JPH0430224B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention receives a data-compressed image signal,
The present invention relates to an image signal receiving device that records an image signal after decompression.

In digital facsimile, in which an image signal is digitized into black and white binary or multi-value signals and transmitted, data compression is performed to shorten the transmission time. Therefore, the amount of code after data compression for the image signal per scanning line is not constant, but changes from line to line. In the case of digital facsimile, such as newspaper transmission, where it is better not to change the sub-scanning speed using a step motor, etc. due to image quality issues, it is recommended not to change the sub-scanning speed using a step motor, etc. In the case of digital facsimile such as newspaper transmission, when the transmission time of one line of code is longer than the recording time of one line, In order to prevent normal recording from becoming impossible, a buffer is usually provided in the receiving device. The receiving device absorbs changes in the amount of compressed data for each line by accumulating the received compressed data in a buffer and then starting decompression and recording. In digital facsimile using such a buffer, the transmission and recording time T from when the transmitting device starts transmitting compressed data until the receiving device finishes recording is expressed by the following equation.

T = T ₁ + T ₂ T ₁ = Time for storing data in the buffer of the receiving device (buffer accumulation time) T ₂ = Recording time of the receiving device Conventionally, the recording time T ₂ of the receiving device within this transmission recording time T was In order to shorten the time, the recording rotation speed of the receiving device can be switched in multiple stages, and the amount of data stored in the receiving buffer is calculated in advance by the transmitting device in a simulated manner, so that the specified buffer capacity B (maximum buffer storage amount, A transmission method was used in which the maximum recorded rotational speed at which the receiving buffer (which may be set to the maximum capacity of the buffer or a value lower than that) underflows is determined, and this is specified to the receiving device. (Patent publication number 55−
(Refer to 12204 "Image Data Transmission Method") However, in this conventional method, the receiving device started decompression and recording after the amount of buffer accumulated in the receiving buffer reached the specified buffer capacity, making it difficult to use a large-capacity buffer. In this case, the buffer accumulation time _T1 becomes long, resulting in an increase in the transmission recording time T.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image signal receiving apparatus that requires less buffer accumulation time by starting expansion and recording after the buffer accumulation amount of a received image signal reaches a specified buffer amount.

The image signal receiving device of the present invention receives, decompresses and records an image signal in which all images of one screen are compressed. means for receiving and storing a predetermined buffer amount indicating whether an underflow of the reception buffer will occur if decompression and recording are started after the image signal has been accumulated in the buffer; means for accumulating the received image signal; and the image signal accumulating means. It is characterized by comprising means for expanding and recording the image signal after the accumulated amount of the image signal reaches the specified buffer amount.

The image signal receiving device of the present invention has the effect of reducing buffer accumulation time and, as a result, reducing transmission/recording time.

The present invention will be described below with reference to drawings showing embodiments.

Some image transmission systems compress images in advance, store them in a storage device such as a magnetic disk, and transmit the images when necessary. In such a system, the transmitting side divides the image into blocks (one block can be one line, multiple lines, or one line divided into several parts) and counts the amount of compressed data for each block. From this, the specified buffer amount (the amount that indicates how much received compressed data must be stored in the buffer on the receiving side before decompression and recording is started to prevent underflow of the receiving buffer). If this specified buffer amount is smaller than the specified capacity of the receiving buffer, by transmitting this specified buffer amount, it becomes possible to shorten the buffer accumulation time _T1 compared to the conventional method, and as a result, the transmission recording time T can be reduced. I can do it.

First, an image signal transmitting device that is closely related to the present invention will be explained.

FIG. 1 is a block diagram showing the configuration of a first embodiment of an image signal transmitting apparatus.

The image input section scans the image and inputs white/black binary, multi-value,
Alternatively, it is converted into an image signal 7 such as color. The compression section 2 performs data compression on this image signal 7 in block units (one line, a plurality of lines, or one line divided into several parts, etc.) to create compressed data 8. As a data compression method, for example, international standard MH or MR encoding can be used for binary images. This compressed data is sent to the storage section 3 and stored therein, and is also sent to the compressed data number counter 5. The compressed data number counter 5 counts the number of compressed data (bit number) in units of one block created by the compression section 2, and sends this compressed data number 9 to the counting section 6. The counting section 6 calculates a specified buffer amount from the number of compressed data in blocks that are sequentially sent by the following calculation.

Let the number of blocks in one image be N, and the number of compressed data for each of these N blocks be C _i (i=1
~N). As an initial value, B _p =0, and i=
The following calculation is performed for each block 1 to N.

