Arbitrarily Shaped Transform Coding Based on Modification of Pixels in Shapes

Abstract—Arbitrarily shaped transform coding is a tool to achieve object-based coding. Two types of arbitrarily shaped cod-ing, which guarantee equivalence between the number of pixels inside shapes and DCT coefficients to be coded, are proposed as [3] and [4]. These methods obtain same DCT coefficients, and the difference is that the former calculates outside pixel values from the inside whereas the latter varies the inside pixels by themselves. They are based on 1D-DCT; therefore, 1D-DCT must be executed twice, namely horizontal and vertical directions. This procedure does not guarantee the equivalence. In this paper, we extend their method to two-dimensional transform. In addition, we discuss methods to optimize position of DCT coefficients and pixels using statistical model. We embedded the proposed method in H.264/AVC, and simulation results indicate all proposed method performed almost same in coding efficiency. Index Terms—Arbitrarily shaped transform coding, padding techniques, H.264/AVC I