AI: THE SOMNIUM FILES - nirvanA Initiative (1449200)

Compatibility Report

• Name of the game with compatibility issues: AI: The Somnium Files -nirvanA Initiative (original AI has this issue too, I think.)
• Steam AppID of the game: 1449200

System Information

Steam Deck, baybee
Also tested on my Desktop running Arch

I confirm:

• that I haven't found an existing compatibility report for this game.
• that I have checked whether there are updates for my system available.

Only gonna put the relevant part of the logs:

winegstreamer error: decodebin1: Your GStreamer installation is missing a plug-in.
winegstreamer error: decodebin1: ../src-gst_base/gst/playback/gstdecodebin2.c(4719): gst_decode_bin_expose (): /GstBin:bin1/GstDecodeBin:decodebin1:
no suitable plugins found:
Couldn't set avdec_h264-0 to PAUSEDCouldn't set avdec_valve_h264-0 to PAUSED

Symptoms

So, okay, here's the real reason I'm opening this issue: This only seems to impact some users. I have been harassing random game journalists on Twitter (and people over @ the AI Steam discussions) and it works perfectly fine on most people's steam decks.

But... It doesn't on mine. I get the colored bars screen (since the video cannot be played). I've tried everything. I have used several versions of Proton and Proton GE (the latest GE displays it, but distorted). I've used Experimental. I even wiped my Steam Deck, made a new user, logged into the Deck with that user, then family shared the game and logged out of my (main) user so that nothing was ever installed by me with that user.

Still no dice (the wipe was from installation media, too!)

The install on the wiped device was before installing anything else, too.

Here is a link from another user for exactly what it looks like.

Reproduction

Above answers that too. More than happy to provide ANY info. I'd love to dig deeper but I've already spent several hours on this and it'd be easiest if I just had a deck that it works on.

Start by reproducing the game on Steam Deck or Arch and capture the reported winegstreamer and GStreamer errors. No source file or test is named; done means the game's videos render correctly without the missing H.264 plugin errors.