JP4645850B2 - Facsimile device - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a facsimile apparatus, and more particularly, a facsimile having a function of preventing buffer underrun caused by delaying transmission of encoded data by encoding image data to generate encoded data. Relates to the device.

  In facsimile transmission, image data read by a document reading device or image data received from a host device and temporarily stored is appropriately encoded according to a coding rule such as MH, MR, MMR, JIBIG, or JPEG. The encoded data is transmitted from the modem to a communication line such as a telephone line at a predetermined transmission rate. At this time, if the amount of encoded data is less than the amount of data transmitted from the modem to the communication line, the data transmitted from the modem is insufficient and a buffer underrun state occurs.

For such a technical problem, Patent Document 1 monitors the data amount of encoded data in the encoding process in units of one line, and when the encoded data amount for one line falls below a predetermined data amount, A technique for adding dummy data so that the encoded data amount for one line becomes the predetermined data amount is disclosed.
JP 2000-261673 A

  In the above-described prior art, dummy data is added in the encoding process. Therefore, if the facsimile apparatus has a plurality of encoding rules, a procedure for adding dummy data must be added to all the encoding processes. In other words, the number of man-hours for changing the design of the encoding process increases, the procedure of each encoding process increases, and the memory capacity for storing each encoding process increases.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems of the prior art and to provide a facsimile apparatus that can prevent buffer underrun by simply changing an existing facsimile apparatus.

  In order to achieve the above object, the present invention provides a facsimile apparatus that divides encoded data obtained by encoding image data and transmits the divided data in units of frames, and a plurality of encoding units having different encoding methods; An encoding method selecting means for selecting one of a plurality of encoding means, a frame generating means for sequentially generating a frame in which a predetermined amount of encoded data is stored, a modem for transmitting each frame, and an encoding A dummy data table storing a dummy data amount to be added to each frame for each combination of a transmission method and a modem, and a dummy data amount corresponding to the selected encoding method and the transmission rate of the modem. Dummy data amount determination means for determining the amount of dummy data to be read from the dummy data table and added to each frame, and the determined amount Characterized in that it comprises a dummy data adding means for adding dummy data to each frame.

  According to the present invention, the process of adding dummy data to the encoded data is set outside the encoding process, and the amount of dummy data to be added to the frame in which the encoded data is stored is adjusted later in the encoding process. Because the buffer underrun is prevented by absorbing the difference between the encoding speed and the transmission speed of the modem, a facsimile machine that can prevent the buffer underrun simply by making a simple change to the existing facsimile machine is provided. become able to.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram showing the configuration of the main part of a facsimile apparatus according to the present invention. Here, illustration of components unnecessary for the description of the present invention is omitted.

  The image data storage unit 10 temporarily stores image data read by a document reading device (not shown) and image data transferred from a host device (not shown). The encoding unit 12 includes a plurality of encoding units having different encoding rules, such as an MH encoding unit 121, an MR encoding unit 122, an MMR encoding unit 123, a JBIG encoding unit 124, and a JPEG encoding unit 125. ing. The encoding method selection unit 11 selects one of the encoding methods based on the content of the image data, the encoding method determined by the modem 15 negotiating with the communication partner, and the like.

  The frame generation unit 13 generates a frame including encoded data with a frame structure compliant with HDLC (High Level Data Link Control). The modem 15 negotiates in advance with the facsimile apparatus of the communication partner to determine the encoding method and transmission rate, modulates the HDLC frame, and sends it to the line.

  The dummy data amount determination unit 14 includes a dummy data table 141 that determines an optimum dummy data amount using the transmission rate and encoding method of the modem 15 as parameters, and the current transmission rate and the encoding method selection unit in the modem 15. 11, the dummy data amount is determined by referring to the dummy data table 141 using the current encoding method selected in 11 as a parameter, and this is notified to the dummy data adding unit 131 of the frame generating unit 13. The dummy data adding unit 131 adds the amount of dummy data notified from the dummy data amount determining unit 14 to the HDLC frame.

  FIG. 2 is a diagram showing an example of the HDLC frame structure, in which each frame starts with a flag sequence F and ends with a flag sequence F. The data content of each flag sequence F is 7EH. In the address field A, the other party address is registered, and in the control field C, control information such as frame type, control contents, frame number, etc. is registered, and FCF (facsimile control field), FIF (data field), FCS (frame) Each field in the check sequence follows. In this embodiment, a CRC method (Cyclic Redundancy Check) is adopted as the FCS.

