I've downloaded and installed the LAVVideo on my office machine to take a look at it. I don't see a "jtv option" anywhere. Also searched the Doom9 thread and found very little on jtv. Did I misunderstand something from your first quote above?
Yes, probably me not being particularly clear about which menu's and where. Apologies.
1. Install LAV Video - done!
2. Go to MC Options (either from the top menubar or Ctrl-O).
3. Select Video on the left hand side
4. Select Red October HQ with Additional filters (under Advanced ->)
5. This splits the right hand pane, in the lower pane, you'll find a list of video types in one of the boxes.
6. Select jtv - I can't remember the exact name for the filetype - JRiver TV or MediaJukebox TV or somesuch. In the next box select the JRiver with directshow or whatever sounds similar (doing this from memory!)
7. In the middle of the three boxes underneath select LAV Video, the o ther two should say 'automatic'
8 . Click on OK
this sets the LAV Video filter to be used only with jtv. The rest of the RO/ROHQ settings and filters will be unaltered.
Try it up to here and see if it works. I think LAV Video will auto-set itself to use Nvidia CUVID. You can bring the LAV Video menu up in the same way as the madvr menu to check the settings.
I guess when I do it shouldn't break anything that wouldn't allow RO Standard to still run okay?
I think RO Standard is pretty bombproof which I guess is why Jim usually (daily?!) recommends people start off with it if having problems. The above will only change playback for jtv (hopefully for the better!). If you change back to ROHQ (without the additional filters) the change will be ignored.
Good luck!
SBR
Edit: changed to ROHQ+additional filters