Crackling at low latencies on M1 Mac, recording audio with no plugins

[RichardT]

I'm not sure there is an issue as such - you may just need to run at 44.1 with a buffer of 64.

[James Perrett]

Checking the activity monitor showed CPU usage around 50% from Reaper -- which seemed high to me, considering I'm doing a minimal test of audio-only recording -- but still not high enough to cause buffer issue. No significant competing processes appeared.

That is ludicrously high. I'd expect it to be well under 1%. I've just checked and my setup uses no more than 2% CPU when recording a stereo track with a 64 byte buffer and that's on a 10 year old i7 machine. So yours should be well under that. At higher buffer settings it only uses around 0.2% CPU.

[Guest]

On a Mac that cpu percentage is the percentage of a single core not the % of the whole cpu.

I just did a quick test here with Reaper and recording a single track at 32 buffer I get 26%-29% cpu/core usage on an I7 4.5ghz.

Claz, are you running the Intel or ARM64 version of reaper?

[Stig Ø]

As mentioned upthread, an M1 Mac is a beast and should not be panting because of the recording, low buffer or not. Time Machine is notorious for interrupting other processes, and even if the CPU has a lot more to go on, it won’t help if the cycles aren’t used where they’re needed. Disabling Tme Machine is easy enough to try. To me, it sounds like a driver issue, or possibly compatibility issues with Reaper. Just for fun, how does Garage Band recordings work on your setup?

[claz]

Just an update: while never solved completely, googling the problem does seem to reveal that folks have problems with buffers below 64 on M1 Macs, despite the SOS review (conducted on Intel, presumably), getting down as low as 16, if I remember correctly.

So, looks like a driver issue. I guess this is why folks here swear by RME!

[genecleaner]

Hi!
Did you manage to resolve the issue?
I am experiencing the very same problem. I have the same hardware as you have: Macbook M1 Max (although the 32 Gb RAM version) + Motu M4, latest drivers etc. I use FL Studio. I can run everything (instruments, recorded audio, and effects) with very low latency using the M1 Max internal audio card, while the Motu M4 will give choppy and crackle sounds. This is really a disappointment.
Hope to hear a solution.
Best regards,
genecleaner, Sweden

[genecleaner]

ISSUE SOLVED

After trying many, many different things, I search and read more in forums and found that some people managed to solved the crackling issue by using the USB-C-to-A cable supplied in the motu M4 box instead of an USB-C-to-C cable (which should in theory work). So, I tried this, connecting the motu M4 through to my M1 Max through an Apple USB adaptor and using the right-side USB C port on the Macbook. This has completely fixed the issue for me (so far).

Hope this will work for other as well.