JPH01277059A - Facsimile receiver - Google Patents

Abstract

PURPOSE:To easily perform the correction of an error by supplying a picture signal to a line memory and a recorder at every line alternately when no error is detected by a detection circuit, and stopping the switching operation of a switch at every line when the error is detected. CONSTITUTION:A control circuit 8 counts the number of image elements of a line signal comprising the picture signal from a runlength demodulator 3 by the detection circuit. And the presence/absence of the error is detected based on whether or not the number of image elements equals to 1782. As a result, when no errer exists, movable contacts 4a and 7a of change-over switches 4 and 7 are switched alternately to fixed contacts 4b, 4c; 7c, 7b, respectively. Also, when the error exists on the line signal on an n-th line, the line signal on an (n-1)th line instead of it is supplied to the recorder 9. Furthermore, when the errors exist on both the line signals on the n-th and (n+1)th lines, the line signal on the (n-1)th line instead of them is supplied to the recorder 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a facsimile receiving apparatus that employs a redundancy suppression coding method.

[Requirement of the invention]

The present invention relates to a facsimile receiving device that demodulates a facsimile signal consisting of a plurality of consecutive run-length encoded line signals to obtain an image signal consisting of a plurality of consecutive line signals, and transmits the image signal to a first changeover switch. to store each line in the first and second line memories, and switch each line signal read from the first and second line memories respectively to the recording device by switching the second changeover switch. Then, the image signal is supplied to an error detection circuit, the number of pixels for each line signal of the image signal is counted, and it is detected whether the number of pixels differs from the standard value. When no error is detected by the error detection circuit, the image signal is alternately switched line by line by the first changeover switch, and the first and second changeover switches are switched line by line. At the same time, the line signals read out from the second and first line memories are alternately switched line by line by a second changeover switch and supplied to the recording device, and an error detection circuit detects an error. When detected, the switching operations of the first and second changeover switches are stopped line by line, thereby making it possible to perform error correction with a simple configuration.

[Conventional technology]

Facsimile communication using a conventional redundancy reduction coding method will be described. On the transmitting side, a photoelectric conversion device is used to scan the original image to be transmitted, decomposing it into pixels, photoelectrically converting this into an image signal consisting of a series of multiple line signals, and converting the image signal into redundancy during transmission. In order to suppress this, each line signal is run-length coded (for example, modified Huffman coding) and converted into a facsimile signal consisting of a series of multiple run-length coded line signals, and this facsimile signal is It is frequency modulated within the system and sent to the telephone line. On the receiving side, the frequency modulated facsimile signal is frequency demodulated to obtain a facsimile signal consisting of a plurality of run-length encoded line signals, and by run-length demodulating the facsimile signal, a facsimile signal consisting of a series of plural line signals is obtained. By obtaining an image signal and supplying this image signal to a recording device,
An image corresponding to the original image is recorded on recording paper.

In facsimile communication using such a redundancy suppressed transmission method, an error causes a bit signal "0" in a run-length encoded line signal to become rlJ, or "1" to "rlJ".
0" or a bit signal is missing, when the transmitting side demodulates this run-length encoded line signal, the demodulated line signal becomes "0".
, "1" pattern is significantly distorted, and the fidelity of the image recorded on the recording paper to the original image is significantly reduced.

Below, with reference to FIGS. 2 and 3, errors in the run-length encoded line signal will be explained using a specific example. FIG. 2 shows an example of a line pixel pattern of an original image to be transmitted. In this case, the total number of pixels in one line is 1
It is 728. In Fig. 2, from left to right, this line consists of 350 consecutive white pixels, then 150 consecutive black pixels, and then 800 consecutive white pixels. Then 28 consecutive black pixels and finally 400 consecutive white pixels.

FIG. 3 shows an example of a bit pattern when the line of the pixel pattern shown in FIG. 2 is converted into a run-length encoded (modified Huffman encoded) line signal. In this modified Huffman code, each run length of white skin and dark skin is 0, 1.2, ..., 63.
When the terminating code of white and black people and each run length of white and black are multiples of 64, that is, 64.1
28, . . . , 1728, it consists of makeup codes for white and black people and line termination codes.

Therefore, in FIG. 3, the 350 white pixels in FIG. 2 are divided into 320 white pixels and 30 white pixels.
The 150 black pixels are divided into 128 black pixels and 22 black pixels, and the 150 black pixels are converted into corresponding run-length code words, respectively.
800 white pixels are divided into 768 white pixels and 32 white pixels and converted into corresponding run-length code words, and 28 black pixels are converted into corresponding run-length code words as they are. , 400 white pixels are 384
white pixels and 16 white pixels, respectively, and are converted into corresponding run-length code words.

