A PARALLEL DECODER OF PROGRAMMABLE HUFFMAN CODES

Huffman coding, a variable-length entropy coding scheme, is an integra l component of international standards on image and video compression including high-definition television (HDTV). The high-bandwidth HDTV s ystems of data rate in excess of 100 Mpixels/s presents a challenge fu r designing a fast and economic circuit for intrinsically sequential H uffman decoding operations. This paper presents an algorithm and a cir cuit implementation for parallel decoding of programmable Huffman code s by using the numerical properties of Huffman codes. The 1.2 mu m CMO S implementation for a single JPEG AC table of 256 codewords of up to 16-b codeword lengths is estimated to run at 40 MHz with a chip area o f 11 mm(2), decoding one codeword per cycle, The design can be pipelin ed to deliver a throughput of 80 MHz for decoding input streams of con secutive Huffman codes, Furthermore, our programmable scheme can be ea sily integrated into data paths of video processors to support differe nt Huffman tables used in image/video applications.