How to change audio speed
1. Drop one audio file you already have. Video and pictures are refused here. 2. Pick 0.5x, 0.75x, 1.25x, 1.5x or 2x, or choose Custom and type a number from 0.25 to 4. 3. Press “Change speed” and play the download next to the original.
2x is twice as fast, so a 6 second voice note becomes about 3 seconds. 0.5x is half speed, so the same note becomes about 12 seconds. GustKit uses the FFmpeg atempo filter, which changes tempo and keeps the pitch close. The file is re-encoded in this tab, so keep the original until it sounds right.
Audio only, not the video speed page
Change video speed moves the picture and the soundtrack together. This page leaves the picture behind. Change volume multiplies loudness and does not change the length. Trim audio is how you cut a long recording under the limit before you change its speed.
The audio stays in this tab
The first visit downloads FFmpeg. Later visits reuse the browser cache. Files longer than the limit on the page are refused, because the whole file is re-encoded here. GustKit does not fetch audio from a link.
How to hear the new speed before you replace the original
1. Play the download from the start. A 2x file should finish in about half the time. 2. Compare a spoken word with the original. The pitch should stay close, not jump up like a chipmunk. 3. Keep the original until a quiet part and a loud part both sound right.
Change video speed is the page that also moves the picture. Change volume does not change the length. Files over the limit are refused because the whole file is re-encoded. Nothing is uploaded.