Low Complexity Fixed-Point Approximation of Inverse Discrete Cosine Transform

This paper presents an efficient algorithm for computing the Inverse discrete cosine transform (IDCT) for image and video coding applications. This algorithm was submitted in response to MPEG´s call for proposals for ISO/IEC 23002-2 (fixed-point 8times8 IDCT and DCT) standard, and was subsequently adopted in the Working Draft 1 of this standard. Our proposed algorithm is a multiplication-free implementation. It is based on a modification of Arai, Agui, and Nakajima´s (AAN) factorization, and requires only 42 addition and 16 shift operations per scaled ID transform. Each register in our scaled ID transform requires at most 22 bits. This implementation complies with the MPEG IDCT precision specification ISO/IEC 23002-1.