Software-based implementations of H.263 and MPEG-2 video standards are well documented, recently reporting faster than or close to real-time performance. Since the complexity of MPEG-4 is higher than its predecessor standards, real time video encoding and decoding can exhaust computational resource without achieving real-time speed. In this paper, we report a software-based real-time MPEG-4 video codec (encoder and decoder) on a single-processor PC, with no frame-skip, or profile simplifying tricks, or quality loss compromise. The proposed codec is an embodiment of a number of novel algorithms. Specifically, we have designed a fast binary shape coding algorithm, a fast motion estimation algorithm, and a technique for detection of all-zero quantized blocks. To enhance the computation speed, we harness Intel's SIMD (Single Instruction Stream, Multiple Data Stream) instructions to implement these algorithms. On the 800 MHz Intel Pentium III, our decoder can play real-time CIF video with less than 20% system resource consumption; and our encoder realizes up to 70 frames per second for CIF resolution video, with the similar picture quality as the reference software.
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