Playing youtube (720p) videos on my laptop is impossible. The CPU usage goes up to 100%, because looks like firefox is not using the hardware acceleration that is available on my gpu. My processor is weak to do the decoding on it's own (it's an old AMD athlon x2 ql-62) but the gpu should be good enough for h264 decoding (ati radeon hd 3200). In settings, the hardware acceleration checkbox is checked. Microsoft Edge (windows 10, amd64) is able to use the gpu acceleration, so it streams 1080p from youtube without dropping frames.