JPH0320102B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a facsimile transmitting apparatus, and particularly to a facsimile transmitting apparatus that compresses image data and transmits the data by controlling the amount of image transmission according to black and white information of pixel signals of one scanning line. CCITT (International Telegraph and Telephone Consultative Committee) on the data compression method used by the group's three machines to transmit an ISO-standard A4 size document in about one minute using a telephone line
T4 recommendations have been made. In this recommendation, the standard one-dimensional run-length encoding method is the so-called modified Huffman (MH) method, and the recommendation also recognizes the modified two-dimensional method as the modified read (MR) method as an option. Also, various transmission speeds are defined, such as 4800bps and 2400bps. In such an encoding method, the amount of image information of one encoded line is different (for example, a completely white line and a line including black), and the transmission time of the image information of one line is also different. On the other hand, facsimile devices that decode received image information in real time and record it line by line are commonly used, and it is difficult to actually record one line of image information received between various devices. The time required varies. For this reason, the CCITT G recommendation stipulates the minimum transmission time for one line of image information, and this minimum transmission time is standardly 20 milliseconds, with other exceptions such as 10 milliseconds, 5 milliseconds, and 0 milliseconds. seconds, 40
Defined as milliseconds as an option. Then, the transmission speed of the modem is determined, and the line information (one line of coded bit information) in which the transmission time of one line of image information is shorter than the minimum transmission time has meaningless bits (fil bits).
is added so that the transmission time of the line information becomes the minimum transmission time. Also, line information for which the transmission time of one line of image information is longer than the minimum transmission time is transmitted as is. Note that the fill bit added to the line information is removed on the receiving side, and this fill bit deletion function is a function that all ordinary facsimile machines have. If the device is manufactured according to this CCITT recommendation,
Since the data compression method and the minimum transmission time per line are set, it becomes impossible to make the most of the capabilities of the device. In particular, the interval between recommended values for the minimum transmission time for one line is large; for example, the minimum transmission time for one line of the equipment is
In the case of 12 milliseconds, the transmission speed differs significantly between making the most of that capability and transmitting while maintaining the 20 millisecond limit. Such standardization is disadvantageous because it limits the capabilities of the device. As mentioned above, in order to make the most of the capabilities of the equipment, various original compression methods were developed in addition to the CCITT recommendations, and transmission was performed in original modes.
While this method makes the most of the equipment's capabilities, it has the disadvantage of complicating the circuitry and increasing costs due to its unique mode. In addition, for transmission using a unique mode, according to recommendations,
MH (MODIFIED HUFFMAN) and MR
Although it is faster than the encoding compression method of (MODIFIED READ), it is
There is no significant difference in efficiency from when using the MR or MR compression methods, and in order to contribute to speeding up the unique mode, it is assumed that the minimum transmission time per line is set to the optimum value for the equipment. Become. In other words, what contributes to the speedup of the unique mode is the problem of transmission efficiency of all-white lines and all-black lines in normal documents. In other words, since the transmission rate is constant whether in the original mode or when using MH or MR, the number of coding bits for one line within the minimum transmission time for one line is a certain fixed number of bits. , using a 4800 bps modem and a minimum per line transmission time of 20 ms, that's 96 bits. For example, if one line has several to ten or more black and white run lengths, the number of compressed bits will exceed the predetermined number of bits and will no longer depend on the minimum transmission time for one line. From this, it can be said that in a normal document, what is limited by the minimum transmission time for one line is mostly all-white lines and all-black lines. Therefore, JP-A-50-17118 and JP-A-55-
