That's right press and hold the navigation keys to turn up/down the volume and left/right to seek forward or reverse a playing video (or vice-verca depending on the screen orientation). I googled a bit to find that this is mentioned only on a few forums. Maybe this will be helpful to someone out there.Cheers Kiara.
BTW , some more shortcuts
Me,Message Reader
Darla
E-Series.org
Gallery shortcuts