JPS61173528A - Encoding device for modified hoffman code - Google Patents

Abstract

PURPOSE:To perform efficient control so that the multiprocessing of each scanning line is performed to begin with another piece of original image information by sending an encoding output of each scanning line as to plural input image signal. CONSTITUTION:When the (m)th scanning line is encoded, final data which is read out of a data informing circuit 9 and stored on the completion of the encoding of the (m-1)th scanning line is set in a data setting circuit 8 and the final position bit is set in a bit position setting circuit 5 similarly. The address of the (l)th byte is set in an address counter 1, the number of bytes to be transferred is set in a transfer byte quantity counter 2, and an encoding circuit 4 is started at this time. The encoding circuit 4 reads and encodes original image signals, and a modified Hoffman code is connected successively to the final bit position of the data set in the data setting circuit 8 which is set in the bit position setting circuit; and serial-parallel conversion is performed and the resulting 8-bit data is written in a buffer memory. Then, codes are written in the buffer memory every time an eight-bit code is formed. The encoding circuit 4 reports the completion of the encoding after one scanning line is encoded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an encoding circuit that generates facsimile signals using a modified Huffman encoding method, which is a one-dimensional encoding method for facsimile signals.

〔overview〕

The present invention relates to a modified Huffman (MH) encoding system that encodes a make-up signal for one-dimensional encoding of a facsimile signal in the vertical direction and a terminating code in the horizontal direction based on black and white run lengths (RL). By adding a register to set the code final bit position in the final data of the immediately preceding scanning line and a control circuit to control reading and writing of the register, it is possible to reliably encode the scanning line without missing it, and to This is to prevent information spanning lines from being included in one output byte information.

[Conventional technology]

Black and white binary facsimile signals generally have extremely high redundancy, so if the redundancy is reduced through appropriate signal processing and only the necessary signals are transmitted, the amount of data can be significantly reduced. For this reason, various band compression methods have been proposed for digital facsimile.

Conventional band compression methods include -dimensional coding, two-dimensional coding, etc.
Modified Huffman coding is recommended as the standard coding method for CCITT Group 3 (G3) aircraft.

This modified Huffman code is a Huffman code constructed based on the probability of occurrence of each run for black and white run lengths, and one run is converted into a make-up code (
(vertical direction) and terminating code (horizontal direction). A code called EOL indicating a separation between scanning lines is inserted between codes for one scanning line.

Modified Huffman encoding or modified Huffman decoding is often processed by a microprogram in conventional devices, taking into consideration the execution of facsimile communication procedures. In this case, the original image signal to be encoded is stored in a buffer memory.

The encoder sequentially reads the original images from this buffer memory and encodes them. The encoded modified Huffman code is also written to a different area in the buffer memory. Assume now that the unit of data exchange between the buffer memory and the encoder is, for example, 8 bits. The encoder reads the original image and encodes it. Since the encoded data is serial data, it is serial-parallel converted after encoding and written into the buffer memory 8 bits at a time. Since the modified Huffman code is a variable length code, the last part of the code is usually less than 8 bits when the encoder finishes encoding one scanning line.

In addition, since conventional encoders sequentially and continuously encode the original image signals for multiple scanning lines stored in the buffer memory, when the encoding for one scanning line is completed, the end of the code is The data that is less than 8 bits is left as is, and when the next scanning line is encoded, the newly encoded data is connected to the remaining data, serial-to-parallel conversion is performed, and the data is transferred to the buffer. It was supposed to be written to memory.

[Problem that the invention seeks to solve]

Therefore, in such a conventional apparatus, several different types of original image signals are stored in separate buffer memories, and these signals cannot be used for multiple processing such as alternately encoding each scanning line.

The present invention solves the above problems, and aims to provide an encoder that enables multiple processing that cannot be performed with conventional encoders as described above.

[Means for solving problems]

The present invention provides an encoding device for a modified Huffman code including an encoding circuit that encodes an input facsimile image signal into a modified Huffman code and outputs the encoded modified Huffman code every n bits. data notification setting means for outputting the encoded data of the last scanning line when the encoding of the last scanning line is completed and holding the data until encoding of the image signal of the next scanning line is started; When the encoding of the image signal of a scanning line is finished, the position information of the last pit of the encoded data of the last scanning line is outputted, and the encoding of the image signal of the next scanning line is started. The encoding circuit includes bit position notification setting means for holding the position information of the bit until It is characterized by a configuration that sends out encoded output.

