JPS6234314B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for performing smooth sub-scanning by continuously varying the sub-scanning speed in sub-scanning in a redundancy suppressed facsimile or the like.

Conventionally, in a facsimile machine using redundancy reduction coding technology, the number of coded bits generated in one line is not constant; it is small in simple parts of a document and increases in complex parts. Therefore, when transmitting and receiving encoded signals at a constant transmission speed, the generation of encoded signals for each line fluctuates over time, so sub-scanning was configured to be fed intermittently by repeatedly starting and stopping. . Therefore, there were the following drawbacks.

Since recording is not possible until the start/stop step response is stabilized, it is difficult to increase the speed of sub-scanning.

Transmission systems such as gears,
The transmitted document, recording paper, etc. vibrate and generate noise.

Feed unevenness occurs due to disturbances in start/stop step response due to load fluctuations, etc.

An extremely powerful motor is required to start and stop the movable table of a stationary original facsimile transmitter, etc., which has a large inertia, at high speed.

Therefore, in order to eliminate these drawbacks, a continuously variable sub-scanning method was proposed in which the acceleration and deceleration of the N-stage sub-scanning speed is controlled by the storage capacity of a buffer memory placed between the encoder or decoder and the modulation/demodulation section. It was then applied to stationary document facsimile transmitters. However, this continuously variable sub-scanning method, which is controlled solely by the amount of storage in the buffer memory, has the disadvantage that, in the worst case scenario, the encoder is required to be as fast as 5 to 10 times the transmission speed. If the codec is slow and the amount of line memory between the reading or recording section and the codec is small,
When a complex line with a large number of encoded bits comes,
Because encoding and decoding takes time, the buffer memory storage capacity does not reach the deceleration range, and before one line is encoded, the transmitter's entire line memory is filled with image signals, and the receiver's line memory is filled with image signals. When all the image signals stored in the line memory are used up, the sub-scanning must be stopped nervously, resulting in large sub-scanning unevenness and noise.

The present invention eliminates the above-mentioned drawbacks, and even if a relatively low-speed codec is used, there is no sudden sub-scanning emergency stop with a small amount of line memory, and even if an emergency stop occurs, The object of the present invention is to realize continuously variable sub-scanning in which uneven feeding is less likely to occur.

FIG. 1 shows a control block diagram of an embodiment in which the present invention is applied to a transmission system.
2 is a line memory placed between the reading unit 1 and the encoding unit 3, 4 is a buffer memory placed after the encoding unit 3, 5 is a modulation unit, 6 is a line memory amount detection unit, 7 is a buffer memory amount detection section, and 8 is a sub-scanning speed control section.

Next, its operation will be explained.

The image signal is first read by the reading section 1. Reading section 1
The image signal for one line read by is temporarily stored in the (n+1) line memory 2. The image signal stored in the line memory 2 is encoded by the encoding section 3, stored in the buffer memory 4, and then sequentially sent to the modulation section 5 and sent out to the line.

Here, the present invention is characterized in that N sub-scanning speeds are set in advance, and the N sub-scanning speeds are set as v ₁ ,
v ₂ ,...v _N (however, v _j > v _j+1 , j=1, 2...
N), the maximum sub-scanning speed v ₁ is set approximately to the minimum transmission time, and the minimum sub-scanning speed v _N is set corresponding to the time required to transmit the expected maximum number of encoded bits for one line. ing.

Selection of these sub-scanning speeds is performed as follows. That is, for each line of sub-scanning, the number M of accumulated bits in the buffer memory 4 detected by the buffer memory amount detection section 7 and the number M of bits accumulated in the buffer memory 4
comparison with reference values M ₁ , M ₂ , M ₃ and the line memory 2 detected by the line memory amount detection unit 6.
By comparing the number of accumulated image signals stored in , that is, the value of the line memory accumulated number SLM with the value of j of the sub-scanning speed v _j of the previous line, the sub-scanning speed V _NEXT of the next line is determined as follows. decided on.

When (0M<M ₁ and SLM<j), V _NEXT =
v _j-1 (acceleration) (0M<M ₁ and SLM=j) or (M ₁ M
V _NEXT = _{v j} (same speed) when (M ₂ < MM ₃ ) or (SLM > _j )
_EXT = v _{j +1} (Deceleration) In this way, each time reading of one line is completed, the scanning speed is selected based on the detection output of both the number of accumulated bits in the buffer memory 4 and the number of accumulated bits in the line memory 2. , the predetermined N sub-scanning speeds are changed one step at a time, making the deceleration operation particularly reliable and reducing unevenness in feeding due to output changes.

