I can make a call using Google Hangouts from either the Google Page directly and via Extension, but I do not have any sound. To clarify, I cannot hear the person I called, but they can hear me. I have reproduced this consistently and even called myself (PC to Cell) with exactly the same result. Sounds from other sources such as youtube while in Opera works fine. Using Hangouts via Chrome works fine.
Version: 49.0.2725.39 (PGO) - Opera is up to date
Update stream: Stable
System: Windows 8.1 64-bit (WoW64)