PCM 5.1 audio playback using VLC 3.0.x on Windows/Mac to stereo headphones

[jharle]

Hello!

I have an audio playback issue that I'd like to understand. The issue has been reproduced on many different computers running VLC 3, on Windows and macOS.

I've recently begun using DVDFab to transcode [the video of] music concerts, while using DVDFab's "copy audio" (passthrough) feature, in an attempt to leave the audio untouched. I have noticed that on source material that uses PCM 5.1 audio, playback (using VLC with headphones) of the DVDFab output sounds different than the source material. Specifically, the "position" of the artists' vocals in the DVDFab output sounds heavy "left" instead of "centered."

I originally thought that DVDFab was not truly passing through the audio correctly - changing levels on the audio track(s) or something.

However, when I perform a comparison using different players (including MPC-HC, and browser playback), the two files sound identical, with no difference in "vocal positioning" that I can detect.

Is this just simply a matter of VLC decoding the PCM 5.1 and playing to a stereo output differently from other players, and should just be ignored? In other words, playback of PCM 5.1 to stereo headphones is known to cause weirdness like this?

Thanks for any help!