Specify vp8 encoder when doing linux stream test

[lukehb]

As the stream test occurs on GHA that has no GPU we must specify use of vp8 so we hit a CPU encoding code path.

Relevant components:

• Github actions

Problem statement:

The Linux stream currently streams a black stream.

Solution

This PR explicitly sets vp8 encoding so we use a cpu encoding code path. This is necessary as the Github actions we use do not have a GPU attached.

[lukehb]

It doesn't actually fix it though....

[PhDittmann]

If you're using a packaged UE 5.4.x application, this topic might be interesting: https://forums.unrealengine.com/t/does-vp8-vp9-work-in-packaged-pixelstreaming-builds-linux/1977282

[lukehb]

@PhDittmann I just replied to your message there (although pending approval).

It seems 5.4 was shipped with ABI mismatch between WebRTC and VPX on Linux.

Would you mind transplanting this into your Linux UE source, recompiling, and repackaging: https://drive.google.com/file/d/1Ny8z9I2KzK_ywoBEnQnP0rVBU-vM-I4G/view?usp=sharing

[PhDittmann]

I replaced the libs in Engine/Source/ThirdParty/WebRTC/5414/Lib/Linux/x86_64-unknown-linux-gnu/Release and it works! (except for Firefox)

Tested with UE 5.4.2, streaming within the UE Editor and after packaging, up to 3 clients simultaneously, VP8 and VP9, Brave, Chrome, Duckduckgo, and Firefox.

• libdenormal_disabler.a is identical.
• libdenormal_disabler.a, libfield_trial.a, libmetrics.a and most of the includes don't have u+w permission anymore.
• Files have Windows line-endings
• NOTE: Sometimes it crashes during negotiation. Needs further investigation.

Mozilla Firefox 129.0 (64-bit) on Fedora and Android stops at 'WEBRTC CONNECTION NEGOTIATED'. The console shows the error Uncaught (in promise) DOMException: Cannot set ICE candidate for level=0 mid=0: No such transceiver.

[lukehb]

@PhDittmann That is great news! Thanks so much for testing!

Files have Windows line-endings

Yeah sorry about that, I am on Windows when I sent you those and P4 did me dirty.

Mozilla Firefox 129.0 (64-bit) on Fedora and Android stops at 'WEBRTC CONNECTION NEGOTIATED'. The console shows the error Uncaught (in promise) DOMException: Cannot set ICE candidate for level=0 mid=0: No such transceiver.

Very curious. Are you certain you have this frontend change applied? #204

[PhDittmann]

You're right. I tested with an outdated version. PixelStreamingInfrastructure 5.4-1.1.7+ solves the Firefox issue.

Thanks for your quick responses!

[lukehb]

Closing for now, we will revisit if we get it working.