Drop video logos: a logo is a picture, never a clip

[ZombieHDGaming]

Why

Video logos were the only reason this plugin linked FFmpeg, and linking FFmpeg is what stops it loading in a newer OBS. readelf -d on a module built from master today:

NEEDED  libavcodec.so.60
NEEDED  libavformat.so.60
NEEDED  libavutil.so.58
NEEDED  libswscale.so.7

Those are hard dependencies on the exact FFmpeg majors the build machine had. OBS ships its own FFmpeg and moves it between releases; the release after a move, those names are files the loader cannot find and the whole module fails to load — every credit roll in every scene collection, gone, over artwork nobody has to use. Keeping the feature safely would have meant a hand-written runtime loader plus a version gate that turns the feature off anyway.

So the video path goes, all of it.

What's gone

• The ENABLE_VIDEO_LOGOS option and the entire FFmpeg block in CMakeLists.txt — no find_package, no linking, nothing to find at configure time.
• The libav decode path in AnimatedLogo.cpp: VideoDecodeContext, decodeWithFfmpeg, sws_scale scaling, frame-duration handling, the CLOSING_TIME_HAVE_FFMPEG define.
• animatedLogosSupportVideo() and videoLogoPatterns(), and the "Video" filter in the logo file dialog.
• The recogniser and everything it fed: isVideoLogoPath(), the container-extension list, the designer's documentUsesVideoLogos() scan, the file-dialog warning, and the Designer.VideoLogoUnsupported string.

Nothing in the plugin knows what a video file is any more. A video dropped into a logo slot is an unreadable picture like any other — LogoCache logs that it could not decode the file, and the slot draws its placeholder box.

419 lines removed, 42 added.

What's unchanged

GIF, APNG and animated WebP animate exactly as before, through Qt — which is where nearly every credit-roll logo comes from. The frame caps, playback settings (loop, start-on-entry, speed), per-frame shadows, the animation cache and the whole strip path are untouched. The logo path is now Qt's image decoders and nothing else.

Testing

• Full plugin module and test harness both build clean.
• The built module now links libobs, obs-frontend-api, Qt (Core/Gui/Widgets/Svg) and the C/C++ runtime — nothing more. No libav*, no libswscale, against master's four.
• 49 suites, 3002 checks, 0 failures.
• clang-format (19) and gersemi clean.

Docs

README's logo and build sections, and ARCHITECTURE's Animated logos section, file map and known-limits list now say a logo is a picture and why — so the next person who reaches for libav finds the reason not to before they write it.