Hi, my Firefox doesn't have support for H.264 decoding, although ffmpeg and other software compiled with support for it. According to https://www.youtube.com/html5 there is no H.264 and MSE & H.264 support. On pages with html5 <video> tag with type="video/mp4" Firefox tells "Video format or MIME type is not supported". At about:support page there is line: "Supports Hardware H264 Decoding = No; Failed to create H264 decoder". I have recompiled Firefox with --enable-debug, and now I see the error "[6748] WARNING: Unable to create a decoder, no platform found.: file /var/tmp/portage/www-client/firefox-49.0/work/firefox-49.0/dom/media/platforms/PDMFactory.cpp, line 153". Video driver is the nvidia proprietary driver. I also ask this question in this thread (with additional info related to distrib) https://forums.gentoo.org/viewtopic-t-1054580.html. Please help.