If compiling transcode for macports has you stuck at ‘undefined symbols’ for _mpeg2convert_rgb24 , the problem is that configure isn’t finding the ports version of pkgconfig, so it can’t find the library’s symbols.
The right thing to do is to make transcode depend on pkgconfig, so the ports version gets installed for you. I submitted a patch for this a few weeks, back, and it just got accepted, so expect to see it in the wild in the near future.