Tag: firefox

WebRender in Firefox 83 in Fedora 33 (KDE 5.20, X11)

I wanted to test out WebRender in Firefox now that it’s on the brink of being turned on by default in GNOME environments. Despite enabling gfx.webrender.all, about:support showed that WebRender wasn’t working and reported errors including Failed to load EGL library: FEATURE_FAILURE_EGL_LOAD_3 and Failed GL context creation for WebRender.

Fixing this in my environment (Fedora 33, KDE Plasma 5.20, X11, AMD Mesa) came down to simply installing libglvnd-gles.

I’m not sure if this is required for other hardware configurations or desktop environments or under Wayland. I like trying out the latter with each KDE Plasma release, but while things seem to be getting better, the number of crashes still makes it feel very far from being ready for prime time.

VA-API hardware video acceleration

A significant advantage of WebRender is that it enables support for VA-API hardware video acceleration. Just set flags media.ffmpeg.vaapi.enabled to true, media.ffvpx.enabled to false and environment variable MOZ_X11_EGL to 1 to give your CPU a nice rest.

In related news, I’m excited to see progress on this long-standing bug that should mean VLC’s VA-API option actually works under AMD Mesa. (Update: Mesa 20.3.2 is available for testing, and it’s working well.)

RealPlayer/RealDownloader poses as Firefox running on 64-bit Linux and sends HEAD and GET requests

I recently noticed some strange HTTP logs where a resource would be requested twice with two different User-Agent headers. In one case, the first request suggested the client was running Chrome on Windows, while the second request indicated that it was coming from Firefox on Linux. This didn’t make a lot of sense, so I did some digging.

The culprit turns out to be RealPlayer (and previously RealDownloader, a separate application that now seems to be abandoned). RealPlayer places an overlay over supported browsers (Internet Explorer, Firefox and Chrome and possibly others) that allows the user to save videos from web pages. It doesn’t seem to be a browser plugin as such – it runs in its own process and sends HTTP requests independently of the browser.

RealPlayer browser overlay

The software just happens to set the User-Agent header to something like Firefox running on 64-bit Linux. I sacrificed a virtual machine and installed all manner of RealPlayer software to try and reproduce this behaviour, and the latest version sends requests like the following:

My browser’s actual User-Agent header is:

Based on this blog post and this Yahoo! Answers question, the following User-Agent header was used by an earlier version of the software:

The Gecko build date and Firefox version number (but not the ‘rv’ token!) have been bumped up, but everything else (including the weird trailing ‘Chrome’ identifier) are the same.