Fast 2D IDCT implementation with multimedia instructions for a software MPEG2 decoder

This paper presents an implementation of a fast two-dimensional inverse discrete cosine transform (IDCT) with multimedia instructions for a software MPEG-2 decoder. IDCT algorithms for sparse blocks which eliminate the calculation for zero coefficients are realized by using multimedia instructions. To reduce the cycle count for IDCT, an adaptive control method for these IDCT algorithms, based on the bit rate and picture type, is proposed and its performance is described. In the implementation of a software MPEG-2 decoder, the execution time for IDCT is reduced to 10% by using MMX instructions from the original C program. Moreover, using the proposed adaptive control, it can further be reduced to 76%.