12A is a fine mode vertical gradation, and each row of data in FIG. 12A is repeated twice to form two rows of data, which is doubled to 960 rows as a whole.

FIG. 13A shows an example of a facsimile signal when a video image captured as a standard mode image (the number of lines is 240) is converted into a 6-dot horizontal gradation facsimile image. In FIG. 13B, the facsimile signal has vertical gradation in the normal mode, and the data in each row of FIG. 13A is repeated twice to form two rows of data, which is doubled to 480 rows as a whole.
FIG. 13C shows the facsimile signal of FIG. 13A with vertical gradation in the fine mode.
Each row of data is repeated four times to form four rows of data, which is four times as large as the total of 960 rows.

FIG. 14A shows a video image captured as a high speed mode image (the number of lines is 120).
7 is an example of a facsimile signal when converted to a facsimile image of dot horizontal gradation. FIG. 14B shows a vertical gradation of the normal mode for the facsimile signal.
The data in each row of FIG. 12A is repeated 4 times to obtain 4
The row data is 480 rows which is four times as large as the whole. Further, FIG. 14C shows the facsimile signal of FIG. 14A in the vertical gradation of the fine mode, and each row of data in FIG. 14A is repeated eight times to form eight rows of data, which is eight times as large as 960. In line.

Since the image captured by the image scanner 33 has 960 lines, it can be transmitted as it is in the fine mode, but in the normal mode, the number of lines is thinned to 1/2. To transmit.

3. <Conversion processing operation to a facsimile image signal> The conversion processing operation from a color video signal to a facsimile signal is performed as follows. FIG. 15 is a flowchart of a process for converting an NTSC color video image signal into a facsimile image signal and transmitting the facsimile image signal.

The color video image signal to be transmitted is JP
Since it is EG-compressed and stored in the RAM 22, the compressed image data is read from the RAM 22 (step 201), sent to the compression / expansion circuit 11, and the compressed image data is expanded and decoded (step 202) to obtain a luminance signal sample. Pixel sample data consisting of Y and color difference signal samples Cr and Cb is obtained and written in the image memory 5 and developed (step 203).

Next, only the luminance signal sample Y is read from the image memory 5 (step 204), and the luminance signal sample Y is level range L0, L corresponding to the gradation mode.
The range of 1, L2 and L3 is determined (step 205). Then, the luminance signal sample Y is converted into a pattern of black and white dots having the number of dots according to the image quality mode, corresponding to the determined level range (step 2).
06).

Next, when the luminance signal samples for one line have been converted into black and white dots (step 207),
The facsimile signal for one line (one line of the facsimile image) is MH compressed (step 208) and transmitted by facsimile (step 209). When the conversion of the still image data of one screen into the facsimile signal and the transmission are completed, this processing is exited (step 210).

[Explanation at the time of reception] As shown in the sequence of FIG. 5, at the time of reception, whether compressed color image data is transmitted from the transmitting side or MH-compressed facsimile data is transmitted. It recognizes and performs processing corresponding to the received signal.

When the compressed image data is transmitted in the sequence as shown in FIG. 5, the received compressed image data is taken into the RAM 22. Also, JPEG compression /
The decompression circuit 11 decompresses and decodes and expands it on the image memory 5. Then, the NTSC encode circuit 8
It is converted into a C color video signal and supplied to the monitor receiver via the output switching circuit 9, and a color still image is displayed on the screen.

Further, the still image in the image memory 5 can be printed out as a monochrome image by the printer 32 by the user's key operation. In this case, the still image signal of the image memory 5 is converted into a black and white dot image signal,
The facsimile image signal is supplied to the printer 32 and printed out. In this case, the method of converting the color video signal of the image memory 5 into an image of black and white dots is the same as that of the above-mentioned conversion into the facsimile image signal.
However, how many dots each one of the luminance signal samples Y corresponds to is determined according to the print quality of the printer.

When a facsimile image signal is sent instead of the compressed image data, it is also taken into the RAM 22. The facsimile data taken into the RAM 22 can be converted into a monochromatic video signal and monitored by a monitor receiver as follows.

FIG. 16 shows the facsimile image signal as NTS.
It is a flowchart of a process when converting into a C video signal (monochromatic image signal). That is, the MH compression-encoded facsimile signal in the RAM 22 is read (step 301), expanded and decoded, and converted into black and white dots (step 302). Next, this black-and-white dot signal is a signal of black-and-white dots of which the number of display pixels of the image memory 5 is 512 or less by thinning out one row of black-and-white dots in the horizontal direction, and also becomes 480 lines in the vertical direction. As described above, the data is thinned out and written in the memory (step 303).

This black and white dot information is written in the image memory 5 in correspondence with the pixels. For example, a white dot is converted into an 8-bit pixel sample of all "0" and written,
The black dots are converted into 8-bit pixel samples of all "1" and written (step 304). Next, the pixel data is read from the image memory 5 and converted into an NTSC video signal by the NTSC encoding circuit 8 (step 305). This is supplied to the monitor receiver via the output switching circuit 9, and a facsimile image is displayed on the screen of the monitor receiver.

It should be noted that the information on the black and white dots is such that the white dot is the white brightness level and the black dot is the black brightness level.
It is also possible to convert it to an NTSC video signal by the SC encoder and display the facsimile image on the screen of the monitor receiver.

JP is used as the compression method of the color video signal.
Instead of the EG method, another compression method can be adopted.

[0078]

As described above, by using the method of converting a standard television color video signal into a facsimile signal according to the present invention, a color video signal can be received by a widely used facsimile terminal. .

