JPS6118266A - Modified huffman coding and decoding device - Google Patents

Abstract

PURPOSE:To decrease the time required for decoding by using a data 13-bit and a white/black discriminating signal including an MH code as an address signal so as to give them to a ROM once in decoding an MH code used for a facsimile equipment. CONSTITUTION:A signal S is read from a storage section 1 by a read circuit 21, and signals S4, S5 are stored respectively in registers 31, 32 in the unit of 16-bit. The register 31 outputs a signal S6 of a high-order 13-bit in the signal S4 and the signal and a signal S2 representing any of white/black picture elements applied from a picture element discriminating circuit 41, in total 14-bit data are given to an address part of a ROM51. Thus, the data representing a run length subject to MH coding is obtained by accessing once the ROM51.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a modified Huffman (hereinafter referred to as MH) code decoding device in a facsimile machine or the like.

[Prior art]

Before explaining a conventional MH code decoding apparatus used in facsimile and the like, encoding using MH code when transmitting a single document or the like by facsimile or the like will be explained.

The data line to be transmitted consists of a series of variable length codes.

Each symbol represents an all-white or all-black run range. White runs and black runs occur alternately, and a total of 1728 pixels represent one horizontal scanning line 215 mm long. All data lines begin with a white run-length code to ensure that the receiver has color synchronization. If the actual scan line starts with a black run, a white run with one run length zero is sent.The black or white run lengths are C, C, I, T until the entire length of one scan line is reached. , T, Recommendation T, 41 The so-called MH specified in the standards for Group 3 facsimile equipment for document transmission, a part of which is shown in Figure 3.
It can be added by the code 86.

There are two types of codes, one is a terminating code and the other is a make-up code.

The run length is one terminating code.

Alternatively, it is represented by one make-up code followed by a terminating code. 'I' in Figure 3 /
In M&d, S6 corresponding to %o'' is a terminating code, and S6 corresponding to 1'' is a make-up code.

Run length in the range of 0 to 63 pixels.

It is encoded by a terminating code corresponding to these. There are different lists of codes for black and white run lengths. From Figure 3, white with run length 1 is '
000111".

Black with run length 1 is represented by 1010''.

Run lengths in the range 64 to 1728 strokes are first encoded with a make-up code representing a run length equal to or shorter than the required run length, followed by the required run length. A terminating code follows, representing the difference between the length and the run length represented by the make-up code. From FIG. 3, the white of run length 199 is obtained by combining the make-up code representing white of thin length 192 and the terminating code representing white of run length 7. '0101111111''
It is expressed as

A conventional decoding device for a document signal encoded by the above-mentioned MH code will be explained with reference to FIG.

The conventional MH code decoding device shown in FIG. 1 includes a storage unit 1 that stores MH encoded data, a readout circuit 2 that reads data from the storage unit 1, and a readout circuit 2 that temporarily stores the read data and stores 1 bit of data. The pixel determination circuit 4 includes a register 3 that outputs each pixel, a ROM 5 that stores the 2nd length and a make-up code/terminating code determination signal, a register 6, and a pixel determination circuit 4 that determines whether one pixel is white or black. ing.

Next, the operation of the conventional device will be explained.

First, the MH code stored in the storage unit 1 is stored in the read register 3 by the read circuit 2. Register 3 shifts the stored MH code S and outputs a signal S□ (1 bit). Pixel determination circuit 4 that determines the signal S□ and white/black of the pixel
Outputs the output signal S2 and the register 6, and outputs the signal S2 to the register 6.
Store 3.

Furthermore, the MH code Sth' is shifted by the register 3, and the next signal S1 is outputted, and is applied to the address section of the ROM 5 together with a portion of the signals S2 and 83, and the next output signal S3 of the ROM 5 is stored in the register 6.

By repeating this operation a number of times according to the code length of the MH code (maximum 13 bits), the MH code is converted into the corresponding run length and make-up code/terminating code discrimination signal, and the run-length and make-up codes are output from register 6. A signal S3 representing an up code/terminating code discrimination signal is output.

This conventional device has the disadvantage that when decoding the MH code 't-, the above operation of accessing the ROM 5 for each bit of the MH code is repeated, which increases the time required for decoding.

[Purpose of the invention]

The purpose of the present invention is to decode an MH code.The MH code has a maximum of 13 bits.The MH code represents one run length between the MH codes indicating mountain comrades or black comrades.The MH code does not include codes representing other run lengths. Particularly, to provide an MH code decoding device which can execute decoding at high speed by accessing the ROM only once by giving 13 pits including the MH code and a black and white discrimination signal to the ROM as address signals. It is in.

[Structure of the invention]

The apparatus of the present invention receives a modified Huffman code signal and a pixel signal indicating either black or white, and generates run length data corresponding to the modified Huffman code signal, data indicating whether it is a make-up code or a terminating code, and the modified Huffman code signal. data generating means for outputting code length data of a code; pulse generating means for generating data for outputting a number of code length data corresponding to the code length data from the data generating means; and a modified Huffman code. a storage means for storing the encoded signal; and a storage means for temporarily storing the signal read out from the storage means, and shifting the stored signal in response to the supply of pulses from the pulse generation means to generate the beginning of the modified Huffman code. a shift register means for outputting the most significant bit as the most significant bit and supplying it to the data generating means; pixel signal generating means for changing the value.

