Strange Speed ramp function

[woytekz]

I have a question about the speed ramping function. I don't quite understand what happens when after creating a keyframe (on time remapping speed mode on video track)  I click shift and drag the keyframe. Premiere is performing some strange function that I do not understand. A black padlock appears when you shift, and you can lengthen or shorten the clip, but I do not know exactly what this function does.

[Ann Bens · Accepted solution]

https://helpx.adobe.com/premiere-pro/user-guide.html/premiere-pro/using/duration-speed.ug.html

[woytekz]

Thanks:)

W