JPS6053979B2 - Multi-stage buffer memory control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for a multi-stage buffer memory, and more particularly to an overflow and underflow control method for a multi-stage buffer memory in a facsimile storage/conversion device.

When transmitting facsimile signals via long-distance telephone lines, storage and conversion devices are used to transmit facsimile signals at low cost.

That is, at the sending terminal, as shown in FIG. 1a, the line scanner 1 scans the original image, converts the density into an electrical signal, and stores and converts the digitized facsimile signal from the terminal via the oil conversion device 2. It is sent to device 3 and temporarily stored there. The storage and conversion device 3 compresses the image, for example l
6X, /wgn scanning lines are compressed to 8 lines/7 nm and stored, and after one block of image information is stored, it is sent to the toll line 9 via the modem 4. On the receiving side, as shown in FIG. 1, the digital signal sent from the toll line 9 is temporarily stored in the storage/conversion device 6 via the modem 5.

The storage/conversion device 6 stores the image compressed to 8 scan lines/wm as it is, but when reading and transmitting it, it is expanded to, for example, 1/wn to improve the image quality, and the DA conversion device 7
The data is then output to the printer 8 of the terminal device. In this way, the storage and conversion device 3 on the transmitting side compresses the image, reduces the linear density, and transmits it to the long-distance line 9 at high speed, and then the storage and conversion device 6 on the receiving side increases the linear density to create a high-quality image. Output. In the example of FIG. 1, the signal compression ratio of the storage and conversion devices 3 and 6 is 1'1.
5), but the compression ratio can be made even smaller. FIG. 2 is a block diagram of a conventional storage and conversion device having a multistage buffer memory. The transmitted facsimile signal is received by each line in the image signal receiving section 11, and
Accumulate in the first buffer memo I river 2. Normally, the first buffer memo 2 is stored in units of scanning lines, and when the facsimile signal for one scanning line is stored, the encoder 13 of the next stage
For example, 16 scanning lines/WfL are compressed and encoded into 8 scanning lines/TOIt, and the encoded signals are stored in the second buffer memory. In that case, the image signal storage section 1
5 to the second buffer memory 14
and transferred to the image signal storage section 15. The image signal storage section 15 normally stores signals in units of one screen. When transmitting, first store data in the third buffer memory 16, and then
For example, the decoding unit 17 converts 16 scanning lines/Trrm into one
It is enlarged to 2 lines/WL and decoded, stored in the fourth buffer memory 18 in units of one scanning line, and sent out from the image signal transmitter 19 for each line.

The encoding unit 13 and the decoding unit 17 operate the encoding unit 13 on the transmitting side of the toll line and the decoding unit 17 on the receiving side, respectively, and perform the function of compressing or enlarging the image.

By the way, in a conventional storage/conversion device having a multi-stage buffer memory, when an overflow occurs in each buffer memory on the receiving side, the common control section 10 is notified through the control lines 21 and 22 independently. Each control unit 10 performs overflow control.

Further, even when an underflow occurs in each buffer memory on the transmitting side, control is performed by the common control unit 10 through control lines 23 and 24, respectively. In other words, an overflow has occurred in the first buffer memory 12. case,
The common control unit 10 uses the buffer memory 12 to rewrite the accumulated image signals line by line, or to discard the signals input after the accumulated image signals.
When notified by , it counts the number of overflows and
Determined in advance! When the overflow is counted the number of times the screen is overflowed, that is, the number of lines that degrade the image quality, the screen is discarded. Further, the second buffer memory 14
Image signals are accumulated in units of 0 lines, but the common control unit 10 receives a notification from the buffer memory 14, and when an overload occurs.
By counting the amount of memory discarded due to the flow or counting the overflow time, when a predetermined limit value for image quality deterioration is reached, the image quality is abandoned. Regarding the third and fourth buffer memories 6 and 16 on the transmitting side, when all the data to be sent to the transmitting section 19 is exhausted, the buffer memories become empty and an underflow occurs. , in this case as well, by independently notifying the common control unit 10, the common control unit 1
0 counts the number of lines or amount of memory interrupted by empty space, and when a certain number is reached, the screen is invalidated.

