JPH04297179A - Data communication system - Google Patents

Abstract

PURPOSE:To shorten time for picture transfer while advancing output starting time and securing consecutive output by performing picture transfer with small blocks while varying block size. CONSTITUTION:A transmitter 12 sends data from picture input 1 to an encoding device 2, and communication lines 71 and 72 notifies it to a transfer control part 4 every time when encoding is ended. A control part 4 finds encoding picture data amount per scanning line and calculates data compression rate through calculation. The using state of a reception memory 9 is estimated from usable memory capacity information in error correction system of the reception memory 9 from a receiver 13, data amount, and data compression rate, and picture block size is selected and decided. Thus, time from data transfer start to output start to a picture output part can be shortened by varying the block size.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a data communication system used in Group 3 facsimiles and the like that are used through telephone lines, and in particular, to how to use memory in an error correction system and control signals therefor. It is.

0002

2. Description of the Related Art FIG. 6 shows a device configuration for realizing an error correction method (error correction mode: ECM) in a group 3 facsimile machine used through a conventional telephone line. In FIG. 6, 1 is an image input unit that inputs an image, 2 is an encoder that encodes the digital signal obtained from the image input unit 1, and 3 is a temporary storage of image data encoded by the encoder 2. 4 is a transmitting side transmission control unit that performs transmission control using an error correction method used in group 3 facsimile in the transmitting facsimile machine; 5 is a transmitting side transmission control unit that performs transmission control in the transmitting side facsimile machine when transmitting image data signals and control signals; is a transmitting modem that performs modulation and demodulation when receiving a control signal,
6 is a telephone line connecting the sending and receiving facsimile devices; 7 is the receiving facsimile device which demodulates the facsimile image data signal and control signal sent from the telephone line 6, and controls the facsimile image data signal and control signal according to the communication procedure. A receiving side modulator/demodulator applies modulation when transmitting a signal; 8 is a receiving side transmission control section that performs reception control of an error correction system used in group 3 facsimile; 9 is a receiving side modulator 7 which modulates the signal; 10 is a decoder that decodes the original image data from the received encoded image data; 11 is an image output unit that records the image data decoded by the decoder 10; It is. Also,
Reference numeral 12 indicates a facsimile machine on the transmitting side, and numeral 13 indicates a facsimile machine on the receiving side.

FIG. 4 shows the error correction mode (ECM), which is standardized in Group 3 facsimiles that use telephone lines.
) shows the procedure in which control signals and image data signals are used. In FIG. 4, the left side is the sending facsimile machine, the right side is the receiving facsimile machine, and 40 is the D
The IS signal is the receiving facsimile machine 13, and the DIS signal is
This is a control signal for notifying the transmitting facsimile machine 12 of the reception capability of the receiving facsimile machine 13. Reference numeral 41 denotes a DCS signal, and the DCS signal is a control signal for notifying the sending facsimile device 12 to the receiving facsimile device 13 of the transmission mode to be used during transmission. Further, 42 is called a TCF signal, and is standardized in Group 3 facsimile to adjust the modulation and demodulation of the transmission signal between the transmitting modem 5 and the receiving modem 7 before transmitting image data. 43 is a CFR signal, and CFR is a control signal that indicates to the transmitting facsimile device 12 that the receiving modem 7 is ready for reception. 44 is a training signal, and this signal is a high-speed control signal sent from the transmitting modem 5 to ensure the demodulation operation of the receiving modem 7 again before transmitting the image data. 45 is an image data signal, and this signal is an image data signal modulated by the transmitting modem 5. 46 is PPS/NULL
This is a control signal that indicates the boundary of a transmission unit of image data called a block. Reference numeral 47 denotes an MCF signal, which is a control signal that notifies the transmitting facsimile machine 12 that one block of image data has been correctly received by the receiving facsimile machine 13. 48 is PP
This is a control signal called S.EOP, which informs the sending facsimile device 12 to the receiving facsimile device 13 that there is a page boundary regarding the data block being transmitted. Note that 49 is a DCN signal for notifying the end of facsimile communication from the sending facsimile machine to the receiving facsimile machine.

FIG. 7 shows the DIS signal 40 used in the conventional Group 3 facsimile error correction system, and FIG. 8 shows the D
4 is an explanatory diagram showing the contents of a CS signal 41. FIG. First, in the DIS signal 40 of FIG. 7, the upper figure shows the frame structure of HDLC (High Level Data Link Control) used for the control signal of the error correction method of Group 3 facsimile, and 20 is a flag indicating the frame boundary of HDLC. ,
21 is a header of the HDLC frame, 22 is frame check information added by calculating the contents of each frame using a predetermined generating polynomial, 23 is a control signal identifier for identifying a control signal, and 24 is a control not used in the error correction method. Indicates other information in the signal. In the lower diagram of FIG. 7, 25 is error correction method information indicating whether or not the receiving facsimile device has an error correction function; 26 is transmission possible speed information indicating the possible transmission speed of the receiving facsimile device; 27 28 is output speed information indicating the output speed that the receiving facsimile device can output, 28 is output width information indicating the output width that the receiving facsimile device can output, and 29 is a decoding method indicating the decoding method of the receiving facsimile device. It is information.

Next, in the DCS signal 41 of FIG. 8, the upper diagram shows the same HDLC frame structure as FIG. 7. In the lower diagram of FIG. 8, 31 is error correction method instruction information that instructs the sending facsimile device to operate according to the error correction method from the receiving facsimile device, and 32 is the information for instructing the data transmission rate and modulation method from the sending facsimile device to the receiving facsimile device. 33 is output speed instruction information that specifies the output speed to be operated, 34 is output width instruction information that specifies the width of image data output, and 35 is decoding method instruction information that specifies the decoding method. be.

