I'm not sure, but I think the audio was added in by the fan that shot the video.
More of the characters revealed can also be seen below.
The Warcraft trailer that was shown was about 8 minutes in length which opened with the Horde featuring the orcs.
Update: Duncan Jones revealed the Warcraft trailer won't be releaed until November.
Blood was spilt for this... "Today has all been about SDCC. Now I want to let you know the trailer will finally release to ALL in November"— Duncan Jones (@ManMadeMoon) July 12, 2015
Warcraft has a June 10, 2016 release directed by Duncan Jones starring Ben Foster, Toby Kebbell, TravisbFimmel, Dominic Cooper, Paula Patton, Clancy Brown and Daniel Cudmore.
Legendary’s WARCRAFT is a 3D epic adventure of world-colliding conflict based upon Blizzard Entertainment’s globally-renowned universe. Directed by Duncan Jones (Moon, Source Code) and written by Charles Leavitt and Duncan Jones, the film is a Legendary Pictures, Blizzard Entertainment and Atlas Entertainment production. The producers are Charles Roven, Thomas Tull, Jon Jashni, Alex Gartner and Stuart Fenegan. Jillian Share, Brent O’Connor, Michael Morhaime and Paul Sams serve as executive producers. Rob Pardo, Chris Metzen, Nick Carpenter and Rebecca Steel Roven co-produce. WARCRAFT will be released by Universal Pictures
Fighting for The Alliance, Warcraft features Dominic Cooper as King Llane Wrynn, Travis Fimmel as Anduin Lothar, Ben Foster as Medivh, Ben Schnetzer as Khadgar, and Ruth Negga as Lady Taria, and on the side of The Horde is also Clancy Brown as Blackhand, Toby Kebbel as Durotan, and Daniel Wu as Gul’Dan, with Paula Patton’s Garona caught in the middle.