Before you start any project related to video in Blender, you should take a look at your video source technical details, to match them in Blender. One of the aspects that you need to identify is the frame rate.
The frame rate is the speed in which all still frames from a video will play. Nowadays, you will find several different types of frame rates for a video—24, 30, 48, and 60 are the most used.
To avoid any potential problems, you must match the frame rate of your video sources to Blender's internal frame rate. For instance, if making a video with your smartphone using 30 FPS, which is the abbreviation for Frames Per Second, you must change Blender settings to match.
In Blender, you must go to the Render ...
