By Douglas Dixon, May 2, 2005
DVD is supposed to be a worldwide standard format, supported across the consumer electronics and computer industries-from silicon chips to consumer electronics devices to PC drives and software players. And yet the act of committing a production to physical disc continues to demand a courageous leap of faith, whether you are burning a single demo disc to DVD-R for a client or stamping out a large run at a replicator. Too often, the resulting disc can have visible flaws and glitches, or even refuses to play, annoying your customers and turning your beautiful product into a batch of useless, shiny coasters.
This problem is driven by the very success of the DVD format-there are a tremendous number of different players on the market, including set-top and portable players, game machines, and software. Guaranteeing DVD playability across all possible playback devices becomes a hopeless quest, especially when you're trying to encompass everything from older legacy devices to current models. But what can you do to ensure that your DVDs will be playable by as many people as possible?
DV spoke to the folks who see mistakes every day to find out how to avoid them. We spoke to two representative facilities-a mastering facility that produces the metal stampers used by replicators to manufacture optical discs, and to the biggest compatibility testing lab in the world.
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| Tom Whitworth, chief operating officer of Synchronicity Mastering Services, states that "people are used to handling CD and DVD discs. But when it comes to an unrecorded piece of DVD media, the disc has to be pristine before it is recorded on -- no lint, fingerprint free, or you're not going to get pits under that piece of lint or fingerprint." |
Mastering facilities see more dirty DVD laundry than anyone. We spoke to the folks at Synchronicity Mastering Services (www.synchro-mastering.com) in Salt Lake City, UT, to find out what errors they see most often. For more on Synchronicity and the services it provides, see the "Mastering Mastering with Synchronicity" sidebar.
DVD mastering facilities provide another level of testing the final bits in the disc image you submit for replication. If you're submitting your final DVD project directly to a replicator, you may bypass a mastering facility, but don't bypass their advice.
Most mastering facilities are usually agnostic about the input formats they accept from DVD producers. Synchronicity, for example, accepts 8 mm Exabyte tape, prerecorded CD, and recordable CD-R for CD mastering. For DVD mastering, they accept Digital Linear Tape (DLT) and recordable DVD (DVD-R and DVD+R).
"One of the major moves we are seeing is people trying to get away from DLT drives," says Tom Whitworth, Synchronicity's chief operating officer, "because it's getting harder to get the older DLT drives, so there's a big move to outputting on DVD-R. Some of these authoring tools even have the ability to put the DDP (descriptor file) on the DVD-R to store the CSS information."
But DVD-Rs must be handled carefully. Synchronicity does see bad DVD-R discs with unreadable sectors, and when one sector is bad, there are usually hundreds more. These problems are typically caused by improper handling, bad media, or are related to the burner.
"People are used to handling CD and DVD discs," says Whitworth. "but when it comes to an unrecorded piece of DVD media, the disc has to be pristine before it is recorded on-no lint, fingerprint free, or you're not going to get pits under that piece of lint or fingerprint." His advice about media: "Do not use the cheapest media as the input piece of media for mastering. We see the cheap stuff come in here, but we cannot read it."
With care and good media, "if you're very careful, that's usually good enough," says Whitworth. However, he suggests writing a backup copy of the disc on a different burner and media, especially if you have a rush job.
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| After DVD masters have been recorded, developed, and metalized, the next step is plating with a uniform layer of nickel, as shown in this shot of Synchronicity's 18 plating cells. The result is a father, which is sometimes the client-deliverable. If clients request it, the father can be used to generate a negative image, called a mother, which can then spawn subsequent sons for future mastering. |
When inputting the disc image, mastering facilities also check for data format errors against the specification for the specific CD or DVD book or format (i.e., Red Book CD audio or DVD-Video). They can even repair common CD problems, including out-of-spec postgap and subcode (tracking) information.
For DVDs, spec violations may require that the disc be reauthored, although subtle issues may be acceptable with a waiver from the client.
Common errors Synchronicity sees include CSS encryption being specified inconsistently in different locations. Another frequent mistake is including only an MPEG audio track for NTSC discs, which are required to have at least one PCM or AC-3 track.
Says Whitworth, "We see a lot more of these format errors, now that there are these low-end authoring tools, than we used to see when everybody was using high-end equipment. Often the people doing the authoring don't even know they are doing it-it's the only option that the tool provides."
Another problem is poor layer breaks, which is unlikely to be a mastering issue because each layer is processed as two separate jobs from two separate DLTs. But Synchronicity still needs to help verify how the layer break was defined in the authoring process.
Mastering facilities are responsible for reviewing each job for copyright compliance, including reviewing the intellectual property rights forms submitted with the job. They actually watch the content to make sure that it matches what the customer defined.
For audio content, Synchronicity uses the RepliCheck Audio Identification service from Audible Magic (www.replicheck.com) to verify submitted audio tracks by looking up their signatures in an online database to check if they are known copyrighted material. And they review any computer-readable data in the ROM portion, perform a virus scan, and also scan for Microsoft executables, which is a requirement of Microsoft certification.