Next, the operation of the error correction system in the conventional Group 3 facsimile will be explained using the diagrams shown in FIGS. 4, 6, 7, and 8. First, the receiving facsimile machine 13 transmits the receiving capability of the receiving facsimile machine 13 to the transmitting facsimile machine 12 using the DIS signal 40. This reception capability includes error correction method information 25 indicating that the receiving facsimile device has an error correction function, and possible transmission speed information 26 indicating the available transmission speed and modulation/demodulation method.
, output speed information 27 indicating the time required to output one scanning line of image data, output width information 28 indicating the outputtable image data width, and decoding method information indicating the decodable encoding method regarding the image data. Contains 29. In addition, in the error correction method standardized for Group 3 facsimile,
In order to declare that the receiving facsimile device 13 has an error correction function, the receiving facsimile device 13 must be
It is a necessary condition that there is a reception memory 9 of 4 kbytes.

[0007] The sending facsimile device 12 that has received the DIS signal 40 confirms that the receiving facsimile device 13 has an error correction method function, and if it determines to operate using the error correction method, it uses the error correction method of the DCS signal 41. The instruction information 31 is used to instruct the receiving facsimile device 13 to operate using the error correction method. DCS signal 41
In addition to this, transmission speed instruction information 32 instructs the speed and modulation/demodulation method to be used for image data transmission determined by the sending facsimile device 12, and output speed instruction information to select the image data output speed in the receiving facsimile device. 33,
It includes output width instruction information 34 that specifies the output width of image data, and decoding method instruction information 35 that specifies the decoding method of image data. Note that in order to operate with the error correction method standardized in Group 3 facsimile, it is necessary that the sending facsimile device 12 has a sending memory 3 of 64 kbytes. Furthermore, since the error correction method only specifies inter-memory transmission from the transmission memory 3 to the reception memory 9, the output speed instruction information 33 that instructs the output speed to the image output unit 11 is based on the current error correction method. Not used in .

By transmitting the DCS signal 41 from the sending facsimile machine 12 to the receiving facsimile machine 13, the operating modes of the sending facsimile machine 12 and the receiving facsimile machine 13 are determined. In other words, whether or not it operates using an error correction method, the modulation/demodulation method and transmission speed for image data transmission, the width and output speed of the image data output by the image output section, and the encoding method of the image data used during transmission. etc. Note that the encoding speed of the encoder 2 is sufficiently faster than the input speed of the image input section 1, and the decoding speed of the decoder 10 is sufficiently faster than the output speed of the image output section 11. The input time of image data is determined by the input speed of the image input section 1, and the output of image data from the reception memory 9 is determined by the output speed of the image output section 11.

[0009] In the error correction method for Group 3 facsimile, image data is converted into 256
Bytes are transmitted as one frame. In addition, 256
One block is made up of frames, and transmission control using the error correction method is such that it is confirmed whether correct transmission has been performed by checking the frame check information 22 of 256 frames for each block. That is, the TCF signal 42
When transmission synchronization is attempted between the transmitting modem 5 and the receiving modem 7, and the transmission synchronization is confirmed by the CFR signal 43, the transmitting facsimile device 12 sends a training signal 44 to confirm the synchronization again. After sending out the image data, one block of image data, that is, up to 256 image data frames of 256 bytes are sent out.

FIG. 10 shows the structure of an image data frame. 21 is an HDLC frame header, 50 is an image data frame identifier, 51 is an image data frame number indicating which frame the image data frame corresponds to in one block, and 52 is an image containing encoded image data. The data section 22 is frame check information.

Returning to FIG. 4 again, the operation of the conventional error correction system will be explained. The image data signal 45 sent from the sending facsimile device 12 to the receiving facsimile device 13 and demodulated by the receiving modem 7 is checked by the frame check information 22 in the receiving side transmission control section 8 to detect transmission errors in the image data frame contents. Check to see if this has occurred. When the sending facsimile device 12 has finished transmitting one block of image data frames, it sends a signal called an RCP frame instructing to complete the transmission of the image data block and move on to transmitting a control signal. PPS・
A control signal 46 called NULL is sent to the receiving facsimile machine 13. Upon receiving the PPS/NULL signal 46, the receiving facsimile device 13 checks the frame check information 22 of each frame to determine whether or not all 256 image data frames have been received without error. The receiving facsimile device 13 has 2
After confirming that all 56 frames have been received without error, the sending facsimile machine 1 sends an MCF signal 47.
2 of the normal reception of one block. MCF signal 47
also means that the next block can be received. Sending facsimile device 12 that received the MCF signal 47
After transmitting the training signal 44 again, transmission starts from frame number 0 of the image data signal 45 of the next block. Subsequently, in FIG. 4, when a page boundary of the facsimile document is reached during the transmission of the second block of image data, the sending facsimile device 12 transmits the RCP signal and then sends the
Notifies the end of page image data transmission.

Next, the operation when a transmission error occurs in the error correction system will be explained with reference to FIG. In FIG. 9, reference numeral 53 indicates a control signal PPR requesting that the receiving facsimile device 13 retransmit the image data frame in which a transmission error has been detected to the transmitting facsimile device 12.
It's a signal. DIS signal 40, DCS signal 41, TCF
The operation and role of each of the signal 42, CFR signal 43, and training signal 44 are the same as described above. Now, suppose that among one block of image data, the image data frame with frame number 100 is not transmitted correctly due to noise on the telephone line 6. At this time, the receiving facsimile device 13 detects that a transmission error has occurred in the image data frame with frame number 100, based on the frame check information 22 of the image data frame. Then, when the receiving facsimile device 13 receives the PPS/NULL signal 46, it responds with a PPR signal 53 instead of the MCF signal 47. The PPR signal 53 includes information on a retransmission frame number that requests the sending facsimile machine 12 to transmit again, in this case frame number 100. The sending facsimile device 12 retrieves the image data frame to be retransmitted from the transmission memory 3 again based on this PPR signal 53 and the above retransmission frame number information, and
resend. If there are multiple erroneously transmitted frames, multiple retransmission frame number information is sent to the PPR signal 53.
, the sending facsimile machine retransmits multiple image data frames. In the example shown in FIG. 9, after retransmitting the image data frame with frame number 100, the sending facsimile device 12 again sends the PPS/NULL signal 46.
This signal causes the receiving facsimile machine 13 to
Request the user to reconfirm whether all image data frames for one block have been received correctly. The receiving facsimile device 13 inserts the retransmitted image data frame into the receiving memory 9 at a location corresponding to the frame number. One block of image data is stored in the reception memory 9 in units of frames, and the reception side transmission control unit 8
The image data is arranged in the order of the image data frame numbers so that the image data of the block can be output to the decoder 10 in the same order in which they were output from the encoder 2. The image data is processed by confirming that the receiving facsimile machine 13 has correctly received all the image data of one block.
After receiving the CF signal 47, it is sequentially sent to the decoder 10, decoded, and output to the image output section 11.

