[spmvg]

Interesting comment! I'm going to figure out if using another driver allows me to get under 20 ms in latency. Right now I'm measuring around 300 ms in latency round-trip, which is not a problem because I can correct for it. (I'm using a Focusrite Scarlett 2i2 with default drivers.)

The reasoning behind my comment about round-trip time was as follows:

  - Right now I'm measuring around 300 ms round-trip time, without processing inbetween
  - In the past I've tried to do live effects in Ableton with ASIO drivers (guitar in -> Ableton effects -> out), and the delay was too noticable. I couldn't play that way without making my ears bleed and I've switched back to pedals since.

One follow up: how could I achieve a total round-trip latency of around 10 ms total, as you describe? If I use a buffer of 500 samples @ 44.1 kHz, then I am spending already 11 ms just filling the buffer. So then the buffers need to become really small, causing more processing overhead, right? Not sure if this is the way to go.

[camtarn]

Yeah, your Scarlett should be capable of single-digit ms latency. If you're on Windows, you need to install its ASIO drivers and figure out how to use them from Python. Then, yes, use tiny buffers and run your audio processing very fast - which is where Python's slowness will probably become a real problem.

10ms latency is how long sound takes to travel 3-and-a-bit metres. So if your amp is a few metres from you, you would experience that delay between hitting the guitar strings and hearing the amplified sound. This should barely be noticeable. If you were noticing a delay greater than that in your Ableton effects setup, your settings needed tweaked. All of this is completely possible - I had a PC-based electronic drum setup in 2006, running through the Reason DAW, which had 8ms latency between hitting a pad and hearing the result.

Hmm, I wonder if Cython (static Python-to-C compiler) would make writing audio code easier/more possible?

[spmvg]

With Ableton and the default ASIO configuration on my Scarlett I get 96 ms combined input+output latency without any processing in between, so that's probably what made my ears bleed before. Tweaking the sample rate and buffer size gets me indeed single digit latencies in Ableton. So I'm definitely going to adjust the section about latency, thanks for this!

I'm a bit on the fence about what this means for the difficult latency calibration routine in the application. Ideally I could throw the calibration routine away, but then I require that users have ASIO installed, while the app now also works with non-ASIO drivers. And indeed Python itself might become a bottleneck (making this work in Python has been half the fun).