Speed up or slow down a video

Speeding up: what each speed is good for

Speeding up keeps the detail of every frame that is shown; it simply skips frames, so a 4× clip in a 30 fps video shows every fourth frame of the original. The timeline shows the new length at once, and the total under the preview follows.

For a timelapse faster than 8×, speed the clip up to 8× and export it, then add the exported MP4 and speed that up again: 8× twice makes 64×. Above about 2× the clip's own sound is rarely worth keeping, so switch on Mute and lay music under it on the Music lane.

Slow down a video

Slow motion needs frames to spread out. A typical phone video has 30 a second. At 0.5× each one shows twice as long, which reads as smooth slow motion for a goal or a jump; at 0.25× the movement starts to step. Octoolo does not invent frames in between: it shows the frames you filmed for longer.

So slow motion is only as smooth as the recording behind it:

• Filmed at 60 frames a second, a clip at 0.5× still has 30 different frames for every second of the video.
• Filmed at 120 frames a second, it can go down to 0.25× in a 30 fps video and every second still gets 30 real frames.
• Set the video's Frames a second to 60 with nothing selected if your slowed footage has the frames to fill it.

The sound slows down with the picture and keeps its pitch, but speech at a quarter of its speed is hard to follow, so many people mute slow-motion parts and let music carry them. Exactly goes as slow as 0.1×.

Change the speed of one part only

Speed belongs to a clip, so to change one part of a video, make that part a clip of its own:

• Put the playhead where the part starts and press S. Do the same where it ends.
• Click the middle piece and choose a speed. The pieces around it stay at 1×.
• For a precise split, the arrow keys move the playhead one frame, and Shift with an arrow one second.

That is how the classic edits are made: normal speed into a jump, 0.5× for the moment in the air, normal again for the landing; or a long setup squeezed to 4× between two parts at normal speed. The change from one speed to the next is instant; there is no gradual ramp between them.

Screen recordings gain the most from this. A 20-minute install shown at 8× takes two and a half minutes, while the steps that matter stay at normal speed with your voice over them.

What happens to the sound

A clip's sound changes speed with its picture, and Octoolo keeps the pitch, so a voice at 1.5× sounds like someone talking quickly, not like a cartoon. There is no control to shift the pitch on purpose, and no way to play a clip backwards. To keep the sound at normal speed but lose it in the fast parts, split first and mute only the sped-up pieces.

Music on the Music lane keeps its own pace: speeding up a clip does not speed up the song. Sounds there have their own Speed choices, from 0.5× to 2×, also with the pitch kept. Since a sped-up video is shorter, a song that fitted before may now run past the end, where it is cut off; drag its end in and give it a fade.