The invention is related to methods and apparatus that decode robustly
encoded video bitstreams. One embodiment of a decoder can advantageously
reconstruct a predictive-coded video object plane (P-VOP) from a standard
motion vector and the previous frame; from a redundant motion vector and
a frame prior to the previous frame; or from both. Advantageously, this
permits the decoder to display a frame based on a reconstructed VOP in
the presence of unfavorable environmental conditions, such as
interference, delays, and the like, which could otherwise corrupt a
previous frame that is used as a reference by a standard decoder, such as
a standard MPEG-4 decoder. One embodiment is advantageously backwards
compatible with standard MPEG-4 compliant bitstreams and retrieves
redundant motion vector information from user data video packets. One
embodiment includes at least one extra frame buffer or memory, which
stores a reference frame corresponding to a redundant motion vector.