A reader who wishes to remain anonymous is curious about the structure of DVDs. He or she writes:

A friend has a DVD that he needs to turn into a QuickTime movie. He’s used a program that copies the contents of the DVD to a folder on his Mac. Inside this folder are VIDEO_TS and AUDIO_TS folders. The audio folder is empty, though. Does that mean that the converted movie won’t have audio?

No, it doesn’t. The original DVD standard didn’t include an AUDIO_TS folder. All content was intended to be found within the VIDEO_TS folder. (In case you’re curious, the TS stands for title set.) This includes video as well as the audio that accompanies that video.

The AUDIO_TS folder was added as an option after the standard was established. This folder was created for standalone audio files much like the audio tracks on a CD. The idea was that DVDs would replace CDs as audio media. It never caught on but the folder remains, even though it's invariably empty.

Nothing to see here. The always-empty AUDIO_TS folder.

Why? The very earliest DVD players required the AUDIO_TS folder. Without it, the DVD wouldn’t play. Players haven’t required the thing for years, yet disc manufacturers continue to include it on most DVDs—perhaps as a courtesy to those using ancient hardware or because that’s just the way their replication software works.

Now to your implied question: How do you now turn this content into a QuickTime-compatible movie? The answer remains HandBrake. This free utility lets you convert the content within a VIDEO_TS folder into a movie playable on computers and mobile devices. Simply launch HandBrake, click the Source button, navigate to the VIDEO_TS folder, allow HandBrake to look for the main title, and from the application’s sidebar, choose an appropriate output preset.

For more information on the process, see Jonathan Seff’s How to Rip a DVD With HandBrake.