MIDI input cracks / latency?

[Domien]

I've been using Reaper for a long time now and I'm running into an issue for the first time.

I have a project with 60+ tracks with many VSTi's on them. This projects uses about 35% CPU but runs very smooth. For a live performance, I'm working together with a friend who uses Ableton. He has all the original reaper MIDI items in Ableton and sends them over MIDI to my system for playback. I've already reduced the project to 10 tracks with only the most important VSTi's (mainly Massive and Battery instances) so now it uses about 6% cpu. However, the playback quickly starts crackling, as if the incoming MIDI can't be timely handled.

I'm running a Windows 10 laptop, 12 GB RAM, Core I7 (3 years old). RME UCX interface over USB. When I reduced the buffersize from 128 to 512 this clearly improved the situation but still. I don't understand why the buffersize should be set that high, when in 128 i can easily record 10 tracks of audio without a problem, but a tiny MIDI signal needs a ridiculously high buffersize. I can't set it even higher because at the same time (for the live performance) I'm also running puredata and that's quite sensitive about the buffersizes, it doesn't like 1024 at all...

Am I missing something here or does anyone have experience with this.

Domien

[EricTbone]

i can easily record 10 tracks of audio without a problem, but a tiny MIDI signal needs a ridiculously high buffersize

You could run 10,000 MIDI tracks, as long as you don't run them through any instruments. Or you can run 1 MIDI note through a fucked up Serum patch and bring your computer to its knees. The MIDI data is almost completely irrelevant. What matters is the instruments you run them through. Your ability to record audio is also irrelevant. Computers could do that without breaking sweat a few decades ago.

You're using an RME interface, so your driver situation is rock solid.

What you need to look at next is DPC latency (https://www.sweetwater.com/sweetcare/articles/solving-dpc-latency-issues/). You can have a 32 core monster CPU sitting mostly idle, but one critical core gets interrupted by a kernel process and you'll get dropout.

[Domien]

Mmm, thanks for the advice. However, I already had checked the latency with that tool and the system seems fine.

It's not about the instruments though, because in the original project I had easily 30 or 40 more plugins on top of the same instruments and that project runs totally smooth.

It's when the midi comes into reaper from an external source that everything starts glitching and crackling. And as said, raising the RME buffersize clearly improves things.