been wondering the same thing. I saw in the VEP instructional video when using logic you need to add an additional audio in/out plugin and bypass it to get around the extra latency,wonder if maybe it's the same deal with Reaper(it's the one thing that really stopped me from switching over to Reaper as my main DAW). I haven;t had time to try it ,let me know if you figure it out.

G

ps
at about 5.38
https://www.youtube.com/watch?v=fKvWy1zwe3g

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Anyone? tried adding and bypassing an audio input in reaper but no change in latency.

I don't have such issues.

But I never set the buffer to zero.

You should ask in the Reaper forum.

By the way, the next Reaper version will have multilane midi editing - perfect for orchestral work.

Since in Reaper a track can be anything it can be confusing sometimes how to set up things. I do it in a way that I separate midi tracks and audio inputs. So if I set up VEPRO I use the VEPRO plugin only as audio in into Reaper. Just drag the plugin from your fxwindow into Reaper. It will ask you if you want to create 32 outs. Do here what ever you like. These are all audio ins from VEPRO server. Now you hav an (activated) track. Click on FX and connect to your VEPRO server. Set the buffer as you like. Now look on the track panel: There is "midi in all all channels". You don't need midi here since you can do that with the event input instrument. Select no input. Now do a right click on the track channel area and choose insert virtual instruemnt to new track. The fxwindow opens. Choose the event input plugin, choose port 1 and assign the VEPRO server instance. If you want to keep your DAW very organized you can create 16 more (Midi) tracks and use those as (midi) sends to you VEPRO event input VSTi. With the track manager in Reaper you can choose which tracks you want to see where. I set it that way up that I see the midi tracks in the track panels / arrangement view while I make the audio inputs there invisible because they are not needed here. In the mixer I make the midi tracks invisible since they are not mixed anyway. I don't have the feeling of a higher latency here with this setup. Hope that helps.

Have you tried using VEPRO on a separate PC? You wouldn't need it with Reaper on the same machine anyway because its the most efficient host around. You wouldn't gain any advantage with VEPRO. I just opened a Reaper file with 2000 (!) G-Player (Solo) on my Macbook. Try the latest prerelease with multilane midi editing. Deselect "run fx when stopped" (Options/Playback) and you'll lower your CPU usage drastically compared to any other host.

Try using Reaper on a Mac. I use it with Win and Mac and I don't think there is any difference in using it on a Mac. U-He demoed their new stuff on Musikmesse with Reaper on Macbooks.

I know this is a very old thread, but I may have found the solution.

I was having the precise problem described when using Event Inputs in Reaper. Unacceptable latency, even though I was getting very good latency just playing my keyboard without the plug-in. The problem being, of course, that I had no way to access the extra ports in VE Pro 6.

I went to Options | Preferences | External MIDI in VE Pro 6 and saw that Vienna Instruments MIDI was not selected. I selected it, and now the latency is unnoticeable.

Hope this helps someone.