One obvious approach to ensure usability is to go for the "lowest common denominator" in functionality—that is, to forsake advanced features. For instance, you can author a perfectly good link to associated Web content for InterVideo's WinDVD player on the varied flavors of Windows, but the dead button will confuse or alienate those who play your DVD on a Macintosh, not to mention a home console. Although not the sexiest solution, lowest common denominator is really the most sensible approach to cross-player authoring, circa 2002. On the other hand, some advanced features, such as music during menu display, are widely available on various DVD player platforms—you just have to pay more for authoring tools that support them. These are described in Table 2, "Advanced Features."
Not available in entry-level DVD authoring
• Music loops: in menus
• Little movies: inside buttons
• Mouseovers: more Web-like
• Alternate camera angles: in movies
• Language: alternate language tracks and subtitles
To demonstrate how General Picture has developed these guidelines, we will share our experiences in developing Tuality Giants, a natural history title for a museum setting, moving from a naive design to a user-centered interface. In the absence of rigorous usability testing, we resorted to the principles of simplicity and consistency to streamline and unify our prototype menu. Along the way, we learned about the pitfalls of simultaneous development for computer and television displays. Our success was a result of accommodating not only the strengths and weaknesses of each medium, but also the realities of user expectations.
A "Clever" Design
To understand how we developed the Usability Checklist, begin by comparing our earliest Top menu with the current prototype. Our first prototype tried to suggest how our Victorian hero, Oregon pioneer nurseryman John Ramsey Porter, would have designed such a user interface. Perhaps he would have salvaged a redwood panel from a logged sequoia, and on its carved surface he would have placed conchos with multicolored glass beads for buttons. The resulting design looks like the distant cousin of a Wild-West roulette wheel. We thought it was a fun idea and that it helped to establish the period atmosphere. In addition, we counted on our bas-relief of Porter's face in combination with the giant sequoias to quickly introduce the user to his role in propagating these majestic Sierra redwoods in Oregon.
Looking back on what seemed like a good approach at the time, we now feel we can bill ourselves almost as experts on what can go wrong in designing for DVD. Once the concept evolved from a mere user-interface layout in Photoshop to a "live" application on a portable DVD player, it racked up problems in every category on the checklist: visual effectiveness, visual consistency, NTSC clarity, arrow-key navigability, and general navigability.
Some of these problems simply didn't exist when the DVD was PC-tested using WinDVD—specifically, the NTSC limitations and arrow-key problems. But, of course, they emerged with a vengeance when we inserted the disc into our portable Toshiba SD-P1500 DVD player. Here's the worst of what happened to the early Top menu prototype:
• The "Intro" button disappeared entirely beyond the safe-titling area.
• Attempts to navigate around the arc of buttons using the east-west-north-south arrow keys proved remarkably difficult.
• The redwood-panel motif took on a harsh, artificial appearance as the high red content overwhelmed NTSC color fidelity.
The work required to resize the completed layout for the safe-titling area was tedious and disheartening enough. But the essential unworkability of buttons placed in an arc practically killed this approach, all by itself. Being forced to "kill our darlings," however, facilitated the reconsideration of even more fundamental design issues.
In the "Just Because You Can, That Doesn't Mean You Should" department, we began to have doubts that users would be interested in skipping to the various segments of our well-planned 13-minute documentary (Introduction, Part One, Part Two, Part Three, Conclusion). We were skeptical that even video thumbnails would generate sufficient curiosity for so much trouble. We noticed that big Hollywood DVDs often avoid such nonlinear access, and use a single button to play the whole movie. Ouch!
In addition, our nagging doubts about the wisdom of angling text labels in a radial fashion got the better of us. From the outset, we'd known there was a tradeoff between ambiance and legibility. But we'd been kidding ourselves when we supposed that users rated ambiance nearly as important as comfort and clarity. If we scrapped the compass/ roulette motif, we could adopt the far tamer, but much more inviting, convention of a column of buttons with strictly horizontal text.