Since the error correction system operates as described above, the sending facsimile machine 12 needs to have one block of transmission memory 3 in case retransmission is requested, and the receiving facsimile machine 13 needs to have one block of transmission memory 3. , regardless of which image data frame is to be retransmitted due to a transmission error, the retransmitted image data frame is inserted into a block that has already been received and stored in the reception memory 9. Therefore, one block worth of reception memory 9 is also required. In the standard error correction method, the memory size for one block is 256 frames of 256-byte data, or 64 kbytes.

[0014]

[Problems to be Solved by the Invention] Since the conventional error correction system for Group 3 facsimile is configured as described above, a transmission error occurs in, for example, the image data frame with the smallest frame number, that is, the first image data frame in the block. If this occurs, the decoder 1 must receive all the image data of one block correctly.
0 and image data output to the image output unit 11 can be started. However, since the data amount of one block, that is, the block size, is fixed at 64 kbytes, if a transmission error occurs in an image data frame with a small block number as described above, regardless of the output speed of the image output unit 11, Until all subsequent image data frames have been transmitted for one block and the image data frame in which an error has occurred is corrected by retransmission,
This means that the facsimile machine 13 on the receiving side cannot start the image output operation. In this case, the block size is 64k
Since the size is fixed to a large size of bytes, the output start time will be significantly delayed. If output is performed continuously without being stopped midway, the time from the start of output to the completion of output of one block of image data is usually constant, so overall the time of output completion is You'll be late.

Furthermore, in the conventional error correction method, when the receiving memory 9 of the receiving facsimile device 13 is filled with image data and the output speed of the image output section 11 is slow, the receiving facsimile device 13 RNR indicating that image data cannot be received temporarily in
By sending a (receive not ready) signal to the transmitting facsimile machine 12 instead of the MCF signal 47, a means is provided to temporarily stop the transmission of image data from the transmitting facsimile machine 12. That is, the sending facsimile device 12 that receives the RNR signal temporarily stops transmitting image data, and the receiving facsimile device 13 outputs the image data until the receiving memory 9 has enough memory area to receive the next block. The RR signal is repeatedly transmitted at a certain time interval until a free space is available, and a query is made as to whether it is okay to start transmitting image data again. After responding to the RNR signal, the receiving facsimile device 13 outputs the image data in the receiving memory to the image output unit 11 through the decoder 10, and transmits the image data when the receiving memory 9 has enough memory area to receive the next block. When receiving the RR signal from the facsimile machine 12 on the side, it transmits an RR (receive ready) signal to the facsimile machine 12 on the transmitting side to inform that it is now possible to receive the next block. In response to this RR signal, the sending facsimile device 12 resumes sending image data. The transmission of this RNR/RR signal requires time to synchronize the transmission signals of the transmitting modem 5 and the receiving modem 7, as well as the image data. This means that time other than that required is required. For this reason, R
It is desirable that no communication of NR/RR signals occur.

Conventionally, in order to avoid this communication of RNR/RR signals, memories each having a capacity of two blocks, that is, 128 kbytes, are prepared as the transmitting memory 3 and the receiving memory 9, and the image data of the previous block is stored as the image data. By designing the output speed of the image output unit 11 to be sufficiently fast so that the output unit 11 transmits the image data of the next block during output, and the output of the previous block is completed during the transmission of the next block, the output speed of the image output unit 11 is designed to be sufficiently fast. When the transmission of a block is completed, the reception memory used by the previous block can be used, and the memory area for two blocks is used alternately for each block, thereby shortening the overall transmission time. Widely used. However, this method is based on the premise that the output speed of the image output section 11 can be made sufficiently faster than the transmission speed, and has the drawback that it requires a high-speed output device, making the device expensive. Furthermore, since the memory requires the capacity of two blocks, it has the disadvantage that the device becomes expensive. Furthermore, the sending facsimile device 1 has a high input speed of the image input unit 1.
In the case of facsimile communication between the receiver facsimile device 13 where the output speed of the image output unit 11 is slow, even if the reception memory for two blocks is prepared as described above, the output of the previous block is Since the transfer of the next block is not necessarily completed by the end of the next block's transmission, even if memory for two blocks is prepared, it cannot be said to be sufficient.

The present invention has been made to solve the above-mentioned problems, and is to shorten the time from when the receiving device starts receiving one block of data until it starts outputting the data to the output section. , Furthermore, in parallel with outputting data to the output unit, the next block is received using the remaining reception memory, so that data is output from the receiving device after transmission starts from the transmitting device. The aim is to shorten the total time.

[0018]

A data communication system according to claim 1 has at least one of the following (a) and (b). (a) A receiving device that sends control data having at least one of the following information to the transmitting device; (a1) capacity information of the receiving memory of the receiving device; (a2) output speed information of the receiving device; (b) A transmitting device that sends control data having at least one of the following information to a receiving device. (b1) Size instruction information indicating the size of data to be transmitted, (b
2) Selection instruction information that instructs the selection of the size of data to be transmitted from next time onwards.

