Algorithmic and architectural enhancements for real-time MPEG-1 decoding on a general purpose RISC workstation

Traditional video decoders require use of specially designed video decompression processors. We present novel algorithmic and architectural enhancements that allowed for the first time the real-time decompression of MPEG-1 video and audio streams on a low-end, general purpose RISC processor. For video decompression, efficient algorithmic implementations were derived by examining the Huffman decoder, the inverse quantizer and the inverse DCT as a single system. For audio decompression, a new DCT based implementation of the subband filtering operation yields 30% speed improvement in the audio decoding process and 17% speed improvement in overall audio and video decoding. Besides algorithmic enhancements, a new set of “multimedia” instructions and minor changes in the design of a traditional RISC ALU allowed increased parallelism of pixel-based operations with minimal design and control overhead. Experimental results show that with the synergistic combination of algorithmic and architectural enhancements a multimedia-enhanced RISC processor can achieve higher decoding rates than generic RISC and CISC processors, even when these processors operate at higher clock rates and have larger instruction and data caches