Open the video in a video-editing program. If you want to rip music from a video that is already on your computer, the easiest way to do so is by using a video-editing program such as Final Cut Pro, Adobe Premiere or Windows Movie Maker. To open a video in your video-editing program, first open the program and then in the file menu select "Open." A browser window will then open allowing you to navigate your computer for the video file you wish to open.
Add the video to the editing timeline, and mute the video track. When your video opens in your video-editing program, add the video into the video-editing timeline. On the far left of the timeline window you should see options that allow you to mute the video or audio tracks. Select the option that allows you to mute the video track.
Export an audio-only file from the program. Though video-editing programs are meant to edit video, you can also export audio files from them. Because the video file is blocked in your timeline, only the audio information can export out of the program. In the file menu, choose the option labeled "Export" and then change the format options to either "MP3" or "AIF." Name the file the name of the song you are exporting and then save the file to your desktop. You can now open this file in your media player as a song.
Connect your DVD player to your computer. If there is a song on a DVD that you want to rip you can do so by using an audio-editing program, such as Garageband or ProTools, and an A/V RCA to 1/8-inch cable. Using the A/V RCA to 1/8-inch cable, plug the red, white and yellow RCA ends into the DVD player outputs and the 1/8-inch side into the audio input on your computer.
Create a new project in your audio-editing program and set the preferences. Open your audio-editing program from your applications menu and then create a new project. Name the project and then save it to your desktop. In the preferences section of your program, change the recording input to the option labeled "Built-in Audio Input."
Record the song. Push "Play" on the section of the DVD you want to record, then push "Record" in your program. Only the audio will record into the program. When the song is finished, press "Stop" on both the DVD player and in the program.
Export the song. In the export menu of your audio-editing program, choose the option to export the song to your media player. A window will then open asking you to name the file and choose a format. You should use the standard format settings and name the file the name of the song. Click "Export" and then wait for the song to export. When the song is done exporting, you will have the ability to open it in your media player.