A type of scalability where the enhancement layer(s) contain only coded refinement data for the DCT coefficients of the base layer. SNR scalability is aimed at transmission in noisy environments, and offers a form of graceful degradation. Under poor reception conditions, only the lower layer (which is covered by the highest error protection) is decoded.

The picture quality is then not the best, of course, but at least a picture is available. The alternative is a total loss of picture (the “brick wall” effect) below a certain SNR. The lower layer and the enhancement layer operate with the same resolution, but the enhancement layer may contain the higher frequencies of the picture.