SMPTE 21DC also met this month, making significant progress with several standards. Voted to move forward for publication are:
- 429-13 DCP Operational Constraints for Alternative Frame Rates,
- 430-10 Aux Content Synchronization Protocol, and
- 430-11 Aux Resource Presentation List.
The 430-10 and 430-11 documents are the last in a suite of four standards, two of which are already published, for closed captions in cinemas. The suite of standards describes how closed captions are distributed, and how the digital cinema server can communicate them to 3rd party closed caption systems.
428-4 DCDM Audio Constraints, which quantifies important characteristics of digital cinema audio tracks, was held back for technical reasons. These should be cleared up in the coming weeks, and the document is expected to then move on for publication.
Work continues on 428-5 DCDM TIFF Mapping. The document describes the used of the TIFF format in post production for uncompressed images. The document did not pass ballot, and more work will need to be done before it can be balloted again.
An important announcement was that of TI, who at last presented plans to produce a document describing the Cinelink 2 link encryption used in 2K projection systems. The document will be prepared as a Registered Disclosure Document. Such documents are not standards as they are not subject to a rigorous development and voting process where a large number of participants have an opportunity to shape the standard. Instead, and appropriate to TI’s link encryption which has been in widespread use for several years, the RDD allows a company such as TI to openly document its work and publish it. It will be subject to a voting process, but votes and comments will be limited largely to the quality of the documentation.
Two important revisions in discussion were those for 430-5 Security Log Event Class and Constraints, and 430-6 Auditorium Security Message (ASM). There are known errors in 430-5, but it has been difficult to get feedback on implementation issues as there has been little implementation taking place. This has recently changed, however, with several parties now preparing to implement security logs, and who are now able to provide the much needed feedback on 430-5.
430-6 ASM poses a more fundamental problem. It is already a SMPTE standard and a requirement of the DCI spec. As originally intended, it will collect one certificate from a Series 1 projector. But the new Series 2 projector has two certificates to be collected, which ASM was not designed to address. A group within SMPTE was formed to so improve the 430-6 ASM protocol, or to recommend an alternative. Alternatives were studied, which were thought to eliminate the need for modifying the 430-6 message. However, one alternative was found to be unacceptable to DCI, and another alternative was found to be unacceptable by projector equipment suppliers. A third alternative exists with a new command implemented by TI. Whether this solution or a direct change to ASM is enacted, there will be a need to update equipment in the field. The result would be two types of 2K servers in use, one type that is compatible security-wise with Series 1 projectors only, and another type that is compatible with both Series 1 and Series 2 projectors. The lack of interoperability causes concern for confusion and to a small extent, dark screens. The issue has not been formally resolved, but the choices are getting narrow.
