A fast algorithm for the conversion of DCT coefficients to H.264 transform coefficients

This paper proposes a fast algorithm that converts DCT coefficients into integer transform coefficients, for the transform domain transcoding from MPEG-x to H.264. For the transcoding in the same resolution, the 8 × 8 DCT coefficients are converted to four 4× 4 integer transform coefficients by decomposing the conversion matrix into sparse ones. For the reduction of resolution by half, we also propose an algorithm that converts DCT coefficients in the lower band into 4 × 4 integer transform coefficients. The sparse matrices derived in this paper require fewer computations than the direct and conventional conversion matrices, and thus the overall transcoding using the proposed algorithm requires less computational complexity.