JFTR after some debugging we have verified that the problem is the VA- API decoder not in webkitgtk
After enabling debug, we could see the following errors: $ GST_DEBUG=3,webkit*:5 /usr/lib/x86_64-linux-gnu/webkit2gtk- 4.0/MiniBrowser ... 0x7fa5cc0f8770 ERROR vaapivideomemory gstvaapivideomemory.c:259:gst_video_meta_map_vaapi_memory: failed to make image current0:00:33.398184225 23681 0x7fa5cc0f8770 ERROR default video-frame.c:161:gst_video_frame_map_id: failed to map video frame plane 0 That was confirmed later on by not whitelisting the VA-API module. GST_PLUGIN_LOADING_WHITELIST="gstreamer:gst-plugins-base:gst-plugins- good:gst-plugins-bad:gst-libav" then the playback starts seamlessly. BR
