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Old 05-05-2019, 09:05 AM   #1
HihiDanni
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Join Date: May 2019
Posts: 7
Default PulseAudio buffer size?

Hi there! I stumbled across Reaper out of curiosity while looking at updated Linux DAW offerings. Turns out this software now has a Linux version, which is pretty cool! But what really grabbed my attention is the fact that it is the first Linux DAW I've seen with PulseAudio support!

My setup is fairly ordinary/"consumer", just a custom-built PC with integrated audio, no professional audio hardware. I have a sound card that I used to use because it provided hardware audio mixing, thus allowing me to run multiple ALSA programs at once without needing PulseAudio, but due to issues with the drivers I had to stop using it. The result is that working with my previous DAW suddenly became a lot less fun. I had to manually start a JACK server before opening the DAW (or everything would mess up), and to get other applications playing audio I had to manually reroute them to the JACK server one-by-one via pavucontrol. Neither the DAW nor other applications had particularly good latency under this system, contrary to what is often said about JACK. It was honestly kind of miserable.

So now I've been trying out Reaper, and so far it seems pretty good for my use case (mostly VST-based). The PulseAudio support works in the sense that it outputs audio, it doesn't seem to Xrun, and other applications can play audio. But the latency leaves a little to be desired. It feels like there's about 150ms latency. Problem is, no matter what I set as the buffer size, it doesn't seem like my setting is honored. I can set it as low as 16 or as high as 2048 but the result is the same.

I do have a workaround for this - I can switch to ALSA, which means I can't play audio in other programs but the latency is much better. It's not a dealbreaker because Reaper makes it easy to get at the audio output driver settings so I can switch between the two on the fly, but it's still a nuisance. The ALSA output automatically suspends PulseAudio, but I feel like it shouldn't really have to. Overall I'd be happy with either the latency under Pulse getting fixed or the ALSA backend gaining an option for non-exclusive device use. After all, most applications use non-exclusive ALSA and this ends up getting mixed through PulseAudio via the compatibility layer, and they work fine. And I have quite a few programs with this setup that have very good latency compared to what Reaper's current Pulse support offers. Is this something that the developers could investigate?

One thing that seems curious to me - the ALSA backend is showing the correct value for latency in the menubar, but the Pulse backend is showing "~3.5/0.0 ms" for Pulse - see attached.
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