Now, in the run-length encoded line signal of FIG. 3, for example, "0
” becomes “1” due to an error, then ro, which is the run-length code word changed due to the error, becomes “1”.
ooolloolool”, it is 1
Since it corresponds to 92 black pixels, the original number was 150 (
=128+22) black pixels are now 214
This means that it has changed to (=192+22) black pixels,
The change in the line signal at fffit[ due to this error is extremely large.

Therefore, conventionally, a line signal or a run-length encoded line signal is encoded for error correction, so that errors in the line signal can be corrected to some extent.

[Problem to be solved by the invention]

However, error correction encoding of such line signals or run-length encoded line signals requires a complicated encoding circuit on the transmitting side and a complicated Φ decoding circuit on the receiving side.

In view of this, the present invention proposes a facsimile receiving device that can perform error correction with a simple configuration for receiving facsimile signals consisting of a series of multiple run-length encoded line signals. This is what I am trying to do.

[Means to solve the problem]

A facsimile receiving apparatus according to the present invention includes a run-length demodulator (3) that supplies a facsimile signal consisting of a series of a plurality of run-length encoded line signals and outputs an image signal consisting of a series of a plurality of line signals; The image signal obtained from the run-length demodulator (3) is switched and supplied by a first changeover switch (4), and first and second line memories (5) store the image signal line by line; (6), and a recording device (in which each line signal read out from the first and second line memories (5) and (6), respectively) is switched and supplied by a second changeover switch (7). 9) and run-length demodulator (3)
An image signal obtained from the image signal is supplied, the number of pixels for each line signal of the image signal is counted, it is detected whether the number of pixels differs from the standard value, and the first and second and an error detection circuit (8) that switches and controls the changeover switches (4) and (7) of 2, and when no error is detected by the error detection circuit (8), the image from the run-length demodulator (3) is The signals are alternately switched line by line by the first changeover switch (4) and written into the first and second line memories (5) and (6), and the signals are written into the first and second line memories (5) and (6). 5), (
When the line signal read from 6) is alternately switched line by line by the second changeover switch (7) and supplied to the recording device (9), and an error is detected by the error detection circuit (8). The switching operation of the first and second changeover switches (4) and (7) is stopped on a line-by-line basis.

[Effect]

According to the present invention described above, when no error is detected by the error detection circuit (8), the run-length demodulator (8)
The image signal from 3) is alternately switched line by line by the first changeover switch (4) and written into the first and second line memories (5) and (6),
The line signals read from the second and first line memories (5) and (6) are alternately switched line by line by the second changeover switch (7) and supplied to the recording device (9). . Further, when an error is detected by the error detection circuit (8), the first and second changeover switches (
Stopping the switching operations of 4) and (7) on a line-by-line basis [Embodiment] Hereinafter, an embodiment of the facsimile receiving apparatus according to the present invention will be described in detail with reference to FIG.

For example, a frequency-modulated facsimile signal transmitted from a facsimile transmitter through a telephone line is supplied from an input terminal (1) to a frequency demodulator (2) and demodulated. The facsimile signal obtained from this demodulator (2) consists of a series of run-length encoded line signals. In addition, a frame synchronization signal indicating the start end of each frame and a frame end signal indicating the end thereof are added to the facsimile signal, and a line synchronization signal indicating the start end is added to each run-length encoded line signal. and a line termination signal indicating its termination. and,
This facsimile signal is supplied to a run-length demodulator (3) and demodulated.

An image signal consisting of a series of a plurality of line signals obtained from the demodulator (3) is supplied to the movable contact (4a) of the first changeover switch (4) and the control device (8). The changeover switch (4) includes fixed contacts (4b) and (4c) to which the movable contact (4a) is switched and connected, and each of the fixed contacts (4b) and (4C) are connected to the first and second contacts, respectively. Connected to the write signal input terminals of line memories (RAM) (5) and (6).

(7) is a second changeover switch, which is equipped with a movable contact (7a) and fixed contacts (7b), (7C), and the fixed contacts (7b), (7C) are connected to the above-mentioned first and It is connected to the read signal output ends of the second line memories (5) and (6), and its movable contact (7a) is connected to the record signal input end of the recording device (9).

(8) is a control device, which is a run-length demodulator (3
), a frame synchronization signal and a frame termination signal for each frame of an image signal consisting of a series of a plurality of line signals, and a line synchronization signal indicating the start end and a line termination signal indicating the termination of each line signal are separated, and based on,
Switching timing of the first and second changeover switches (4), (7), first and second line memories (5), (
6) controls the write and read timing.

This control device (8) also includes a run-length demodulator (3).
An error occurs depending on whether the counted value matches the standard value (for example, 1728). It includes an error detection circuit that detects whether or not the error occurs. Then, the above-mentioned first and second changeover switches (4) are activated by the detection output of the error detection circuit.
, (7) are controlled in different ways depending on when an error is detected and when no error is detected, as will be described later.