  FIG. 3 is a diagram showing an example of the dummy data table 141. In this embodiment, since the encoded data amount stored in the FIF field of the HDLC frame is fixed to 256 or 64 octets, the amount of data transmitted from the modem 15 is the flag sequence F assigned to each frame. Controlled by number.

  In this embodiment, for each combination of the encoding method selected by the encoding unit 12 and the transmission rate of the modem, a data amount Δd deficient in the frame period is obtained experimentally, and a flag sequence corresponding to this difference Δd The number dij of F is stored in advance in the corresponding column of the dummy data table 141.

  Next, the operation of this embodiment will be described in detail with reference to the flowchart of FIG. In step S1, the encoding method selected by the encoding method selection unit 11 is determined. In step S2, the current transmission rate of the modem 15 is determined. In step S3, the dummy data table 141 is referred to based on the determination result of the coding method and the transmission rate, and the corresponding dummy data amount (flag sequence number) number dij is read.

  In step S4, a variable-length HDLC frame including the dij flag sequences F is generated. In step S5, the data is transferred to the modem 15. In step S6, it is determined whether or not encoding of all image data has been completed. If not completed, the process returns to step S2 and the above-described processes are repeated.

  Thus, according to the present embodiment, as the encoding speed of the encoding unit 12 with respect to the transmission speed of the modem 15 becomes slower, the amount of dummy data increases in each frame and the frame length becomes longer. As a result, transmission data Since the amount increases, buffer underrun can be prevented.

  In the above-described embodiment, the case where the amount of encoded data stored in each frame is constant and the frame length of each frame is variable has been described as an example. However, the present invention is not limited to this. However, the present invention can also be applied to the case where the amount of encoded data stored in each frame is variable and the frame length of each frame is fixed.

  In such a case, for each combination of the encoding method and the transmission rate of the modem, the amount of encoded data that is insufficient with respect to the transmission amount is experimentally obtained, and the number of flag sequences F that can compensate for this insufficient data amount is determined as dummy data. The number eij is stored in advance in the corresponding column of the dummy data table 141. At the time of facsimile communication, the number of eij flag sequences F read from the dummy data table 141 are added to the frame including the amount of encoded data corresponding to the encoding speed, the frame length is made constant, and the modem 15 at the subsequent stage is added. You can forward to

  As described above, according to the present embodiment, the ratio of the dummy data amount to the encoded data amount increases in each frame as the encoding rate of the encoding unit 12 with respect to the transmission rate of the modem 15 decreases. Since the transmission rate of the digitized data is reduced, buffer underrun can be prevented.

1 is a functional block diagram showing a configuration of a facsimile apparatus according to the present invention. It is the figure which showed the HDLC frame structure. It is the figure which showed an example of the dummy data table. It is the flowchart which showed the operation | movement of this embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Image data storage part, 11 ... Coding method selection part, 12 ... Coding part, 13 ... Frame generation part, 14 ... Dummy data amount determination part, 15 ... Modem, 131 ... Dummy data addition part, 141 ... Dummy data table

Claims (4)

In a facsimile apparatus that divides encoded data obtained by encoding image data, registers it in a predetermined field of the frame, and transmits it in units of frames.
A plurality of encoding means having different encoding methods;
An encoding method selection means for selecting any of the plurality of encoding means;
Frame generating means for sequentially generating frames in which a predetermined amount of encoded data is stored;
A modem for transmitting each frame;
For each combination of encoding method and modem transmission rate, a dummy data table storing dummy data amount to be added to each frame,
Dummy data amount determining means for reading the dummy data amount corresponding to the selected encoding method and the transmission speed of the modem from the dummy data table and determining the dummy data amount to be added to each frame;
And a dummy data adding means for adding the determined amount of dummy data to each frame.   2. The facsimile apparatus according to claim 1, wherein the dummy data is a flag sequence given before and after a frame, and the dummy data amount is represented by the number of flag sequences.   The frame has a variable frame length, a field in which the encoded data is stored has a fixed length, and the amount of dummy data increases as the encoding speed of the encoding means relative to the transmission speed of the modem decreases. 3. The facsimile apparatus according to claim 1, wherein the frame length is long.   The frame has a fixed frame length, a field in which the encoded data is stored has a variable length, and the amount of dummy data increases as the encoding speed of the encoding means relative to the transmission speed of the modem decreases. 3. The facsimile apparatus according to claim 1, wherein the amount of encoded data decreases.

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