〔Example〕

The present invention will be explained below with reference to the drawings.

FIG. 2 is a block diagram showing one embodiment of the present invention.

The MH code decoding device shown in FIG. 2 includes a storage unit 1 that stores MH encoded data, a readout circuit 21 that reads data from the storage unit 1, and registers 31 and 32 that temporarily store the read data. and.

A pixel determination circuit 41 that determines whether a pixel is black or white, and a ROM 51
, a pulse generating circuit 7 , and a counter 8 .

The signal S is data composed of an MH code, and the signal S2 is a signal indicating either white or black of the pixel; '0' indicates white and '1' indicates black. Signal S4 is in register 31
The signal S5 is the code stored in the register 32, the signal S6 is the output signal of the ≠≠Dou register 31, the signal S7 is a signal indicating the MH code code length, and the signal S8 is the run length and makeup code/ Terminating code determination “It is a signal.

Next, the operation of the MH code decoding device shown in FIG. 2 will be explained.

As an example, storage unit 1 that stores M1 encoded data
, white with run length 2 (0111 in MH code), black with run length 4 (011), white with run length 197 (0101111100), and black with run length 2 (
11) and white with run length 65 (110110001
11) and black (10) with run length 3 (011101101011111001111011
00011110) is read out by the readout circuit 21, and 1
A case where signal 54 (0111011010 111110) and signal S5 (0111101100011110) are stored in registers 31 and 32 in units of 6 bits will be explained.

The register 31 outputs a signal S (0111011010111) expressed by the upper 13 bits of the signal S4, and together with the signal S2 supplied from the pixel determination circuit 41 indicating whether the pixel is black or white, it becomes 14-bit data e.
It is given to the address part of ROM51.

The initial value of the output signal S2 of the pixel determination circuit 41 is white, that is, "0#", and the make-up code//
1ON to 11# or 11 in response when the terminating code determination signal indicates a terminating code
Change the value from " to 10'.

The storage status of data in the ROM 51 is as shown in FIG. Parts of FIG. 3 are omitted for simplicity.

FIG. 3 shows a ROM5117) signal S output from the data section in response to signals S2 and 86 applied to the address section.
8 and 87 are shown. Regarding signal S6 in the figure%''''
" means that the corresponding bit can be either 0 or 1. Referring to FIG. 3, in the above example, S2 is 10" and S6 is (01110110101
11), the signal S as the output signal of the ROM 51
8 is (0000010) and signal S7 is (010
0) becomes. When bit 6 of signal S8 is 10'', it indicates a terminating code, and %1#
indicates that it is a makeup code. signal S8
Bit 2 from bit 5 to bit +-ot indicates the run length. Signal S7 indicates the code length.

Above S2. S7. At S8, it is found that the first MH code is a terminating code, is white, and has a run length 2 code length of 4, which means that it has been decoded.

Next, the signal S7 is supplied to the pulse generator 7, and the pulse generator 7 generates a number (4 in this case) according to the code length indicated by the signal S7.
) Code length data is generated and supplied to the counter 8 and registers 31 and 32.
Shift the data stored in . The counter 8 counts the supplied code length data and the output data.

As a result of the shift operation, the signal S4 stored in the register 31 becomes (0110101111100111), and the multi-signal S4 becomes (1011000111100000).

This shift operation shifts by the code length, so register 3
The output from 1 is always with the beginning of the MH code as the most significant bit. On the other hand, since the signal S8 indicates that it is a terminating code, the pixel determination circuit 41 changes the signal S2 from "kO" to 11# in response.

Thus, a new decoding operation begins. By repeating such operations, the signal sB is decoded as shown in Table 1.

*T indicates a terminating code, and M indicates a makeup code.

The counter 8 counts the code length data supplied from the pulse generation circuit 7 and outputs the code length data, and when the counted value becomes an integral multiple of 16, supplies a read request signal to the read circuit 21. Data is read in bits and stored in the register 32, and processing continues.

As described above, in this embodiment, data representing one MH encoded run length can be decoded by accessing the ROM t once.

[Effects of the Invention] One aspect of the present invention is that by supplying 13 pits of data including the MH code and a black/white discrimination signal to the ROM at once as an address signal, decoding can be performed with only one access to the ROM, and the decoding time can be reduced. This has the effect of significantly shortening the time.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional device, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a diagram showing data storage in a ROM used in FIG. 1...Storage unit, 2.21...Readout circuit, 3.31.32...Register, 4.41.
...Pixel judgment circuit, 5.51 ...ROM
, 6...Register, 7...Pulse generation circuit, 8...Counter. Y1珂′v-2″l￥T

Claims (1)

[Claims] In response to supply of a modified Huffman code signal and a pixel signal indicating either black or white, run-length data corresponding to the modified Huffman code signal, data indicating whether it is a mekup code or a terminating code, and the modified data generating means for outputting code length data of a Huffman code; pulse generating means for generating a number of pulses corresponding to the code length data from the data generating means;
storage means for storing a signal encoded by a modified Huffman code; and storage means for temporarily storing a signal read out from the storage means and shifting and modifying the stored signal in response to supply of a pulse from the pulse generation means. shift register means for outputting the beginning of the Huffman code as the most significant bit and supplying it to the data generation means; 1. A modified Huffman code decoding device, comprising pixel signal generation means for changing a signal value.