JPS6249780B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides image signal transmission in which a signal indicating whether the error rate of image information received on the receiving side is below a predetermined value is returned to the transmitting side to select a transmission mode. It is related to the control method.

Conventionally, there are the following two methods for image signal transmission methods such as facsimile. The first method is to check for data errors on the receiving side using a CRC (Cyclic Redundancy Check), etc. every 5 frames for a certain section of image information from the transmitting side, and the transmitting side checks the transmitted data correctly to the receiving side. Check whether the data was successfully sent or not, and if there is a mistake, send the data again.
In the second method, the transmitting side continuously transmits data without checking whether the receiving side has correctly received the data. In the former case, the transmitted data can be communicated correctly, but the line efficiency is not good because the time required for the confirmation response sequence after transmitting a certain section of image information is as much as 30%.

In the latter case, the transmission data can be transmitted continuously, so the line efficiency is good, but since the data is not checked, the transmission data may be erroneous.

On the other hand, the image information transmission system has the characteristic that if the error rate is very small, it is sufficiently acceptable as an image, so it should be possible to improve line efficiency without retransmitting data.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image signal transmission control system that allows data confirmation and improves line efficiency.

In order to achieve the above object, the image signal transmission control method of the present invention requires the transmitting side to transmit the next image information after waiting for a status confirmation response from the receiving side every time a certain amount of image information is transmitted. The image signal transmission control method has an image signal transmission mode and a second transmission mode for transmitting the next image information without waiting for status confirmation from the receiving side, wherein the image signal is received by the receiving side in the first transmission mode. A circuit is provided to create an error rate signal indicating that the error rate of the image information is less than a predetermined value, and the transmitting side transmits one page of image information in the first transmission mode at the start of transmission, and detects the error. The first transmission mode is maintained until the return of the error rate signal is received, and after the error rate signal is received, the second transmission mode is selected and the image information of the subsequent page is transmitted. That is.

The present invention will be described in detail below with reference to examples.

FIGS. 1a and 1b are a diagram illustrating the principle of the present invention, and a diagram b showing a transmission frame.

Here, a case will be considered in which a predetermined section of image signal information, for example, data D1 of one page of a manuscript, is transmitted from the transmitting side to the receiving side.

First, the calling party calls the called party on the receiving side using a telephone line in a normal calling method, notifies the party that facsimile communication will be performed, and then operates the facsimile transmitter. At this time, the called party on the receiving side also operates the facsimile receiver so that the facsimile receiver can receive the image signal.

The facsimile transmitter and receiver have an equalizer to remove line delay or distortion on the line through which the image signal is propagated. ,
Send a training signal to the equalizer on the receiver side. When the equalizer is in a predetermined state, for example, the tap coefficients in the equalizer are set and the equalizer is ready for equalization, the transmitting side sends a control signal with a transmission sequence number attached to the receiving side. This control signal includes, for example, information indicating the image signal band compression method, original size information, information on the transmitter's transmission capability such as image signal linear density information, information on the original to be sent, the transmission serial number, and other check bits and flag bits. It consists of

After receiving this control signal, the receiver side sends information including information indicating reception capabilities, such as reproducible original size, reproducible transmission speed, image information compression method, etc., and a reception sequence number to the transmitter side. Send to.

The transmitting side receives this information and selects a transmission method according to the reproduction capability of the receiving side. For this reason, at least the transmitting side needs to have the ability to transmit using a transmission method that is compatible with the reproduction capability of the receiver.

As shown in FIG. 1 below, the transmitting side sends out a start of page signal (SOP) containing information indicating the actual transmission method, such as transmission speed, compression method, linear density, etc. When the receiving side receives this start-of-page signal (SOP), it starts or prepares these corresponding circuits or programs and sends out a response signal (ACK) so that it can adopt a reproduction method according to the transmission method. . After the sending side receives a response signal (ACK) from the receiving side,
Data D1 is sent and finally an end of page signal (EOP) is sent.

These data and control signals are arranged in the transmission frame as shown in FIG. 1b.

The transmission frame FL includes parts F1 and F2 for frame synchronization, part A indicating the receiving side address, command part C specifying the operation of the receiving side, part IF where information is placed, and inspection bit part.
Constructed by CRC. Data D1 or the aforementioned control signal is placed in the information portion IF.

Further, a request command signal requesting a response is arranged at a predetermined bit position of the command portion C. For example, when the request command signal requires a response from the receiving side to information transmitted from the transmitting side, the bit thereof is set to level "1" on the transmitting side.

Also, data D1 is sent to the information part IF in the transmission frame.
Only image signals for the number of rows in which FL does not exceed a predetermined bit are arranged. Furthermore, in the transmission frame in which this data D1 is placed, the request command signal of the command portion C is set to level "1" to request a response signal.

