Hmm...
VLC Player with Scene video filter.
I haven't tested it with bigger resolution videos than monitor itself, but should work.
At least, it will work vice-versa. E.g when video is 1600x900 but you view it on 1920x1080 monitor and in full screen, the screen captures are still in the original file video resolution. For this example, in 1600x900 reso.
Guide on how to set it up:
View: https://www.youtube.com/watch?v=1h_lDu_wvR0
Downside: Video has to play for it to take screen captures. And if you scroll/seek the video, it takes screens of whatever is currently showing. And it will continue to do so with all played videos, until you uncheck the Scene Video Filter box (seen at 0:55 in video).
E.g at one time, i took some scenes but forgot it on. Then watched 2h movie and it screen captured entire movie.
![ROFL :ROFLMAO: :ROFLMAO:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Of course, you don't have to view entire video. You can just enable Scene Video Filter, hit Play, quickly seek to the point you want to capture, and then let it roll until the part you wanted to capture is done. Then Stop and uncheck the Scene Video Filter.
Oh, "Recording ratio" is the value at which it takes the screen captures. E.g
1 = at every single frame.
2 = at every two frames.
20 = at every 20 frames.
And so forth.
Output file formats are .png (higher quality and file size), .jpg (lesser quality but much lesser file size) and probably some more. Haven't tried others since i've ever used only these two.
Oh, VLC Player also has dedicated Snapshot button that you can use to take frame shots of the video. I use it in combination of Frame-by-Frame button. E.g seek the video into proper spot, Pause, then using Frame-by-frame button to move onwards one frame at a time and when i see the spot to take the screen capture, i either hit the Snapshot button, or use hotkey for convenience. Hotkey is Shift + S, but i don't remember if that was default one, or if i defined it such years ago.