The behaviour is different in unity7 and gnome-shell. In unity7 screen blanking is disabled during video playback. Tested on the same machine with same settings.
On unity7 I did the following test:
1. Set screen blanking to 2 min
2. Wait 2 min with nothing playing
-> The display goes black after 2 min
3. Play a netflix video in Chrome
-> The display does not go black after 2 min
The behaviour is different in unity7 and gnome-shell. In unity7 screen blanking is disabled during video playback. Tested on the same machine with same settings.
On unity7 I did the following test:
1. Set screen blanking to 2 min
2. Wait 2 min with nothing playing
-> The display goes black after 2 min
3. Play a netflix video in Chrome
-> The display does not go black after 2 min