depend how old is your MBP. Anything before 2010 is unable to play sound through the display port. But if yours is newer, you can go System Preference>Sound>Output and select the output.
Tried before on my 2011 mbp. No sound too. In the end got appletv to stream instead
Mine says the selected device has no output control...how ?
it is normal that your MBP cannot control the TV. but once you select the tv, use your volume control on the tv to control the volume.
ok, for some reason, it manage to work again. thanks !