Mpeg4 can be a lot of things, there are a lot of variations of it out in the real world. H264 is the most widely used version. You need to ask for specifics from the client, then test. If the AJA software doesn't work QT Pro can record a live feed to H.264 via the IoHD so that is another Option. The thing is the IoHD is not does the encoding, the Mac is so the question is can it keep up with the live feed.