I’ve been using Cubase for MIDI composition for many years (currently using v10.0 and a Steinberg UR22 audio interface). For the first time while attempting to do a real time export of a project with only 3 VSTs, it renders part of the file and then stops with the notice, “CPU overload…”
A thread on the forum says Kontakt 6 can max out the CPU. The thread suggested using a different instance of Kontakt for each VST, which they claim will divide up the processing better among the multiple cores. My project has two VSTs in one instance of Kontakt Player, so instead I assigned them to two instances of Kontakt Player.
Another thread says that using effects within the VST such as reverb takes a lot of CPU resources, so they suggest using a reverb in Cubase rather than in the VST.
Combining these two approaches is the best technique I came up with to export in real time.
Before finding that solution I tried another, I changed the ASIO driver to “Generic Low Latency ASIO Driver,” by going to Studio > Studio Setup. This allows me to do a real time render, however the generic driver on my Windows 7 PC runs at 44.1kHz, not at the 192kHz which my Steinberg ASIO driver runs at, workable but not ideal.
After some poking around I discovered another solution: Instead of switching to the generic ASIO driver, I stayed with the Steinberg ASIO driver, and went to Studio > Studio Setup > Yamaha Steinberg USB ASIO > Control Panel and reset the buffer size from 8192 samples to 4096 samples. This enabled real time export using the Steinberg ASIO driver at 192kHz. (When finished exporting, I reset the buffer back to 8192 to ensure smooth playback from the timeline.)
Why use real time export? Interestingly, when doing real time export using the generic driver, my computer actually renders the file at about 1/3-speed, not actual real time. This subtly affects the way the VST instruments respond, for example when listening to the exported file the vibrato in violins starts earlier than when I listen to the project playing from the timeline. When I export without real-time export checked, the file renders much faster than the actual time duration of the piece, but it seems the VST instruments don’t have as much time to respond in the same way they do when I play the project from the timeline, so the resulting exported file also sounds subtly different than what I’m used to hearing from the timeline. I’m guessing that VSTs respond with a fixed timing no matter what speed the export, so if the export is faster or slower than actual “real time” the VST may sound slightly different. I’m curious to know if this analysis is correct?
This particular project has a lot of very fast playing with lots of different articulations, lots of CC activity, two Kontakt VSTs with reverb, so I guess it was just too much for my little CPU… I hope this info is helpful to others.
I am amazed and grateful every day that I have such a deep and powerful tool as Cubase on which to compose and perform MIDI music.