Variable length code decoder and moving picture decoder having variable length code decoder
AssigneeOki Electric Industry Co., Ltd.
InventorKenichi Natsume
Life of this patent
Estimating the term…
Abstract
In a variable length code decoder, code information containing a variable length code composed of a variable length bit numerical part and a 1-bit sign part is supplied to a decoding unit. A numerical part decoding unit decodes the numerical part and outputs numerical data. A code length decoding unit decodes code length of the variable length code, and outputs a value one less than the code length as code length information. A shift unit shifts the code information by the value of the code length information and outputs the sign part as sign data. Since a sign part decoding circuit having logic gates is not needed, circuit size can be reduced.
Claims25
A variable length code decoder capable of converting a variable length code into a fixed-length binary value and sign data, comprising:
- a shifter which has said variable length code as an input, and shifts said variable length code by a designated number of bits to produce a shifted code;
- a decoding unit which receives said shifted code from said shifter, outputs a prescribed bit of said shifted code as said sign data and decodes said shifted code for outputting a code length and said fixed-length binary value of said shifted code;
- and
- a shift control unit which outputs said designated number of bits to said shifter based on said code length.
A variable length code decoder capable of converting a variable length code into a fixed-length binary value and sign data, comprising:
- a shifter which has said variable length code as an input, and shifts said variable length code by a designated number of bits to produce a shifted code;
- a decoding unit which receives said shifted code from said shifter, outputs a prescribed bit of said shifted code as said sign data and decodes said shifted code for outputting a code length and said fixed-length binary value of said shifted code;
- a shift control unit which outputs said designated number of bits to said shifter based on said code length;
- a code buffer for temporarily holding said variable length code;
- and
- a controller which outputs a timing signal to said code buffer based on said code length for controlling an output timing of said variable length code,
- wherein said code buffer includes,
- a first register which temporarily holds said variable length code, and
- a second register which receives said variable length code temporarily held in said first register and successively holds said variable length code,
- wherein said first and second registers supply said variable length codes held in said first and second registers to said shifter in parallel.
A variable length code decoder capable of converting a variable length code into a fixed-length binary value and sign data, comprising:
- a shifter which has said variable length code as an input, and shifts said variable length code by a designated number of bits to produce a shifted code;
- a decoding unit which receives said shifted code from said shifter, outputs a prescribed bit of said shifted code as said sign data and decodes said shifted code for outputting a code length and said fixed-length binary value of said shifted code;
- and
- a shift control unit which outputs said designated number of bits to said shifter based on said code length,
- said shifted code including a numerical part of said variable length code, and said fixed length binary value consists of said sign data and a fixed length numerical value, wherein said decoding unit including
- a numerical part decoding unit for decoding said numerical part to produce said fixed length numerical value,
- a code length decoding unit which produces said code length of bits that constitute said variable length code based on said numerical part, and
- a shift unit for receiving said shifted code from said shifter and outputting said prescribed bit as said sign data.
A decoding method of a variable length code into a fixed-length binary value and sign data by a variable length code, said method comprising the steps of:
- loading said variable length code into a code buffer;
- transferring said variable length code from said code buffer to a shifter;
- shifting said variable length code transferred to said shifter by a designated number of bits to produce a shifted code;
- outputting a prescribed bit of said shifted code as said sign data;
- and
- decoding said shifted code for outputting said fixed-length binary value.
A decoding method of a variable length code into a fixed-length binary value and sign data by a variable length code, comprising:
- loading said variable length code into a code buffer;
- transferring said variable length code from said code buffer to a shifter;
- shifting said variable length code transferred to said shifter by a designated number of bits to produce a shifted code;
- outputting a prescribed bit of said shifted code as said sign data;
- decoding said shifted code for outputting said fixed-length binary value;
- producing a code length of said shifted signal;
- adding up said code length and outputting an addition result;
- and
- outputting said designated number of bits based on said addition result.
A video decoder for decoding a bit stream of a video transformed into compressed codes using a discrete cosine transform, and outputting an uncompressed digital video signal, comprising:
- an interference which receives said bit stream;
- a controller which examines said bit stream and selects a variable length code;
- a variable length code decoder unit which decodes said variable length code and outputs fixed length codes;
- an inverse quantizer which quantizes discrete cosine transform coefficients including said fixed length codes to produce a discrete cosine transform block;
- and
- an inverse discrete cosine transform unit which applies an inverse discrete cosine transform on said discrete cosine transform block,
- wherein said variable length code decoder unit includes
- a shifter that shifts said variable length code by a designated number of bits to produce a shifted code,
- a decoding unit which outputs a prescribed bit of said shifted code as sign data and decodes said shifted code for outputting a code length and a fixedlength binary value of said shifted code, and
- a shift control unit which outputs said designated number of bits to said shifter based on said code length.
Dependencies are inferred from the claim text.