With my 2012 rMBP (first gen retina, with nVidia GT 650M) I cannot play video on various websites using Firefox since about a year or two. Did an OS reinstall,

With my 2012 rMBP (first gen retina, with nVidia GT 650M) I cannot play video on various websites using Firefox since about a year or two. Did an OS reinstall, switched to nVidia native drivers, nothing helps. It plays the first second of video, then freezes, audio does continue. Youtube does work, but performance is poor.