Reversible variable length codes for efficient and robust image and video coding

The International Telecommunications Union (ITU) has 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 little or no efficiency loss relative to the corresponding non-reversible variable length codes. We present the ideas behind two general classes of RVLCs and discuss the results of applying these codes in the framework of the H.263+ and MPEG-4 video coding standards.