Custom Filter reliably glitches in URP and HDRP projects

[jinpavg]

Loading a RNBO plugin as a custom filter using the OnAudioFilterRead() callback reliably glitches after a few seconds in projects using the Universal Render Pipeline. In the dropbox link here, you can find two projects, identical except one is using the built-in renderer and the other is using the URP. I've also attached the RNBO patch (it's the rnbo~ @title one-parter) below.

https://www.dropbox.com/s/yt712g2noj7knlw/AudioGlitch.zip?dl=0

gen-two-parter.zip

[jinpavg]

Okay, I can refine this. In an HDRP project, the custom filter, when paired with an AudioSource with spatial blend set fully to "3D" will have the same glitches as one in a URP project.

[x37v]

Can you see if this happens when you build the project and run outside of the editor?

[jinpavg]

Okay! this build (which should run on Windows), does not glitch like it does in-editor! So it does seem to be an editor issue.

GenAudioGlitchURP.zip

[jinpavg]

My Unity version is: 2021.3.21f1

[x37v]

@jinpavg are there more repro instructions for the glitch? I have run both "GenAudioGlitch" and "GenAudioGlitchURP" in my windows VM and the glitch isn't reliable.. sometimes, sporatically, like at most once a minute or two, I get a retrigger like stutter.. Is that what you're talking about? BTW, I noticed that the URP project wasn't set to render in the background, so I updated that.

[jinpavg]

This doesn't seem to be a RNBO issue, but rather a Unity Editor issue. I can repro this with a completely empty URP project and the following script:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

[RequireComponent(typeof(AudioSource))]
public class SineTest : MonoBehaviour
{

    public float gain = 0.5F;

    private double phase = 0.0;
    private double sampleRate = 0.0F;

    void Start()
    {
        sampleRate = AudioSettings.outputSampleRate;
    }

    void OnAudioFilterRead(float[] data, int channels)
    {
        double sample = AudioSettings.dspTime * sampleRate;
        int dataLen = data.Length / channels;

        int n = 0;
        while (n < dataLen)
        {
            float x = gain * Mathf.Sin((float)phase);
            int i = 0;
            while (i < channels)
            {
                data[n * channels + i] += x;
                i++;
            }
            phase += 0.03;
            n++;
        }
    }
}