SMPTE DCP Compliance is On the Way
by Michael Karagosian
©2009 MKPE Consulting LLC All rights reserved worldwide
originally published in the 15 November 2009 issue of Digital Cinema Report
Since the release of the DCI specification in 2005, there has been no shortage of talk about compliance to the spec. While deployment agreements demand it, and manufacturers strive to achieve it, not a single manufacturer, at the end of 2009, has yet to announce one compliant product. The reasons for this are many, not the least of which are the 256 errata released for the DCI spec since first published, with more on the way.
The DCI specification can be thought of as having two major components: distribution and security. Naturally, there is a relationship between these two subjects, but we don't need to dive into that for this article. What this article addresses is distribution, as this area touches everyone all along the supply chain.
A DCI-compliant distribution meets a subset of the group of standards we call SMPTE DCP. (SMPTE stands for the Society of Motion Picture and Television Engineers. DCP stands for "digital cinema package.") Early this year, SMPTE completed the suite of standards that anyone can follow, on a royalty-free and license-free basis, to create a SMPTE DCP-compliant distribution. Note that DCI requires compliance to only a subset of these standards. The complete set of standards goes beyond DCI, and in particular, encompasses a full feature set for the support of audience members with disabilities. This is the first time in the history of cinema that standards have dictated how accessibility at the distribution level and at the playback level can be supported.
Needless to say, not only do digital cinema systems NOT meet DCI specifications today, but the entire supply chain has yet to embrace the suite of SMPTE DCP standards.
To help move the industry along, two significant steps were taken this year. The first step occurred earlier in June with a meeting held by the Inter-Society Digital Cinema Forum (ISDCF) in conjunction with the National Association of Theatre Owners (NATO). In the course of the meeting, a date was set for the introduction of SMPTE DCP compliant products, including the introduction of SMPTE-standardized accessibility features. The latest version of the "Timeline for Accessibility" document that was a product of this meeting is published online at http://mkpe.com/timeline. The timeline targets April 2010 for the introduction of SMPTE DCP-compliant upgrades, with the goal of completing the installation of these upgrades by April 2011. If the industry follows suit, then we can expect the movie supply chain to fully switch to SMPTE DCP distributions in April 2011. While this will only guarantee partial DCI compliance, traversing the road to SMPTE DCP compliance and full support for the accessibility features dictated by SMPTE standards would be a major accomplishment for the digital cinema industry.
The second step, for which the planning stage has begun, is an opportunity for products to demonstrate SMPTE DCP and accessibility compliance in March 2010. This should be thought of as a "show-and-tell," as opposed to a test. By means of this demonstration, manufacturers are offered a venue for presenting the degree to which their products comply to the SMPTE DCP and SMPTE accessibility standards. As mentioned earlier, the standards for which compliance is sought are listed in the "Timeline to Accessibility" document online at http://mkpe.com/timeline. More information on the demonstration can be found at http://isdcf.com. Note that, since this is not a test, there will be no results published as a result of this demonstration.
One of the areas of SMPTE DCP compliance that has not received its due attention is that of audio distribution. Only one SMPTE standard calls out the details for audio distribution in digital cinema, and this is SMPTE 429-2 DCP Operational Constraints (available for purchase at http://smpte.org). SMPTE standards call for audio distributions to be digitally labeled by format. The need for format labeling was identified by work documented in SMPTE 428-3 Audio Channel Mapping and Labeling, where some 26 unique audio channels used at some point in the history of film are listed. Even so, the list is not comprehensive, as it doesn't include the channels that may be required by future cinema audio formats. Assigning a unique channel for every possible audio channel would result in a distribution format that could encompass 32 channels or more. Fortunately, in spite of all of the possibilities, no one format has been found that approaches 16 audio channels. For practical reasons, a limit on distributions was needed, and the channel limit on audio distribution was placed at16. Format labels were introduced so that the available 16 distribution channels can be assigned as needed within the boundary of each format.
As many server companies are new to the cinema industry, few if any have taken note that the logic behind digital cinema audio format labeling could lead to playback systems having more than 16 audio outputs. While the need for such installations may be rare, universities and other entities that pride themselves in being able to play every format known to man might take heed.
Manufacturers and exhibitors need to be aware of the product requirements imposed by SMPTE 429-2. Audio that arrives on channel 7, for instance, could be a Hearing Impaired track, a rear speaker Center Surround track, or a front speaker Left Center track, depending on the assigned format. Obviously, in an installation where multiple formats are supported, it isn't a good idea to automatically send incoming channel 7 audio to the channel 7 audio output of the server. Such response could lead to Hearing Impaired audio in an auditorium speaker. Multi-format installations, by the way, are often found in the largest premier houses around.
There are several ways that a manufacturer can produce a product that adequately responds to audio format labels. One such way is recommended in the chart below. The table on the left depicts the distribution channel assignments prescribed in SMPTE 429-2. The table on the right is the recommended playback output channel assignment to guide digital cinema media block and server manufacturers. Exhibitors might take note and include this chart in your equipment specifications.
Recommended Audio Output Assignment Table For SMPTE 429-2 Audio
While hurdles remain to be crossed, SMPTE DCP is on the way.