Image coding with rational spatial scalability

In the digital TV and mobile operators scene, there is an increasing demand for a wider scalability range when delivering content to heterogeneous client devices which have different screen sizes. Subband image coding with classical wavelet transform only provide dyadic scalability factors but we have shown that M-band transforms can offer rational scalability factors with an appropriate modification of the synthesis filters. In this paper, we evaluate the image coding efficiency offered by some M-band transforms combined with the rational scalability feature. We show that they offer an increased compression performance compared to the popular dyadic 9/7 wavelet transform.