Studio One no longer uses Quicktime on Windows machines as Apple has discontinued support for the Windows version. If you are running Studio One 3, the program uses Microsoft Media Foundation on Windows. As Studio One 2 is no longer updated, it still uses Quicktime for both Mac and Windows. If you import a video into Studio One 2 Professional, there is an option in the video window to extract the audio. If you extract the audio from the video, you can then import it into one of your tracks inside of the song that you are working with and then mute the audio in the video window. You can then add your effects to the extracted audio that you imported into a track. You can export the track to audio, but Studio One will not combine the audio with the video. You would need to do this in a video editing program.
*If you are running Studio One 2 Professional on a Mac, you will need to run the program in 32-bit mode in order to extract the audio. Once you have extracted the audio, you can then switch back to 64-bit mode. To change the bit-version, simply right-click (ctrl + click) the application in the Applications folder and go to "Get Info." You can then check the box to run in 32-bit mode.