As described above, in the conventional method, the common control unit 10 processes overflow or underflow using a program or a counter each time there is a notification from each buffer memory, which makes the process complicated. ing.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate such drawbacks in a storage/conversion device having a multi-stage buffer memory, without activating a common control unit for each buffer memory overflow or underflow. buffer·
The object of the present invention is to provide an economical control system that unifies overflow and underflow processing for a memory, thereby simplifying the processing of a common control section. The buffer memory control method of the present invention is applicable to a facsimile storage/conversion device having an image signal receiving section, a transmitting section, a storage section, and a multi-stage buffer memory. It has a line specification means for requests, and when an overflow or underflow occurs in any buffer memory, it stops line specification and continues to stop line specification for subsequent transfer requests. Insufficient memory or signal is sequentially transferred from the buffer memory closest to the storage section to the buffer memory close to the reception section or transmission section, and processing such as counting the number of lines is performed in the buffer memory closest to the reception section or transmission section. It is characterized by doing the following. Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram showing the storage and conversion device of the present invention.

As in FIG. 2, the facsimile image signal receiving section 11
、． A receiving side having a first buffer memory 12, an encoding section 13, a second buffer memory 14, and an image signal storage section 15, a third buffer memory 15, a decoding section 17, and a fourth buffer memory 8 and a transmitting side having an image signal transmitting section 19, and a common control section 10 for controlling these.

In the present invention, when a memory shortage occurs in the second buffer memory 14, the second buffer memory 14 ignores the transfer request from the first buffer memory 12, so that memory is added to the first buffer memory 12. When a shortage occurs and overflow processing is performed only in the first buffer memory 12, when a signal J interruption occurs in the third buffer memory 16, the third buffer memory 16 handles the overflow from the fourth buffer memory 18. By ignoring the transfer request, a signal interruption occurs in the fourth buffer memory 18, and the fourth buffer memory 18 performs the Aninoda flow processing only. As a result, even if multiple stages of buffer memories are provided, overflow and underflow processing only needs to be performed in the buffer memory closest to the image signal receiving section 11 and the image signal transmitting section 19. Only two control lines 30 and 31 are required, common control, part 1
The number of activations of 0 is reduced, and the processing operation is also simplified. Fourth
3 is a block diagram of the first buffer memory of FIG. 3. FIG.

The facsimile image signal for each line received by the image signal receiving section 11 is input to a first buffer memory 12.

As shown in FIG. 4, in the first buffer memory, storage memories 121 to 129 are arranged in units of one scanning line in correspondence with lines, and after one scanning line signal is accumulated, the next scanning line signal is input. By issuing a transfer request, the encoder 13
will be forwarded to. In the second buffer memory 14, the scanning line signals for each line are multiplexed and converted into time-division signals. The scanning line signals for each line are transferred to the second buffer memory 14 via the encoding unit 13 and multiplexed each time a line is designated. In the present invention, since the second buffer memory 14 has the right to specify the line to be transferred and has a storage area corresponding to the line, the second buffer memory 14 does not overflow. Regarding the line, even if a transfer request arrives from the first buffer memory 12, the line is not specified, causing the first buffer memory 12 to overflow. In the first buffer memory 2, when an overflow occurs, the common control section 10 is notified via the control line 21 and the number of overflows is counted by a counter, as in the conventional case. Or the first buffer●Memo I
A counter is provided in the river 2 itself to count the number of overflows, and only when a certain number of times has been reached is a report sent to the common control section 10. In this way, the first buffer memory 1
Both the overflow that occurred in the second buffer memory 14 and the overflow that occurred in the second buffer memory 14 are treated as an overflow of the first buffer memory 12 by the common control unit 10.
is reported to unify overflow processing. Also,
Similarly, an underflow that occurs in the third buffer memory 16 on the transmitting side and an underflow that occurs in the fourth buffer memory 18 are both transferred to the fourth buffer memory 1.
8 underflow is reported to the common control unit 10, so the control unit 10 abandons the screen when the saw constant is reached by counting the time when the buffer memory becomes empty or the amount of memory. , the signal of that screen is traced back to the beginning and retransmitted from the image signal storage section 15.

