A new padding technique for coding of arbitrarily-shaped image/video segments

Object-based coding is becoming more and more important in today´s multimedia applications. Shape-adaptive DCT (SA-DCT) provides a useful tool for coding of arbitrarily-shaped image/video segments which is indispensable to achieve object-based coding. In this paper, we introduce a new padding technique based on which the arbitrarily-shaped DCT can be implemented using normal N×N DCT. The new padding is carried out for each arbitrarily-shaped block in such a way that the number of non-zero coefficients after DCT is guaranteed to be no more than that of the original image data, thereby never expanding the data set in the DCT-domain. Arbitrarily-shaped DCT coding based on this padding technique is developed, and then analyzed and compared against some of the existing algorithms in terms of rate-distortion performance, computational complexity, and implementation cost.