Error Concealment In A Video Decoder
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'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.
1 . A method performed by a video decoder, the method comprising:
receiving, at the decoder, an encoded video bitstream comprising a plurality of synchronization points;
initially designating each macroblock of a video frame as a lost macroblock;
as the video frame is decoded, re-designating each successfully decoded macroblock as a good macroblock;
if an error is detected by receiving a predetermined sequence of error bits, ceasing to update a reference frame.
2 . The method of claim 1 wherein the predetermined sequence of error bits is inserted into the bitstream by a data link layer monitor residing in a component selected from the group consisting of a bridge, a gateway, and a multipoint control unit.
3 . The method of claim 1 wherein the predetermined sequence of error bits is designed to generate an error for one or more of a plurality of video codec supported by a video decoder.
4 . A video decoder configured to implement a video decoding method according to claim 1 .