The data communication system according to claim 2 has the following elements. (a) on the basis of prescribed criteria;
(b) a first size determining means that determines a capacity that is less than or equal to the capacity of the receiving memory of the receiving side device as one size; (b) a second size determining means that determines the size using a different standard from that of the first size determining means; (c) Transmission means for transmitting data according to the sizes determined by the first and second size determination means.

[0020]

In the data communication system according to the first and second aspects of the invention, the data block size can be appropriately selected by the transmitting device. For this reason, transmission of one data block is started with a small block, for example 4K bytes, and then the next block is transmitted using the time that the receiving device is outputting the data of this block to another output section. For example, it is transmitted in 8K bytes. As a result, if a transmission error occurs, the block size is smaller than the reception memory (64K bytes) of the receiving side device, so the time until retransmission is shortened and data is continuously transmitted. The time from when the first data frame is transmitted until it is output to the output section of the receiving device is shortened. Furthermore, even if a transmission error does not occur, even if output starts after the first block is correctly received, the next block will have been transmitted before the output of the first block is completed. The output is continuous and does not cause any delay.

In the data communication system according to the first aspect of the present invention, the receiving device transmits the receiving memory capacity (for example, 64 Kbytes) or the output speed of the receiving device to the transmitting device as control data. Based on the receiving memory capacity or output speed of the receiving side device, the sending side device first notifies the receiving side that it will start transmission in a small block (for example, 4 kbytes) as size instruction information. Similarly, the sending device determines the next block size (for example, 8k bytes, 16k bytes, etc.) based on the reception memory capacity or output speed of the receiving device.
The selection instruction information is transmitted to the receiving side.

In the data communication system according to the invention of claim 2, the first size determining means first calculates a size that is less than or equal to the capacity of the reception memory and is efficient based on a predetermined criterion, and The received block size (for example, 4 kbytes) is determined to be the transmission size. Further, the second size determining means is configured such that an RNR signal is not generated (for example, 8 kbytes, 16 kbytes, . . . k
Determine the block size (in bytes). Then, the transmission means transmits and receives data in the sizes determined by these first and second size determination means.

[0023]

[Example] Example 1. DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of the configuration of a facsimile apparatus according to the present invention. In the figure, 71 is a scanning line boundary notification line that informs that image data equivalent to one scanning line has been sent from the image input unit 1 to the transmission side transmission control unit 4 to the encoder 2; This is a code boundary notification line that notifies the transmission side transmission control unit 4 of the completion of encoding from the encoder 2 every time the encoding of image data corresponding to a scanning line is completed. From the signals of the scanning line boundary notification line 71 and the code boundary notification line 72, the transmitting side transmission control unit 4 knows the amount of encoded image data per scanning line, and calculates the data compression rate of each scanning line for the encoded image data. Amount/Amount of image data for one scanning line of input original, and the data compression rate over multiple n scanning lines: Amount of encoded image data for n lines/(Amount of image data for one scanning line of input original *n) Find it by

FIG. 2 shows that in the present invention, the DIS signal 40
Alternatively, it indicates the information content included in the NSF signal. In FIG. 2, 20 to 29 are the same information as in the prior art, but 30 is memory capacity information indicating the receiving memory capacity of the receiving facsimile machine 13. FIG. 3 shows the information content contained in the DCS signal 41 or NSS signal used in the present invention. In FIG. 3, 31 to 35 are the same information as before. 36 is block size instruction information (size instruction information) for transmitting the block size determined by the sending facsimile device 12 to the receiving facsimile device 13, and 37 is a block size selection method for instructing the method for determining the size of the following block. This is instruction information (selection method instruction information).

Next, the operation will be explained using the communication procedure diagram in the error correction method shown in FIG. First, the receiving facsimile device 13 uses the DIS signal 40 to determine the reception capability of the receiving facsimile device 13 to the transmitting facsimile device 1.
2 is the same as before. However, this reception capability includes error correction method information 25 indicating that there is a conventional error correction method function, possible transmission speed information 26 indicating the available transmission speed and modulation/demodulation method, and information necessary to output one scanning line. In addition to output speed information 27 indicating time, output width information 28 indicating outputtable image data width, and decoding method information 29 indicating decodable encoding methods for image data, use of reception memory 9 of receiving side facsimile device 13 Contains memory capacity information 30 indicating the amount of available memory.

The sending facsimile device 12 that has received the DIS signal 40 confirms that the receiving facsimile device 13 has an error correction function, and if it decides to operate using the error correction method, it corrects the error in the DCS signal 41 as before. The correction method instruction information 31 is used to instruct the receiving facsimile device 13 to operate using the error correction method. D.C.
In addition to this, in the S signal 41, the sending facsimile device 12
transmission speed instruction information 32 that instructs the speed and modulation/demodulation method to be used for image data transmission, output speed instruction information 33 that selects the image data output speed at the receiving facsimile device, and instructs the width at which the image data is output. The output width instruction information 34 to specify the decoding method for image data and the decoding method instruction information 35 to specify the decoding method for image data are specified as before, but in addition, the block size information 34 that transmits the block size determined by the sending facsimile device 12 to the receiving facsimile device 13 is provided. Instruction information 36 and block size selection method instruction information 37 that conveys the method for determining the block size for the second and subsequent blocks are newly included. When transmitting the DCS signal 41, the transmitting side transmission control unit 4 determines the block size using the following logic.

