Efficient coding and mapping algorithms for software-only real-time video coding at low bit rates

This paper presents efficient coding and mapping algorithms that lead to a significant speed improvement in low bit rate H.263/H263+ video encoding while maintaining high video-reproduction quality. First, by exploiting the statistical properties of low resolution and slowly varying video sequences, we reduce significantly the computation times of the most computationally intensive components of video coding, particularly the discrete cosine transform, the inverse discrete cosine transform, quantization, and motion estimation. We also map some of the single instruction multiple data (SIMD)-oriented functions onto Intel´s MMX architecture. The developed algorithms are implemented using our public-domain H.263/H.263+ encoder/decoder software. Using the above algorithms, our H.263/H.263+ baseline video-encoder implementation can encode more than 15 fps in QCIF resolution on a Pentium MMX 200-MHz computer