For high quality ingest (lossless) it's worth to try new codec utvideo (it requires quite new ffmpeg build- eg 1.0). I'm not 100% sure if ffmpeg implementation is well threaded, but original codec is blazing fast- it can easily encode/decode 4K on i7 machine.
Codec can be fund here (it works basically in every NLE once installed- Premiere, Edius-very well, Vegas, Avid...):
There is also MAC version.
FFmpeg uses its own implementation, which is quite new but even on single 2.5Ghz core it should be able to record HD.
-vcodec utvideo (no bitrate as it's 100% lossless codec)- typical compression ratio is around 2.5, but can be as low as 1.5 or as high as 3.5 depending on the source nature
note- if incoming signal is RGB it will use RGB mode, if YUV it will encode in YUV 4:2:2 mode. For forced 4:2:2 encoding:
-pix_fmt yuv422p -vcodec utvideo (for Windows it needs to be AVI for MAC rather MOV)
update- looks like ffmpeg utvideo encoding is not threaded yet, but it can do 45fps on one core of 3Ghz i7