First, the second size determining means will be explained first. The second size determining means is a size determining means for transmitting without generating an RNR signal, and its details are as described below. Now, the transmission speed of image data on the telephone line 6 is k b
ps, image output unit 11 in the receiving facsimile device
The output speed is ot msec/line (output speed per scanning line), the amount of image data per scanning line before encoding, that is, the amount of image data for one scanning line determined by the document width is a bit, and transmission The side transmission control unit 4 calculates the image data compression rate r obtained from the signals of the scanning line boundary notification line 71 and the code boundary notification line 72 by the above calculation, and calculates the image data compression rate r, the receiving side number reserved for the data block to be transmitted first. Let the buffer size of one block be b1 bits, and the buffer size of the second block on the receiving side reserved for the next data block to be transmitted be b2 bits. At this time,
When the first buffer of the receiving facsimile device 13 is filled with image data, and if the data compression rate for the image data for this b1 bit is r1, the amount of image data passing through the decoder 10 is (b1÷r1). The time t required to record one block of image data is t=(b1÷r1)÷a×ot [sec]
Transmission speed: k bps Output speed of receiving side device: ot msec/line (
(Output speed per 1 scanning line) Image data amount for 1 scanning line: a bit Buffer size of the first block on the receiving side: b1 bit, Buffer size of the second block on the receiving side: b2 bits Data compression rate: r1 Decoder 10 Amount of image data passed through: (b1 ÷ r1) bits Time required to record one block of image data: t
becomes. If the input speed of the image input section 1 is high, the first
It is possible to transmit (t x k) bits of the image data of the second block during the t seconds during which the image data b1 of the block is recorded, but if the inequality (t x k) ≦ b2 holds. That is, if the block size reserved for the second block is larger than the amount of data transmitted in t seconds, no RNR signal is transmitted from the receiving facsimile machine. Here, if the ratio b2/b1 of the first block size and the second block size is set as Br, ot
If the ratio of the block sizes of two consecutively transmitted blocks is selected so that ×k÷(r1×a)≦Br, no communication of RNR signals occurs. For example, r1 = 0.06 (encoding method that compresses to about 1/15), a = 1728 [bit; A4 width original]
, ot=20 [msec/line], and k=9600 [bit/sec]. If Br≧1.85 is satisfied, no RNR signal communication occurs. Here, r1 is the compression rate of the image data regarding the block existing in the receiving memory 9, and is not the compression rate of the image data in the sending memory 3 of the sending facsimile device 12 or about to be input.

Now, considering the input speed required of the image input unit 1 in order to accumulate a sufficient amount of image data on the transmission memory 3 during the transmission of the first block, t
The amount of image data that can be stored in the transmission memory 3 per second is s.
The input speed of the image input unit 1 in the sending facsimile device 12 is i sec/line (input speed per scanning line), the amount of image data for one scanning line determined by the document width is a bit, and the transmission memory 3 is The following relationship holds true between the data compression rate of image data stored in r0 and r0. s=t÷i×a×r0 Amount of image data that can be stored in the transmission memory 3 in t seconds: s
bit Input speed of sending device: i sec/line (input speed per scanning line) Amount of image data for one scanning line: a Bit sending memory 3
Data compression rate: r0 If more than (t x k) bits of data transmitted in t seconds is stored in the transmission memory 3, the image input unit 1
The input speed can be said to be fast enough. Therefore, if t×k≦s, that is, i≦a×r0÷k, the input speed of the image input unit 1 is sufficient. Here, r0 = 0.06 (encoding method that compresses to about 1/15), a = 1728 [bit; A4 width original]
, k=9600 [bit/sec], and if i≦10.8 [msec/line], this condition described above is satisfied. The above is the operation of the second size determining means.

Next, the first size determining means will be explained. Control signal PPS/NU every time one block is transmitted
A communication time tx between the LL signal 46 and the MCF signal 47 is required, and if the size of one block is made too small, time will be spent only on transmitting the control signal, and time will be spent in areas other than the image data transmission time. Become. Therefore, the time t required to output one block of image data needs to be longer than the two control signal transmission times tx, so t>tx needs to be satisfied. In other words, b1÷
Since r1÷a×ot>tx, b1>a×tx×r1÷ot is required, and if tx=2.2 [sec], then b1 needs to be larger than 11404 bits (1425 bytes). Assuming that one frame is 256 bytes, the first block must consist of five or more frames. Therefore, for example, it is efficient to use 8 frames (2 kbytes) as the initial block size. The above is the operation of the first size determining means.

Now, from the above, for example, if we set the initial block size to 8 frames (2 kbytes),
From Br≧1.85, set Br=2, and set the second block to 4
By setting the third block to 8k bytes, the fourth block to 16k bytes, even if the reception memory of the receiving facsimile machine is 64k bytes, the
+4+8+16+32=For image data of 62k bytes or less, no RNR signal is responded and 2k
Recording can be started immediately after the byte of image data is correctly transmitted. In this method, even if the recording speed of the image output unit of the receiving facsimile device is slow, for example, if the above value of ot is ot=10 [msec], the condition is that Br≧3.70, and Br= If you select 4, you can set the first block to 2k bytes, the second block to 8k bytes, and the third block to 32k bytes.
Even if the reception memory of the receiving facsimile machine is 64k bytes, image data of 42k bytes or less cannot be processed.
Transmission without RNR signals can be guaranteed, and recording can be started immediately after the first block of image data is correctly transmitted. For the first block, once the encoding method is determined, the sending facsimile device 12 must immediately read the image data from the image input unit 1 and generate encoded data for the size of the first block. There is. If the input speed of the image input unit 1 of the sending facsimile machine 12 is fast, this time is short and the delay until the DCS signal 41 is sent is small. For example, if the input speed of image input unit 1 is now i = 5 m
sec/line (input speed per scanning line), the amount of image data for one scanning line determined by the document width is a = 17
28 bits, and the data compression rate of the image data stored in the transmission memory 3 is r0=0.06, for example, s=
In order to accumulate 2 kbyte = 16 kbit of data, from the formula s = t ÷ i × a × r0, which indicates the amount of image data s that can be accumulated in the transmission memory 3 for the above t seconds, t = s × i ÷ (a × r0 ) indicates the time required for the first block of data to be accumulated. In the above example, t=approximately 0.77 seconds.

Thus, in the present invention, in the transmitting facsimile device 12, the receiving facsimile device 13 described in the DIS signal 40 or the control signal equivalent thereto
The block size is selected according to the above algorithm using the available transmission speed information 26, output speed information 27, output width information 28, decoding method information 29, and memory capacity information 30, and is applied to the DCS signal. 41 or an equivalent control signal to transmit the block size of the image data to the receiving facsimile device 13 using the block size instruction information 36 and the block size selection method instruction information 37, thereby determining the size of the image data block. can be made variable, thereby shortening the time from the start of the first data transmission of image data to the start of output to the image output section. Note that if the size of one block exceeds 64 kbytes as calculated above, it is sufficient to set the size of one block to 64 kbytes and perform transmission using the conventional error correction method.

