advice on live capture to disk

[John Bazik]

I’ve been trying to construct a pipeline to reliably capture a 720p camera feed (w/ pcm audio) for 1 to 2 hours and save it to disk.  It needs to be sufficiently high quality for me to transcode it later into lower resolutions and bitrates for streaming on demand.  I’m capturing from a blackmagic intensity pro, on a reasonably powerful 6-core machine.  I knock it down from 60fps to 30fps, but I’m otherwise trying to preserve the quality and resolution.

I’ve tried a variety of codecs (theora, x264, mjpeg, huffyuv) and I find myself stymied.  I’m not so concerned about compression, though at 200GB/hr, raw video is a bit unwieldy.  I spent hours tinkering with x264, but could not eliminate weird wavy artifacts.  I could not get high quality from theora without dropping frames.  I couldn’t get mjpeg to work (openmjpegenc).  I thought I had it with huffyuv (even at 96GB/hr), but it, too, dropped frames after a while, though it was running at about 25% cpu.  I don’t need a perfect copy, perfect-looking is good enough.

It feel like this should work.  Can anyone point me in the right direction?  Am I better off with something like x264, or with huffyuv?  When I’m using lossless compression, could I be dropping frames due to i/o bandwidth limitations to a standard 7200rpm sata hard disk?

John