From 8-tap DCT to 4-tap integer-transform for MPEG to H.264/AVC transcoding

H.264 uses a 4-tap integer transform (DCT-like) to produce transform coefficients. This is different from the 8-tap DCT that is used in most prior video coding standards such as MPEG-x. The paper propose two integer algorithms for transcoding from 8-tap DCT data to 4-tap DCT-like data. The approximate nature of the integer transcoding algorithms is quantitively evaluated. The results show that the approximation is hidden in most cases when bit rate reduction is considered.