| 摘要 |
A method, and associated apparatus is described for calculating an inverse transform for transform coded data. In a main embodiment, an 8x8 Discrete Cosine Transform (DCT) (200) is arranged in columns of coefficients (202,204,206), the last coefficient is selectively modified to control mismatch in a known manner. The inverse DCT is performed selectively so as to apply abbreviated processing to groups composed entirely of zero-valued coefficients (204). For the purpose of selecting whether abbreviated processing is to be applied, a data group (206) is considered a zero-valued group if the only non-zero coefficient contained therein is a coefficient modified for mismatch control. Further the effect that the modified coefficient has on the output can be pre-calculated, said pre-calculated values being used to compensate for ignoring the non-zero coefficient. |
