What is the basis of the L button (Fast Forward)?

I’m trying to set up the ShuttlePRO V2 to work with Shotcut. I downloaded the default profile for Shotcut but I’m tailoring the jog wheel to my liking.

At this stage my fundamental question is about the fast forward function in Shotcut (keyboard shortcut “L”). Press once = normal play speed. What does the second press do in terms of speed? And, is it time-based or frame-based fast forward?

Also… The same question for shortcut key “J” pressed twice (as it does not seem to rewind at the same rate at “L” (x2) does for fast forward (I’d have though the two would be the same?).


It is not true or real-time fast forward and rewind where each frame is played more quickly. Each keypress doubles the numbers of frames skipped by each frame request by the player. Reverse is slower on most video formats due to seeking backwards and temporal compression where frames depend on the previous frames.

Thanks for explaining. Since posting I have used a mix of multiple right-arrow presses with the fast forward command to get the incremental change I was seeking.

I used to be able get a “fast forward” just by dragging the frame line across the timeline. This doesn’t seem to work any longer - dragging starts out speedy, but then stops rendering altogether until I let go of the timeline. What’s the best way to speed through a video clip while being able to see a decent representation of the action?


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