This function modifies the volume of the video specified by id. If
the video is currently playing, the volume will be modified on-the-fly
which can be used for sound fades etc. The volume argument can also be
a string containing a percent specification, e.g. "50%".
Inputs
id
identifier of the video
volume
new volume for the video (range: 0=mute until 64=full volume
or percent specification)