Standardization of IDCT approximation behavior for video compression: the history and the new MPEG-C parts 1 and 2 standards

This paper presents the history of international standardization activities and specifications relating to the precision of inverse discrete cosine transform (IDCT) approximations used in video compression designs. The evolution of issues relating to IDCT precision and the “drift” effects of IDCT mismatch between encoder modeling of decoder behavior is traced, starting with the initial requirements specified for ITU-T H.261 and continuing through the MPEG-1, H.262/MPEG-2, H.263, MPEG-4 Part 2, and H.264/MPEG-4 Part 10 AVC projects. Finally, the development of the new MPEG-C Part 1 and Part 2 standards is presented. MPEG-C Part 1 contains a centralized repository for specification of IDCT precision conformance requirements for the various MPEG video coding standards prior to MPEG-4 Part 10. MPEG-C Part 2 specifies one particular IDCT approximation for adoption in industry implementations of existing standards. The use of MPEG-C Part 2 by encoders can eliminate IDCT mismatch drift error when decoded using an MPEG-C Part 2 conforming decoder, resulting in a deterministic decoded result. MPEG-C Part 2 also provides an example for guiding implementers on how to design a decoder with high precision and without excessive computational resource requirements.