As described above, in the first embodiment, in a facsimile device that transmits still images using a telephone line,
An image input section that inputs an image, an encoder that encodes the digital signal obtained from the image input section, a transmission memory that temporarily stores the encoded image data, and an HDLC (HDLC) that transmits the image data and control signals to be transmitted. Frames containing image data are assigned frame numbers and transmitted according to a procedure based on the error correction method (error correction mode) used in Group 3 facsimile. A transmitting side transmission control unit that retransmits the frame in which an error has occurred, a transmitting side modulator/demodulator that modulates and transmits image data and modulates and demodulates a control signal, and a transmitting side modulator that modulates and demodulates the modulated image data. A receiving modem that receives the original encoded image data and also demodulates and modulates the control signal, and an HDLC (high level data link control) for the transmitted image data and control signal.
a receiving side transmission control unit that disassembles or generates the frame format of the frame and requests the transmitting side to retransmit the frame in which a transmission error has occurred according to the procedure of the error correction method (error correction mode) used in Group 3 facsimile; a receiving facsimile device, comprising: a receiving memory for temporarily storing received encoded image data; a decoder for decoding the encoded image data; and an image output section for outputting the decoded image data. In the control signal frame from , error correction method information declaring that it has the error correction method function according to the present invention, transmission possible speed information declaring the speed and modulation/demodulation method that can be used for transmission, and image output output speed information that declares the output speed of the image data, output width information that declares the width per scanning line of image data to be output, decoding method information that declares the decodable encoding method, and reception memory The sending side transmission control unit of the sending facsimile machine receives the above information notified by the control signal and the encoded image data obtained by encoding the image data. Based on the image data compression rate, which indicates the ratio between When an error occurs, the same image data is quickly retransmitted, and at the same time, image data output to the image output unit is started early, and reception of the second and subsequent blocks is performed according to the output speed of the image output unit. The error correction method according to the present invention is used in a control signal frame that determines the block size so that output from the memory to the image output unit is continuously performed, and that is transmitted from the transmitting side to the receiving side prior to transmitting image data. error correction method instruction information that instructs the transmission of image data, transmission speed instruction information that indicates the transmission speed used for image data transmission, output speed instruction information that instructs the output speed of the image output section, and Output width instruction information that specifies the width per scanning line, decoding method instruction information that specifies the decoding method of image data, and the first block of a block that is a unit for transmitting image data and is composed of multiple frames. Having block size instruction information that indicates the block size and block selection method instruction information that indicates the method for selecting block sizes for the second and subsequent blocks, it has the function of instructing the receiving side of the block size to be used in the error correction method. This paper describes a facsimile communication system characterized by the following.

As described above, in the facsimile communication system according to the first embodiment, in order to make the block size variable as described above, the block size is determined between the receiving facsimile machine 13 and the transmitting facsimile machine 12. exchange information for the purpose of In the facsimile apparatus according to this embodiment, memory capacity information indicating the usable capacity of the receiving memory 9 is added to the DIS signal 40 or the NSF signal, which is an optional control signal defined in the group 3 facsimile, and Side facsimile machine 1
3 informs the sending facsimile machine 12 of the memory size that can be used when operating in the error correction system. Next, the sending facsimile device 12 receives the receiving side memory capacity, available transmission speed information 26, output width information 28, and decoding method information 29, which were notified by the above signal or the NSF signal, as well as information that was not previously used. Output speed information 2
7 and the data compression rate of the encoding method detected by the sending facsimile device 12, that is, the data compression rate from the image input unit 1 to the encoder 2.
The usage state of the receiving memory 9 in the receiving side facsimile device 13 is estimated by calculation from the ratio of the amount of data transferred to the encoder 2 and the amount of data passed from the encoder 2 to the transmitting memory 3, so that the receiving memory 9 can be used effectively. Determine the size of the image data block. Based on the determined block size, the sending facsimile device 12 sends the DCS signal 41,
Alternatively, using the NSS signal, which is an optional control signal defined in Group 3 facsimile, the first block size is determined using the newly added block size instruction information, and the block size of the second and subsequent blocks is determined using the block size selection method instruction information. The above objective is achieved by instructing the determining method and appropriately selecting and instructing the block size to be used for image data transmission for each block.

According to the first embodiment, since the block size can be made variable as described above, it is not necessary to exchange information between the receiving facsimile machine 13 and the transmitting facsimile machine 12 to determine the block size. Become. In the facsimile apparatus of the present invention, memory capacity information 30 indicating the remaining capacity of the receiving memory 9 is added to the DIS signal 40 or to the NSF signal, which is an optional control signal defined in Group 3 facsimile, and the sending side facsimile In the device 12, the above-mentioned DIS signal 40 or N
Memory capacity information 30 and possible transmission speed information 26 of the receiving facsimile device 13 informed by the SF signal
, output width information 28, decoding method information 29, output speed information 2
7 and the data compression rate of the image data detected by the sending facsimile device 12, the usage state of the receiving memory 9 in the receiving facsimile device 13 is estimated, and based on this, the size of the selected image data block and its size are estimated. Since the method for selecting the block size to be determined can be notified to the receiving facsimile device 13 using the DCS signal 41 or the NSS signal, which is an optional control signal defined in Group 3 facsimile, the image data block size can be notified to the sending side facsimile device 13. By allowing the facsimile device 12 to select as appropriate and reducing the number of RNR/RR signal communications, the time from the start of the first data transmission of image data to the start of output to the image output section can be shortened. There is an effect.

