HD videos are slow

[jrpc2000]

When I download HD videos on You Tube (720p or 1080p) they are too slow (actually the sound is not synced with the image). This happens only with Mozilla or Chrome Google, not with Intrnet Explorer. How can I fix it?

 

[popatim]

Possibly you need to update Adobe Flash player in Firefox but since Chrome has Flash built in you would need to update the whole browser to get the latest version.