ouh, I also search something like that for VLC and did not thought that it very complicated feature
what if use "indexing during playing" as first step, do "sec
preview" only for the video that already played? means only for the past time... something like "partial index", ...
it also good feature
second step, do "realtime scan" only for video codecs that not "very compressed" or something, and not required a lot action (CPU usage) for "get the frame for time" action...
third step, do it for all video codecs, combine "indexing during playing" + "realtime scan", but allow to disable it for slow PC
very naive?