To sync video and audio is to line them up so the audio matches the video in a new video file. Sometimes, through video conversion, download or other means, the video and audio can become out of sync so the audio is delayed or plays too soon in a video. It will look like an old Chinese movie with a bad English dubbing--the lips will move before the words are spoken or visa versa. Fortunately, with the use of digital video software, you can sync audio and video if the two go out of sync.
Launch Windows Movie Maker and press "CTRL + i" and use the window that appears to find your audio file and your video file you wish to sync. When you find them, hold down the left mouse button and highlight them. Then, click on the "Open" button and Windows Movie Maker will import the two files.
Drag your audio file and video file down to the timeline at the bottom of the screen. The timeline at the bottom looks like long blue rectangles with numbers above them. Your video file will be placed at the top of the timeline while the audio file will go towards the bottom of the timeline next to the words "Audio/Music."
Drag the movie and audio files left or right to place them how you want them in terms of "sync." In most cases, if the audio and video files are the same length, they simply need to be parallel to each other to be synced. Sometimes one file is longer than the other, though, and it takes more tweaking to sync the two. To test your audio and video sync at any time, click on the play button on the preview screen on the right side of the program window. The play button is in the bottom left corner of the preview window.
Save your video once you have it synced with the audio the way you want it. Save it by clicking on "File," then "Save movie file." In the window that appears, select "My computer" and click "Next."
Assign your new video a name and choose where you want to save it in the next window, then click "Next." Leave the settings as they are in the next window and move on by simply clicking on the "Next" button.
Wait for Windows Movie Maker to sync your video and audio file into one new video file. Depending on how long your audio and video files were, the video might take a little time to save. It could complete in a few minutes or a few hours. You'll know when it is done because it will display the message "Play video when I click finish." At that point, exit out of the program. You've now synced your audio and video files into one new movie file.