especially the three typical architectures were firstly outlined and compared.Emphasis was put on how to reduce the complexity and improve the video quality by exploiting the informa-tion
which can be easily extracted from the input video bitstream.Other active research topics in recent years such as in-formation
especially watermark and error resilient data
insertion transcoding and H.264 bitstream related video transcoding were discussed in detail.Future directions on this topic were also prospected.