Further, by using the method for converting a facsimile signal into a color video signal of a standard television system according to the present invention, a facsimile image can be monitored by a widely used television receiver. In the case of the conventional videophone, it was necessary to provide a monitor receiver with a small screen, but it is also possible to monitor with a TV receiver having a large screen size.

Further, according to the still image transmitting apparatus of the present invention, when the transmission partner device has a function of decoding digital data obtained by compressing a color video signal, the transmission partner device transmits the compressed image data and the transmission partner device transmits the compressed image data. In the case of a facsimile terminal having no function, a facsimile signal converted from a luminance signal of a color video signal can be transmitted. Therefore, unlike the conventional videophone, it is not necessary to use a device having the same function on the transmitting side and the receiving side, and a widely used facsimile terminal can be used. Therefore, the still image transmitting device according to the present invention is widely used. There is a merit that it is easy to spread.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a still image transmission apparatus according to the present invention.

2 is a block diagram of an embodiment of the NTSC decoding circuit of the example of FIG.

3 is a block diagram of an embodiment of the NTSC encoding circuit of the example of FIG.

4 is a flowchart showing an outline of a transmission operation of the apparatus of the example of FIG.

5 is a diagram for explaining a sequence at the time of transmission of the apparatus of the example of FIG.

FIG. 6 is a diagram for explaining an HDLC frame.

FIG. 7 is a diagram for explaining display pixels of a color video image.

FIG. 8 is a diagram for explaining the number of black and white dots forming a facsimile image.

FIG. 9 is a diagram for explaining lateral gradation when converting a color video image to a facsimile image.

FIG. 10 is a diagram showing an example of a conversion table for converting a color video image into a facsimile image.

FIG. 11 is a diagram for explaining a vertical gradation when converting a color video image into a facsimile image.

FIG. 12 is a diagram for explaining vertical gradation at the time of conversion from a color video image to a facsimile image.

FIG. 13 is a diagram for describing vertical gradation when converting a color video image to a facsimile image.

FIG. 14 is a diagram for explaining vertical gradation at the time of conversion from a color video image to a facsimile image.

FIG. 15 is a flowchart of an example of a conversion process from a color video image signal to a facsimile image signal.

FIG. 16 is a flowchart of an example of conversion processing from a facsimile image to a color video image.

[Explanation of symbols]

 4 NTSC Decoding Circuit 5 Image Memory 7 Memory Controller 8 NTSC Encoding Circuit 11 Image Data Compression / Expansion Circuit 20 CPU 21 Program ROM 22 RAM 35 Modem 36 NCU

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ko Goto 2-18-20 Marunouchi, Naka-ku, Nagoya, Aichi Prefecture Let's Corporation

Claims (6)

[Claims] 1. A method of converting a standard color television system image signal into a facsimile signal for forming a facsimile image composed of a plurality of black and white dots, wherein the luminance signal of the standard color television system image signal is sampled. Then, the luminance level of each luminance signal sample is detected, the line of the image of the standard color television system is made to correspond to the horizontal row of the facsimile image, and one of the luminance signal sample and the facsimile image Corresponding to a plurality of horizontal black-and-white dots, each of the plurality of black-and-white dots corresponding to the luminance signal sample is either "white" or "black" according to the luminance level of each luminance signal sample. Decide what to do,
An image signal conversion method characterized by forming the facsimile signal. 2. The image signal conversion method according to claim 1, wherein the maximum level range that can be taken as a brightness level is divided into a plurality of areas, and which of the divided levels the level of the brightness signal sample belongs to. By detecting and determining the pattern of the plurality of black and white dots according to the detected division level, and changing the division position of division of the maximum level range to N (N is an integer of 2 or more), An image signal conversion method, characterized in that the gradation mode of a facsimile image is changed in the above N ways. 3. The image signal conversion method according to claim 1, wherein the number of samples of the luminance signal sample per line is changed to a plurality of types, and a facsimile image for the one luminance signal sample is obtained. The image signal conversion method is characterized in that the number of black and white dots in the horizontal direction is changed in plural according to the number of samples. 4. The image signal conversion method according to claim 1, claim 2 or claim 3, comprising a horizontal row of dots of a facsimile image corresponding to one line of the image of the standard color television system. An image signal conversion method, characterized in that the gradation in the vertical direction of a facsimile image is changed by changing the number of lines. 5. A method for converting a facsimile signal forming a facsimile image composed of a plurality of black and white dots into an image signal of a standard color television system, wherein one row in the horizontal direction of the facsimile image is the luminance signal. In addition to being associated with one line, the horizontal black and white dots of the facsimile image are appropriately thinned out, and each dot is associated with one of the luminance signal samples of the image signal of the standard color television system to be stored in the image memory. Writing, black-and-white dot data from the image memory is read as a luminance signal in synchronization with an image signal of a standard color television standard system, and the image signal of the standard color television system is encoded from this luminance signal. An image signal conversion method characterized by the above. 6. A standard color television system color still image signal data compression means, a storage means for storing the data compressed color still image signal, and only a luminance signal of the color still image signal. It is provided with means for forming an image consisting of a plurality of black and white dots having a gradation distribution corresponding to the brightness level, converting the color still image signal into a facsimile signal, and a network control unit connected to a telephone line. The device on the receiving side is recognized using the information transmitted and received when performing the handshake between the transmitting side and the receiving side via the telephone line, and the data from the storage means is compressed according to the recognition result. The color still image signal is transmitted as a voice band signal through the telephone line or the signal converted into the facsimile signal is transmitted. Still image transmission apparatus so as to select either transmitted via the telephone line as a signal of a voice band by condensation coding.