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Optimization of image sequences scalable coding

In a previous article (see Proc. 3rd International Workshop on Image/Signal Processing, p.249-52, 1996), we examined to what extent and in what conditions scalable coding of image sequences as defined in MPEG-2 could be a useful tool. We thus showed that, at a constant coding quality, up to 35% of the base layer rate could be spared by scalable coding. This gain was achieved mostly on the luminance (on I and P frames particularly) and increased when the motion content of the sequences coded was difficult to handle. This previous work, however, entirely relied on earlier results provided by literature. This contribution aims at further investigating the optimization of scalable coding based on our own previous observations. As will be seen our experiments confirm the choices made in MPEG-2, but also give some interesting insights on the mechanisms of scalable coding, examining problems such as motion handling and optimal segmentation in a scalable scheme.