Rpi/puredata zero lattency?


since it’s not cheap, I was wondering if pisound offered low to zero lattency before buy?
any demo ?

so far I use an usb behringer card and I can’t get rid of that damn lattency

I am planning to do HEAVY audio processing with puredata


Hi, there’s always going to be some latency. :slight_smile: Using I²S based audio card like Pisound of course helps reduce the latency compared to USB audio cards. Depending on your configuration settings and the kind of processing you do, you could expect latency between 2-5ms.

then how do boss pedal work ?
it always sound like it’s a bad idea to do DSP on a RPI

Conversion between analog and digital domains is always going to incur some latency.

in that matter…does pisound behave like a boss pedal where the latency is inaudible??

that’s all I wanna know

‘inaudible latency’ is hardly a quantifiable measure. :slight_smile: It really depends on personal preference. For me everything up to 5ms seems instant, 8ms or more can already be felt.

Using the settings on the ‘more stable’ side, you can get 5ms latency. If you’re careful and the kind of effect processing you’re doing allows it, you can try reducing the audio buffer size and/or increasing sampling rate, to reach 2ms.

The latency can be usably set very low. I typically run mine with just 64 sample block size. At 48kHz sample rate, that achieves under 3ms.

My set up on the Pi/Pisound runs: 3 parametric filters, 2 sweep filters, four delay lines, and reverb. That all very comfortably can run in this setup.

As @Giedrius said, perceptual latency is very dependent on what you are doing. For end-of-chain effects like the set up I have, the 3ms is not noticable. If you are doing heavy processing, especially anything involving time based effects (delay, glitch, slice, stutter, reverb, looping, etc…) you can tolerate much more.

Lastly, to answer your question about guitar pedals: Pure analog pedals have no audible latency (though there are phase delays - and these sometimes are of a concern when mixing). Many pedals are digital, and architecturally are no different than Pisound: convert to digital, send a block for processing, then convert back to analog. The latency is dominated by the size of the block used for processing, but processing in larger block sizes is more efficient. So the trade off is between cheaper DSP systems that need bigger block sizes and hence more latency - vs. more expense to bring the latency down. I’m sure pedals are all over the map in what they choose and what latency they have.

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any reason why nobody mentioned this ? https://blokas.io/patchbox-os

I’m not sure what you mean… low latency like @Giedrius and I have been discussing is possible with both Patchbox OS and straight Raspian OS.

My original set up was built before Patchbox OS was created… but now I have one Pi that runs it - and one that runs my original set up.

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I am trying patchbox, we’ll see, I’ll also soon order a pi sound if it’s not enough to get rid of raspbian/patchbox/whatever lattency

Ah, now I think I understand why you were asking about Pathcbox OS: Changing OS isn’t going to reduce the latency a USB Behringer audio interface has on your Raspberry PI. It is fundamental to the way the audio interface is designed.

It is only recently that USB interface in the lower price ranges have lower latency. The Focusrite Scarlett Gen 3 or later, for example has great latency for a ~$150 interface. But as @Giedrius started with, an I²S solution, like Pisound, will generally always have less latency.

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yeah, I’ll go for the pisound, good to gnow recent usb are getting better

thanks a lot for your precious help