Number Cruncher Box (video encoder)


I've been having issues developing a decent number cruncher machine designed to encode video for streaming purposes. 

Basically, it needs to take a 3G-SDI signal at 2.970 Gbit/s (comes in over a video capture card) and squeeze it into a H.264 feed at 1080p/50 that can be send out at 4500kbp/s without any frame drops, letting the CPU running over 75% capacity or too much loss in overall quality. 

And it needs to be done in realtime. 

If anyone can help me with a cost effective solution then that would be absolutly awesome. I've personally been looking at dual Opteron's or Haswell's (The machine doesn't need a dedicated videocard). Oh and fitting it all in a Shuttle case so I can take it onto the road also needs be possible.