Due to an attempt on OS upgrade and thus kernel upgrade I'm grudgingly (it worked for me for months with no issues so why would I want to change it for now?) trying to make the transition from multiproto to S2API. I have two DVB-T cards and a NOVA-S2-HD (HVR4000 lite). I have downloaded a vanilla vdr-1.7.0 applied the h264 patch and the s2api patch and install S2API from Steven Toth's mercurial repository.
Can you try with vdr-1.7.4, that's the first version from vdr 1.7x series that i got working with s2api and hvr-4000. I have testeed it with streamdev server plugin and mplayer&vlc.
Mika