KR100275267B1 - High speed variable length code decoding apparatus - Google Patents

Abstract

PURPOSE: A high-speed variable length decoding unit is provided to improve a data processing speed by changing a structure of a variable length decoding unit. CONSTITUTION: The first table(110) extracts header information including a codeword length and a decoding characteristic of variable length code data provided from a transfer data processing portion(100) and outputs the codeword length and the header information. The first latch portion(130) latches the header information provided from the first table(110) according to a rising edge of a clock signal. The second latch portion(150) latches the header information provided from the first table(110) according to a rising edge of a clock signal. A selection portion(170) receives the header information from the first and the second latch portions(130,150) and outputs the header information. The second table(190) decodes the codeword provided from the transfer data processing portion(100).

Description

High speed variable length code decoding device

BRIEF DESCRIPTION OF THE DRAWINGS Fig. Is a block diagram schematically illustrating the operation of a fast decoding apparatus according to the present invention.

* Explanation of symbols for main parts of the drawings

100: transmission data processing unit 110: first table

130: first latch portion 150: second latch portion

170: selection unit 190: second table

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high speed variable length code decoding apparatus, and more particularly, to a high speed variable length code decoding apparatus in which time delay does not occur in data processing due to structural improvement.

In high definition image systems, variable length coding is used for various lossless data compression. Variable-length coding converts fixed-length data into variable-length data based on the statistics of the data.The frequency of occurrence of each code included in the information source is shorter and less frequent. This is a method of displaying a long length code. In this way, the average value of the codeword lengths can be reduced compared to allocating the same length to all the codes. A typical variable length code is the Huffman code.

In general, the coding process may be implemented by a lookup-table that uses input data for a table address, and includes a codeword and a codeword length. -length) is stored as the table contents. However, the decoding process is very complicated. That is, because of the variable length feature, each codeword is divided from the received bitstream of the variable length code and then decoded into an information source codeword. Therefore, the design of the variable length code decoding apparatus is generally more difficult than the design of the variable length coding apparatus.

Various methods have been proposed for such variable length code decoding, and the most known one is a fast variable length code decoding apparatus first proposed by "Ming-Ting Sun". In more detail, the fast variable length code decoding apparatus proposed by "Ming-Ting Sun" sequentially inputs a predetermined number of bits of code data, that is, bitstream data, sequentially by predetermined bits according to a length signal. It includes a barrel shifter and a decoding table for dividing the output. The decoding table is composed of first and second decoding tables, and detects a meaningful variable length code interval, that is, a codeword, among the series of variable length codes applied from the barrel shifter, and detects the detected variable length. The number of bits in the code interval is detected and output as the codeword length, and the detected variable length code interval is decoded and output. At this time, the upper bits of each code word are header information, and the information includes the total number of bits and decoding characteristics of each code word. The second table has a plurality of decoding tables for decoding input codewords. The header information provided from the first table designates a decoding table for decoding each codeword.

However, the conventional fast variable length code decoding apparatus having the first and second decoding tables as described above requires an additional barrel shifter for providing a variable length code to the first decoding table, and processes the codeword length. Adder for is necessary. Therefore, there has been a big problem that not only the structure is complicated but also a large time-delay occurs in the data processing due to the complicated structure.

Accordingly, an object of the present invention is to provide an improved fast variable length code decoding apparatus in which time delay does not occur in data processing due to structural improvement.

In order to achieve the object as described above, a bit stream of a variable length code input is latched, and a code word length of the latched bit stream data is input. Fast variable-length code decoding of the present invention having a transmission data processing unit for outputting a high-order bit corresponding to) as a codeword and outputting variable-length coded data of a predetermined number of bits from a position following a higher-order bit output as the codeword. The apparatus detects header information including a codeword length and a decoding characteristic among variable length code data of a predetermined number of bits provided from the transmission data processing unit, and outputs codeword length and header information, respectively. A first latch section for latching header information provided from said first table in response to a first table, a rising edge of a clock signal, and a clock; In response to a falling edge of the call, receiving a second latch portion for latching header information provided from the first table, header information from the first and second latch portions, and in response to a rising edge of a clock signal; A selection unit for outputting header information provided from the first latch unit and header information provided from the second latch unit in response to the falling edge of the clock signal, and in response to the header information provided from the selection unit, And a second table for decoding and outputting a codeword provided from the transmission data processor.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram schematically illustrating an operation of a fast variable length code decoding apparatus according to the present invention. The transmission data processor 100, the first table 110, the first latch unit 130, and the first latch are shown in FIG. The unit 150 includes a selector 170, a selector 170, and a second table 190.

