At $395, Blackmagic’s UltraStudio SDI is an extremely affordable SDI capture and playback solution for computers that have USB 3.0 support (Mac users see below) The device provides 10 bit SDI capture and playback, plus HDMI monitoring all powered from the USB connection on your computer. HDMI monitoring allows you to use consumer displays for monitoring. You also get genlock and RS-422 deck control built in.
The good news, newest generation Mac users and Macbook Pro users can now have HDSDI capture. Bad news? It will cost you $995 (as compared to above). The Blackmagic UltraStudio 3D uses Intel’s new Thunderbolt™ technology (10 Gb/s connection that’s up to 20 times faster than USB 2.0) to allow for SD, HD or 2K captureand even supports two streams of full resolution video up to 1080p HD for new stereoscopic 3D workflows.