Example 2. Next, another embodiment according to the present invention will be described with reference to the drawings. FIG. 5 shows the PP according to this invention.
The frame structure of the S.NULL signal 46 is shown. In FIG. 5, the identification code of the PPS/NULL signal 46 is written in the control frame identifier 23. The block size instruction information 36 has the same content as the block size instruction information 36 in the DCS signal 41 or NSS signal.

Next, the operation will be explained using FIG. 4 again. First, the receiving facsimile device 13 transmits the receiving capability of the receiving facsimile device 13 to the transmitting facsimile device 12 using the DIS signal 40, which is the same as in the first embodiment. Transmission possible speed information 26, output speed information 27, output width information 2
8. Decoding method information 29 and memory capacity information 30 are the same as in the first embodiment.

The operation of the transmitting facsimile device 12 that receives the DIS signal 40 is also the same as in the first embodiment except for the points described later.
1. Transmission speed instruction information 32, output speed instruction information 33, output width instruction information 34, decoding method instruction information 35, and block size instruction information 36 indicating the block size of the first block are transmitted. The difference from the first embodiment is that the block sizes of the second and subsequent blocks are not considered at this point, and the block size selection method instruction information 37 is DCS.
This point is not included in the signal 41. Thereafter, in this embodiment, as in the first embodiment, the TCF signal 41, CFR signal 43, training signal 44, and image data signal 45 are transmitted in accordance with the procedure shown in FIG. After one block of image data has been transmitted, the sending facsimile device 12 selects the block size for the next block to be sent when transmitting the PPS/NULL signal 46. As described in the explanation of the first embodiment, what is considered regarding the compression rate of image data is the compression rate of the image data of the block in the reception memory of the receiving facsimile device 13, which is about to be transmitted. It is not the block image data compression rate. Therefore, in determining the size of the next block, it is not necessary to know the image data compression rate of the next block to be transmitted. That is, it is not necessary to input the image data of the next block and complete encoding. However, according to the first size determining means described in the first embodiment, when determining the size, it is necessary to know the image data compression rate of only the first block before transmission. However, regarding the image data compression rate for this first block, if the average compression rate of the encoding method used for transmission is known in advance, the size of the first block may be determined using that compression rate. This is because the first block is usually selected to be sufficiently small compared to the capacity of the receiving memory 9, and even if the ratio of the first block to the second block shown in the first embodiment is taken into account, the image data up to the second block cannot be received. This is because there are many cases where there is enough reception memory 9 to do so. The second size determining means of the sending facsimile device 12 determines the size of the next block based on the size of the block just transmitted and the size of the block just transmitted by the receiving facsimile device 13 shown in the first embodiment. In accordance with the time required for processing and the block size selection method shown in the first embodiment, the smallest possible block size is selected that satisfies the condition that the image output section 11 of the receiving facsimile device 13 continuously outputs image data. , its block size is P in Figure 5
Block size instruction information 36 of PS/NULL signal 46
The information is transmitted to the receiving facsimile machine 13 as follows. The receiving facsimile device 13 checks the occurrence of a transmission error in the block currently being transmitted, and also checks the receiving memory 9.
Check the remaining capacity of the receiving memory 9 and confirm that there is no image data frame to be retransmitted and that the remaining capacity of the receiving memory 9 is PPS/NULL signal 46.
If the block size is larger than the block size indicated by the block size instruction information 36, an MCF signal 47 is sent as a response. When the sending facsimile device 12 receives the MCF signal 47, it moves on to sending the next image data block. Normally, the compression rate of image data varies depending on the local characteristics of the image data, and the usable size of the receiving memory 9 may also be limited if the receiving facsimile machine 13 has an application that uses the memory for other purposes. Therefore, with this method, the optimal block size for the second and subsequent blocks can be selected according to the image data compression rate and reception memory capacity at the time, and the transmission of image data is improved. After the start, image output section 1
This has the effect of shortening the time it takes to output the data to the first page.

In addition, the transmission speed and the image data compression rate of the encoding method are high, and the input speed of the image input section 1 and the image output section 1 are
If the output speed in step 1 is not sufficient, the second size determining means selects the smallest block size within a range that does not cause wasted time due to communication of control signals, so that the facsimile original can still be transmitted to the sending facsimile machine. The total time from the start of transmission to the end of output to the image output unit 11 of the receiving facsimile device 13 can be shortened.

As described above, in the second embodiment, there is no block size selection method instruction information that instructs the selection method of the block size for the second and subsequent blocks, and instead, the data is transmitted immediately after transmitting one block of image data. The control signal transmitted from the side facsimile machine to the receiving side facsimile machine contains the block size instruction information as set forth in claim 1 regarding the next block to be transmitted, and one of the image data.
Using the compression rate of image data that changes for each block,
A case has been described in which the block size of the next block is indicated each time the transmission of each block is completed.

