You will need to install a user script manager extension to install this script.
Personal script i share with you.
As the Name said: This script AUTO Play the video. TEST link: NEW SET " VICE-CITY "
▶ Work well with this 2 Userstyles (by me):
▶ And for a dark gray flavour: Flickr WideScreen - Dark & Grey
OR ▶ NEW (2020.04): To install all parts of "Flickr Widescreen - ALLinONE TOTAL" at once, you can use my userscript [Greasyfork]: Flickr WideScreen - BigONE v.120 - TEST UserCSS style
Greasy Fork now supports User CSS as defined here for use with Stylus or as UserScript, read: [Beta] User CSS support
Idea found in Stackoverflow : http://stackoverflow.com/questions/12252701/how-do-i-click-on-this-button-with-greasemonkey?lq=1 With a Library /script of Brock Adams waitForKeyElements (Thanks to him!): https://gist.github.com/raw/2625891/waitForKeyElements.js