How does iphone speed up video?

Let's take the one-click watermark app in the iPhone6s mobile phone as an example to show you.

1. First, click a key on the mobile phone desktop to watermark the app.

2. Then click Video Shift and click it.

3. Then click on a video to change the speed.

4. Then choose double speed or quadruple speed.

5. Finally, click Finish in the upper right corner of the screen. When this operation is completed, the video on Apple's mobile phone will be accelerated.