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| Intellikey keeps a current sampling of over 350 DVD players in its testing matrix, which is designed to represent the top-selling players on the market.
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The first step to improving your DVD's compatibility is to understand how compatibility is determined. The most widely respected compatibility testing facility is Intellikey Labs (www.intellikeylabs.com) in Burbank, CA. They test the content and viewing experience of video DVDs and audio CDs, checking the video playback, the menus and navigation, and compatibility with a wide variety of devices.
You can set up your own in-house test lab with some representative DVD players, or make a run to Best Buy to try your disc in as many current demo units as possible (until they kick you out). Testing facilities like Intellikey offer a better solution: structured, rigorous testing of DVDs and CDs using numerous kinds and models of devices.
For testing video titles, Intellikey supports a DVD device matrix of over 350 DVD player devices. These are a representative profile of both the domestic and international consumer DVD player market encompassing all world regions.
For testing audio titles, Intellikey includes over 350 CE devices designed to test CD audio as well as the effect of copy control technologies on compact discs. These include CD and some DVD players, from portable to in-car units to clock radios, game consoles, DVD Audio, and SACD.
These devices are not just random collections of equipment; they are weighted toward more popular players, based on market research data for sales of specific models of DVD players. The Domestic matrix (NTSC Region 1) is divided into four tiers, currently covering the period from July 2001 through June 2004, and updated periodically to include the latest data.
Tier 1: The top-selling 20 DVD players, approximately 50 percent of this market.
Tier 2: The next 30 DVD players; approximately 75 percent of market.
Tier 3: The next 50 DVD players; approximately 92 percent of market.
Tier 4: Additional DVD players plus legacy devices; approximately 125 players.
The Intellikey international matrices are organized in two tiers. These include a series of players across all regions for NTSC and PAL. Intellikey Labs also has purchased all HD players available in the market to date.
Having so many different levels helps a compatibility testing facility quantify the seriousness of problems or issues that it uncovers. In its testing reports, Intellikey Labs includes a proprietary AMP (Affected Market Percentage) value for each identified playback issue. This specifies the specific market percentage of DVD players within the tested time range that are affected by a particular issue.
With this tier structure, "Intellikey Labs can customize a test protocol to meet any budget," says Tish Hendershot, director of sales and business development. "The average cost of our standard test is $1,200. Depending on disc content and the requested test protocol, this price could be higher or lower."
The testing turnaround varies, depending on DVD content and the size of the test. Typical DVD testing turnaround can be between 1 to 4 days. Same-day rushes and weekend work are available at an additional fee if the workload permits. Intelli-key Labs sometimes uses as many as 10 testers on a single project.
According to Hendershot, a more recent development is that "independent producers build our services into their proposals to their clients
. So producers are actively including QA in their services because it provides them peace of mind, and their client receives a product that has been tested."
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| Linear playback testing consists of viewing all video to uncover problems like video degeneration, file corruption, audio dropouts, layer switch problems, and subtitle errors and anomalies. |
Why might a DVD have playback problems? First, the authored data on the disc may violate the DVD specification; for example, by exceeding the video bitrate (although today's authoring tools should prevent this). Second, the navigational structure of the disc may be incomplete or incorrect, with missing or broken links, although, again, an authoring tool can check for these kinds of errors.
But even if a disc is within spec and properly designed, it may happen to use a combination of features that stress some DVD players. It may push too close to the limit in the video decoding buffer due to high-bitrate video that's complex to decompress.
And even when a title plays successfully, its design may be confusing or difficult to use when compared with the experience and expectations that consumers have formed from playing other discs.
The answer is to test as much as possible, as best as you can, within available constraints of time and budget. Intellikey draws on the experience of the testers, particularly when working with clients who are new to DVD or who are taking advantage of advanced DVD features. "Some companies we work with are just breaking into DVD production," says Hendershot, "and because we look at the title from an end-user perspective, we can make suggestions to improve performance." This can include noticing issues such as unassigned menu keys or poor-quality video encoded at an extremely low bitrate. The test results allow the clients to redesign the title to ensure that features worked as intended on a much larger percentage of players.
As an example of how DVDs are tested, Intellikey Labs offers four types of procedures: Initialization, Playback, Functionality, and Compatibility testing. This is how they verify the disc's compatibility with devices, and the proper playback and navigation of the disc's contents. If you decide to do your own DVD testing, the following points make for a good QA checklist.
Initialization testing verifies the compatibility of the disc over a large array of players. It's used, says Hendershot, "when a client is saying they just want to get as many devices under their belt as possible. We load it, let it play to the main menu, start the feature, and ensure that the chapter skip works properly." This is particularly useful when introducing a new media or format to test it quickly across a wide variety of playback devices.
Linear playback testing focuses on the actual video content, viewing the full feature presentation and all additional videos from beginning to end, with a combination of audio and subtitle streams selected by the client. It's designed to discover issues such as video degeneration and corruption, audio dropouts, layer switch problems, and subtitle errors and anomalies.
