JPS5813068B2 - Fuakushimirishingotounofugoukahoushiki - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for encoding facsimile signals and the like using a so-called run-length encoding method in which two amplitude levels encode the temporal length of a temporally sampled signal sequence. It is something.

In general, facsimile signals having two values, 1 and 0, have a property that when a signal at one of the two levels is generated, there is a high probability that a signal at that level will occur consecutively.

Therefore, rather than directly transmitting the length of this series of signals at the same level with a code whose length is proportional to the time length, a so-called run-length code is used that converts the length into binary numbers, encodes it, and transmits it. This method is widely used.

That is, in this type of conventional system, the length of a run of 1 and the length of a run of 0 are alternately encoded and transmitted.

However, in the case of staggered scanning in which pixels on adjacent scanning lines are alternately scanned rather than linearly, the number of runs tends to increase compared to linear scanning.

In particular, measurements show that 1 and 0 runs of length 1 account for nearly 50% of them.

When a signal sequence with such statistical properties is subjected to run-length encoding, which was designed for a signal with a small number of runs of length 1, the length of the code word for a run of length 1 is 2. Since the number of bits is about 4 bits, there is a drawback that the encoding efficiency is significantly reduced.

In order to eliminate the above-mentioned drawbacks, the present invention
For length encoding, runs of 0 (or 1) and runs of 1 (
or 0), as well as a 1 consisting of one 1 and one 0
, 0 (or 0, 1), and for runs with two or more consecutive 1s (or 0s), a pattern including one bit of 0 (or 1) immediately after that is encoded. The present invention provides an encoding method for facsimile signals, etc., which encodes the length.

Embodiments will be described in detail below with reference to the drawings.

Figure 1 shows the measurement results of the run length (RL) distribution of a facsimile signal obtained by scanning a document not in a straight line but alternately in a staggered pattern on two adjacent straight scanning lines. and A is the run length distribution of white,
B shows the black run length distribution.

FIG. 2 shows an example of three modes that are a feature of the present invention, and hereinafter, for simplicity, the white level is represented by O and the black level is represented by 1.

Figure 2 A shows the first mode consisting of O runs of length 5;
Figure 2 shows a second mode consisting of a combination of 1 runs with a length of 5 and O runs with a length of 1, and Figure 2 C shows a mode consisting of a combination of 1 and 0 runs with a length of 1. 3 shows the third mode.

Figure 3 shows the run length (RL) distribution focusing on the three modes of runs in Figure 2, where A is the run length distribution for the first mode, B is the run length distribution for the second mode, and C is the run length distribution for the second mode.
respectively show the run length distribution of the third mode.

In this way, by introducing a third mode run in addition to the conventional 1 and 0 run, and adding a 0 whose length is 1 as shown in the second mode to the 1 run, the run The sum of the total numbers decreases by 40%.

Therefore, if the total number of runs is reduced, an encoding configuration that reduces the number of encoded bits per screen is possible, and the encoding efficiency is significantly improved.

Note that the first mode, second mode, and third mode may hereinafter be referred to as mode 1, mode 2, and mode 3, respectively.

Next, FIG. 4 shows an example of detection of each mode using an example of a facsimile signal. First, pixels G1 to 4 are part M1 of mode 1 in which a run of 0's with a length of 4 continues. , the level is inverted at 5 from pixel G4, the run length 1 of level 1 is detected, and then mode 3 enters part M3, detection of the length is started, and pixels G5, G6, G7 and so on are sequentially detected. When the level is alternately inverted and the same level as pixels G8 and G9 continues, the end of mode 3 is detected, and it is detected that the run length of part M3 of this mode 3 was 2. Next, the pixel Since the level is inverted from G9 to GI0, at this point, a mode 1 portion M1 with a run length of 1 is detected.

Also, since two or more 1's are consecutive with pixels G10 and G11, the run length of part M2 of mode 2 is detected, and the level is inverted from pixel G11 to G12, so mode 2 whose length is 2 is detected. Part M2 is determined.

