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.
PortAudio M1 Latency
Link post
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 fromdefaultHighOutputLatency
todefaultLowInputLatency
I see: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
afterbrew 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.
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