Places where I've observed this behaviour: * The 4th video in the '''description''' of https://store.steampowered.com/app/1363080/Manor_Lords/ (ignore the media carousel at the top of the page) * This video https://dolphin-emu.org/m/user/blog/progress-report/2603/rebelstrike-texturestreaming-av1.webm that's loaded in an embed at https://dolphin-emu.org/blog/2026/03/12/dolphin-progress-report-release-2603/ When these videos are in view and playing, they're decoded using the CPU and the browsers frame rate tanks (heavy/laggy scrolling when scrolling with mouse scroll wheel), I have a Geforce 3070 which includes support for AV1 decoding so I'm not sure what's happening. AV1 videos found on Youtube like https://www.youtube.com/watch?v=foqVJq-XPTg are fully hardware accelerated by the GPU (Stats for nerds confirms it's playing an AV1 copy) and doesn't exhibit any performance issue. GPU usage is monitored by Task Manager in Windows 10. For the problematic videos the GPU Decoding is at 0% with a workload being spread across many of the CPU cores. For the non-problematic 4K video the GPU Decoding is around 60-70% and no workload is distributed across multiple CPU cores.