DVD Under the Hood: 
    Exploring DVDs with DVD Software Players

    (11/2002)

    by Douglas Dixon

DVD Structure: Chapters and Streams
Basic DVD Players: Mac and Windows
Enhanced DVD: InterActual Player
Enhanced DVD Players: 
    CyberLink PowerDVD and InterVideo WinDVD
Exploring DVDs
References

Whether you are starting to get into creating your own DVDs, or just a naturally an inquisitive kind of person, software DVD player applications are wonderful tools for not only playing DVDs on your desktop, but also for looking under the hood to explore their structure. We are used to accessing DVDs from their menus, but hidden under the hood is a deeper structure and advanced capabilities. Yes, DVD software players have all kinds of cool features for enhancing your video and audio viewing experience, but they also can do more to help you explore the content and organization of the discs.

As you get deeper into DVD authoring, these player applications allow you to explore commercial movies on DVD to learn how the Hollywood designers structured their discs. And as you author your own discs, you can use these tools to test and check your own creations.

DVD Structure: Chapters and Streams

DVDs actually can have a rather complex structure. Of course, they include video and audio clips, and interactive menus, and links between the menus and clips. But the DVD-Video format provides much more flexibility, in dividing clips into Chapters, grouping Chapters into Titles, and providing alternate Streams of video, audio, and subtitles.

Chapters are useful to organize menus for long video segments like a two-hour movie, allowing you to mark important scenes within the clip. While movies are intended to be watched from beginning to end, the chapter points let you skip rapidly through the movie between key scenes by pressing the Previous and Next Chapter buttons on the remote control. They also allow the use of a scene index menu, which can provide thumbnail images of each scene so you can jump directly to a favorite part. But notice that the chapters are just marked points in the longer segment. As you play the movie, the playback continues from the chapter point to the end, flowing through the chapter points.

The other way of using menus is to organize individual clips, as is typically done with consumer DVD authoring tools (including Apple iDVD, MediaoStream NeoDVD, Pinnacle Express, Sonic MyDVD, and Ulead DVD MovieFactory). In this approach, you first assemble a group of various video clips that you want to burn to DVD, such as different places you visited on vacation. The DVD authoring tool then can lay out the DVD with a clip index menus that includes thumbnail buttons for each clip. In this case, the contents of the DVD do not play end to end. Instead, you select a clip from the index menu, that clip then plays, and then the DVD returns to the menu again, instead of continuing on to the next clip. Things can get even more interesting if you add chapter point marks within the individual clips.

The next organizational structure in the DVD-Video format is Title Sets. Chapters can be grouped into Titles, that share a common root menu and contain same basic media format (such as 16:9 widescreen or standard 4:3 aspect ratio). Titles are not needed for authoring simple DVDs, but are commonly used for commercial movies. The entire widescreen movie content is typically stored in one title, and the extra material such as trailers and documentaries, filmed in standard TV format, are stored in additional titles

In addition, each video segment or track on the DVD can actually contain multiple Streams. A basic track might contain just video, plus audio, plus subtitles. In addition, a track can contain alternate video streams (i.e., for multiple angles of a concert performance), audio streams (i.e., for different languages or commentary), and subtitle streams (i.e., for different languages).

If you are playing a movie on a set-top DVD player, the DVD designer typically creates a Setup menu to permit you to select the desired audio and subtitle streams. Sometimes a Special Features menu also includes an option to listen to the director's commentary, which actually just selects another alternate audio track.

The multi-language support in the DVD-Video format actually goes even further. The alternate audio and subtitle streams on a DVD-Video disc can be tagged with a language identifier. You then can select a desired language to use for all your DVDs by using the Setup menu designed into the DVD player itself. Thereafter, when you play DVDs that have been authored in this way, the DVD will automatically display the corresponding audio and subtitle streams for the selected language, and even alternate versions of the menus.

