The Refiner's Fire: Quality Assurance Testing for DVD

Emedia Professional, Jan, 2000 by Mark Fritz

DVD production is a complex process in which many different media types, Like strands of wool, are woven into an intricate tapestry. Consequently, the Slightest glitch can cause a domino effect that ends up as a major headache.

According to Randy Berg, business development manager for Rainmaker Digital Pictures of Burbank, California, "it can take eight hours to change one video clip. So one little problem equals one day."

And if one small glitch kills a day, you can imagine how many days a big problem could waste. As a result, Quality Assurance (QA) testing, though among the duller aspects of DVD development, is paramount to any title's successful completion. Every producer/ developer and replicator has a Quality Assurance (QA) horror story he or she will tell you, though the names will be changed (or left out) to protect the innocent. Take for example the story about the DVD movie that had to be recalled after 100,000 discs were stamped, labeled, packaged, warehoused, and distributed. Or the non-QA'd DVD presentation that got into the hands of the CEO on the podium before anyone realized that it simply wouldn't play. "That one bit us big time," says the developer, who admitted under promise of anonymity to still having bad dreams about the experience.

When a developer lets an error-infected project go to pressing, the ramifications can become legal if the client is hard-nosed and unforgiving. QA problems rarely end up in court, however, because according to Berg, a good developer will almost always bite the bullet and make things right, even if that means re-doing the entire disc. "If a client never comes back, that's far more disastrous in the long run than anything else," says Berg. "It may cost us $5,000 to make repairs, but that client could be spending hundreds of thousands a year with us. Fixing a glitch gets us good will and the next job."

How can the legal liabilities, additional costs, and embarrassment of disc disasters be avoided? By taking Quality Assurance very seriously. Good QA requires a good attitude. Every developer should institute formal QA procedures, including guidelines and checklists. Instituting serious QA measures in a company can add 25-35 percent more time (and therefore money) to a project, Randy Berg estimates, but the effort will pay off in the long run, he insists. And the good news is, several software products are available to help DVD producers with this all-important job.

THE P&L OF QA

QA isn't fun, but somebody's got to do it. In some companies, that "somebody" is the QA manager, who may have a team of assistants. At Rainmaker, Berg says, "the whole organization does QC," starting even before the project begins. Quality Assurance, he argues, should start with the pre-planning stage and continue throughout the project cycle. The worst thing you can do is leave all the QA for the end of the project.

Chris Armbrust, owner of San Rafael, California-based Marin Digital, agrees. "QA should start up front, with the design, and be done in pieces, and as a concurrent track of the development process," he says. "If you wait till the end to QA, you're lost."

Chris Armbrust believes that it is helpful to think of Quality Assurance as a process having four or more basic levels or steps. Rainmaker uses a similar layered approach to QA, but puts more emphasis on QA's role in the planning stages. Armbrust highlights the following levels:

* Level 1: Check the physical parameters of the disc itself. * Level 2: Check input elements and assets. * Level 3: Cheek the encoded data streams: MPEG and AC-3. * Level 4: Check the authoring, including navigation, interactivity, and usability.

LEVEL ONE

At the lowest level, you have to address the physical properties of the disc itself, search out physical defects, and get right down to the pits and lands. This bit-by-bit checking is called disc validation. Thankfully, most of this chore is handled for DVD developers by the replicator.

LEVEL TWO

At Level Two, the producer carefully checks and inventories all the project raw materials that have come in--videotapes, audio tapes, text files, graphics files, menus, photos, subtitles, art, and the like. Most of these materials can be spot-checked, but audio and video deserve closer attention.

Wise developers will head off problems down the road (in the encoding stage), says Berg, by thoroughly checking the video and audio assets when they first get them, noting any deficiencies and recommending special encoding treatment such as filtering, noise reduction, and preprocessing.

LEVEL THREE

Level Three testing begins as soon as all the audio and video is encoded. MPEG-2 and AC-3 streams are checked for encoding problems such as mosquitoing, macroblocking, digital hits, skip frames, picture breakup, invalid DCT coefficients, and 3:2 pull-down errors. Among the software tools that can aid the developer with the stream-checking tasks are MpegRepair from Cupertino, California-based PixelTools, and MProbe from San Jose-based Interra Digital Video Technologies.