The operation of the facsimile receiving apparatus shown in FIG. 1 will be explained below. At the output side of the run-length demodulator (3), an image signal consisting of a series of a plurality of line signals is obtained. This image signal is supplied to the control circuit (8) and the first
It is switched by the changeover switch (4) and supplied to the first and second line memories (5) and (6), and is written for each line signal, and the second and first line memories (6) , (5) is switched by the second changeover switch (7) and supplied to the recording device (9), where the recording means prints an image based on the image signal on recording paper. Scanned and recorded.

In the control circuit (8), the error detection circuit counts the number of pixels of the line signal that constitutes the image signal from the run-length demodulator (3), and the number of pixels is 17.
28, it is detected whether there is an error or not.

If there is no error, each movable contact (4a), (4b) of the first and second changeover switches (4), (7)
are fixed contacts (4b) and (4c) for each line;
(7c) and (7b) are alternately switched. That is, in a certain line, the movable contact (
4a) is connected to the fixed contact (4b), the movable contact (7a) of the second switching switch (7) is connected to the fixed contact (7c), and in this state, the line is connected to the first line memory (5). The second line memory along with which the signal is written
A line signal is read from (6). Thus, in the next line, the movable contact (4a) of the first changeover switch (4) is connected to the fixed contact (4c), and in this state,
The movable contact (7a) of the second changeover switch (7) is connected to the fixed contact (7b), and the second line memory (6)
A line signal is written to the first line memory (5), and at the same time, a line signal is read from the first line memory (5).

Also, considering the case where there is an error in the image signal from the run-length demodulator (3), for example, the nth line signal, the movable contact (4a) of the first changeover switch (4) is connected to the fixed contact (4b) side, and the movable contact (7a) of the second changeover switch (7) is connected to the fixed contact (4b) side.
7C) side, the line signal of the nth line is supplied to the first line memory (5) through the first changeover switch (4), and is written into the first line memory (5). The error-free line signal of the (n-1)th line read from the line memory (6) is transferred to the recording device (9) through the second changeover switch (7).
). In the (n+1)th line, the movable contact (4a) of the first changeover switch (4) remains connected to the fixed contact (4b), and the movable contact (4a) of the second changeover switch (7) remains connected to the fixed contact (4b). 7a) remains connected to the fixed contact (7c) side, and the line signal of the (n+1)th line is transferred to the first changeover switch (4).
The line signal of the nth line is rewritten with the line signal of the (n+1)th line, and at this time, the line signal of the (n+1)th line read from the second line memory (6) is The error-free line signal of the n-1)th line is subsequently supplied to the recording device (9) through the second changeover switch (7). That is, if there is an error in the line signal of the nth line, the line signal of the (n-1)th line is supplied to the recording device (9) instead of the line signal of the nth line. .

In this case, if there is an error in both the line signals of the n-th line and the (n+1)-th line, instead of the line signals of the n-th line and the (n+1)-th line,
The line signal of the (n-1)th line is supplied to the recording device (9).

〔Effect of the invention〕

According to the present invention described above, in a facsimile receiving device that receives a facsimile signal consisting of a series of a plurality of run-length encoded line signals, it is possible to simply check whether the number of pixels of the line signal matches a standard value or not. If they do not match, it is determined that it is an error, and the line signal is replaced with the signal of the previous line. Therefore, it is possible to obtain a device capable of error correction with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of a line pixel pattern, and FIG. 3 is an explanatory diagram showing an example of a run-length encoded line signal. (3) is a run-length demodulator, (4) is a first changeover switch, (5) is a first line memory, (6) is a second line memory, (7) is a second changeover switch, ( 8
) is a control circuit, and (9) is a recording device.

Claims (1)

[Scope of Claims] A run-length demodulator that supplies a facsimile signal consisting of a plurality of consecutive run-length encoded line signals and outputs an image signal consisting of a plurality of consecutive line signals; and from the run-length demodulator. The obtained image signal is switched and supplied by a first changeover switch to first and second line memories that store the image signal line by line; and from the first and second line memories, respectively. A recording device to which each read line signal is switched and supplied by a second changeover switch, and the image signal obtained from the run-length demodulator are supplied, and each line signal of the image signal is an error detection circuit that counts the number of pixels, detects whether the number of pixels differs from a standard value, and controls the first and second changeover switches based on the detection output; When no error is detected by the detection circuit, the image signal from the run-length demodulator is alternately switched line by line by the first changeover switch and written into the first and second line memories. At the same time, the line signals read from the second and first line memories are alternately switched line by line by the second changeover switch and supplied to the recording device, and the error detection circuit detects an error. When detected, the switching operation of the first and second changeover switches is
A facsimile receiving device characterized by stopping in line units.