"The testers need a lot of attention to detail," says Chio Wells, the technical operations manager at Intellikey. "It's not something you can automate. We find digital hits (pixelation and graphic corruption), errors in the subtitles (such as misspellings), and synchronization problems (such as audio or subtitles out of sync)."
Functionality testing then examines the disc menus and navigation to verify the programmed menus and features included in the disc. The testers review all disc menus and access each menu button, checking for spelling errors and ensuring that menu highlights, backgrounds, and graphics all appear as intended by the author.
"We see navigation problems such as the highlight moving up when you press down on the remote," says Wells. "Another problem often found is menu buttons linking to the incorrect menus. These issues might sound minor, but they severely impact the user experience."
This testing can be helped along when the client provides menu structure diagrams that define the expected look of the disc, but it can still be performed without such materials. "With production houses, the discs are typically always supposed to be the same," says Wells, "so we know what it is supposed to look like. If we see something different, they may have done it intentionally, but we'll let them know."
Compatibility testing focuses on the interaction between DVD player devices and a particular disc's authoring. It also hinges on replication compatibility. This testing examines how firmware settings interact with the disc, verifies that all disc menus and video titles load properly, and notes performance inconsistencies among player models and manufacturers. The firmware settings include the default audio and subtitle languages, as well as video and audio configurations, such as widescreen display and surround sound.
This testing can reveal issues such as discs failing to load on specific players, firmware settings not functioning properly, and the parental lock feature set to the wrong level for the movie rating.
For more on Physical Properties and Applications and Internet Testing at Intellikey, see the Web-only sidebars at DV.com.
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| Compatibility testing focuses on the interaction between DVD players and the particular manner in which each disc is authored. It also considers replication compatibility. Intellikey sometimes uses as many as 10 testers on a single project. |
Although better tools and deep experience in DVD authoring can reduce the risk of problems, even a carefully designed disc can run into unexpected difficulties once it gets out in the wild and is challenged by the ever-growing profusion of DVD playback devices.
Whether you're duplicating a marketing disc or replicating a mass release, performing some kind of testing is the only hope to retain your sanity and provide some level of assurance to your clients that your discs will play as expected. Or, as Intellikey's Hendershot hears her clients say, "This is our brand, this is our product, and it's got to be tested before we do this mass release."
- CSS encryption inconsistently specified in different locations.
- Poor layer breaks.
- Including only an MPEG audio track for NTSC discs, which are required to have at least one PCM or AC-3 audio track.
- Disc violates DVD specification; for example, by exceeding video bitrate limits.
- Digital hits, such as pixelation and corrupted graphics.
- Errors in subtitles, such as misspellings.
- Synchronization problems, such as audio or subtitles out of sync.
- Navigational structure incomplete or incorrect, with missing or broken links, or highlights that move in the wrong direction.
- Confusing or difficult design.
- Combination of legal features stresses some DVD players; for example, high-bitrate video that is too complex to decompress.
- Keep unrecorded DVD media pristine: no lint or fingerprints.
- Don't use the cheapest media for DVD masters.
The history of Intellikey has tracked the history of the DVD format. "Originally we were testing mostly film titles for the studios on DVD," says Tish Hendershot, director of sales and business development. "We expanded to everything from educational software, interactive games, healthcare information, DVD Audio, and Web site testing. There has been a sharp increase in nonmovie material, mostly in the last year. DVD is used as a medium for information by all sectors."
Intellikey Labs was founded in 1997 as a garage shop start-up by the current president, Lauren Evers, and her husband, Darrell. The original testing matrix had 18 players, including some prototypes. "It was a slow and careful process to work with entertainment companies," says Hendershot, "as they were just beginning to understand mitigating risks associated with DVD production. We helped to decipher the root of early consumer complaints."
Even now, "The majority of our business is still DVD and DVD-Audio" says Hendershot. "With the emergence of new formats and technologies, we are also testing different new formats such as DualDisc, dual-layer burnable media, and copy control protection for CD and DVD." Intellikey Labs is the only RIAA-authorized testing facility in the U.S. for copy control testing.
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| In addition to DVD video and CD audio testing, Intellikey and other testing facilities offer DVD-Audio testing services. |
Synchronicity Mastering Services is an independent mastering facility that produces masters, the metal stampers used by replicators to manufacture optical discs.
With three laser-beam recorders and 18 plating cells, Synchronicity has the capacity to master up to 210 CD and 84 DVD orders per day, including "zero-day" turns, where the orders come in and leave in the same day. Mastering jobs for DVDs run between $250 and $300, and between $100 and $125 for CDs, for average turnaround times of 3 days.
Synchronicity and other mastering facilities also offer custom mastering services, adjusting the pit structure to optimize the master for the manufacturing line's specific equipment and processes. The same kind of customization can be used to tighten the track pitch and linear velocity to cram more data onto optical discs, such as CD business cards, or to cram more than 80 minutes on a CD.
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| Synchronicity's laser beam recorders make up the foundation of its mastering division. |
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