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The Importance of Verification
Compared to DVD, Blu-ray is a massively more robust and therefore more complicated format. "There are so many facets to complying with the specification when you're authoring Blu-ray," says Rob Aubey, technical specialist for Sony Creative Software. "It's just a much higher level of complexity and the constraints of content in the Blu-ray space are a little finer than they ever were in DVD." Just looking at video alone there are three different codecs, "but that's just one level of compliance," Aubey states. There are also variables related to maximum and constant bitrates, I-frame positioning, I-frame starting points, and more. "What anybody authoring a Blu-ray disc has to comply with is the Blu-ray specification, which is a monster, 1,200-page document," Aubey continues. The process of verification compares the construction of a Blu-ray disc against this document to verify compliance. If you don't run a disc through a verifier before sending to replication, the results can be devastating to the end user experience. "It could fail in a number of ways," says Aubey. "It could stutter during playback. It could stop playing altogether. You could get an error on the screen. Or it may not be the feature title stream that gets interrupted, it may be one of the bonus features that are out of compliance. It's hard to say how the players themselves will react to a problem on a disc." These issues become more pronounced the higher of the programming complexity ladder you go. "It's mostly to do with the more advanced programming," says Andy Parsons, SVP for Pioneer Electronics and chairman of the Blu-ray Disc Association (BDA). "Video and audio are pretty straightforward so it's very rare to have a problem from our experience with those. Usually what'll happen is somebody will try to do something interesting by pushing the programming, and it sometimes causes the player to not handle it in the way that the software designer intended it to." The basic reality is that while BD-J leverages Java to enable endless possibilities in the types of features and functionality that can be built into Blu-ray Discs, in doing so it also introduces a host of complexity wherein errors can be hidden throughout a title that only using a verifier can catch. "Things can be a bit more hidden than they are on DVD because there's just a lot more places to bury data," says Chris Armbrust of high-end authoring outfit Marin Digital. And if these errors aren't caught before going to replication, not only does it potentially mean a wasted run of discs, it can also be that much more difficult to identify whether the error stems from something the author did wrong in the programming or the replicator did wrong in the replication. "We consider [verification] a necessary step, especially for BD-J and BD-Live discs," says Joe Rice, VP of technology for MX Entertainment. "It's easy to make mistakes with BD-J and BD-Life configuration, especially in the area of security. Furthermore, there are still player compatibility issues being resolved, and it's easier to work those out when one is confident in the content." Rice continues, "We often use the verifiers as troubleshooting tools. They don't catch everything, but they have certainly saved us hours of hunting on our own for subtle issues that can cause a disc to fail, like text encoding or XML configuration of a BD-J permission request file, or a type in an organization ID, etc." So the general consensus is that to help guarantee a smooth process from authoring through replication, verifying discs is an essential step. The Verification Proces
There are currently three verifiers on the market today, and their manufacturers should come as no surprise: Sony, Panasonic, and Mitsubishi. These systems' job is to check every part of a Blu-ray Disc against the Blu-ray specification. They're serious apps with a serious price; in the case of Sony's full verifier, that means paying $10,000 for a single security-dongled seat. Running a disc through a verifier can be a time-intensive process. "Depending on how powerful the system you're running [the verifier app] on, a full studio dual-layer Blu-ray disc can have close to fifty gigabytes of content and could take a day and a half to verify," says Sony's Aubey. "And I've even seen them go longer than that." To help add another layer of redundancy in order to keep a project moving forward instead of having to backtrack to fix issues, most authors will run a disc through a verifier more than once. The first verification pass happens at the first mux, or multiplex stage, following encoding, which validates the content on the disc. The next verification pass happens just before the project ships to the replicator. But having a verifier and running discs through it multiple times often isn't enough as each verifier varies from the others in what they catch. "We actually have all three," says Marin Digital's Armbrust. "They each highlight issues in slightly different areas of the spec, so they complement one another fairly well. And often you're able to put two cryptic messages together from different verifiers and by doing so can more accurately figure what's caused the error." Having to purchase multiple $10,000 verifiers can be an overwhelming expense for smaller authoring houses, but for those who can't afford to buy their own verifiers, companies like BluFocus have begun offering outsourced verification services, though none of these facilities have yet to be officially licensed by the BDA. And having to send discs off to be verified only adds more time onto the verification process. Whether you do it in-house or farm it out, Blu-ray verification is a time-consuming and expensive but ultimately necessary process. Should Everyone Have to Verify?
