Hello, all experts, I am a Ph.D student working on video communication. I am wondering about how the video transcoder/gateway works between H.261 and H.263, and between IP network and PSTN or ISDN, in paticular i wonder whether there is a method by which bitstreams can be translated directly between H.261 and H.263 format. Who knows the technique details on above topics or where may i get some useful reference infomation? Any help will be approciated. Weiming Shen