First, the transmission data processing unit 100 at a constant rate from a buffer unit (not shown) that temporarily stores bit stream data of a variable length code transmitted from a transmitting end (not shown). The bitstream data is received and latched, and an upper bit corresponding to a codeword length provided from the first table 110 described later among the latched bitstream data is converted into a codeword. And variable length code data of a predetermined number of bits are output from the next position after the upper bits output as the codeword.

Subsequently, the first table 110 detects and outputs header information among variable length code data of a predetermined number of bits provided from the transmission data processing unit 100. In this case, the header information has the total number of bits of the codeword to be decoded in the second table 190 to be described later, that is, the codeword length and the decoding characteristic. The first table 110 extracts the codeword length from the header information. To the transmission data processing unit 100.

As described above, the header information provided from the first table 110 is latched by the first and second latch units 130 and 150. That is, in response to the rising edge of the clock signal CLK, the first latch unit 130 latches the header information provided from the first table 110. In addition, in response to the falling edge of the clock signal, the second latch unit 150 latches the header information provided from the first table 110. As a result, the header information provided from the first table 110 is alternately latched to the first latch 130 and the second latch 150 at every half period of the clock signal.

Subsequently, the header information latched in the first and second latches 130 and 150 is provided to the selector 170. The selector 170 selectively outputs in response to the rising and falling edges of the clock signal. That is, in response to the rising edge of the clock signal, the selector 170 outputs the header information provided from the first latch unit 130. In response to the falling edge of the clock signal, the selector 170 outputs the header information provided from the second latch unit 150.

The second table 190 decodes the codeword provided from the transmission data processing unit 100. At this time, the second table 190 has a plurality of decoding tables for decoding the code words for each codeword length and decoding characteristics. The decoding table for decoding the currently input codeword is selected by the selection unit 170. It is determined by header information provided from. Through this process, the decoded word is output from the second table 190 every half period of the clock signal.

By the above-described process, the fast variable length code decoding apparatus according to the present invention is improved in structure, so that an additional barrel shifter, an adder, and the like are no longer needed, and thus there is no significant time delay in data processing. There is an advantage.

Claims (2)

A bitstream of an input variable length code is latched, and an upper bit corresponding to an input codeword length among the latched bitstream data is converted into a codeword. A fast variable length code decoding apparatus having a transmission data processing unit (100) for outputting and outputting variable length code data of a predetermined number of bits from a position following a higher bit output as the code word. Among the variable length code data of a predetermined number of bits provided from the transmission data processing unit 100, header information including a codeword length and a decoding characteristic is detected and outputs codeword length and header information, respectively. A first table 110; A first latch unit 130 for latching header information provided from the first table 110 in response to a rising edge of a clock signal; A second latch unit 150 for latching header information provided from the first table 11 in response to a falling edge of a clock signal; The header information is received from the first and second latch units 130 and 150, the header information provided from the first latch unit 130 in response to the rising edge of the clock signal, and the clock signal falls. A selection unit 170 for outputting header information provided from the second latch unit 150 in response to an edge; And a second table 190 which decodes and outputs a codeword provided from the transmission data processing unit 100 in response to the header information provided from the selection unit 170. Code decoding device. The method of claim 1, The second table 190, It includes a plurality of decoding table for performing codeword decoding for each decoding word length and decoding characteristics, Fast variable among the plurality of decoding table, characterized in that the decoding table to decode the code word currently input from the transmission data processing unit 100 is determined by the header information provided from the selection unit 170 Length encoding device.