1349619 - YouTube audio is not played back

Status: RESOLVED DUPLICATE of bug 1348432

(Core :: Audio/Video: Playback, defect)

Description

[Emil Ghitta, QA [:emilghitta]]

[Affected versions]:
Firefox 55.0a1 (Build Id:20170316030211)

[Affected platforms]:
Windows 10 64bit
MacOs 10.11 
Ubuntu 16.04 64bit. 

[Steps to reproduce]:
1. Launch Firefox.
2. Access the https://www.youtube.com/ webpage.
3. Open a random video,
4. Open another video (in the same tab).
5. Observe that the audio is not working and the Sound Tab button disappears.

[Expected result]:
The audio is properly played back.

[Actual result]:
After following the up mentioned steps two actual results can be observed:
1. The Sound Tab button disappears shortly after opening a video.
2. No sound can be heard from the video.

[Regression range]:
This seems to be a recent regression:

Last good revision: 06e12bb9737bfdb5df0a8282c82e871f7f525951
First bad revision: 23cfb067130f6225f9b63c752c349fd607e69c46

Pushlog:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=06e12bb9737bfdb5df0a8282c82e871f7f525951&tochange=23cfb067130f6225f9b63c752c349fd607e69c46


[Additional information]:
Please access the following link to observe the reproduced issue:
https://drive.google.com/open?id=0B94iuIVMr-TEV3Vnb0kzYzUyY0U