NAB2003 saw an influx of DVD authoring tools and production equipment that are making this delivery format more affordable and approachable to any video production team. Content creators are using DVDs to distribute educational materials, entertainment and corporate communications. The level of sophistication needed to produce professional DVDs depends largely on your application, but you'd be surprised at how much you can do on a small budget. Here we'll explore the features and limitations of today's spectrum of tools in terms of preparing the audio and video signals and generating the required user interface elements to meet the DVD format specification.
Applications abound, starting at under $100 and ranging upwards of several thousand dollars. Entry-level authoring applications are often wizard-driven and have limited access to the interactivity features of the DVD specification. Generally, they target the prosumer market. This article will focus more on the mid-range applications, priced from $200 to $700, and these days offering more flexibility and built-in features than ever before. Most have software MPEG encoding engines, which can suffice for content that can fit the bit budget of the destination disc.
Professional studios that need to create DVDs on a daily basis will look toward hardware encoding tools and high-end authoring systems from companies such as Sonic Solutions. A look at the requirements for authoring will reveal how the mid-range products can fit into the video production facility to author professional quality DVDs.
Encoding audio and video
MPEG is the standard format used on DVDs for video and audio, although the specification also allows for PCM and AC-3 audio formats. Encoding engines are generally built into these professional applications, but they may be limited in their flexibility. That won't be a problem if you have about an hour of content for your project or if you can afford to produce a DVD-9, which will handle more than two hours of video and audio encoded at an average bit rate of 8Mb/s.
A good compression engine with features such as variable bit-rate encoding, full search algorithms for motion estimation and field-based encoding options is required to tweak the encoding process when bit budgets are tight. Also, sophisticated pre-processing of the signals can reduce the encoding requirements by removing unnecessary detail. For instance, if your source originated as film at 24fps but has been converted to video at 30fps, you'll need an inverse telecine operation to remove redundant fields prior to encoding. If the target delivery platform is a desktop DVD-ROM, you'll also want a good de-interlacing filter to accommodate the progressive scanning of the computer's display.
Professional audio processing is another area that won't necessarily be included in a standard DVD authoring or encoding package. Any special effects, signal sweetening or noise reduction is best left to a separate professional audio application.
You can use the DVD authoring applications to accomplish other basic encoding operations. Some even allow you to do variable-bit-rate encoding and adjust the GOP structure of the MPEG video stream. If you want to do more sophisticated encoding outside of the authoring environment, these applications will always allow you to import the MPEG A/V streams already compressed. Otherwise, some applications will be bundled with capture applications, or you can import AVI, QT or DV source material already stored on your system.
Interactive authoring features
Interactivity on a DVD can range from basic chaptering in a tree-like structure to sophisticated user controls for viewing different camera angles in a scene. Most basic authoring packages will easily accomplish the former but will not handle the latter. Those that do are priced higher, such as Apple's DVD Studio Pro and Sonic Solution's ReelDVD.
Figure 1. A typical menu page, button construction and links to chapters on a DVD are shown here. Video objects (VOBs) are linked to a chapter menu screen in a DVD authoring application. The buttons themselves consist of an overlay that can change states and a subpicture, which can be a graphic, frame-grab or motion sequence. Click here to see an enlarged diagram.
A menu page to reach the various sections of the DVD will also be created in your DVD authoring application. Ease of use and integration with other content creation tools you have in the facility will depend on the DVD authoring application itself. For instance, an interactive menu is defined on the DVD with layers representing the background, the area or overlay that composes the button and the visual information that is placed in that button. A typical menu page, button construction and links to chapters on a DVD are shown in Figure 1. Most applications will allow you to import still images from Photoshop, where you have more control over the artistic look of the menu. Only Adobe's new Encore DVD will permit you to make revisions to those layers right in the authoring application. Otherwise, you'll need to go back to the original source and edit there.
On a DVD, the overlay image can actually be a motion sequence, for instance showing a scene from each chapter point on the DVD. Again, motion menus are supported in the higher end authoring applications, but not necessarily those in the $200 to $300 range.
One other feature that you may find relevant to your content is the e-DVD support on the disc you create. This uses the “DVD others zone” defined in the specification to store Web links and data that the user can access while viewing the DVD. Courseware distributed on a DVD could link the user to a Web site that logs test results and gives them feedback on their instruction. E-commerce capabilities can also be programmed onto a large catalog database stored on a DVD.
DVD sales and rentals are beginning to surpass VHS tapes and low-cost players, and drives are finding their way into the corporate environment as well. Video producers need to look toward new tools to keep them competitive in this arena, and developers are answering that call with affordable and feature-rich applications to create professional content on a DVD.
Barb Roeder is president of Barb Wired LLC, a technology consultancy specializing in the formatting and delivery of digital media. She can be reached through her Web site atwww.barb-wired.net.