JP3687304B2 - Decoding method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a decoding method and apparatus used for facsimile communication or the like, and more particularly to a decoding method and apparatus for improving error detection accuracy.
[0002]
[Prior art]
As an encoding method in a facsimile, an MH (Modified Huffman) method, an MR (Modified Read) method, and an MMR (Modified Modified Read) method are known. The MR method and the MMR method are called two-dimensional encoding methods, and image information of a scanning line (encoding line) to be encoded is encoded with reference to the preceding scanning line (reference line). It becomes. The detailed rules are described in Recommendation T. of the International Telecommunications Union ITU. 4.
[0003]
Conventionally, when decoding a code using the MR method (hereinafter including the MMR method), the sum of the number of decoded pixels on one scanning line matches the predetermined number of pixels on the scanning line defined by the document size and resolution. In this case, it is determined that the decoding has been normally achieved.
[0004]
[Problems to be solved by the invention]
By the way, the MR mode is provided with a pass mode code. In the pass mode, as shown in FIG. 3, the first and second change pixels a1 and a2 (a2 in the drawing) are present on the right encoding line with respect to the reference change pixel a0 on the encoding line. When the first and second change pixels b1 and b2 existing on the reference line are defined, it means that the change pixel b2 exists on the left side of the change pixel a1.
[0005]
It is an error if the last code of the scan line is a pass mode code. However, since the pass mode code has no information about the pixel to be decoded, it does not affect the number of decoded pixels. As described above, in the related art, when the sum of the number of pixels on one decoded scanning line matches the predetermined number of pixels, it is determined that the decoding has been normally achieved. For this reason, if the sum of the number of pixels on the scanning line matches the predetermined number of pixels, no error is determined even if the pass mode is detected at the end of the scanning line.
[0006]
Accordingly, an object of the present invention is to provide a decoding method and apparatus that solves the above-described problems and improves the error detection accuracy.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the method of the present invention, when decoding image information encoded by the modified read two-dimensional encoding method, the sum of the number of pixels on one decoded scan line In the decoding method in which an error occurs if the number of pixels does not match, if the sum of the number of decoded pixels on one scanning line matches the predetermined number of pixels on the scanning line, the last code of the scanning line is the pass mode. If the code is, a decoding error is assumed .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, the decryption apparatus is a facsimile apparatus having a G3 and G4 facsimile communication function. FIG. 1 shows an error detection procedure performed when the facsimile apparatus is a soft codec. FIG. 2 shows a circuit configuration of the facsimile apparatus.
[0011]
As shown in FIG. 2, the facsimile apparatus includes a main control unit, a display unit, an operation unit, a reading unit, a recording unit, an external storage reading unit, a RAM, an image memory, a modem, and an NCU.
[0012]
The main control unit (CPU) 1 can control each part of the hardware through the bus and can execute software (program) such as encoding / decoding and auto dialer communication procedure.
[0013]
The display unit 2 includes a display such as an LCD display, and can display the operation state, image data, operation instructions, and the like of the facsimile apparatus.
[0014]
The operation unit 3 includes a numeric keypad for inputting numbers, an abbreviated dial key for performing an abbreviated dial operation, a one-touch key for performing a one-touch operation, various function keys, a start key, and the like. The numeric keys, speed dial keys, and one-touch keys also have a function for inputting letters such as alphabets.
[0015]
The reading unit 4 can read a document with an image sensor such as a CCD and generate black and white binary image data.
[0016]
The recording unit 5 includes an electrophotographic printer or the like, and can record (print output) image data received by facsimile communication from another G3 or G4 facsimile apparatus.
[0017]
The ROM 7 is a program recording medium that stores a program executed by the main control unit 1 in order to operate the facsimile apparatus.
[0018]
The RAM 8 is composed of SRAM, flash memory, etc., and stores temporary data generated during program execution.
[0019]
The image memory 9 is composed of a DRAM and stores image information (MR code).
[0020]
The modem 10 has a fax modem function and is used when image data is transmitted by facsimile.
[0021]
An NCU (Network Control Unit) 11 can close and open an analog line.
[0022]
Next, the operation will be described with reference to FIG.
[0023]
The main control unit 1 sequentially extracts and decodes the image information (MR code) stored in the image memory 9 (S1). This process is repeated until an EOL indicating a line end is detected. When EOL is detected, error detection is performed. For error detection, first, the sum of the number of pixels on the scanning line (main scanning) (sum of run lengths) is calculated. It is checked whether the sum of the number of pixels matches the predetermined number of pixels (line size) (S2). If the sum of the number of pixels does not match the predetermined number of pixels, it is determined that an error has occurred because the line size has been exceeded or the line size has not been reached (S3). When the sum of the number of pixels matches the predetermined number of pixels, it is checked whether or not the last code of the scanning line is a code of the pass mode (P mode) (S4). If a pass mode code is detected, an error is determined (S3). If the pass mode code is not detected, it is checked whether it is RTC (end of telegram). If it is not an RTC, the image information of the next scanning line is sequentially extracted and decoded. If it is RTC, the operation of the soft codec is terminated.
[0024]
In the above-described processing, when it is determined that there is an error, the scanning line having the error is not output to the recording unit 5, but instead, the previous scanning line is output again. By doing so, the image printed by the recording unit 5 is not disturbed by the error.
[0025]
【The invention's effect】
The present invention exhibits the following excellent effects.
[0026]
(1) Since an error that has not been detected in the past is detected, the error detection accuracy is improved, leading to an improvement in image quality.
[Brief description of the drawings]
FIG. 1 is a flowchart showing an error detection procedure according to the present invention.
FIG. 2 is a configuration diagram of a facsimile apparatus showing an embodiment of the present invention.
FIG. 3 is a diagram of image information resulting in a pass mode.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Main control part 2 Display part 3 Operation part 4 Reading part 5 Recording part 6 External storage reading part 7 ROM (program recording medium)
8 RAM
9 Image memory 10 Modem 11 NCU
S2: Check whether the sum of the number of pixels matches the line size. S4: Check whether the last code is a pass mode code.

Claims (1)

When decoding the image information encoded by the modified read two-dimensional encoding method, if the sum of the number of decoded pixels on one scanning line does not match the predetermined number of pixels on the scanning line, decoding is performed as an error. In the method, when the sum of the number of decoded pixels on one scanning line coincides with the predetermined number of pixels on the scanning line, if the last code of the scanning line is a pass mode code, a decoding error is generated. The decoding method.

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