B _i =B _i-1 +C _i -D If B _i <0, set B _i =0. ...(1) (However, D is the number of data that can be transmitted within one block picture signal recording time of the receiving device.) Specified buffer amount = MAX {B _i } (i = 1 to N) ...(2) In this way, the total When the data compression of the image is completed, all the compressed data is stored in the storage section 3, and the specified buffer amount is calculated and stored in the counting section. Similar processing is repeated for a plurality of images, and the prescribed buffer amount for each is determined.

Next, when a request to transmit a certain image occurs, the line output unit 4 first reads the specified buffer amount 10 of the image to be transmitted from the counting unit and notifies this value to the receiving device through the line, and then sends it from the storage unit. , reads the compressed data of the transmitted image and outputs it continuously to the line.

However, if there is a risk that the buffer of the receiving device may overflow, it receives a signal from the receiving device through the line indicating the status, and stops transmitting compressed data until the risk of overflow is resolved.

In the receiving device, the risk of buffer underflow is eliminated by starting data decompression and recording after storing received compressed data in the buffer up to a specified buffer amount.

If the units of images to be data compressed and the units of images to be transmitted at one time are the same, there is no problem in determining the prescribed buffer amount as described above. However, when data compression is performed in units of partial images, and a plurality of arbitrary images are selected from among these partial images and a composite image of these images is transmitted, the following calculation method is required.

Each block i (i=1 to N) in each partial drawing line A _j
Let B _nax (j) be the maximum value of B _i found using equations (1) and (2), and B _eod (j) be the value of B _i in the final block. Counting part 6
Then, when data compressing a partial image, these values are counted and stored. When one transmitted image is composed of L composite images of A ₁ to A _L , the required B _nax (j) (j = 1 to L) and B _eod (j) (j =
1 to L), the counting section 6 performs the following calculation to determine the prescribed buffer amount.

For j=1~L B _le (j)=B _le (j-1)+B _eod (j) B _ln (j)=B _le (j-1)+B _nax (j) However, B _le (o) = 0 ... (3) Specified buffer amount = B _ln (j) (j = l ~ 1) ... (4) In the line output, the specified buffer amount obtained in this way is sent from the storage unit 3 to the receiving device.
The compressed data of each partial image A ₁ to A _L is read and transmitted.

However, the calculation method of formulas (3) and (4) is only a simple method for determining the specified buffer amount, and A ₁ to A _L
There is a possibility that the specified buffer amount will be determined as a value somewhat larger than the accurate specified buffer amount obtained by successively performing calculations of equations (1) and (2) for the entire composite image.

Next, second and third embodiments will be described as embodiments for determining an accurate prescribed buffer amount for such a composite image of partial images.

FIG. 2 is a block diagram showing the configuration of a second embodiment of the image signal transmitting apparatus. Next, points different from the first embodiment will be explained.

The compressed data number counter 5 counts the number of compressed data for one block, and sends this compressed data number 9 to the storage section 3 to be stored therein. Therefore, storage unit 3
The compressed data and the number of compressed data are stored in block units.

When a request to transmit a composite image, etc. occurs after data compression has been performed on a partial image, a completed image, etc. in this way, the counting section 6 calculates the block unit of the image to be transmitted from the storage section 3. The number of compressed data is read out in the order of transmission, and the specified buffer amount 10 is calculated by the calculations shown in equations (1) and (2) and sent to the line output section 4. The operation of the line output section 4 is the same as in the first embodiment.

FIG. 3 is a block diagram showing the configuration of a third embodiment of the image signal transmitting device. Next, points different from the first embodiment will be explained.

The compression section 2 compresses data block by block, and this compressed data is stored in the storage section. If a request to transmit a composite image, etc. occurs after data compression has been performed on a partial image or a completed image, the compressed data of the image to be transmitted is first read out from the storage unit in the order of transmission, and then compressed. The data is sent to the data number counter 5 and the block detection section 11. The block detection section detects a synchronization signal for each block included in the compressed data, and at the time of detection, notifies the compressed data number counter 5 that it is a block boundary. The compressed data number counter 5 calculates the compressed data number 9 in block units from this boundary and sends it to the counting section. If the compressed data does not include a synchronization signal in block units, the block detection unit 11 performs processing similar to decompression processing, and when the length of the decompressed signal becomes equal to the length of one block, compression is performed. The data number counter 5 must be notified of the block boundary.

The counting section 6 calculates the prescribed buffer amount 10 by the calculations shown in equations (1) and (2), and sends it to the line output section 4. The operation of the line output section 4 is the same as in the first embodiment.

In the first to third embodiments described above,
The compressed data is continuously read from the storage section 3 and sent out from the line output section, and the sending is stopped if there is a risk of buffer overflow in the receiving device. Therefore, it is necessary for the receiving device to notify the transmitting device of the buffer status.

