Stereo Tool

When listening to my OGG Vorbis stream in StereoTool (384kbit/s, HTTP stream via libVLC, follow main sample rate) through VLC media player (3.0.16) on a client Windows PC, the frequency shifts up about 18Hz, then down again to the correct frequency. This happens only when I open/connect to the stream.
I attached a gif showing a frequency counter while streaming a 1kHz sine wave.
This happens while bypassing ST as well as while the processing is active.
What causes this behaviour and does anyone know how to deal with it?

Input/Output Sync ON ?

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control point
control point2

All my physical sound devices are disabled (no Normal, FM or LQLL, only stream). The settings are thus greyed out, but still set to 'off' and 0% relative adjust.
The behaviour only occurs in OGG streams, MP3 and FLAC are fine.

Then idk. Did you try other programs to stream and check same? ALso if other codecs are fine, that indecates that something in VLC's OGG lib is doing something.

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control point
control point2

I think that VLC Media Player resamples the audio to sync with the incoming signal. So that might be what's happening here, not sure. The encoding of the stream doesn't change, so if this happens when you start the player, not the encoder, then it's definitely something in VLC Media Player.