As VLC offers instantaneous pause and allows playback in frames, as you can see here. You might need to take a snapshot of either specific frame or an instant paused frame. Guess what? VLC lets you take screenshots as well. You can capture a frame either by pausing the video, or while playbacking video frame-by-frame. To take snapshot more promptly assign a hotkey to snapshot feature from VLC Preferences. Otherwise from Video menu, click Snapshot to capture a screenshot of a frame.