Currently the only verification requirements handed down by the BDA apply to Blu-ray Disc replication facilities. "Your job as a replicator is to produce product that meets specs," says Parsons. "You're expected to send samples of your discs in to make sure your plant makes discs that conform to BD specs." Given the importance to the industry of avoiding any issues related to discs not playing back on the consumer end, when it comes to convincing the public to adopt this new format en masse, there's talk of extending some verification requirements to Blu-ray authors. And of course there's nothing to stop a replication facility from passing that responsibility on to the authoring studios by refusing to replicate a disc that hasn't been verified. "Some have asked, what is the BDA doing to help control this?" asks Aubey rhetorically. "One of the things that's being discussed is the possible requirement that all BD projects at least can prove that they cleared the verifiers without any errors." But considering the time and expense of verifying discs, despite its widely agreed upon importance, mandating verification may be excessive. "It just becomes impractical to verify every single title that's being verified," says Parsons. "No one has to do that for DVD. Even if a disc were sent in for verification testing, that doesn't necessarily mean it'll work on every player, as different players may interpret the spec differently than others. And there'd be no way that the verification lab can test every function of a title." Most of today's Blu-ray Disc titles are verified, which is most likely attributable to the fact that they're coming from the big film studios. The studios have the financial wherewithal to do so, and their investment in large replicated runs demands a higher level of assurances that those discs will play. But the issues surrounding verification--and the inclination of authoring studios to try to sidestep it--will start to come to a head as more independent titles from smaller authoring houses start coming onto the market. What will be interesting to watch is how Blu-ray Disc replicators react if they end up facing a string of bad runs due to unverified discs. Eventually the replicators or the BDA may decide that the only titles they'll accept are those that produce a clean bill of health through a verifier. But we're not quite there yet. Not Just Verification, Also Compatibility
No matter how vital verification may be, it's actually only one piece of the overall puzzle for ensuring a Blu-ray Disc will play back properly in a consumer's player. The other major variable was alluded to by the BDA's Parsons above: how the Blu-ray Disc players interpret the Blu-ray Disc spec relative to how the discs have implemented it. "Verification alone isn't enough," says Marin Digital's Armbrust. "You have to run it on the players. In DVD, if the you put a disc into one player and your navigation works, it's good. On a Blu-ray Disc, particularly with BD-J, you can do all your navigation and it'll be one way on one player and another on another due to the timing differences on the different players. You can end up with an unexpected experience on one player or one family of players if you don't test for it." "Everything individually may pass verification testing, but that doesn't necessarily mean that every combination of player and disc will work right together," says Parsons. Technicolor, which offers full-service Blu-ray Disc compression, authoring, and replication, has set up a matrix of players that authors can rent time on to test out their discs. On the BD-Live side of things, the fact that there's really only one player on the market, the PS3, means that there's a temporary reprieve for authors testing for the compatibility of BD-Live titles. But that's only a temporary state of affairs as a host of new BD-Live-capable players are slated for launch in the fall. Even if you have a matrix to work with, though, testing discs against all players is a time-consuming challenge. But this isn't an insurmountable hurdle, as the ability for Blu-ray Disc player firmware to be updated provides the opportunity for manufacturers to step in and help resolve some of these compatibility issues. "If we have access to titles prior to going to replication, we'll test them on our player," says Parsons. "If it doesn't work right we'll often make changes to our firmware especially if it's a big tent pole title." Parsons contends that if the compatibility issue is more due to a specific player than the disc, they'll make the firmware update regardless of the size of the title. Just because the players' firmware can be updated doesn't mean it's an easy thing to do, though. "Remember, we can't just make a tweak in the firmware file. To do a firmware update takes a pretty extensive amount of effort," says Parsons. "You're just terrified that when you pass something on that you'll unintentionally screw something else up. It takes a lot of manpower to get a firmware update out there that improves something and harms nothing." And the scary reality is that while it hasn't yet happened in any major way, it's possible that a firmware update on players could render features on existing titles incompatible. Verifiably Satisfied
Despite all the work and complexities of verifying Blu-ray Discs and checking their compatibility against players, the industry seems more than satisfied with where things stand today with Blu-ray, especially relative to the early days of DVD. "This is kind of a natural course for format evolution," says Rolf Hartley, SVP and GM at Sonic Solutions. "It happened in DVD, but I would say that we're miles, light years ahead of where we were now with Blu-ray than we were with DVD when it came out. We've got a lot more experience and a much bigger knowledgebase from which to build on in understanding what to do. "Remember the problems of non-compatible titles coming out in the the early DVD days?" Hartley continues. "We really don't have that. While there are subtle changes in the format and these things are ongoing, nothing is causing rampant incompatibility today. I would characterize this for a content publisher as probably the safest time for getting involved in creating product." Blu-ray Disc authors echo this sentiment about the verification process. "With the state the verifiers are in now, we're happy with the process," says MX Entertainment's Rice. "Verification of an entire disc, including all stream verification, is time-consuming, and until recently one would have to do that full verification even if wanting to only check on aspect of the disc, like BD-J application security validity. Fortunately, the verifiers continue to be updated, and it's now possible to get more granular in verifying specific aspects of a disc." And as the format and technologies surrounding it mature, different aspects of this process should begin locking into place, helping further reduce issues with disc errors. For example, Sony has just begun selling the BAE-VX1000 encoder that's been designed specifically to encode video for Blu-ray Disc titles. "The output will be completely compliant to the BD spec," says Sony's Aubey. "This encoder will just about guarantee that the streams that you're encoding are compliant." While we're likely a long ways away from the day when BD-J and BD-Live titles can be produced without the need for verification, the new generation of prosumer- and consumer-level Blu-ray authoring tools will begin allowing for some basic interactive features in such a way that discs can be made using only those functionalities that are widely known to work across all players. And in the meantime, the collaborative spirit of the Blu-ray Disc community is allowing for all parties involved, from authoring houses to replicators to player and media manufacturers and beyond, to come together, test what's working, discuss how they're interpreting the spec, and, through the BDA, establish the path to the future where Blu-ray Disc can become a verifiably overwhelming success. Geoff Daily (geoffdaily at gmail.com) is a contributing editor to StreamingMedia.com, a frequent contributor to EMedialive and EventDV, and a writer and media consultant based in the Washington, D.C. area.
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