Basic DVD Players: Mac and Windows

These days when you buy a new computer with a DVD drive, whether Macintosh or Windows, it should come with a built-in DVD player application. Apple provides the DVD Player application for Mac OS 9 and OS X (www.apple.com/macosx). 

The new Windows Media Player for Windows XP also can play DVDs (www.microsoft.com/windowsxp), but requires a third-party plug-in to decode the DVD video. Most PC manufacturers therefore preload a separate enhanced DVD player application such as CyberLink PowerDVD or InterVideo WinDVD, which also allows Media Player to play DVDs.

These DVD players all provide basic controls for navigating the DVD menus, playing and skipping through the video sequences, and jumping directly to the main Title menu or the local Menu in the current hierarchy. They also provide controls for cycling through the available streams, video (angle), audio, and subtitle. When you are exploring commercial movies to see how they were designed, these players provide a useful visual display of the current play location, including elapsed time and title, chapter, and stream numbers.

The Apple DVD Player provides a separate Info window to display the current playback information, and even the names of the audio and subtitle languages. The Windows Media Player for Windows XP can look up information about commercial DVDs in an online database, and display descriptive names for the chapters.

For testing your own DVDs, these players provide several useful capabilities. Before you build your DVD, you can check your individual clips, even if they are already converted to MPEG format, in Media Player or with the Apple QuickTime Player. To test your design, many DVD authoring tools permit you to create a copy of your DVD on hard disk. This creates a VIDEO_TS directory with exactly the same directory structure and files as would be burned to DVD.

Many DVD players now permit you to play the DVD content from disk to view and test it. Use the Advanced options in newer versions of the Apple DVD Player to play VIDEO_TS directories, or you can use Media Player to play the individual .VOB video files in the directory.

Part of testing your DVDs is verifying the menu designs, button interactivity, and navigational links. With these DVD players, you can check the menu buttons access from a remote control by clicking Up / Down / Left / Right and Select. But on a computer, you also can use the mouse to hover the cursor over the menus to see how the button areas highlight, and to click quickly through menu selections.

Enhanced DVD: InterActual Player

Many DVDs for commercial movies also contain additional material that only can be accessed when the DVD is played on a computer, including additional information on Web pages, links to special on-line content, games, and even Web-enhanced DVD playback. This DVD-ROM or Enhanced content is stored in data files on the DVD, along with the regular DVD-Video content. Set-top DVD players then can simply play the DVD-Video material and ignore the rest. Computers see the DVD disc as just yet another mass storage device, and can therefore access data and even load and run applications from the additional files.

Many commercial movies on DVD include this kind of enhanced content using technology from InterActual Technologies (www.interactual.com). These DVDs are typically identified with the InterActual logo on the back of the cover ("i" in "A"), or the PC Friendly logo that was used in earlier releases.

When inserted in a PC, these DVDs will automatically run the installer for the InterActual Player application, which is included on the disc. The InterActual Player 2.0 replaced the previous PC Friendly player in the summer of 2000. Unfortunately, the InterActual technology currently is not supported on Macintosh OS X.

One result of all this choice on the Windows platform is that you may end up with several different DVD player applications, all wanting to run by default when you insert a DVD disc in your system. Use the Preferences for the DVD drive and set the AutoPlay option to tame this behavior.

Enhanced DVD Players: PowerDVD and WinDVD

But for digging in deeper to explore and check the structure of DVDs, you need to roll out the enhanced DVD players for Windows such as CyberLink PowerDVD and InterVideo WinDVD.

First, these players support a wide range of disc formats, not just DVD-Video, but also Video CD (VCD), Super Video CD (SVCD), and even Audio CD and the new VR (Video Recording) format used on set-top DVD players. For reviewing your stored video clips, they also can serve as general media players, so you can create playlists of media files to play from hard disc, in a wide variety of formats such as Windows Media and AVI, QuickTime MOV, MPEG, and MP3.

