JP3868149B2 - Decoding method and decoding apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a decoding method and a decoding device for an image encoded by a JBIG (Joint Bi-level Image Coding Experts Group) method.
[0002]
[Prior art]
The JBIG system is an international standard for predictive coding of binary images, and a system based on the ITU-T.82 recommendation or the ITU-T.85 recommendation is known.
[0003]
According to these recommendations, when encoding a transmission image, in the default state, 128 lines of image data are set to one stripe, and transmission / reception is performed in units of stripes. Also, at the end of one stripe, an SDNORM or SDRST marker code is used. Is added. In addition, consecutive zeros (0x00) existing at the end of one image may be deleted on the transmission side. In this case, decoding is performed by inserting a continuous zero (0x00) on the reception side. Done.
[0004]
In addition, according to the ITU-T.85 recommendation, when transmitting JBIG data, the total number of lines of one transmission image can be notified to the other party as supplementary information. There are a method of setting the total number of lines in the header portion (leading portion), a method of assigning a NEWLEN marker code and setting the total number of lines here, and a method of using these in combination.
[0005]
The NEWLEN marker code is basically added to the beginning of one of the stripes up to the final stripe, but Amendment 1 of the ITU-T.85 recommendation (modification of JBIG method for facsimile machines) In this case, the condition of “applying to the beginning of the stripe” is relaxed, and “modified use of applying after the last stripe is completed” is also permitted.
[0006]
FIGS. 5A and 5B are diagrams showing a data format in transmitting a JBIG compressed image according to the image image, and FIG. 5A is a NEWLEN marker code (denoted as NW in the figure). (B) shows the case where the NEWLEN marker code (NW) is given after the last stripe (modified type allowed by Amendment 1 of the ITU-T.85 recommendation). Yes.
[0007]
As shown in the figure, one image consists of 500 lines, a header (BIH) is added to the head of the image, and the SDNORM marker code (SD is shown in the figure) at the end of each stripe (128 lines). Is added.
[0008]
FIG. 6 is a diagram showing an example of a data stream when JBIG compressed data is transmitted in the format of FIG. 5B when an image is transmitted in parallel with reading an image with a facsimile. is there.
[0009]
In the example of FIG. 6, “Y _D = 0x00000400 = (1024), L ₀ = 128, VLENGTH = 1” is described in the header (BIH). This is because the maximum number (0x00000400 = 1024) that can be taken is specified for the time being as the total number of lines (Y _D ) for one image, the number of lines (L ₀ ) for one stripe is set to 128 lines, and the NEWLEN marker code This means that transmission is performed in a mode in which a NEWLEN marker code may be used by setting “1” to VLENGTH, which indicates whether or not use is possible. An SDNORM marker code is assigned to the end of one stripe (128 lines), and a NEWLEN marker code is assigned after all stripes have been completed. From this last NEWLEN marker code information (NEWY _D (= 500)), it becomes clear that the actual total number of lines was 500 lines.
[0010]
[Problems to be solved by the invention]
When the facsimile transmission is performed using “format that adds NEWLEN marker code after the end of the last stripe” allowed by Amendment 1 of the ITU-T.85 recommendation, it is added at the end on the receiving side. When the detection of the NEWLEN marker code is delayed, the receiving side erroneously recognizes that one image is still continued, and continues to decode the code data, resulting in a problem that the wrong image is decoded.
[0011]
That is, taking the case of FIG. 5B as an example, the last stripe is 116 lines, which is less than the standard 128 lines, but the discovery of the last NEWLEN marker code (NW) is delayed on the receiving side. Determining that the last stripe is still continuing (that is, it has been transmitted by deleting the consecutive zeros (0x00) at the end of the stripe) and performing decoding by inserting consecutive zeros (0x00) Therefore, an unnecessary image is added at the end of the original one image.
[0012]
When printing an image, the exact total number of lines in one image is known when the NEWLEN marker code is detected. If a measure is taken not to output unnecessary data after that, the problem of unnecessary image output will occur. There is no.
[0013]
However, if the receiving side (decoding side) encodes the decoded data again using a coding method such as MH, or if the decoded data is subjected to enlargement / reduction processing or mask processing, it is added to the end of one image. It is difficult to selectively remove the erroneous data that has been performed thereafter, and as a result, the quality of the reproduced image is degraded.
