"Analogue" distortion on Dolby Atmos?

[duckofdeath]

I'm getting some sort of intermittent audio distortion and I only think it happens on videos with a Dolby Atmos sound track. The distortion sounds like a good old cassette tape speed problem. Almost like the sound is slowing down for half a second, similar to if you'd put your finger on a cassette reel while it's playing. I don't know if this is an issue with the player, codec or something else. I have reinstalled my PC completely, but I'm still getting the distortion. It happens maybe 3-4 times during playback of a normal length movie.

File types I've tested and getting the same issue on are x264 and x265 containers with a TrueHD Dolby Atmos sound track.

I only use Dolby Atmos for Headphones on my PC.

My PC specs:
Windows 10 Pro x64
VLC 3.0.0 x64. I have also tried 3.0.1 and the 4.x beta, all with the same issue.
Intel Core i5-4440 8GB
Radeon RX480 4GB graphics
Asus Xonar DSX sound card
Dolby Atmos for headphoens installed and enabled.

I don't have any other third part media players or codecs installed on my PC. The issue happens no matter if there's something else running on my PC. I have a 75Hz freeSync monitor, but the issue happens if I turn off FreeSync and also if I lower the refresh rate to 60Hz.

[Rémi Denis-Courmont]

Is it happening with or without pass-through? VLC sometimes resamples to compensate for drift, but of course only without pass-through.

[duckofdeath]

All my codec (audio and video) settings are at default. I'm using the built-in sound card, outputting to a headphone amp. So, no audio pass-through.

(edit: clarification. By built-in sound card I mean I'm using a PCI-Ex Asus Xonar DSX card )

[Jean-Baptiste Kempf]

Have you tried with and without headphones?

[duckofdeath]

I'll do some further troubleshooting, to see if it's the media. With both the integrated motherboard audio codec and with bluetooth audio....

[robUx4]

Maybe we detect we can "passthrough" Dolby since you have ` Dolby Atmos for headphoens installed and enabled.` ?

Can you provide some logs of the playback that has the problem ?

[duckofdeath]

Sorry for not coming back on this. I decided it has to be the media files using harsh fix to correct sync between video and audio on their transcoding.