With widely applications of digital video

the requirement of video transcoding is very exigent.Video transcoding is defined as the conversion of one coded video format to another and becomes a key technique of digital multimedia network gateway.In this paper

a survey on video transcoding in DCT-domain

including several typical architectures

key techniques and an optimal transcoding strategy

and various existing algorithms to analyze their advantages and disadvantages respectively are presented.An intrablock refreshing architecture for reduced spatial resolution transcoding in DCT domain and a soluton of an optimal transcoding strategy are introduced.Several research aspects in the future are proposed.