JPH0813132B2 - Blocked entropy encoder - Google Patents

Description

DETAILED DESCRIPTION [Outline] In a blocked entropy coding apparatus for band compression of an image signal, in order to enable effective data compression, an input signal sequence is divided into blocks and a specific event (for example, 0 ) Only outputs the identification code consisting of 1 bit in the binary value that identifies this block, and the second block containing a non-specific event (for example, a signal other than 0) is in the second block. The peculiar event is subjected to run length coding, the non-specific event is subjected to Huffman coding, and an identification signal consisting of 1 bit in the binary value for identifying the second block is additionally output.

[Industrial applications]

The present invention provides a blocked entropy coding device (variable when the average run length of a signal of a specific event (0) or a non-specific event (a signal other than 0) is long, such as a prediction error output in band compression of an image signal. Long coding device).

It is desirable that the blocked entropy coding apparatus be capable of more effective data compression.

[Problems to be solved by conventional technology and invention]

As a conventional block entropy coding device, a case of outputting a prediction error of an image signal will be described as an example with reference to FIG.

The signal of the peculiar event (0) or the non-peculiar event (other than 0) of the prediction error output of the image signal which is the output of the DPCM circuit 1 is input to the valid / invalid block discrimination circuit 2, where it is divided into blocks. The first block, which is a unique event (0) only
It is determined whether the block is an invalid block or a valid block that is a second block including a signal of a non-specific event (other than 0), and valid / invalid block information is input to the multiplexing circuit 4 and the selector 5.

The prediction error output is input to a Huffman encoder (encoder that gives an optimum code length according to the occurrence frequency) 3, and all signals are Huffman encoded and input to a multiplexing circuit 4.

In the multiplexing circuit 4, according to the valid / invalid block discrimination information, the Huffman code output from the Huffman encoder 3 for each second block (valid block) is a 1-bit 1 as an identification code.
Are multiplexed and input to the selector 5.

According to the valid / invalid block information, the selector 5 outputs a 1-bit code of 0 as an identification code for one block when the block is an invalid block as the first block.
When the block is an effective block, the identification code 1 and the Huffman code are output for each second block which is the output of the multiplexing circuit 4.

However, since the prediction error output of the image signal is Huffman-encoded for all the signals, the average run length of the signal of the specific event (0) in the second block (effective block) is output, If there are n signals in one block, even if 1 bit is given to each signal, the accumulated value will be n, and there is a problem that sufficient data compression cannot be performed.

[Means for solving problems]

According to the present invention, the above-mentioned problem is determined by dividing the signal sequence into blocks each having a predetermined number of bits to determine whether the first block is composed of only specific events or the second block including non-specific events, and outputs a determination result. Means, second means for discriminating between peculiarity and non-uniqueness of each bit of the signal sequence, third means for detecting the run length of only the peculiar event in the second block and performing run length coding, and Huffman for the signal sequence An identification code consisting of 1 bit in the binary value for identifying the first block based on the outputs from the Huffman encoder to be encoded and the first, second and third means and the Huffman encoder. For the second block, it is called an output selection means for selectively outputting a run length code of the run length of the peculiar event, a Huffman code of the non-specific event, and an identification code consisting of 1 bit in a binary value for identifying the second block. It is solved by a blocked entropy coder.

[Action]

According to the present invention, attention is paid to the fact that the average run length of the peculiar event (0) in the second block (effective block) is long, and the peculiar event (0) in the second block is run-length encoded and non-unique. Since the Huffman coding is performed on the event (a signal other than 0), the code length of the special event (0) is remarkably shorter than that in the conventional case, and more effective data compression is possible.

〔Example〕

 FIG. 1 is a block diagram of an embodiment of the present invention.

In the figure, 2 is a valid / invalid block discriminating circuit as the first means, 6 is a zero / non-zero discriminating circuit as the second means, and the zero run length detector 7 and the zero run length encoder 8 are the third. 3 is a Huffman encoder, and the output selection means is composed of a selector 9, a multiplexing circuit 4 and a selector 5.

 The same reference numerals indicate the same functions throughout the drawings.

FIG. 1 is also an encoding device for the prediction error output of the image signal corresponding to FIG.

1 is different from FIG. 2 in that the zero / non-zero discriminating circuit 6 as the second means, the zero run length detector 7 and the zero run length encoder 8 constituting the third means, and the output selecting means are included. Is that the selector 9 is provided and the function of the output selecting means is changed accordingly.

Explaining mainly this point, the signals of the peculiar event (for example, 0) and the non-peculiar event (other than 0) of the prediction error output which is the output of the DPCM circuit 1 are sent to the zero / non-zero discriminating circuit 6 of the second means. The signal of 0 level is output in the case of a peculiar event, and the signal of 1 level is output in the case of a non-specific event. The zero / non-zero discrimination information is input to the selector 9 and the zero run length detector 7.

In the zero run length detector 7, valid / invalid block information from the valid / invalid block discriminator 2 of the first means is also inputted, and the run length of the specific event in the second block (valid block) is detected to be zero. Input to the run length encoder 8.

In the zero run length encoder 8, the run length of the peculiar event is run length encoded and input to the selector 9 in the output selection means. The Huffman code of the non-specific event of the second block is also input to the selector 9 according to the determination result of the second means.

Therefore, the selector 9 outputs the run length code of the peculiar event and the Huffman code of the non-peculiar event for the second block (effective block) according to the zero / non-zero discrimination information, which is input to the multiplexing circuit 4. Further, the multiplexing circuit 4 uses the valid / invalid block discrimination information from the first means as a block identification code for the second block (valid block).
Bit 1 is input. Therefore, the multiplexing circuit 4 outputs the block identification code of the second block and the input from the selector 9, and inputs them to the selector 5.

On the other hand, a 1-bit block identification code for the first block (invalid block) is input to the selector 5 depending on the determination made by the first means.

Therefore, from the selector 5, 1 for the first block
The bit block identification code, the 1-bit block identification code for the second block, the run length code of the specific event and the Huffman code of the non-specific event in the second block are output.

Therefore, compared to the conventional case, the first block (invalid block)
However, the code length is the same, but the code length of the 0-specific event in the second block (effective block) is significantly shortened, so that more sufficient data compression can be performed.

〔The invention's effect〕

As described in detail above, according to the present invention, the code length of the invalid block as the first block is the same as that of the conventional one, but the continuous event of the specific event (0) of the valid block as the second block is the same. Since the code length becomes significantly shorter,
There is an effect that more sufficient data compression can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional example. In the figure, 1 is a DPCM circuit, 2 is a valid / invalid block discriminating circuit device as a first means, 3 is a Huffman encoder, 4 is a multiplexing circuit, 5 and 9 selectors are both output selecting means configurations, and 6 is Zero / non-zero discriminating circuit as second means, zero run length detector 7 and zero run length encoder 3
The structure of a means is shown.

Claims (1)

[Claims] 1. A first means for determining whether a signal block is divided into blocks each having a predetermined number of bits to determine whether it is a first block including only specific events or a second block including non-specific events, and outputting a determination result. Second means for discriminating between peculiarity and non-uniqueness of each bit of the signal sequence, third means for detecting the run length of only the peculiar event in the second block and performing run length coding, and Huffman coding for the signal sequence Based on the outputs from the Huffman encoder, the first, second and third means and the Huffman encoder, the first block is identified by a 1-bit identification code for identifying the first block. The two blocks are composed of a run length code having a run length of a specific event, a Huffman code of a non-specific event, and an output selecting means for selectively outputting an identification code consisting of 1 bit in a binary value for identifying the second block. Blocking entropy coding apparatus characterized.