I’ve used the h264 recorder from blackmagic. It won’t help you with live streaming as it only allows you to capture directly to file (h264 mov on a Mac) using the blackmagic Media Express software. If you’re looking to push out an h264 stream using rtmp then Adobe Flash Media Live Encoder is what you need. In that case you can use any of the Decklink capture cards. We use FMLE to live stream, but other people on here might suggest other software such as Wirecast, etc.