Embedded DCT coding with significance masking

We evaluate two schemes for significance switching of DCT coefficients for block-based embedded DCT image compression. Both schemes deliver their best compression at any PSNR or vice versa, within a data stream that can be terminated within a few bits of any point. An image is partitioned into equal sized blocks, and a fixed point DCT of each block is calculated. The coefficients are then passed through successive `significance sweeps´ of the whole image from the most significant down to the least significant coefficient bitplanes. The coded data stream includes bits to refine only the significant coefficients at each sweep. With each new sweep, newly significant coefficients may appear within a block, and the two switching schemes evaluated are efficient methods based on block addressing and block masking. Both methods give good compression when used losslessly to the fixed point DCT precision. The best coder outperforms the baseline JPEG method in PSNR at any compression, and is similar to state of the art wavelet coders