You cannot use Flash to take video directly from a tape or a camera. You will need to use a video-editing program like Adobe Premiere Pro, iMovie or Final Cut Pro for this.
In order to bring video into your computer, it must first be converted into a digital form that your computer will understand.
There are several ways to do this:
Use a digital video camera and input/output the video via an IEEE 1394/Firewire cable connected from the camera to an IEEE 1394/Firewire port on the computer.
Use a traditional analogue camera or video deck and connect this to a video capture card installed inside your computer. This will ...