Parallel implementation of discrete cosine transform and its inverse for image compression applications

This paper presents the graphics processing unit (GPU) implementation of two-dimensional discrete cosine transform (2D DCT) and inverse discrete cosine transform (2D IDCT) for image compression applications. Based on the trigonometric properties, the transform matrices are simplified, resulting in reduced computation over the naive implementation. To assess its performance, the output image quality is measured in terms of several metrics and found to be better than all other existing transforms. To further improve the timings, a GPU implementation of the proposed transforms is obtained by exploiting the inter-level parallelism among threads and blocks in addition to efficiently accessing data from the shared memory resources. This has resulted in significant improvement in speedup (more than 5k) for both the transforms. The proposed GPU implementation of 2D DCT is compared in terms of processing time and is shown to outperform the existing work across all image dimensions.