Can a DVD Have Multiple Video Title Sets?

A standard DVD-Video disc can contain multiple independent Video Title Sets (VTS), each accompanied by its own dedicated set of VOB, IFO, and BUP files. This article explains how the DVD-Video file structure supports multiple title sets, the technical limitations defined by the DVD specification, why authors use separate title sets for different media formats, and how navigation operates between them.

The DVD-Video Title Set Structure

According to the official DVD-Video specification, a disc is managed by a single Video Manager (VMG) but can contain up to 99 independent Video Title Sets, designated from VTS_01 to VTS_99.

Each Video Title Set acts as a self-contained container on the disc. A complete VTS consists of:

• VTS_xx_0.IFO: The control file that stores navigation, chapter marks, audio mapping, and subtitle data specific to that title set.
• VTS_xx_0.BUP: An exact duplicate of the IFO file acting as a backup in case of read errors.
• VTS_xx_0.VOB: The video object file containing the menu system dedicated to that specific title set (optional).
• VTS_xx_1.VOB through VTS_xx_9.VOB: The core video, audio, and subtitle streams for the main titles, split into maximum file segments of 1 GB each.

Because each VTS uses its own numbered sequence (such as VTS_01_1.VOB for the first title set and VTS_02_1.VOB for the second), their media streams are physically and logically segregated in the disc's VIDEO_TS directory.

Why Multiple Title Sets Are Necessary

Within a single Video Title Set, all video titles must adhere to matching video attributes. A new, independent VTS is required whenever video or audio parameters change significantly.

Authoring a disc with multiple independent title sets allows creators to:

• Mix Aspect Ratios: Display a 16:9 widescreen main feature in VTS_01 while placing 4:3 standard-definition bonus features in VTS_02.
• Vary Video Formats and Resolutions: Combine standard NTSC/PAL resolutions with lower alternate resolutions supported by the DVD standard.
• Change Audio Configurations: Isolate a main film using 5.1 Dolby Digital or DTS audio from supplementary materials using basic 2.0 stereo or LPCM audio.
• Provide Dedicated Subtitle and Menu Languages: Implement isolated navigation menus that cater strictly to the content within that specific set.

Navigation Between Independent Title Sets

While each Video Title Set functions independently with its own dedicated VOB assets, a player cannot transition directly from a title in one VTS to a title in another VTS.

Navigation across different title sets must pass through the disc’s Video Manager (VMG), located in VIDEO_TS.IFO. When a user selects a bonus feature residing in VTS_02 while watching content in VTS_01, the player exits the current title set domain, passes execution to the Video Manager Menu (VMGM), and then routes into the target title set. This hierarchical architecture ensures playback stability while allowing distinct content formats to coexist seamlessly on a single DVD.