I was never all that impressed with original Multibridge from Blackmagic Design. It was not an I/O interface for your computer, it was just a Analog to SDI convertor, both ways. When the Multibridge Extreme was released, and with every major revision since then, computer I/O was added in a brilliant way. Basically they embeding their Decklink electronics within the breakout box, and then devised a way to tap directly into the PCIe bus. I don’t believe they created the original concept of External PCIe, but they were the first by a long shot to market a product utilizing the concept. Caldigit and Ciprico, among others, have recently developed drive arrays with an external RAID controller that uses the same basic connection.
Another major feature that the Multibridge was the first to offer, was DVI output for monitoring on an LCD in full screen independent of the graphics card. It was also the first simple solution for monitoring 2K at fullscreen, using the DVI port to drive a 2560×1600 pixel LCD. This has been replaced by HDMI in the newest revisions, removing integrated 2K monitoring support, but that is now offered through the HDLink Pro. The most recent version, the Multibridge Pro, can capture or convert to and from HDMI, SDI, and Analog formats. Their newest feature is support for 3Gb/s SDI, allowing HD 4444 and 2K 444 over a single cable in realtime. (Which allows 2K preview on an 30″ LCD though the HDLink Pro, which is a separate item)
On the PC side, they support three basic editing modes, well really two and a half. Uncompressed is their primary format, 8 or 10bit, 422 or 444, and now 2K. They recently added a compressed MotionJPEG codec, but they have not unlocked all of the options to vary the quality yet. This allows the realtime capture and playback of compressed files through their I/O. Their MotionJPEG codec is 8bit 422, and from my use, I would class it as a great codec for full rez and frame rate offline editing, if you are finishing to HD or Film. For Web encodes or SD, it is probably fine for online work, unless you need 10bit for Digibeta. The last option is a Capture only one, into the Cineform codec. I know for a fact that this works over HDMI on the Intensity card, but I have heard that all of the Blackmagic products are supported. Blackmagic products are the only way to capture RGB over dual link SDI in realtime to the new Cineform 444 codec, and possibly even to Cineform2K.
There are a few disadvantages I am aware of. Low realtime effects or rendering support in their hardware or editing modes. They don’t support many compression schemes, MotionJPEG being somewhat limited. The big issue in using it with Cineform is that it seems that realtime monitoring is not available from Cineform RT projects in Premiere. Lastly, Blackmagic products are known for their reasonable prices, but not their long lifespans.