Low-complexity arbitrarily shaped transform and coefficient ordering method based on the four-point DCT

In this paper we develop an effective method for arbitrary shape coding based on a four-point DCT. The improvements results from two sources: (1) an effective use of the DCT by efficiently inducing zero-valued transform coefficients, and (2) a novel method of ordering the coefficients allowing the decoder to skip the locations of induced zeros. The algorithm is low complexity, as it only requires only arithmetic and shifting operations in the encoder, and shifting and masking operations in the decoder. The performance is comparable to published techniques in the literature, with the added benefit of low complexity and good performance at both high and low bit rates.