0.25x–4x video speed with audio kept in sync (atempo) — slow-mo & timelapse.

Halving a 4-minute lecture to 2 minutes at 2x

The Video Speed Changer re-times any clip from 0.25x slow motion up to 4x timelapse while keeping voices at their natural pitch. My commute trick: a 4-minute lecture capture runs 240 seconds, so I set 2x and the export plays in 120 seconds flat — same lecture, half the sitting. The audio speeds up with the video but the pitch stays human, because the engine runs sound through a tempo filter instead of simply playing samples faster. I've used 0.5x the same way to stretch a 20-second golf swing into 40 seconds of study material.

Match the speed to the material. 2x suits talking-head lectures and software walkthroughs; 1.5x is friendlier when the speaker mumbles or the slides carry dense text. For timelapses, tick Remove audio — a soundtrack that's been squashed to 4x adds nothing to a construction montage. Remember that one value applies to the whole clip, so there's no speeding up just the boring middle; trim the section, change its speed, and merge it back if you need a snappy intro with a real-time demo in the middle. It's three passes instead of one, but the result actually watches well.