Upload a video file into a course as a file resource - set the Display option for it to "Open"
Click on the resource
You should see the video in your browser.
Add "?preview=bigthumb" onto the url in your browser
You should see a video icon (without this patch you get nothing).
MDL-40759 switched a lot of icons over to the font awesome icon library.
MDL-58356 reverted these back to the standard PNG set that was used previously - however it did not revert the preview generation code to use the png's (which exist) instead of svg's (which don't).
is a regression caused by
MDL-40759Use the Font Awesome icon font for all icons in Moodle
Closed
will help resolve
MDL-58356Dont use font-awesome for file-type icons
Closed
MDL-60255Media Gallery Thumbnails are not being displayed for video and audio content