I think there is a small shift with the display of the subtitles with the video played in Wikimedia Commons. I discovered that, by working on https://commons.wikimedia.org/wiki/File:SRINIVASA_RAMANUJAN-_The_Mathematician_%26_His_Legacy.webm
I started to copy the English subtitles, so that it will be easier to translate in other languages from English. We can see the shift for example at 0:43. It is I think less that one second but with other software, such as VLC media player, the "srt subtitle" appears at exactly the same time as the "incrusted subtitle".