Is Audio/Video Delay safe?

Delays audio or video playback to help synchronize media in the browser.

This extension runs locally and lets you enable or disable playback delay from its interface. It delays video by default, can switch to delaying audio, and lets you enter a delay amount in milliseconds without refreshing the page. The description notes that DRM video delay shows a black screen and subtitles are delayed only on YouTube and JW Player videos.