As disclosed in Japanese Patent No. 13550, a system is known in which a skip signal is assigned and transmitted for image information of an all-white line, and when the receiving side detects a skip signal while receiving the image information, the recording scan is skipped by one line. However, in the case where a skip signal is assigned to an all-white line as described above, communication cannot be performed unless the receiving side has a function to decode and process the skip signal. Then, during the image information reception process, a configuration is required to decode and process a skip signal, which is a special signal different from the image information, and the configuration of the receiving side device becomes complicated. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a facsimile transmitting device that eliminates these conventional drawbacks and can efficiently shorten document transmission time by making full use of the capabilities of the facsimile device at low cost. shall be. In order to achieve this object, the present invention focuses on the fact that the reception recording time of an all-white line on the receiving side is normally short, and when the image information of one scanning line is not all-white information, the first minimum transmission time is Accordingly, by transmitting image information and transmitting the image information according to a second minimum transmission time that is shorter than the first minimum transmission time when the image information of one scanning line is all white information. , the amount of fill bits added when transmitting all-white lines is reduced, and the time for transmitting information on all-white lines is shortened. That is, the present invention provides a memory for storing image information for each scanning line, a detection means for detecting whether the image information for one scanning line in the memory is all-white information, and a minimum transmission time for one scanning line. , select a minimum transmission time from a plurality of minimum transmission times including at least a first minimum transmission time and a second minimum transmission time shorter than the first minimum transmission time, according to the detection result of the detection means. and means for transmitting the image information in accordance with the minimum transmission time selected by the selection means, and the transmitting means is configured to transmit the image information for one scanning line so that the transmission time satisfies the selected minimum transmission time. If not, the film information is transmitted following the image information of one scanning line until the transmission time reaches the minimum transmission time, and when the image information of the one scanning line is all-white information, the selection means selects the second The present invention provides an image communication device which selects the first minimum transmission time when the image information of the one scanning line is not completely white information. Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In FIG. 1, a document 10 having characters 11 is illuminated by an illumination system (not shown), and its image is projected onto a CCD (charge coupled device) 14 through a lens 13 in the main scanning direction (direction along the line). ) is scanned. When the main scanning in the line direction is completed, the next line is similarly scanned by a sub-scanning device (not shown), and the entire document is sequentially scanned. The scanning line 12 is sometimes on the character 11, and sometimes on the all-white (meaning there is no image) line as shown. The pixel signals of the CCD 14 are shaped by a shaping circuit 15 and then stored in a line buffer 16 for one line. Usually two or three line buffers are used to store pixel signals of multiple lines, but
In this embodiment, a buffer with a capacity for one line is used for simplicity. The pixel signals stored in the line buffer 16 are sequentially read out in response to the readout clock appearing on the line 16a and input to the encoder 17 and the all-white detection flip-flop 19 via the line 16b. The image data sent to the encoder 17 is sent to the control circuit 21
is sequentially encoded via the lead wire 21a and the second
The signal is sent to the first-in first-out shift register (hereinafter referred to as the FIFO shift register) shown in the figure. The line counter 18, which is controlled by the control circuit 21, determines whether or not all the data for one line has been processed.
When counting the number relative to the pixels of the line, the line 18b
A signal is sent to the control circuit 21 to inform the control circuit 21 of one line of data processing. On the other hand, the above-mentioned one line of image data is input to the J input of the all-white detection flip-flop 19. Flip-flop 19 here is line buffer 16
It is cleared by the line readout start pulse 21 that appears on the line readout line 21b of the control circuit 21 before reading out one line from the line, and is set if there is even one black pixel during the readout of one line. , and is not set for all white pixels. Therefore, through the Q output, the control circuit 21 can determine whether the line in question is completely white or not. If that one line is completely white, the control circuit 21
The 8-bit latch 26 is activated in response to the data bit clock on 21c via data buses 0-7 of the figure.