FIG. 2 shows an example of changes in line memory amount, buffer memory amount, and sub-scanning speed when using the method of the present invention, where A is the sub-scanning speed, B is the encoding state, and C is the line memory storage. The number and D indicate the buffer memory amount.

This example is for the case where the buffer memory standard value M ₁ = M ₂ , the number of sub-scanning speed settings is 4 stages, and the data amount of each line is l ₁ , l ₂ , l ₄ to l ₁₀ , l ₁₂ to _{l 15} is the number of encoded bits corresponding to the minimum transmission time, l ₃ and l ₁₁ are the number of encoded bits corresponding to the minimum sub-scanning speed, truncated sub-scanning is performed at the maximum sub-scanning speed v ₁ , and each line The number of buffer memory storage bits at each end is M ₁
It is assumed that they match and are balanced. This is the state when lines with a large amount of data such as l ₃ and l ₁₁ are read, and once it is decelerated due to the amount of data of l ₃ , it is accelerated again, and when it is balanced, it is again
This is the case when l ₁₁ data amount is read, and while l ₁₁ data is being read and encoded, the number of bits stored in the buffer memory is in the acceleration region of M ₁ or less, but the number of line memory storage increases. This is an example in which the deceleration of the sub-scanning is performed by doing so, and the sub-scanning emergency stop does not occur, and good variable speed control is performed.

Figure 3 is an example of a conventional method shown for comparison with Figure 2, in which a continuously variable sub-scanning method is implemented using only the number of buffer memory storage bits when handling the same amount of data as in Figure 2. This is an example of a case in which the number of bits stored in the buffer memory is less than M ₁ while the amount of data of l ₁₁ is being read and encoded, so the sub-scanning is accelerated, and when the reading of the line of l ₁₅ is finished. As shown by the X mark, image signals are accumulated in all line memories, indicating that the sub-scanning stops abruptly from the maximum sub-scanning speed _v1 .

In the above explanation, the present invention was applied to a transmitting system, but it is clear that it can also be applied to a receiving system, and in this case, a buffer memory is provided before the decoding section, A line memory may be provided between the recording section and the recording section. In addition, in the above description, the number of line memories is N+1, which is the number of stages set for the sub-scanning speed plus one.
However, it is of course not limited to this.

As described above, according to the present invention, the sub-scanning speed is controlled not only by the number of bits accumulated in the buffer memory but also by the accumulation state of the line memory, so there is no sudden sub-scanning stop, and even if the sub-scanning stops Even when the speed of encoding/decoding is low, the stopping operation is smooth, which prevents uneven feeding and noise.Also, when the encoding/decoding speed is low, it can be handled with a small number of line memories, which saves memory capacity. It has many advantages and is extremely effective in practice.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment in which the present invention is applied to a transmission system, and Fig. 2 is a diagram showing an example of changes in line memory amount, buffer memory amount, and sub-scanning speed when the present invention method is used. , and FIG. 3 shows examples of changes in line memory amount, buffer memory amount, and sub-scanning speed in the case of the conventional method shown for comparison with FIG. 2. 1... Reading section, 2... Line memory, 3... Encoding section, 4... Buffer memory, 5... Modulating section,
6... Line memory amount detection section, 7... Buffer memory amount detection section, 8... Sub-scanning speed control section.

Claims (1)

[Claims] 1. In a device such as a facsimile machine using a redundancy suppression coding method, N sub-scanning speeds v ₁ ,
v ₂ ,...v _N (v _j > v _j+1 ) are set, and in the transmission system, a line memory is provided between the reading section and the encoding section, and a buffer memory is provided after the encoding section. From the buffer memory storage amount M, the buffer memory reference values M ₁ , M ₂ (M ₁ ≦M ₂ ), the line memory storage number SLM, and the value of j of the sub-scanning speed v _j of the previous line, (0≦M<M When ₁ is SLM<j), one step acceleration, (0≦M<M ₁ is SLM<j) or (M ₁ ≦M≦
In the receiving system, the sub-scanning speed of the next line is set as follows: when M ₂ and SLM≦j), the sub-scanning speed is the same as that of the previous line, and when M ₂ <M or SLM>j, the sub-scanning speed of the next line is reduced by one step. , a buffer memory is provided before the decoding section, and a line memory is provided between the decoding section and the recording section, and when (M ₂ ≦M and SLM > j), one step acceleration, (M ₁ ≦M≦M ₂ and SLM≧j) or (M ₂ ≦M
and SLM=j), the sub-scanning speed is the same as that of the previous line, and when 0≦M≦M ₁ or SLM<j, the sub-scanning speed of the next line is selected as follows. Facsimile sub-scanning method.