Note that the pixel G12 is expressed as being included in this mode 2 portion M2.

Thereafter, in a similar manner, it is detected that a mode 3 portion M3 having a length of 1 is formed by pixels G13 and G14, and mode detection for all pixels is completed.

Figure 5 shows the run length (RL
), FIG. 6 shows a code conversion table for the run length (RL) of mode 3, and FIG. 7 shows a code conversion table representing transitions between modes.

In Figure 7, 0 is assigned when transitioning from mode 1 to mode 2, 1 is assigned when transitioning from mode 1 to mode 3, and it should be noted that there is a transition from mode 2 to mode 2 only for mode 2. .

Generally, it is safe to assume that one scanning line starts from mode 1, and for the second and subsequent modes, encoding is performed sequentially for each mode using the mode transition code and the run length code of the mode. .

FIG. 8 shows an example of encoding the facsimile signal in FIG. 4, where R1 is the mode 1 portion M1 with length 4,
R3 is the mode 3 part M3 with length 2, R5 is length 1
The mode 1 parts M1 and R7 are the length 2 mode 2 parts M2 and R9 are the length 1 mode 3 parts M3, respectively, and R2 is the code for the mode 1 to mode 3 parts.
, R4 represents a mode transition from mode 3 to mode 1, R6 represents a mode transition from mode 1 to mode 2, and R8 represents a mode transition from mode 2 to mode 3.

Next, the operation at the time of decoding will be described, taking as an example the case where the receiving side receives code sequences R1 to R9 as shown in FIG.

As mentioned above, it is assumed that the first mode is mode 1 when decoding of each scanning line is started.

That is, it is assumed that the first code R1 of the received code string is a code representing the run length of mode 1.

The next code R2 is a mode conversion transition code, and as described above, the code representing the run length and the mode conversion transition code alternate sequentially.

In this way, since the order of the codes in the code string is determined in advance, each code is decoded according to that order, and the run length shown in FIG. 5 or 6 is used for the code representing the run length. Decoding is performed sequentially and alternately using a code conversion table (RL code conversion table) for the length and a code conversion table shown in FIG. 7 for the mode transition code.

That is, the first code is decoded using the RL code conversion table for mode 1 shown in FIG.
), it is found that the length of mode 1 is 4, and the portion M1 in FIG. 4 is reproduced.

Next, decoding is performed using the mode transition code conversion table shown in FIG. 7, and it can be seen from the code "1" (R2 in FIG. 8) that mode 1 has transitioned to mode 3.

Therefore, the next step is to decode using the RL code conversion table for mode 3 in Figure 6, and from the code "10" (R3 in Figure 8), it is found that the length of mode 3 is 2, and the part M3 in Figure 4 is is played.

Next, decoding is performed using the mode transition code conversion table shown in Figure 7, and it is found that the transition from mode 3 to mode 1 has occurred from the code "1" (R4 in Figure 8), and from the RL code conversion table shown in Figure 5, the code By decoding "000" (R5 in FIG. 8), it is found that the length of mode 1 is 1, and the portion M1 in FIG. 4 is reproduced.

Next, according to the mode transition code conversion table in Figure 7, the code “0”
(R6 in Figure 8) to know the transition from mode 1 to mode 2, and use the code "001" (R7 in Figure 8) from the RL code conversion table for mode 2 (shared with mode 1) in Figure 5. ), it is found that the length of mode 2 is 2, and the portion M2 in FIG. 4 is reproduced.

Further, from the mode transition code conversion table in Fig. 7, the code is “01”.
(R8 in FIG. 8) is decoded, and it can be seen that the transition from mode 2 to mode 3 has occurred.