Example 3. Next, another embodiment of the present invention will be described. In Example 1 above, “first
Although a case has been described in which a sufficiently large amount of image data is accumulated on the transmission memory 3 during block transmission, a case in which this is not the case will be described here. The time t[s during output of the first block in the receiving facsimile machine 13
ec], it is possible to transmit t×k image data using a modulation/demodulation method with a transmission rate k [bit/sec];
e] (input speed per scanning line) is slow, the formula shows the conditions for a sufficiently large amount of image data to be accumulated on the transmission memory 3 during the transmission of the first block shown in Example 1. In other words, when the amount of image data for one scanning line determined by the document width is a bit, and the data compression rate of the image data stored in the transmission memory 3 is r0, the inequality i ≦ a×r0÷k can be satisfied. If this is not possible, the sending facsimile device 12 will send an HDLC flag sequence (a plurality of flag strings) because there is insufficient image data to send on the line. During the transmission period of this flag string, no valid data is being transmitted. For example, the image data compression rate of the encoding method used for transmission r0 = 0.05, a = 1728 [bit; A4
original width], k=9600 [bit/sec], the input speed of the image input unit 1 sufficient to satisfy the inequality i≦a×r0÷k is i≦9.
0 [msec/line], and the input speed was sufficient when r0=0.06 i=10 [msec
/line], the above equation cannot be satisfied. According to the above inequality, the condition for this input speed is the output speed o of the image output unit 11 of the receiving facsimile device 13.
It can be seen that there is no relation to t [msec/line], and the value is determined only by the compression rate of the image data, the transmission speed, and the width of the document. In other words, the compression rate of the encoding method adopted by the encoder 2 is very high, or the transmission capacity of the line is very high, so even if data is read from the image input unit 1, the transmission capacity (transmission speed) of the line is It can be seen that the situation is such that it is not possible to generate enough data for one block to catch up. In such a case, it is better to sequentially transmit the generated encoded image data in small blocks and output them sequentially from the receiving facsimile device 13, thereby reducing the time from the start of image data transmission to the completion of output. can. This is because, if output of the last block of a page is started after the last block has been transmitted, the smaller the amount of image data in the receiving memory 9 at the time of starting output, the faster the output will be completed. The block size in this case is the control signal PPS/NU shown in Example 1.
It is desirable to select and transmit a block size as small as possible within a range that does not cause wasted transmission time due to communication between the LL signal 46 and the MCF signal 47. In this way, if the input speed is not sufficient, Example 1
The second size determining means shown in FIG. 1 instructs the receiving facsimile device 13 to transmit the second and subsequent blocks with the same block size as the first block in the block size selection instruction information 37. Further, in the case shown in the second embodiment, the second size determining means repeatedly uses the block size instruction information 36 transmitted by the control signal PPS/NULL signal 46 every time each block is completed to determine the same block size. You can achieve the same goal by declaring: Furthermore, the block size for each block is determined according to the compression rate of the image data and the remaining capacity of the reception memory 9, and by keeping the above block size as small as possible, the reception side facsimile machine 13 can be Even if the receiving memory 9 is 64 kbytes or less, there is an effect that transmission can be performed using an effective error correction method.

Furthermore, in facsimile transmission, the demodulation state of the receiving modem 7 may not be stable immediately after communication is started and at the time when the first block is transmitted; in this case, the initial training If the demodulation adjustment using the signal 44 fails, all subsequent image data transmissions will fail, and all transmissions of one block will require retransmission. In the facsimile communication system according to this embodiment, the size of the first block is set small, so even if the demodulation adjustment of the receiving side modem 7 is not successful, the retransmission operation is quickly performed, thereby reducing the loss of transmission time. It has the effect of being able to be kept to a minimum.

In the first embodiment, the capacity and output speed of the receiving memory 9 of the receiving facsimile machine 13 are transmitted to the transmitting facsimile machine 12. It is not necessary to always notify the sending facsimile machine 12; the sending facsimile machine 12 can transmit the first , or alternatively, a second size determining means may be implemented.

Further, in the above embodiment, the case of a facsimile machine has been explained, but it goes without saying that the present invention can be applied to other data communication systems.

[0044]

As described above, according to the present invention, by making the data block size variable (for example, by reducing the block size of the image data to be transmitted first), the receiving device can You can shorten the time from when you start receiving block data to when you start outputting data, and furthermore, by using the remaining reception memory to receive the next block in parallel with the output of the above data. This has the effect of shortening the total time from the start of data transmission by the sending device until the end of data being output to the receiving device.

[Brief explanation of drawings]

FIG. 1 is a facsimile device configuration diagram showing the configuration of a certain facsimile device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a DIS signal used in the error correction method of the present invention.

FIG. 3 is a configuration diagram of a DCS signal used in the error correction method of the present invention.

FIG. 4 is a communication procedure diagram in the error correction method.

[Fig. 5] PPS/NULL according to claim 2 of the present invention
Signal configuration diagram.

FIG. 6 is a diagram showing the configuration of a facsimile machine that implements a conventional error correction method.

FIG. 7 is a diagram showing the configuration of a DIS signal used in a conventional error correction method.

FIG. 8 is a DCS signal configuration diagram used in a conventional error correction method.

[FIG. 9] A communication procedure diagram in an error correction method when a transmission error occurs.

FIG. 10 is a configuration diagram of an image data frame.

[Explanation of symbols]

1 Image input unit 2 Encoder 3 Transmission memory 4 Transmission side transmission control unit 5 Transmission side modem 7 Receiving side modem 8 Receiving side transmission control unit 9 Reception memory 10 Decoder 11 Image output unit 12 Sending side facsimile device 13 Receiving side Facsimile machine 20 Flag 21 Frame header 22 Frame check information 23 Control frame identifier 25 Error correction method information 26 Transmission possible speed information 27 Output speed information 28 Output width information 29 Decoding method information 30 Memory capacity information 31 Error correction method instruction information 32 Transmission possible Speed instruction information 33 Output speed instruction information 34 Output width instruction information 35 Decoding method instruction information 36 Block size instruction information 37 Block size selection method instruction information 40 DI
S signal 41 DCS signal 42 TCF signal 43 CFR signal 44 Training signal 45 Image data signal 46 PPS/NULL signal 47 MCF signal 48 PPS/EOP signal 53 PPR signal 71 Scanning line boundary notification line 72 Code boundary notification line

Claims (2)

[Claims] Claim 1: A data communication method having at least either of the following (a) or (b): (a) a receiving device that sends control data having at least one of the following information to the transmitting device; A transmitting device that sends control data having at least one of the following information to the receiving device: a1) capacity information of the receiving memory of the receiving device; (a2) output speed information of the receiving device; and (b) at least one of the following information. (b1) Size instruction information indicating the size of data to be transmitted, (b
2) Selection instruction information that instructs the selection of the size of data to be transmitted from next time onwards. Claim 2: A data communication system having the following elements (
a) a first size determining means that determines a size that is less than or equal to the capacity of the receiving memory of the receiving device based on a predetermined standard; (b) determining the size using a different standard than the first size determining means; a second size determining means, (c
) Transmission means for transmitting data according to the sizes determined by the first and second size determination means.