Bugzilla

Thanks for the report! (layers.acceleration.force-enabled is deprecated, only WebRender matters going forward.)
* Basic compositor (software rendering) has partial present, WebRender doesn't have it yet due to missing support in Mesa:
bug 1648799, bug 1625070 and https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6132 are about this.
* The video is software-decoded. Linux VAAPI hardware video decoding is being developed in bug 1610199.
You can try it out with the following steps:
Download https://nightly.mozilla.org and start it always with `$ MOZ_X11_EGL=1 path/to/firefox`. Open about:config, set the following prefs and restart Nightly afterwards: gfx.webrender.all=true (OpenGL rendering), media.ffmpeg.vaapi.enabled=true (hw decoding), media.ffvpx.enabled=false (vp8/9 hw decoding).
With `$ vainfo` you can see which codecs are supported by your GPU.
Optionally you can install the intel-gpu-tools package and launch intel_gpu_top as root to see hw decoding workload.
With https://addons.mozilla.org/en-US/firefox/addon/enhanced-h264ify/ you can disable codecs that are not supported by your GPU (e.g. disable VP8/VP9/AV1 if only h264 is supported).
If you have multiple GPUs (bug 1588904), you might need to set another env var: MOZ_WAYLAND_DRM_DEVICE=/dev/dri/renderD129 (for x11/wayland).

Thanks for the report! (layers.acceleration.force-enabled is deprecated, only WebRender matters going forward.)
* Basic compositor (software rendering) has partial present, WebRender doesn't have it yet due to missing support in Mesa:
bug 1648799, bug 1625070 and https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6132 are about this.
* The video is software-decoded. Linux VAAPI hardware video decoding is being developed in bug 1610199.
You can try it out with the following steps:
Download https://nightly.mozilla.org and start it always with `$ MOZ_X11_EGL=1 path/to/firefox`. Open about:config, set the following prefs and restart Nightly afterwards: gfx.webrender.all=true (OpenGL rendering), media.ffmpeg.vaapi.enabled=true (hw decoding), media.ffvpx.enabled=false (vp8/9 hw decoding).
With `$ vainfo` you can see which codecs are supported by your GPU.
Optionally you can install the intel-gpu-tools package and launch intel_gpu_top as root to see hw decoding workload.
With https://addons.mozilla.org/en-US/firefox/addon/enhanced-h264ify/ you can disable codecs that are not supported by your GPU (e.g. disable VP8/VP9/AV1 if only h264 is supported. But disabling VP9 means that you can't play back videos above 1080p).
If you have multiple GPUs (bug 1588904), you might need to set another env var: MOZ_WAYLAND_DRM_DEVICE=/dev/dri/renderD129 (for x11/wayland).

Thanks for the report! (layers.acceleration.force-enabled is deprecated, only WebRender matters going forward.)
* Basic compositor (software rendering) has partial present, WebRender doesn't have it yet due to missing support in Mesa:
bug 1648799, bug 1625070 and https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6132 are about this.
* The video is software-decoded. Linux VAAPI hardware video decoding is being developed in bug 1610199.
You can try it out with the following steps:
Download https://nightly.mozilla.org and start it always with `$ MOZ_X11_EGL=1 path/to/firefox`. Open about:config, set the following prefs and restart Nightly afterwards: gfx.webrender.all=true (OpenGL rendering), media.ffmpeg.vaapi.enabled=true (hw decoding), media.ffvpx.enabled=false (vp8/9 hw decoding).
With `$ vainfo` you can see which codecs are supported by your GPU.
Optionally you can install the intel-gpu-tools package and launch intel_gpu_top as root to see hw decoding workload.
With https://addons.mozilla.org/en-US/firefox/addon/enhanced-h264ify/ you can disable codecs that are not supported by your GPU (e.g. disable VP8/VP9/AV1 if only h264 is supported. But disabling VP9 means that you can't play back videos above 1080p).
If you have multiple GPUs (bug 1588904), you might need to set another env var, e.g.: MOZ_WAYLAND_DRM_DEVICE=/dev/dri/renderD129 (for x11/wayland).

Thanks for the report! (layers.acceleration.force-enabled is deprecated, only WebRender matters going forward.)
* Basic compositor (software rendering) has partial present, WebRender doesn't have it yet due to missing support in Mesa:
bug 1648799, bug 1625070 and https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6132 are about this.
* The video is software-decoded. Linux VAAPI hardware video decoding is being developed in bug 1610199.
You can try it out with the following steps:
Download https://nightly.mozilla.org and start it always with `$ MOZ_X11_EGL=1 path/to/firefox`. Open about:config, set the following prefs and restart Nightly afterwards: gfx.webrender.all=true (OpenGL rendering), media.ffmpeg.vaapi.enabled=true (hw decoding), media.ffvpx.enabled=false (vp8/9 hw decoding).
With `$ vainfo` you can see which codecs are supported by your GPU.
Optionally you can install the intel-gpu-tools package and launch intel_gpu_top as root to see hw decoding workload.
With https://addons.mozilla.org/en-US/firefox/addon/enhanced-h264ify/ you can disable codecs that are not supported by your GPU (e.g. disable VP8/VP9/AV1 if only h264 is supported. But disabling VP9 means that you can't play back videos above 1080p on YouTube).
If you have multiple GPUs (bug 1588904), you might need to set another env var, e.g.: MOZ_WAYLAND_DRM_DEVICE=/dev/dri/renderD129 (for x11/wayland).