Investigations on an Object–Based Layered Coding System

An object–based layered coder for the transmission of image sequences at very low bit rates between 8 and 64 kbit/s is presented. In layer 1, only colour parameters are transmitted, whereas in layer 2 additionally motion parameters are transmitted in order to apply motion compensated prediction. In layer 3, in addition to colour and motion parameters, shape parameters of arbitrarily shaped moving objects are transmitted, since the consideration of the object shape can improve motion compensation at moving object boundaries. For each frame, the most efficient layer is chosen by an appropriate layer selection. Compared to a block–based coder according to the ITU–T Rec. H.263, simulation results show that the bit rate for coding of colour parameters can be reduced by about 5% at the same image quality.