Why Does a VOB File Play Commentary Audio?

When you play an isolated VOB (Video Object) file directly, your media player frequently defaults to a commentary or secondary audio track instead of the main movie audio. This occurs because standalone VOB files lack the navigational instructions and stream assignments stored in the DVD's companion IFO (Information) files. Without these instructions, media players fall back on default behavior—typically playing the very first audio stream mapped inside the file, which DVD authors often used for alternate, stereo, or commentary audio tracks.

The Role of IFO and VOB Files

A standard DVD-Video structure separates multimedia content from playback instructions:

• VOB Files: Contain the actual multiplexed data, including video, multiple audio streams (such as 5.1 surround sound, stereo, director's commentary, and foreign languages), and subtitles.
• IFO Files: Act as the DVD’s brain. They contain the menu structure, chapter points, and crucial control commands that tell a DVD player which specific audio stream to activate upon starting the feature.

When you open a full DVD folder or disc, the player reads VIDEO_TS.IFO or VTS_01_0.IFO. These files tell the player to select the primary audio track (for example, the Dolby Digital 5.1 mix) and bypass the secondary tracks until the user selects them via a menu.

Why Stream Order Causes Issues

Inside a VOB container, audio streams are assigned specific IDs (such as Stream 0, Stream 1, or hex values like 0x80, 0x81).

During DVD authoring, audio streams were not always arranged in order of importance:

1. Audio Track 1 (Stream 0): Often used for a standard 2-channel stereo track or a director's commentary because it required less bandwidth or served as a legacy fallback.
2. Audio Track 2 (Stream 1): Often assigned to the high-bitrate 5.1 surround sound main mix.

The authoring studio relied on the IFO file to explicitly instruct the DVD player: "When the movie starts, play Stream 1."

When a VOB file is played in isolation, the media player cannot access the IFO instructions. Lacking any roadmap, most media players instinctively play the very first track they encounter—Stream 0. If Stream 0 is the director's commentary, that is what you hear.

Player Fallback Logic

Media players like VLC, MPC-HC, or MPV try to guess user preference based on system language, but raw VOB files rarely contain rich language or track-type metadata embedded directly in the stream headers. To the player, both tracks simply look like valid audio streams. With no metadata specifying "Main Feature" versus "Commentary," the player defaults to the first indexed track.

How to Resolve the Issue

• Switch the Audio Track Manually: Use your media player’s audio menu (typically under Audio > Audio Track) to toggle to the second or third stream.
• Open the Entire Folder: Instead of opening the .VOB file directly, open the containing VIDEO_TS folder in your media player. This allows the software to parse the .IFO file and respect original DVD track defaults.
• Remux the File: Use modern container tools like MKVToolNix or HandBrake to convert the VOB files into an MKV or MP4 container. During this process, you can delete unwanted commentary tracks or reorder the streams so the main feature audio sits permanently as Track 1 with the "Default" flag enabled.