DCT/subband coding techniques in frequency scalable video coding

In MPEG compatible image sequence encoding platforms, the discrete cosine transform is used both for encoding and for resolution scalability purposes. The paper describes techniques for introducing wavelet transforms in frequency scalable applications. Using the fact that wavelets allow perfect reconstruction of low-resolution low-frequency images, the proposed approach permits the implementation of variable resolution decoders from an already available nonscalable MPEG encoded bitstream. A further improvement of quality for the low resolution sequences may be obtained through conventional reconstruction techniques (e.g. drift correction) or by altering the wavelet filter bands according to error metrics computed at the encoder.