On the receiving side, the received data is inspected based on the check bit CRC for the transmission frame in which the data D1 is arranged, the command part C is determined, and if a response signal is requested, a predetermined line of data is sent. If there is an error, a data retransmission request signal is returned, and if there is no error, an acknowledgment signal ACK is placed in the information portion IF and returned.

On the sender side, if an acknowledgment is received,
If a retransmission request signal is received for a predetermined line of data that is continuous with a predetermined line of image data that has already been sent out, the same data is sent again, until the data for, for example, one page of the manuscript is sent out. Send repeatedly.

An end-of-page signal (EOP) is placed in the information portion IF when one page of image data ends.

On the receiving side, the first one is checked by CRC check etc.
If there is no error in the data for the page, or if the error E is less than a small predetermined value _E1 , unnumbered information (UI) is sent to the sender, and the sender sends the first
As shown in figure a, the data D ₂ of the next page, below
D ₃ , D ₄ , etc. are continuously transmitted as so-called UI frames without checking. If, as a result of error checking of the data D1 on the receiving side, the error E is larger than the predetermined value _E1 , the next page is also transmitted using the same transmission method as the first page. In other words,
The receiving side specifies to the transmitting side whether to set the above-mentioned request command signal to level "1" or level "0" depending on the number of transmitted frames or line data in which data is erroneous.

In addition, although it was explained above that the request command signal is specified from the receiving side, data indicating the number or rate of error data is placed in the response signal corresponding to the end-of-page signal (EOP), and the sending side specifies the request command signal. A request command signal may be created according to this data. Furthermore, if a retransmission request signal is always returned if there is a reception error on the receiving side, the sending side may compare the error E with a predetermined value _E1 to create a request command signal for the next page. That is clear.

On the transmitting side, if the error E is smaller than the predetermined value _E1 , the request command signal is set to level "0" and data D1, D2, . . . are placed in the information portion IF one after another and transmitted.

As described above, the first page of transmission data uses the first transmission mode that performs an acknowledgment, and if the error check result in this case is free of errors or less than a small predetermined value, the next page is transmitted. From then on, the data to be transmitted uses a second transmission mode using so-called UI frames without acknowledgment. In this way, error-free data can be efficiently transmitted.

FIG. 2 is an explanatory diagram showing the structure of an embodiment of the present invention according to the principles shown in FIGS. 1a and 1b. The same device is used on both the transmitting and receiving sides. In the figure, an image signal input is inputted from the line through an input/output switch to a demodulator 1 combined with an equalizer 2, and then inputted to a flag detection "0" deletion circuit 5 via a demodulator interface circuit 4 to generate a frame. A flag for identification is detected and "0" unnecessary for error detection is deleted. The resulting output is input to the CRC circuit (A) 6 to check for erroneous frames, and then input to the gate circuit 7 together with the flag of the circuit 5. The gate circuit 7 separates the image signal into a general control signal, the image signal is decoded by the image code decoding circuit 9 and recorded in the recording section 15, and the general control signal is detected by the control signal detection circuit 8 and its The start of page signal (SOP) and end of page signal (EOP) are input to the UI determination circuit 16 along with the CRC error signal (CRCE) from the CRC circuit (A) 6.
The UI determination circuit 16 indicates whether the number of errors in certain information is less than or equal to a predetermined number with "1" or "0".
Outputs the UI signal, and in addition to the response signal generation circuit 10
Create a UI frame and add CRC circuit (B)11 to it.
Add CRC code. Furthermore, the flag creation "0" insertion circuit 12 adds a flag before and after the UI frame, contrary to the case of demodulation, inserts a "0" bit, and modulates the carrier wave with the modulator 3 via the modulation interface circuit 13. , and sends it to the line via the input/output switch. Further, the control signal detection circuit 8 detects the request command signal of the command portion C and outputs it to the control circuit 14. The control circuit 14 switches the switch SW according to the level "1" or "0" of the request command signal. Further, when the request command signal is at level "0", the control circuit 14 is prevented from generating the response signal as described above. Note that timing control is performed by the control circuit 14 for each of the necessary circuits of the transmitting section and receiving section.

FIG. 3 is a detailed circuit example of the UI determination circuit 16 of the embodiment shown in FIG. 2, and FIGS. 4 a to 4 j are time charts showing its operation. The explanation will be given below in accordance with FIG. 3 and with reference to FIGS. 4 a to 4 j. In the same figure, the SOP and EOP shown in FIG. 4 a and b detected by the control signal detection circuit 8 in FIG.
When inserted into the J, K, and CK terminals, respectively, the FF
The Q output of 21 has a waveform shown in d in the figure.

