the error concealment technique disclosed herein relates to the use of existing information by the decoder to conceal bitstream errors regardless of what the encoder does . examples of existing information include , for example , the previous reference frame , macroblock information for the previous reference frames , etc . another aspect of the system described herein relates to the steps that the encoder can take to enhance the decoder &# 39 ; s ability to recover gracefully from a transmission error . exemplary steps that can be taken by the encoder include intra walk around and sending gob headers . although these encoder techniques can provide greatly enhanced results , they are not strictly necessary to the system described herein .