[0014]
As a factor that delays the detection of the NEWLEN marker code added to the end of one image on the receiving side, a factor associated with buffering received data as shown in FIG. 7 can be considered.
[0015]
That is, in FIG. 7, the JBIG code data received via the modem 60 is sent to the two buffers 61 and 63 via the bus (BUS), each buffer accumulates alternately, and the accumulated data is alternately decoded. The buffering method (double buffering method) that outputs to 64 is adopted.
[0016]
At this time, code data corresponding to one image is accumulated in the buffer 61, so that there is no free space in the buffer 61 and only the last NEWLEN marker code is accumulated in the head area of the buffer 63. In the meantime, the decoding unit 64 cannot recognize the presence of the NEWLEN marker code, and unnecessary decoding is performed during that time. In FIG. 7, the two buffers 61 and 63 are hatched to visually indicate the data accumulation status.
[0017]
In FIG. 7, the read delay due to double buffering is a problem, but the same problem occurs when a buffering method using three or more buffers cyclically is employed.
[0018]
The present invention has been made paying attention to the above-mentioned problems, and it is an object of the present invention to reliably prevent unnecessary decoding caused by a delay in detection of a NEWLEN marker code without placing a special burden on hardware. And
[0019]
[Means for Solving the Problems]
In the present invention, when there is a possibility that the NEWLEN marker code arrives late before inputting the code data to the decoder, a waiting time (waiting period) is provided to wait for the arrival, and then the data When it arrives, it is determined whether or not the arrival is a NEWLEN marker code, and then the code data is input to the decoder.
[0020]
Therefore, even when there is a situation where the detection of the NEWLEN marker code added at the end is delayed, there is no situation in which decoding is started. That is, since decoding is performed after the NEWLEN marker code is reliably detected at the end of one image, excessive decoding is reliably prevented.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
In the first aspect of the present invention, when code data encoded by JBIG (Joint Bi-level Image Coding Experts Group) is input to a decoder and decoded, the code data waits for input to the decoder. When a state occurs in which the stripe end marker code is detected but the NEWLEN marker code is not detected, it is possible that unprocessed code data will subsequently arrive, and may arrive. In this case, a waiting period is provided for waiting for the unprocessed code data to arrive, and input of code data to the decoder is stopped during the waiting period, and the unprocessed code data is stopped during the waiting period. When the data arrives, it is confirmed whether the code data includes a NEWLEN marker code, and after the confirmation, the waiting period is terminated, and the waiting code data is input to the decoder. Performs decoding.
[0022]
By waiting for the arrival of subsequent data by providing a waiting period, for example, even if the output from the buffer of the NEWLEN marker code is delayed, the delay can be absorbed and a detection delay of the NEWLEN marker code occurs do not do.
[0023]
According to a second aspect of the present invention, in the first aspect, the possibility of arrival of the unprocessed code data is determined using information based on the state of the communication line.
[0024]
In the first mode, the delay of arrival of the NEWLEN marker code is absorbed by setting a waiting time for the subsequent data, but the arrival of data is awaited even though communication of all data of one image has already been completed. For example, if the exact total number of lines is specified in the header (BIH) and the NEWLEN marker code is not added at the end, the decoding process of the code data at the stripe end will not start any time. The unreasonable that occurs. Therefore, in such a case, it is notified from the outside that there is no need to wait. That is, when transmission / reception is performed using a communication line, control information is exchanged according to a predetermined communication protocol between the transmission side and the reception side. Since it is understood that the transmission of one image has been completed, in this case, the decoding unit is notified that there is no possibility that unprocessed code data will arrive.
[0025]
Also, in the third aspect of the present invention, in the first aspect or the second aspect, the code data waiting for input to the decoder is monitored, a waiting period is provided in a predetermined case, and NEWLEN is added to the arrived code data. A series of determinations and processes for ending the waiting period after confirming whether a marker code is included are performed after the decoding of one line is completed and until the next one line is decoded.
[0026]
By inserting the period of the above-described standby operation after the end of decoding of one line, detection delay of the NEWLEN marker code at the stripe end is surely prevented.
