Applescript to capture the current frame in VLC (using the snapshot function in the app) and advance to the next frame. It'll keep going until it hits the specified end time, which you have to set in the script itself.

capture-range.scpt

global endTime

set starttime to 2510
set endTime to 2528

on captureAndStep()
        tell application "VLC" to activate
	tell application "System Events"
		keystroke "s" using {command down, option down}
		keystroke "e"
	end tell
end captureAndStep

on checkTime()
	tell application "VLC"
		set elapsed to current time
	end tell
	if elapsed < endTime then
		captureAndStep()
		checkTime()
	end if
end checkTime

checkTime()