Mpv – A free, open-source, and cross-platform media player

I use it to inspect video frames by frames, particularly being able to go back one frame. VLC doesn't support it, this thread about the feature is hilarious https://forum.videolan.org/viewtopic.php?t=120627

i wonder why he's such an ass about it, and totally adamant that it's impossible when multiple players already do this fast. ego?

To do this well you need to keep the old frames around...or go back to the previous keyframe and re-render. That might be hard if your design is playback-optimized.

Re-rendering shouldn't be hard, it's just a specialized version of seeking. VLC has seeking.

The claim that you would have to decode all previous frames in the entire video is... completely baffling to see coming from the dev. He's arguing a stupid technicality that a video might not have keyframes. That's not a reason to omit the feature entirely.

You misunderstand. The point is you have to go backwards to find a keyframe, then render forwards from that.

Going backwards might be hard because if you structured your code in certain ways you may not be able to go backwards efficiently. You can "seek", but how far back to you want to seek? A second? Two seconds? current-X frames?

key frames may be in a standard cadence, but they may not be. So again, how far back do you seek to go back one frame? And keyframes may be abstracted away from the player itself, since really, the codecs are the ones that deal with that stuff. For example, I believe mjpeg doesn't do frame differencing (I'm probably wrong about that).

The ideal implementation would save the last X frames then re-render once you go back like X/2 frames. But again, it depends.