Created attachment 8849096 [details] Recording #10.mp4 Tested on Mac OS X 10.12, Windows 10 x64 with FF Nightly 55.0a1(2017-03-20) Here are the scenarios for reproducing this bug: STR 1: 1. Open a youtube video and let it play for a few seconds. 2. Click on next video button ( >| ) 3. The next video starts Expected results: You have audio output. Actual results: The audio is not outputted. Note: If I click again on next video button, the third video, doesn't have sound. This happens also when I click on skip the ad button, the video that start doesn't have sound. If I refresh the page the audio is outputted. Please see the attached video, for a better understanding. STR 2: 1. Play any video on youtube 2. Mute the video 3. Press on the next video button (>|). 4. The next video that starts is on mute, unmute the video Expected results: The audio is outputted. Actual results: The audio is not outputted.