At the same settings, x264 lossless is slower than lossy. It does all the same computations (except DCT, but that's fast anyway). But the time spent in CABAC is directly proportional to bitrate.
Yes, x264 lossless should be faster than HQ-slowest because there's no point in using most of the advanced features for lossless. B-frames are valid, but don't reduce bitrate by more than 1-2%, multiref is similarly disappointing (may even increase bitrate), rate-distortion optimization doesn't do much when you have no distortion, ...
Sharktooth's CQ-Lossless profile includes many of said near-useless options.
My lossless settings are just
If that's not enough for realtime, then try in order:
Code:
x264 -q0 -m1
x264 -q0 -m1 -A i4x4
x264 -q0 -m1 -A i4x4 --no-cabac
Note that the reason most lossless codecs are fast is that they don't do any motion compensation. The exceptions being x264, Snow, and MSU.