From the RL code conversion table for mode 3 in Figure 6, the code “0” (
R9) in FIG. 8 is decoded, the length of mode 3 is found to be 1, the portion M3 in FIG. 4 is reproduced, and the decoding of the embodiment is thus completed without any contradiction. FIG. 9 shows an embodiment of encoding/decoding of the present invention, in which a series of 1, 0 image signals inputted from the signal input terminal 10 are inputted to the mode detection circuit 11, where the mode Three types of detection are performed: 1, mode 2, and mode 3.

The lengths of the runs in mode 1 and mode 2 are detected by the counter 12, encoded by the encoding circuit 13, and code bits 17 for the runs in mode 1 and mode 2 are output to the code bit array circuit 20.

On the other hand, the run length of mode 3 is detected by the counter 14, encoded by the encoding circuit 15, and code bits 18 for mode 3 are output to the code bit array circuit 20.

Further, the mode transition code generation circuit 16 detects a newly generated mode from the previous mode, and the mode transition code bit 19 is input to the code bit array circuit 20.

This code bit array circuit 20 has each code bit string 17.1.
8.19 are arranged sequentially and connected to the line 22 via the modulation circuit 21.
to the receiving side.

On the receiving side, the code bit strings 17, 18, and 19 sent via the line 22 are demodulated by the demodulation circuit 23 and input to the mode transition code detection circuit 24.

When the mode transition code detection circuit 24 detects the mode, the code bit string 25 of mode 1 and mode 2 is detected by the decoding circuit 24.
bit string 2 of the run in mode 1 and mode 2
9 is played.

Further, the mode 3 code bit string 26 is decoded by the decoding circuit 28, and the mode 3 run bit string 30 is reproduced.

The decoded signal arrangement circuit 31 sequentially arranges these reproduced signals 29 and 30 and outputs them from the facsimile terminal 32.

As explained above, according to the present invention, in addition to the conventional run of 1 and 0, a combination of one bit of 1 (or 0) and 0 (or 1) is considered as a third mode, and further, For the second mode, which consists of a run of 1 (or 0), the length of the run is 2 bits or more, and by adding 1 bit of 0 (or 1) immediately after it, the length of the run in the facsimile signal can be changed. can greatly reduce the number of runs of 1 or 0. Therefore, for example, the above three modes can be detected for a facsimile signal obtained by performing plover scanning, and an appropriate method can be applied for each of them. There is an advantage that the compression efficiency is greatly improved by performing the encoding, and therefore, the present invention can provide a very useful encoding method for facsimile signals.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the white and black run length distribution obtained by ploidy scanning, FIG. 2 is a diagram showing an example of the three modes that are the characteristics of the present invention, and FIG. Figure 4 is a diagram showing an example of a facsimile signal and detection of each mode. Figure 5 is code conversion for run lengths in mode 1 and mode 2. FIG. 6 is a diagram showing an example of a code conversion table for mode 3 run length. FIG. 7 is a diagram showing an example of a mode transition code conversion table. FIG. 8 is a diagram showing an example of a mode transition code conversion table. 9 is a diagram showing an example of encoding, and FIG. 9 is a block diagram of an embodiment of the encoder/decoder of the present invention. 10... Signal input terminal, 11... Mode detection circuit, 12, 14... Counter, 13,
15... Encoding circuit, 16... Mode transition code generation circuit, 20... Code bit array circuit, 21... Modulation circuit, 22... ... line, 23 ... demodulation circuit, 24 ... mode transition code detection circuit, 27.28 ... decoding circuit,
31...Decoding signal array circuit, 32...
Signal output terminal.

Claims (1)

[Claims] 1 In a coding method that counts the temporal length of the same level in a signal sequence obtained by temporally sampling a facsimile signal etc. with two amplitude levels (1 or 0) and encodes this length, consecutive A first mode length consisting of 0 (or 1) and two or more consecutive 1s (or 0s)
and one 0 (or 1) immediately after it, and the second mode consists of a combination of one 1 (or 0) and one 0 (or 1) immediately after it. 1. An encoding method for facsimile signals, etc., characterized in that the lengths of three modes are detected, and the types and lengths of these modes are encoded for each of the three modes.