[0027]
In the fourth aspect of the present invention, the decoding device includes a plurality of partitioned memory areas, and a buffer memory in which input and output to the plurality of memory areas are periodically switched, and the buffer A data buffer for temporarily storing JBIG code data waiting for decoding, output from each of the plurality of memory areas of the memory, a decoder for decoding code data output from the data buffer, and the data A control unit that controls movement of data from a buffer to the decoder, and the control unit in the data decoding unit stores the code data stored in the data buffer. When a state occurs in which the stripe end marker code is detected but the NEWLEN marker code is not detected, the unprocessed code data is Determining whether or not there is a possibility of arrival in the data buffer, and if there is a possibility of arrival, a waiting period is provided for waiting for the unprocessed code data to arrive, and during the waiting period, When input of the code data stored in the data buffer to the decoder is stopped and the unprocessed code data arrives in the data buffer during the waiting period, the code data includes a NEWLEN marker code. After the confirmation, the waiting period is terminated, and the code data stored in the data buffer is input to the decoder.
[0028]
By providing a data buffer (wait buffer) that stores code data that is waiting for decoding and waiting for the arrival of subsequent data, the arrival delay of the NEWLEN marker code is absorbed and the detection delay of the NEWLEN marker code is not generated. It is a thing. The configuration is simple, and it is only necessary to add or change some judgments mainly by software.
[0029]
According to a fifth aspect of the present invention, in the fourth aspect, the possibility of the unprocessed code data arriving at the data buffer is determined based on information given from outside the decoding apparatus. I did it.
[0030]
This avoids a situation in which the operation of waiting for subsequent data at the end of one image does not end and the end of one image is locked.
[0031]
According to a sixth aspect of the present invention, there is provided a communication device including the decoding device according to the fourth or fifth aspect and a modem.
[0032]
According to this communication device, even in the case of communication in a format that allows a NEWLEN marker code to be added at the end, which is permitted by Amendment 1 of the ITU-T.85 recommendation, it is possible to prevent unnecessary decoding and restore. It is possible to surely prevent the image quality from deteriorating.
[0033]
Next, embodiments of the present invention will be described more specifically with reference to the drawings.
[0034]
FIG. 1 is a block diagram illustrating a configuration of a main part of a communication device on the receiving side.
[0035]
As shown in the figure, the communication device 20 on the receiving side is integrated with the operation of the modem 21 that demodulates the JBIG-compressed code data sent from the communication device 10 on the transmission side and the communication device 20 on the reception side. A host processor 22 for controlling, two code buffer memories 23 and 24, a memory controller 25 for controlling data transfer of the code buffer memory, a decoding unit 26, and an image data memory 30 for storing the decoded image data. Have.
[0036]
In addition, the decoding unit 26 includes a control unit 27 that performs overall control of the operation of the decoding unit 26, a FIFO memory 28, and an arithmetic decoder 29.
[0037]
The two code buffer memories 23 and 24 read data from the other when data is written to one, and conversely, data is written to the other when data is read from one. They are in a complementary relationship and are used for temporarily storing code data received by the modem 21 in a so-called double buffering format.
[0038]
As described above with reference to FIG. 7, when the buffering method in which the memory area is cyclically switched is used, the encoding is performed when the transmission side transmits in parallel while reading the image. There is a risk that the processed image data and the last NEWLEN marker code are separated and accumulated in each buffer. In this case, detection of the NEWLEN marker code in the decoding unit 26 is delayed, and unnecessary decoding with consecutive zeros (0x00) added is performed until the NEWLEN marker code is detected.
[0039]
Therefore, in the present embodiment, in the decoding unit 26, a FIFO memory (first-in first-out memory) 28 is provided as a data buffer for temporarily storing data waiting for input to the arithmetic decoder 29, and subsequent data arrives with a delay. If there is a possibility, the control unit 27 stops supplying the data in the FIFO memory 28 to the arithmetic decoder 29 and waits for subsequent data. Thereby, even if the arrival of the NEWLEN marker code is delayed, the delay can be absorbed, and the detection delay of the NEWLEN marker code is surely prevented.
[0040]
FIGS. 2A and 2B are diagrams for explaining a data wait operation (standby operation) in the FIFO memory 28, respectively.
[0041]
As shown in FIGS. 2A and 2B, the FIFO memory 28 includes m-stage registers B-1 to Bm, and in the state (a), image data is stored in B-4 to Bm. , B-3 stores the SDNORM marker code added to the end of the stripe, and data has not yet arrived at B-1 and B-2.
