3D Visual Communications

8.5 Multiple Description Coding

Multiple description coding is a source compression technique where the bit stream at the output of the encoder instead of having the usual single coded representation of the source, it now has multiple representations. For example, Figure 8.12 illustrates the particular case of a dual description encoder and decoder, where the number of descriptions is two. Encoding using multiple description coding also has the property that during decoding, each description can be decoded independently of the others, each resulting in a reconstruction of the source that can be considered to have a baseline quality. At the same time, the decoder can combine multiple descriptions (in principle, those that had been received with no errors in a communication setting) and obtain a reconstruction of the source with better quality than the baseline obtained from individual descriptions. Multiple description codecs are usually used in communication scenarios where each description can be communicated through a different link, independent of the others. In this way, each description will be affected through channel impairments that are independent of the others. With multiple description coding, receiving only one description is all that is required to recover a description of the source of usually fair quality. If more than one description is received, they can be combined at the decoder to obtain a reconstruction of the source with better quality. It is because of this ...