mpReverb seems deviating waveform on short-looped samples

[Fabrice]

Hi there!

I like mpReverb as I find it really smart and convenient, but recently I had this issue on a track:

You can see that the waveform deviate on the top.

if I go with only with a chiptune super-short handdrawed sample and use mpReverb with “cavern warm” preset, I have this extrem result:

I first tough that was my synths or another setting, but after some tries, I remplace mpReverb by the old Ambience reverb vst, so then all become okay:

Also I’ve tried with samples a bit more long and VST, then this is ok, no issues with that, seems only to be on shorty samples like this, when click on “draw” on an empty slot in sample editor:

In Renoise 3.3.1 (and tried also in 3.2.1)

[OopsIFly (a brave star was da far eye)]

What if you place a highpass filter with very low cutoff or dc blocker before the reverb? The waveform looks like it will induce a dc shift that can be removed. I also noticed some renoise fx having troubles with dc shifted input.

[Fabrice]

Effectively when I place a digital filter (a bit cutted in the basses) before or even after the mpReberb, then the signal stay constant.

before or even after the mpReberb, this seems that work same. Rather particular.

[OopsIFly (a brave star was da far eye)]

before fixes the input that makes the reverb derail, after it fixes the error the reverb produces. I’d rather keep it before, else the error might accumulate and maybe even crash the reverb after an unknown time (I know the diode filter can be “broken” this way).

[Bluethereal (Bryan)]

I’d also like to say that I can’t move the Mixer EQ sliders without my output clipping to earrape hell (with DC values of 1 the whole time), EQ 5 is always fine, tho.

[ffx]

It is because of a dc offset in the source and then the reverb uses a feedback buffer, so with any further feedback loop, the dc offset will increase (since mixed together), or so.

Found this filter settings useful as DC offset killer, but not sure if it works in any case:

Copy paste code

<?xml version="1.0" encoding="UTF-8"?>
<FilterDeviceClipboard doc_version="0">
  <DeviceSlot type="DigitalFilterDevice">
    <IsMaximized>true</IsMaximized>
    <IsSelected>true</IsSelected>
    <SelectedPresetName>dc offset fix</SelectedPresetName>
    <SelectedPresetLibrary>User Library</SelectedPresetLibrary>
    <SelectedPresetIsModified>false</SelectedPresetIsModified>
    <IsActive>
      <Value>1.0</Value>
      <Visualization>Device only</Visualization>
    </IsActive>
    <OversamplingFactor>1x</OversamplingFactor>
    <Model>Chebyshev 8n</Model>
    <Type>
      <Value>3</Value>
      <Visualization>Device only</Visualization>
    </Type>
    <Cutoff>
      <Value>0.00799999759</Value>
      <Visualization>Device only</Visualization>
    </Cutoff>
    <Q>
      <Value>0.125</Value>
      <Visualization>Device only</Visualization>
    </Q>
    <Ripple>
      <Value>0.0</Value>
      <Visualization>Device only</Visualization>
    </Ripple>
    <Inertia>
      <Value>0.0078125</Value>
      <Visualization>Device only</Visualization>
    </Inertia>
    <ShowResponseView>true</ShowResponseView>
    <ResponseViewMaxGain>18</ResponseViewMaxGain>
  </DeviceSlot>
</FilterDeviceClipboard>

[Fabrice]

Thanks, well at this point I’m not really understanding about these technical things
At the moment I keep the solution with the digital filter before reverb, seems more easy to apply.