Reversible variable length codes for robust image and video transmission

The International Telecommunications Union (ITU) adopted reversible variable length codes (RVLCs) for use in the emerging H.263+ video compression standard. As the name suggests, these codes can be decoded in two directions and can therefore be used by a decoder to enhance robustness in the presence of transmission bit errors. In addition, these RVLCs involve essentially no efficiency loss relative to the corresponding non-reversible variable length codes. We present here the ideas behind two general classes of RVLCs that include the new H.263+ codes as a special case, and present results on the probability of error detection when these codes are used.