Making speed ramps with time remapping in Video by Zaweba
Keyframe a clip's speed from 0 to 400 percent in Video by Zaweba, start from five ready-made ramps and see how linked sound follows the ramp like tape.
Plain speed changes make a whole clip faster or slower. A speed ramp changes speed during the clip: real time as a skateboarder approaches the jump, a sudden drop into slow motion at the top, then a snap back to speed for the landing. Video by Zaweba builds ramps by keyframing speed, and it keeps the rest of your edit in order while you do.
Where to find it
Select a clip and open the Inspector. Under Speed and time is Ramp the speed. Here you keyframe the speed over the course of the clip, from 0 to 400 percent. Zero percent holds the picture still, which gives you a freeze in the middle of a ramp without making a separate freeze frame clip. A hundred percent is real time, and 400 percent is four times as fast.
Commands allow a wider range, from minus 400 to 1,000 percent, so you can push a ramp into reverse or very fast motion when you need to.
Starting from a ready-made ramp
Five ready-made ramps are there to start from. Pick one, play it, and adjust the keyframes to suit your footage. Most ramps need tuning to the action: the slow part should land on the moment that matters, and that moment is different in every shot.
Starting from a preset is often quicker than building from scratch, and it shows you how a ramp is put together, which helps when you design your own.
The clip keeps its length
A ramp does not change the clip's length on the timeline. If the speed rises in one part, the extra time is used up elsewhere in the clip's footage, not added to the edit. That means a ramp will not push the rest of your timeline around, and your music and cuts stay where they were.
Split, trims and slip keep every moment where it was. If you split a ramped clip, both halves keep their part of the ramp. If you slip it, the ramp stays tied to the same moments of footage. This is what makes ramps practical in a real edit rather than only on a single test shot.
What happens to the sound
Linked sound follows the ramp like tape. As the speed rises, the pitch rises with it. As it falls, the pitch falls. When the speed is held at zero, the sound is silent. That is how a tape recording behaves when you speed it up or slow it down, and it can sound striking on purpose, a low, slowed down whoosh on a slow motion moment.
For dialogue, though, a ramp usually sounds wrong, so many editors detach or mute the clip's own sound and lay music or effects under ramped shots.
Plain speed changes behave differently. Set a constant speed between 0.25 and 4 times and the sound keeps its pitch, because the app uses the atempo filter to change tempo without changing pitch. So a talking head played at 1.25 times sounds faster but not squeaky.
Making ramps look smooth
Ramps into slow motion look best when there are enough frames to work with. Footage shot at a high frame rate gives the smoothest slow parts. With ordinary footage, the clip's in-between setting matters. Video by Zaweba can repeat frames, blend frames or use optical flow, which creates new in-between frames and can make slow sections much smoother. That choice is covered in its own guide.
Easing into and out of the slow part also helps. A sudden step from fast to slow can look like a jump, while a curved change feels deliberate. Keyframe eases and the keyframe graph give you control over how the speed changes.
Sports and action are the classic home for ramps, landing the slow section on the peak of a jump or the moment a ball is struck. Travel films use them to rush through a walk and slow down for a view. Music videos time ramps to the beat, speeding up into a drop and slowing on a hit.
Ramps that fall flat
The common one is ramping without a clear moment to slow down on. A ramp needs a reason, so find the peak of the action first and build the ramp around it. Another is pushing very slow speeds on ordinary footage and getting stutter; use optical flow or keep the slowest part a little faster. Finally, listen to the sound. In Video by Zaweba it follows the ramp faithfully, which is great for effect and less so for speech.