Note that when a signal shortage occurs in the third buffer memory 16 near the storage section 15, the transfer request from the fourth buffer memory 18 is ignored, and the third buffer memory 16 only receives the white signal. By accumulating, under-
This eliminates the flow condition and transfers the signal shortage to the fourth buffer memory 16. Figure 5 is a chart of the facsimile signal reception sequence in Figure 3.
In particular, it shows the occurrence and transition status of overflow by focusing on a specific line.

In FIG. 5, the first and second buffer memories each consist of two buffer memories, A and B, for each line, and store images alternately.

In FIG. 5, t1 to t1 indicate sequential event occurrence points. First, the B side of the second buffer memory becomes empty. This is because transfer permission has been received for the transfer request previously sent to the common control unit, and B
This is due to the completion of transferring the surface data to the file memory. After that, as data is received from the first buffer memory via the encoder, side A of the second buffer memory becomes full at T2, and a transfer request is sent to the common control unit. Since the B side is empty, accumulation on the B side is immediately started. As a result of subsequent data reception, the B side of the second buffer memory becomes full and a transfer request is sent to the common control unit, but between T2 and T3, the B side of the second buffer memory becomes full. Since no data transfer is being performed, both sides of the second buffer memory become full at a later point in time. At this time, the second buffer memory stops sending the line designation in response to the transfer request from the first buffer memory, and the first buffer memory stops data transfer due to the stop of the line designation. At the same time, the overflow is notified to the common control unit. However, the number of times this overflow notification is performed immediately may be counted, and the notification may be sent to the common control unit after a certain number of times has been reached. It is also possible to wait until both sides of the first buffer memory are full before determining overflow, but in order to quickly release the encoder, which is a common resource for many lines, the example shown in FIG. In this case, it is immediately determined that an overflow has occurred. T3l). After, T4
In the meantime, files are transferred from the second buffer memory.
Since no data is transferred to the memory and the second buffer memory remains full on both sides, no line specification is returned in response to a transfer request sent from the first buffer memory during that time. As a result, at time T4, both sides of the first buffer memory are full, causing an overflow. At this point, when the data on side A of the second buffer memory has been transferred to the file, from this point on, the second buffer memory can receive data transferred from the first buffer memory. Become. In addition, in Fig. 5, A and B indicate that side A or B is full;
Showing surface or B-side release.

As explained above, according to the present invention, the multi-stage buffer
Since memory overflow processing and underflow processing can be integrated into one, the processing of the common control section of the facsimile storage and conversion device is simplified and has the advantage of being economical.

[Brief explanation of drawings]

Figure 1 is a block diagram of the facsimile storage and conversion system.
FIG. 2 is a block diagram of a conventional storage/conversion device having a multi-stage buffer memory, and FIG. 3 is a block diagram of a multi-stage buffer memory according to an embodiment of the present invention. 4 is a block diagram of the first buffer memory in FIG. 3, and FIG. 5 is a facsimile signal reception sequence chart in FIG. 3. 1: Line scanner, 2: AD converter, 3, 6: Storage converter, 4, 5: Modem, 7: DA converter, 8: Printer, 10: Common control section, 11: Image signal receiving section, 12: 1st buffer memory, 13: Encoding unit, 14: Second buffer memory 15: Image signal storage unit, 16: Third buffer memory 17: Decoding unit, 18: Fourth Buffer memory, 19: Image signal transmitter, 21 to 24, 30,
31: control line, 121-129: 1 scan line buffer.

Claims (1)

[Claims] 1. In a facsimile storage/conversion device that has an image signal receiving section, a transmitting section, a storage section, and a multi-stage buffer memory, the buffer memory closer to the storage section is connected to the buffer memory farther away.
It has a line specification means for memory transfer requests, and stops line specification when an overflow or underflow occurs in any buffer memory, and continues to stop line specification for subsequent transfer requests. By this, memory shortage or signal shortage is sequentially transferred from the buffer memory close to the storage section to the buffer memory close to the reception section or transmission section, and the buffer memory closest to the reception section or transmission section is used to count the number of lines, etc. A multi-stage buffer memory control method characterized by performing processing.