After setting a value shorter than the minimum transmission time of the normal line, the encoded information is sent to the FIFO flip-flop 22 according to the encoded data input clock on line 21d. If the line is not completely white, the latch 26 is set to a value equal to the normal minimum transmission time. This minimum transmission time is determined as will be described later, taking into consideration the receiving capacity of the receiver. In this embodiment, the FIFO flip-flop 22 is composed of 3 bits to simplify the explanation, and when all 3 bits are occupied by the encoded code, the FIFO full signal is sent on the line 22a, and if no encoded code is stored. In this case, a FIFO empty signal is generated on line 22b, and the control circuit 21 and
It is input to the NAND gate 25. The one line transmit start initialization pulse appearing on line 21 causes the data in latch 26 to be loaded into 8-bit counter 27 and clears D flip-flop 28. The counter 28 starts counting according to the transmitting clock on the line 24a of the modulator 24, and when it has counted a predetermined number, it generates a carry signal CA and inputs it to the D input of the D flip-flop 28. The Q output is inputted to the control circuit 21 via the line 21f as a one line minimum transmission bit transmission completion signal. The output of the NAND gate 25 controls the AND gate 23 and guides the data in the FIFO shift register 22 to the modulator 24 as transmission data. The operation of the facsimile device configured as described above will be explained. First, before transmitting data, the transmitter communicates with the receiver and uses the DIS of the CCITT T30 recommendation.
Know the optimal minimum transmission time for one line and the transmission speed of the modulator/demodulator to be used via DCS, DTC signals, NSF, NSC, and NSS signals, and calculate the minimum number of transmission bits using these two pieces of information. The actual minimum number of bits depends on the speed of the modem and the minimum transmission time:

[Table] In this embodiment, the minimum number of bits to be transmitted is assumed to be 5 bits for simplicity of explanation, and is latched into an 8-bit latch 26. As mentioned above, this minimum number of transmission bits can be changed for each line based on the image information of one line on the transmitting side. In the first line data transmission, FIFO
FIFO empty line 22b of shift register 22
is at H (high level) (see FIG. 3e), and the D flip-flop 28 is at H, so the NAND gate 25 outputs "0" (low level), which causes the AND gate 23 to output "0" (low level). The output, ie, the transmitted data, becomes "0" (see FIG. 3j). Next, based on the encoded data input clock of FIG. 3c, the first line is encoded with the code "101110" (see FIG. 3b. Note that A and B are the last bit of the first line and the second line, respectively. (indicating the last bit of the FIFO shift register 22) are sequentially input to the FIFO shift register 22. In this case, an EOL (END OF LINE), that is, a line end signal, is input prior to the actual encoded code. When the first bit of the code of the first line is input, the FIFO empty line 22b becomes "L", and the code data is transferred to the transmission clock (8 for simplicity) as shown in FIG. The signal is sent to the modulator 4 as transmission data (see FIG. 3j) through the AND gate 23 in synchronization with the clock signal (which ends the transmission of one line). At the same time as setting the encoding code in the FIFO shift register 22, an initializing pulse to start transmission of one line is issued as shown in FIG. As shown, in this embodiment, the D flip-flop 28 is cleared at the same time as the D flip-flop 28 is cleared. Thereafter, the counter 27 is incremented every time transmission data is sent out in accordance with the transmission clock. It then appears on line 22a of shift register 22 as shown in FIG. 3d.
The control circuit 21 inputs the encoded code to the shift register 22 according to the encoded data input clock until the FIFO full signal becomes "H", that is, until 3 bits of the encoded code are input, and then the FIFO
The encoded code is input to the shift register 22 every time the full signal becomes "L", and this continues until the end of one line of data (A in FIG. 3b). If the total number of bits of the encoded code for one line is greater than the value set in latch 26 (5 bits) as in this line, that is, if the transmission of one line takes longer than the minimum transmission time, then Counter 2 during the encoded code transmission as shown in g.
7's carry output CA becomes "H", thereby setting the D flip-flop 28 and outputting line 2.
