2030101030015 ; 電機工程學系 ; In this paper, we propose a two-pass intra-refresh transcoding scheme for inserting error-resilience features to a compressed video at the media gateway of a three-tier streaming system. The proposed transcoder can adaptively vary the intra-refresh rate according to the video content and the channel's packet-loss rate to protect the most important macroblocks (MBs) against packet loss. In this work, we consider the problem of multicast of video to multiple clients having disparate channel loss profiles. We propose a minmax loss-rate estimation scheme to select a single intra-refresh rate for all the clients. Experimental results show that the proposed method can effectively mitigate the error propagation due to packet loss, and its fairness for multicast.