[For production]

In the modified Huffman arrangement example, m-1
When the encoding of the scanning line is completed, the stored final data is set in the setting circuit, and the encoding circuit is activated when the number of transfer bytes is set. The encoding circuit reads the last set bit from the data notification circuit and can know the entire bit without omission.

〔Example〕

Next, an embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of a modified Huffman encoding circuit according to an embodiment of the present invention. Address counter 1 and transfer byte number counter 2 are connected to control circuit 3 and bus 10, respectively.
connected between. The bit position setting circuit 5 and the bit position notification circuit 6 are connected between the control circuit 3 and the bus 10, respectively. The focus position setting circuit 5 is coupled to a serial/parallel conversion circuit 7. This conversion circuit 7 is connected between the encoding circuit 4 and the bus 10. The control circuit 3
is connected to bus 1 via data setting circuit 8 and data notification circuit 9.
Combined with 0.

FIG. 2 shows an example of how modified Huffmans are arranged in a buffer memory (not shown) after modified Huffman encoding is performed. Here, 8 bits are used as an example of parallel data. Let us now consider the case of encoding the m-th scanning zigzag in FIG. 2. At the end of encoding the m-1 scanning line, the final data read from the data notification circuit 9 and stored is set in the data setting circuit 8, and the final position bit is similarly set in the bit position setting circuit 5.

Then, the address of the β-th byte is set in the address counter 1, the number of transferred bytes is set in the transfer byte number counter 2, and the encoding circuit 4 is activated at this point. The encoding circuit 4 reads out the original image signal, encodes it, and sends it to the data setting circuit 8.
Following the final bit position set in the bit position setting circuit of the data set in , the modified Huffman code is dropped, the data is serial-to-parallel converted, and then written to a buffer memory (not shown) as 8 bits. Thereafter, each time 8 bits of code are accumulated, they are written to the buffer memory.

When the encoding of l scanning lines is completed, the encoding circuit 4 notifies the completion of encoding. By reading the transferred byte number counter 2 after the encoding is completed, it is possible to know the number of bytes of the modified Huffman code for one scanning line written in the buffer memory. Further, the final data remaining in the encoding circuit can be read out from the data notification circuit 9. The final bit position can be known by reading the bit position notification circuit 6. These pieces of information are stored and used in the next m+l scan scan conversion.

〔Effect of the invention〕

According to the present invention, in modified Huffman encoding, image signals in different areas can be encoded one scanning line at a time. Therefore, since information that spans scanning lines is no longer included in one byte information, it is possible to expand the scope of application by enabling efficient control such as performing multiple processing for each scanning line using different original image information. It is very effective.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a modified Huffman encoding circuit according to an embodiment of the present invention. FIG. 2 is a diagram showing an example of how modified Huffman codes are arranged in the buffer memory of FIG. 1. 1... Address counter, 2... Transfer byte number counter, 3... Control circuit, 4... Encoding circuit, 5...
・Bit position setting circuit, 6...Bit position notification circuit,
7... Serial/parallel conversion circuit, 8... Data setting circuit, 9... Data notification circuit, 10... Bus.

Claims (1)

[Claims] (1) In a modified Huffman code encoding device that includes an encoding circuit that encodes an input facsimile image signal into a modified Huffman code and outputs the encoded modified Huffman code every n bits, a data notification setting means for outputting the encoded data of the last scanning line when encoding is finished and holding the data until encoding of the image signal of the next scanning line is started; When the encoding of the line image signal is finished, the position information of the last bit of the encoded data of the last scanning line is output, and the position information is output until the encoding of the image signal of the next scanning line is started. The encoding circuit includes a bit position notification setting means for holding bit position information and a control circuit for controlling the above two notification setting means, and the encoding circuit encodes and outputs each of the plurality of input image signals for each scanning line. 1. A modified Huffman code encoding device, characterized in that it is configured to send out a modified Huffman code.