On the other hand, by adopting a configuration in which a buffer is placed between the storage section 3 and the line output section 4, overflow of the receiving buffer can be avoided without monitoring the buffer status of the receiving device.

FIG. 4 is a block diagram showing the configuration of a fourth embodiment of the image signal transmitting device. This embodiment is obtained by adding a buffer 12 to the first embodiment.
When transmitting compressed data, the buffer 12 reads one block of compressed data from the storage section 3 every recording time of one block of image signal in the receiving device. After notifying the receiving device of the prescribed buffer amount, the line output section 8 reads compressed data from the buffer 12 in accordance with the transmission speed and transmits it. After the buffer storage amount becomes 0, the buffer 12 sends out a dummy signal to the line output section. By sending this dummy signal, buffer overflow in the receiving device is avoided.

In the second and third embodiments as well, by arranging a buffer between the storage section and the line output section, it is possible to avoid overflow of the reception buffer through similar processing.

Next, an image signal receiving device according to the present invention will be explained.

FIG. 5 is a block diagram showing an embodiment of the image signal receiving apparatus of the present invention.

The line input unit 20 responds to the transmitting device through the line, controls the transmission procedure, and receives the specified buffer amount and the data-compressed image signal. The received specified buffer amount 26 is stored in the specified buffer amount storage section 2.
1 and stored. Further, the compressed data 27 of the received image is sent to the buffer 22 and stored therein. The control unit 23 compares the specified buffer amount stored in the specified buffer amount storage unit 21 with the compressed data storage amount 28 of the buffer 22, and determines the compressed data storage amount 28.
When the buffer amount reaches a specified buffer amount, the expansion/contraction unit 24 starts reading and decompressing data from the buffer 2, and when the expansion unit 24 has expanded one block of data, the recording unit 25 is instructed to start recording. Thereafter, the decompression section 24 repeatedly performs the decompression operation for each block, and the recording section 25 continuously records the decompressed image signal.

If the transmitter does not use a buffer and the dummy signal is not added to the image signal as in the first, second, and third embodiments of the image signal transmitter described above, the buffer 22 of the receiver will overflow. Because of this danger, the control unit 23 constantly monitors the buffer storage amount 28, and when there is a risk of buffer overflow, the line input unit notifies the transmitting device of a data transmission stop request.

Furthermore, when the transmitting device has a buffer as in the fourth embodiment of the image signal transmitting device and adds dummy signals as necessary, there is no risk of the receiving buffer overflowing. No monitoring required.

In the embodiments of the transmitter and receiver described above,
Although the recording rotation speed of the receiving device is assumed to be fixed, as claimed in Patent Publication No. 55-12204 ``Pixel Data Transmission Method'', the maximum recording rotation speed at which the receiving buffer does not cause underflow can be simulated using the transmitting device. It is also possible to calculate Therefore, a method may be considered in which the highest recorded rotational speed and the specified buffer amount at this rotational speed are determined in the transmitting device and these are sent to the receiving device. In this case, the receiving device transmits the recording rotation speed and the specified buffer amount, and starts expansion and recording operation at the specified rotation speed after the amount of data stored in the reception buffer reaches the specified buffer amount.

As explained above, the image signal receiving device of the present invention reduces the buffer accumulation amount by starting decompression and recording after the received buffer amount and the buffer accumulation amount of the received image signal reach the specified buffer amount. As a result, the transmission/recording time can be shortened.

[Brief explanation of drawings]

FIG. 1, FIG. 2, FIG. 3, and FIG. 4 show first, second, and
FIG. 5 is a block diagram showing the structure of the third and fourth embodiments, and FIG. 5 is a block diagram showing the structure of the image signal receiving apparatus of the present invention. The numbers in the figure indicate the following, respectively.
1... Image input section, 2... Compression section, 3... Storage section, 4...
Line output unit, 5... Compressed data number counter, 6... Counting unit, 7... Image signal, 8... Compressed data, 9... Number of compressed data, 10... Specified buffer amount, 11... Block detection unit, 12... Transmission buffer, 20 ... Rotation input section, 21... Specified buffer amount storage section, 22... Reception buffer, 23... Control section, 24... Expansion section, 25... Recording section, 26... Specified buffer amount, 27... Compressed data, 28... Buffer storage amount .

Claims (1)

[Claims] 1. In an image signal receiving device that receives, decompresses, and records an image signal in which all images of one screen are data-compressed, the receiving side transmits the received compressed data from the transmitting device, and determines how much buffer the received compressed data has been accumulated before decompressing and recording. means for receiving and storing a predetermined buffer amount indicating whether an underflow of the reception buffer will occur when recording is started; means for accumulating the received image signal; 1. An image signal receiving device comprising means for decompressing and recording an image signal after reaching .