초록 ▼

In a digital coding apparatus or a digital coding and decoding apparatus for image data compression and expansion by means of Huffman coding, a Huffman coding circuit converts a combination of ZERO RUN and VALUE into a variable-length code. A code length calculation circuit has an AC code length tab

In a digital coding apparatus or a digital coding and decoding apparatus for image data compression and expansion by means of Huffman coding, a Huffman coding circuit converts a combination of ZERO RUN and VALUE into a variable-length code. A code length calculation circuit has an AC code length table for prestoring variable-length codes and their code lengths in corresponding relationship. The code length calculation circuit inputs not a ZERORUN-VALUE combination but a variable-length code from the Huffman coding circuit, thereby calculating from the variable-length code inputted its code length according to the AC code length table. The present invention can provide a downsized AC code length table in comparison with a conventional one that stores ZERORUN-VALUE combinations and code lengths in corresponding relationship.

대표청구항 ▼

[ The invention claimed is:] [1.] A digital coding apparatus comprising:an orthogonal transform circuit for performing an orthogonal transform on data to find a great number of transform coefficients, each of said transform coefficients having either a value of zero or a value other than zero;a vari

[ The invention claimed is:] [1.] A digital coding apparatus comprising:an orthogonal transform circuit for performing an orthogonal transform on data to find a great number of transform coefficients, each of said transform coefficients having either a value of zero or a value other than zero;a variable-length coding circuit for converting transform coefficients from said orthogonal transform circuit into a variable-length code, for padding said variable-length code to a fixed-length code, and for providing said fixed-length code to outside said digital coding apparatus;said variable-length coding circuit including:a first logical table for storing, in corresponding relationship, combinations of the numbers of consecutive zero-valued transform coefficients and nonzero-valued transform coefficients, and variable-length codes;a coding circuit for receiving in sequence transform coefficients from said orthogonal transform circuit, and for converting, based on said first logical table, a combination of the number of consecutive zero-valued transform coefficients and a nonzero-valued transform coefficient of said received transform coefficients, into a variable-length code;a second logical table for storing variable-length codes and code lengths thereof in corresponding relationship;a code length calculation circuit for receiving a variable-length code from said coding circuit, and for calculating, based on said second logical table, a code length of said received variable-length code;a padding circuit for receiving a variable-length code from said coding circuit and a code length from said code length calculation circuit, and for padding, based on said received code length, said received variable-length code to a fixed-length code.