Also, the error signal from the CRC circuit (A) 6 in Figure 2
Insert CRCE into the CK terminal of the counter 20, and
Assume that the signal is cleared by the Q output of 21 and counting is started, and five error signals as shown in FIG. 4c are obtained. In this case, the Q output of FF21 constitutes a gate. When Q _B of the frequency divider output of the counter 20 is extracted, the waveform rises at the second error and falls at the fourth error, that is, the waveform shown in Figure 4 f, and when there is 0 or 1 error, the UI frame is This is the transmission mode to be used, but when there are two or more, the criterion is to set the transmission mode to return a normal response signal. The Q _B output of this counter 20 is FF23
The Q output is input to the clock (CK) terminal of the _QB output and the SOP
forms a pulse that is reset by the inverted signal of
On the other hand, connect the Q and output of FF21 to the J and K terminals of FF22, respectively, and connect the output of FF21 and FF22.
By taking out the Q output of , and passing it through the AND circuit 26, the output of the AND 26 generates one clock due to the falling edge of EOP, as shown in FIG. 4e. Connect the Q and output of FF23 to the J and K terminals of FF24, respectively, and connect the output of the AND circuit 26 to the CK
By applying this to the terminal, the Q output of FF24 generates a pulse that is reset by the inverted signal of rising EOP, as shown in Figure 4h, and this output
The signal is supplied as a UI signal to the response signal generation circuit 10 in FIG. 2 via the NOR circuit 27.

In addition, since the line status on the receiving side is unknown at first, in order to use a transmission mode that always returns a normal response signal, FF25 is provided, high and low levels are input to the J and K terminals, respectively, and EOP is input to the CK terminal. is input and the output is outputted as a UI signal via the NOR circuit 27. As shown in Figure 4j, the output of this FF25 is reset to high level on the first page, and therefore the UI signal in Figure 4i is set to low level.
A non-UI state is given, and it is inverted at the falling edge of EOP, and thereafter a non-UI or UI signal is returned depending on whether the Q output of the FF 24 mentioned above is high or low level. In the example of Fig. 4, the number of error signals detected on the first page is as shown in c of the figure.
The UI signal becomes low level because two or more are heated.
Non-UI state is set. The error signal on the next page is as shown in c in the same figure. If there is one error signal detected in the Q output gate of FF21 of main d, this is a state suitable for UI, and as shown in f in the same figure. Q _B output of the counter, Q output of FF23 in g in the same figure,
None of the Q outputs of the FF 24 shown in h in the same figure are generated, and therefore UI in i shown in the same figure becomes a high level.

This procedure is performed for each page, and if the state of the line is determined to be good, the UI signal level is fixed at a high level, and the required number of pages can be continuously transmitted from then on. In addition, when the UI determination circuit explained in FIG. 3 is provided on the transmitting side, the counter 20 counts the number of circuits for which retransmission has been requested, and is configured to output when the number exceeds a predetermined number, and the request command signal is , the second and subsequent pages of the manuscript are created based on the output of this counter 20. As a result, if there are few data errors on the first page of the manuscript, the second and subsequent pages can be transmitted as UI frames.

As explained above, according to the present invention, a signal indicating whether the error rate of image information received on the receiving side is less than or equal to a predetermined value is sent back to the transmitting side to select a transmission mode. First, the data is thoroughly checked, and then when it is determined that continuous transmission is possible, the process shifts to continuous transmission, making it possible to satisfy both image quality and transmission speed. It is.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is an explanatory diagram showing the configuration of an embodiment of the invention, Fig. 3 is a detailed explanatory diagram of the main part of the embodiment of Fig. 3 is a time chart showing the operation of FIG. 3, in which 1 is a demodulator, 2 is an equalizer, 3 is a modulator, 4 is a demodulator interface circuit, 5 is a flag detection "0" deletion circuit,
6 and 11 are CRC circuits, 7 is a gate circuit, 8 is a control signal detection circuit, 9 is an image signal decoding circuit, 10 is a response signal generation circuit, 12 is a flag generation "0" insertion circuit, and 13 is a modulator interface circuit. , 14 is a control circuit, 16 is a UI judgment circuit, 20 is a counter,
21 to 25 indicate flip-flops.

Claims (1)

[Scope of Claims] 1. A first transmission mode in which the transmitting side waits for a status confirmation response from the receiving side every time a certain amount of image information is transmitted and then transmits the next image information; An image signal transmission control system having a second transmission mode for transmitting the next image information without waiting for confirmation of the image information, wherein the error rate of the image information received by the receiving side in the first transmission mode is a predetermined value. A circuit for creating an error rate signal indicating that An image signal transmission control system characterized in that the first transmission mode is maintained, and after receiving the error rate signal, the second transmission mode is selected and image information of subsequent pages is transmitted.