ABSTRACT -- The detection and concealment of error in the H.261 standard video stream is important in any video conferencing session as error in the bitstream can affect not only its corresponding picture element but also other neighbouring elements in the same frame and also other frames that references the errornous element. The error can propagate until the starting of a new Group of Block (GOB) if it is not detected. This paper presents a method for concealment of error in macroblock upon detection of error while decoding the H.261 bitstream. Temporal error concealment using motion vector from current and previous frames is applied. An array of macroblocks for concealment which formulated from motion vectors in current and previous P-frames by average, interpolate and extrapolate. Then, the best macroblock to conceal the error macroblock is selected.

KEYWORDS -- GOB , Macroblock