AVC/H.264 is the new international standard for video coding jointly developed by ISO-MPEG and ITU-T, which offers a substantial compression gain when compared with H.263 andMPEG-4 simple profile. One of the main characteristics of H.264 is the introduction of a integer version of the Discrete Cosine Transform initially applied to 4x4 pixels blocks, and later extended to 8x8 pixels for High Quality video encoding. In this work, a unified architecture is proposed for parallel 8x8 integer DCT and iDCT, also able to process 4x4 DCT, iDCT and Hadamard transform. A very fast quantization/de-quantization scheme is presented based on prediction that allows parallel quantization with a single multiplier. This architecture also implements all-zero detection, eliminating coefficients with high cost as specified in the standard and anticipates entropy encoding. The proposed design has been synthesized in AMS 0.35? technology and achieves a maximum speed of 67 MHz.