I want to accelerate the speed of a video and decelerate some seconds before it ends. I wonder if it's possible to do it into the video editing. I know how to increase the speed of a strip but, what I need is a trasition between normal speed and fast speed.
In the VSE with your video strip selected add a speed control effect strip. With the speed control strip selected, in the properties sidebar N under Effect Strip is an option 'Stretch to input strip length', this needs to be off, when it is off you will get a speed factor setting. The speed factor can be keyframed to alter the speed as you want.