1f, the control circuit 21 is notified that the minimum transmission bit transmission for one line has been completed. Since the output becomes "L", AND gate 23 is opened,
The data entered in the shift register 22 is transmitted until one line of data has been transmitted (indicated by the first line in FIG. 3j). At the same time as all the last data of one line is transmitted, the FIFO empty becomes "H". After confirming that the minimum transmission bit for one line has been transmitted and that the FIFO is empty, the control circuit 21 issues an encoding code of "11" for the next line as shown in FIG. 3b.
are sequentially input to the shift register 22, and at the same time, an initialization pulse for starting transmission of one line is issued, and the above-described operation is repeated. If the transmitted data (2 bits) is smaller than the minimum number of transmission bits per line, which is the set value of the latch 26, as in this second line, the encoded data is input to the shift register 22 and the FIFO empty is When the signal becomes "H", the FILL bit "0" is inserted as shown in FIG. 3j.
At this point, as shown in FIG. 3i, the 1-line minimum transmission bit transmission completion flag, that is, the Q output of the flip-flop 28, has not yet been set, so the output of the NAND gate 25 becomes "L" and the transmitted data is automatically transmitted. becomes “0”. That is, a "0" signal is sent out through the AND gate 23 until the minimum transmission time latched by the latch 26 has elapsed, that is, until the carry signal CA is output from the counter 27. As a result, as for the second line, three fill bits are filled as shown in FIG. 3J. Thereafter, the control circuit 21 detects that the 1-line minimum transmission bit transmission completion flag has become "H" and sequentially inputs the encoded code of the next line to the shift register 22, and then immediately sends the 1-line start initialization pulse. is output and the same operation as described above is repeated to transmit data. As described above, when the information on one line is completely white, a shorter minimum transmission time is selected and set in latch 2b than when the information on a line includes black, so all lines have the same minimum transmission time. Therefore, the amount of fill bits added when transmitting an all-white line can be reduced compared to when transmitting an all-white line, and the transmission time can be shortened. Normally, when recording information on an all-white line on the receiving side, it takes a shorter time than recording a line including black, so there is no particular problem even if the minimum transmission time is shortened for an all-white line. In such a facsimile transmitter
CCITT test chart No. 1 main scanning 8 pels/
mm, A4 size with sub-scanning 8 lines/mm (main-scanning 1728 pixels,
CCITT's G with a minimum transmission time of 20ms/line for 2376 sub-scanning lines using a 4800bPS modem.
Compared to the case of transmission using the standard method, in the method of the present invention, when the minimum transmission time for one line is set to 12ms, and assuming that only all white lines (1418 lines) are regulated by this minimum transmission time, 1418× (20−12)
= 11344ms = 11.344sec The result was that it could be transmitted quickly. As described above, according to the present invention, by applying a minimum transmission time shorter than that of a normal line when transmitting image information of an all-white line, it is possible to shorten the time for transmitting information of an all-white line. Moreover, according to the present invention, there is no need for a configuration for decoding and processing special signals different from image information during reception processing of image information, such as white line skipping, so that the configuration of the receiving side device does not become complicated.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a schematic configuration of a facsimile device of the present invention, Fig. 2 is a block diagram showing a circuit for sending data, and Figs. 3 a to j explain the operation of the circuit shown in Fig. 2. It is a pulse waveform diagram for. 10... Original, 12... Scanning line, 14...
CCD, 15... Shaping circuit, 16... Line buffer, 17... Encoder, 18... Line counter, 19... All-white detection flip-flop, 21...
...control circuit.

Claims (1)

[Scope of Claims] 1. A memory that stores image information for each scanning line, a detection means that detects whether image information of one scanning line of the memory is all-white information, and a minimum transmission time of one scanning line. From a plurality of minimum transmission times including at least a first minimum transmission time and a second minimum transmission time shorter than the first minimum transmission time, the minimum transmission time is determined according to the detection result of the detection means. and means for transmitting image information according to the minimum transmission time selected by the selection means, the transmitting means transmitting the image information for one scanning line in accordance with the selected minimum transmission time. If it is less than
The selection means transmits the film information following the image information of one scanning line until the transmission time reaches the minimum transmission time, and when the image information of the one scanning line is all-white information, the selection means selects the second minimum transmission time. A facsimile transmitting apparatus characterized in that the first minimum transmission time is selected when the image information of the one scanning line is not all-white information.