me: damn, hmm this thing i want seems like a no-brainer, why doesn't it exist? eh, i guess i'll just make it myself.
me, halfway through it: ah i see. this is actually super fucking annoying.
Forward frame-by-frame is implemented, and it's been for quite a few years. But it's very buggy because the VLC buffer and flow control code was really not designed for that purpose. Unfortunately, fixing that properly is a massive undertaking that nobody has had the time and courage (and salary) for.
Reverse frame-by-frame is impossible. It simply is not feasible within bound and reasonable computational, memory and bandwidth limits because video codecs and container formats are not meant to be played in reverse.
Sure, professional tools do it. But there are two big differences:
VLC consumes a lot less resources (typically).
VLC supports all sorts of video codecs and file formats.Professional editing software typically only works with specific file formats and video codec profiles that are precisely meant for the purpose of supporting frame-by-frame.
To make it work with normal video files, in general, VLC would have to re-read the file from the beginning for every frame.
source: https://forum.videolan.org/viewtopic.php?t=126609#p449758