In addition, these players provide enhanced video and audio playback. For video, this includes features such as picture enhancement, digital zoom and pan, full-screen playback, and even playback on a second monitor. For audio, this includes dynamic range control, equalization, dialog enhancement, bass enhancement, and virtual surround sound through two speakers or using Dolby Headphone. You can use these features to examine and enhance the picture and sound quality, especially for difficult material with darker scenes and low audio levels.

But for our purposes in exploring commercial DVDs and testing our own authored DVDs, these applications are especially useful for browsing the title and chapter structure of discs and stepping and scanning through the video in detail. With these tools, you can scan through your video quickly to check that it looks correct, and play at slow speeds to check specific clips or even individual frames. You also can use these tools to bookmark specific points in the DVD to come back to look at later, much like adding your own chapter points to the disc.

CyberLink PowerDVD

CyberLink PowerDVD (www.gocyberlink.com) has several tremendously useful features for browsing the structure of a DVD. The skinnable control panel displays lots of information about the current playback state, including the video and audio modes and selected streams. You can use the control panel buttons like a remote control to navigate the menus, play through the video, and cycle through the available streams.

Even better, you can right-click in the PowerDVD window and use the pop-up menu to view all the available options and directly select the desired stream. The Goto menu option even expands into a full hierarchical view of all the Titles on the disc, and all the Chapters within each title, so you can explore the entire disc structure and jump to any chapter in any title in one click. This will help you verify that your DVD authoring tool is creating the disc as you expected, and that your chapter points are marked correctly.

PowerDVD goes further to provide two other mechanisms for exploring the disc structure. The Browser is a separate window that shows an Explorer-like view of the disc structure, with expanding folders for each title. The Viewer displays thumbnails of the first frame of each chapter in a resizable window. When authoring your own discs, 6this view is very helpful in visually confirming your chapters.

CyberLink PowerDVD 4.0 XP was released in November 2001. It is available in a Standard version for $54.95 ($49.95 download only) and a Deluxe version with DTS digital Surround and SRS TruSurround XT audio enhancement for $74.94 ($69.95 download).

InterVideo WinDVD

InterVideo WinDVD (www.intervideo.com) provides a similar Bookmark browser that can display thumbnails for both the chapters in the DVD and any additional bookmarks that you have defined.

WinDVD provides additional support for playing through your video at different speeds. While it is always a good idea to play through all the video on a disc to make sure the video and audio has been compressed and processed correctly, this can be a tad tiresome. WinDVD provides convenient controls for scanning quickly through the video, with both a rotating jog dial and Faster / Slower buttons to easily adjust the playback speed. 

Even better, WinDVD has a time stretching feature that preserved normal-sounding audio even when playing faster or slower, typically from around 0.7x to 1.3x to even 2x speed. You can even specify that you want to watch a movie in a fixed amount of time (i.e., before the aircraft lands), and WinDVD with adjust the speed accordingly.

InterVideo WinDVD 4 was released in May 2002. It is available for $49.95, or in a Plus version for $79.95 with features including enhanced surround sound.

Exploring DVDs

As you start authoring your own DVDs, you can take advantage of the capabilities of these software DVD players, both to check your own discs, and to learn more about how commercial DVDs are designed. The enhanced players like CyberLink PowerDVD and InterVideo WinDVD are particularly useful for playing and checking both the content and the structure of DVDs, whether played from a disc or authored to your hard disc.

Sonic Solutions (www.sonic.com), the developer of a wide range of DVD creation products from consumer to high-end professional, also acquired the RAVISENT DVD player technology in May 2002, and has added the CinePlayer player to its product line.

You can try out these DVD players to see how you like them. Visit the company web sites to download trial versions. Then open up the hood on your DVDs to explore and learn.

References

Apple - Mac OS X
    www.apple.com/macosx

Microsoft - Windows XP
    www.microsoft.com/windowsxp

InterActual Technologies
    www.interactual.com

CyberLink - PowerDVD
    www.gocyberlink.com

InterVideo - WinDVD
    www.intervideo.com

Sonic - CinePlayer
    www.sonic.com