[0042]
If decoding of the stored image data is started in this state, the next data is a NEWLEN marker code, and if that code arrives with a delay, an arithmetic decoder is used during that time. There is a risk that decoding will be performed by spontaneously adding zeros (0x00) in which 29 continues.
[0043]
Therefore, in the state of FIG. 2A, a notification that data for one image has been completed (for example, the modem 21 of FIG. If there is no sign data input completion notification in the document, the subsequent data is waited.
[0044]
Then, as shown in FIG. 2 (b), when data arrives at B-1 and B-2, it is confirmed whether or not the NEWLEN marker code is included in the arrived data. The accumulated data is supplied to the arithmetic decoder 29. Such an operation is realized by the control unit 27 of FIG.
[0045]
FIG. 3 is a flowchart showing a series of characteristic operation procedures of the present embodiment. In the process of FIG. 3, every time decoding of one line is completed, the data wait and the NEWLEN marker code determination process as described in FIG. 2 are performed. However, the present invention is not limited to this, and it can be performed every several lines.
[0046]
In FIG. 3, when the decoding of one line is completed (step 40), it is first checked whether or not the stripe end marker code (SDNORM) has been detected (step 41). If the marker code at the stripe end is not detected, input of the marker code is awaited (step 42). When the presence of the marker code is confirmed (step 43), the detection process is performed (step 44). Then, the process proceeds to step 45. If the marker code at the stripe end has been detected in step 41, the process proceeds to step 45.
[0047]
In step 45, it is determined whether or not the NEWLEN marker code has been detected. If it has not been detected, a code data input end notification (in this case, the modem 21 in FIG. If the data has been transmitted, the process proceeds to step 48 if it has already been received, otherwise it proceeds to step 47 and the subsequent data Loop processing (waiting period processing) that waits for is executed.
[0048]
Even if the NEWLEN marker code arrives late by this process of waiting for subsequent data, the delay can be absorbed, and this process is extremely important.
[0049]
When the subsequent data arrives, the process exits the standby period processing loop and proceeds to step 49.
[0050]
On the other hand, if it is determined in step 46 that a code data input end specification has already been received, it is not necessary to perform a loop process for waiting for subsequent data, and the process proceeds to step 48. Since there is the processing of step 46, the subsequent data waiting loop processing (steps 46 and 47) does not become an infinite loop (that is, processing lock) does not occur.
[0051]
Then, the presence / absence of unprocessed code data is determined (step 48), and then the process proceeds to step 49.
[0052]
In step 49, it is detected whether the NEWLEN marker code is included in newly arrived data during the subsequent data wait loop processing (steps 46 and 47) or unprocessed code data confirmed to exist in step 48. If it is included, the detection process is performed (step 50). This prevents the detection delay of the NEWLEN marker code.
[0053]
If there is next line data to be decoded (step 51), the next decoding is started (step 53). If there is no next line data, the decoding is terminated (step 52).
[0054]
As described above, in this embodiment, even when a new memory marker code is added to the end of one image and the detection is delayed due to the addition of the FIFO memory and simple determination by software. It is possible to absorb the delay and prevent a detection delay. Further, when the data of one image has already been completed, the processing loop for waiting for the arrival of the subsequent data is exited, so that there is no concern that a lock will occur due to an infinite loop.
[0055]
Therefore, unnecessary decoding due to the detection delay of the NEWLEN marker code can be surely prevented, and the quality of the restored image does not deteriorate.
[0056]
FIG. 4 is a block diagram showing a hardware configuration of a facsimile machine equipped with the configuration described above.
[0057]
As shown in the figure, a facsimile apparatus 101 includes a host processor 102, an MH / MR / MMR encoding / decoding circuit 103, a resolution conversion circuit 104, a QM (arithmetic) encoding / decoding circuit 105, and an image data memory. 106, a code buffer memory 107, a communication interface such as a modem (functioning as an interface for wired transmission using a telephone line 113) 108, an image input device 111 such as a scanner, and an image recording / recording device such as a printer. And a display device 112. Each block can exchange information with each other via the internal buses 109 and 110.
