I recently tried to get my whistle-controlled bass synthesizer working on my Mac, as a backup to my Raspberry Pi version. [1] It's written on top of PortAudio, a cross-platform audio library, so getting it to compile and run was mostly a matter of getting the library installed, which went quickly. Unfortunately, the latency was far too high to be useful as a real-time musical instrument.
Testing with PortAudio's demo paex_read_write_wire.c
[2] with suggestedLatency changed from
defaultHighOutputLatency to
defaultLowInputLatency I see:
Input device # 2.
Name: MacBook Pro Microphone
LL: 0.0528542 s
HL: 0.0621875 s
Output device # 3.
Name: MacBook Pro Speakers
LL: 0.0187083 s
HL: 0.0280417 s
Num channels = 1.
This is 72ms of round-trip latency, or 3,156 samples. You can easily
hear the latency, and it's pretty painful for live music. It's even
higher than the 67ms I see in the web
browser. [3] Changing FRAMES_PER_BUFFER from the
default of 512 to 128 doesn't have any effect, so I think this is
lower level buffering.
I also tried with a Scarlett 2i2
audio interface, and latency wasn't any lower. Setting
PA_MIN_LATENCY_MSEC also doesn't do anything. I'd try
turning off ambient noise
reduction but this option doesn't exist for
M1 Macs.
I don't have this problem when running the Reaper DAW so it's definitely possible to get low latency on this machine. I wonder if there's some kind of default processing running on the audio system, and Portaudio doesn't ask to turn it off?
(I could go back to running my code as a Reaper plug-in, but I'd much rather have something stand-alone.)
[1] In setting up at Adirondack
Dance Weekend I couldn't find one of my two Pis. It turns out I'd
missed that it was under my mixer and forgotten to pack it:
[2] Built with gcc -I/opt/homebrew/include/ -L/opt/homebrew/lib/
-lportaudio paex_read_write_wire.c -o paex_read_write_wire
after brew install portaudio to get the library.
[3] Suspiciously this is quite a bit higher than I used to see on my Intel Mac. I used to get 19ms in Chrome and 14ms in Firefox, and I'm now getting 67ms in Chrome and 64ms in Firefox.