[0058]
Since the decryption apparatus of the present invention has a simple configuration, it can be sufficiently installed in a facsimile apparatus that is strictly required to be downsized and reduced in cost. Therefore, it contributes to the improvement of the communication performance of the popular facsimile machine. The present invention can be variously modified. For example, the 0x00 counter may only count the number of output 0x00 and output 0x00 as it is. When the stripe end is reached, the number of 0x00 is notified to the software, and the software that has received this notification deletes the number of 0x00 for the number of notifications from the end of the code data, and at the end for the stripe end You may make it attach the marker code of.
[0059]
【The invention's effect】
As described above, according to the present invention, it is possible to reliably prevent unnecessary decoding due to a delay in detecting the NEWLEN marker code without imposing a special burden on hardware. In other words, even when there is a situation where the detection of the NEWLEN marker code added at the end is delayed, decoding is performed after the NEWLEN marker code is detected at the end of one image, so that extra decoding is ensured. Is prevented.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a main configuration of a decoding apparatus according to an embodiment of the present invention. FIG. 2 (a) is a diagram showing a state in which subsequent data has not arrived at the FIFO memory. FIG. 3 is a flowchart showing the main operation procedure of the decoding apparatus according to the embodiment. FIG. 4 shows the hardware configuration of a facsimile apparatus equipped with the configuration of the present invention. [FIG. 5] (a) A diagram showing a data format (example in which a NEWLEN marker code is added at the beginning of the last stripe) when transmitting a JBIG compressed image according to the image image. (B) A JBIG compressed image. Fig. 6 shows the data format for transmission (example in which NEWLEN marker code is added after the last stripe) in line with the image image. Fig. 6 FIG. 7 is a diagram showing an example of a data stream when JBIG compressed data is transmitted in a format in which a NEWLEN marker code is added after the last stripe when performing communication. Figure [Explanation of symbols]
10 Communication device (transmission side)
20 Decoding device (receiving side communication device)
21 modem 22 host processor 23 code buffer memory 24 code buffer memory 25 memory controller 26 decoding unit 27 control unit 28 FIFO memory 29 arithmetic decoding unit 30 image data memory

Claims (6)

When decoding by inputting code data encoded by JBIG (Joint Bi-level Image Coding Experts Group) method to the decoder,
The code data waiting for input to the decoder is monitored, and if a stripe end marker code is detected but a NEWLEN marker code is not detected, there is a possibility that unprocessed code data will arrive later And a waiting period for waiting for the unprocessed code data to arrive, and stopping the input of the code data to the decoder during the waiting period, When the unprocessed code data arrives during the waiting period, it is confirmed whether the code data includes a NEWLEN marker code, and after the confirmation, the waiting period is ended, and the waiting code data is A decoding method, wherein the decoding is performed by inputting to a decoder.   2. The decoding method according to claim 1, wherein the determination of the possibility of arrival of the unprocessed code data is performed using information based on a communication line status.   A series of judgments and processes for monitoring the code data waiting for input to the decoder, providing a waiting period in a predetermined case, and ending the waiting period after confirming whether the arrived code data includes the NEWLEN marker code, 3. The decoding method according to claim 1, wherein the decoding is performed after the decoding of one line is completed and before the next one line is decoded. A buffer memory including a plurality of partitioned memory areas, and the input and output to the plurality of memory areas being periodically switched;
A data buffer for temporarily storing JBIG code data waiting for decoding, output from each of the plurality of memory areas of the buffer memory, and a decoder for decoding the code data output from the data buffer; A data decoding unit comprising: a control unit that controls movement of data from the data buffer to the decoder;
The control unit in the data decoding unit monitors the code data stored in the data buffer, and if a stripe end marker code is detected but a NEWLEN marker code is not detected, unprocessed code data is generated. Thereafter, it is determined whether or not there is a possibility of arrival in the data buffer, and if there is a possibility of arrival, a waiting period is provided for waiting for the unprocessed code data to arrive, and during the waiting period Stops the input of the code data stored in the data buffer to the decoder, and when the unprocessed code data arrives in the data buffer during the waiting period, a NEWLEN marker code is added to the code data. The code stored in the data buffer is confirmed after confirming whether the waiting period is ended. Decoding apparatus characterized by inputting the over data to the decoder.   5. The decoding device according to claim 4, wherein the determination of the possibility that the unprocessed code data arrives at the data buffer is performed based on information given from outside the decoding device.   A communication device comprising: the decoding device according to claim 4 or 5; and a modem.

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