Sustainability of Digital Formats
Planning for Library of Congress Collections
Sustainability of Digital Formats
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | Digital Cinema Initiative Distribution Master (DCDM) Described in the Digital Cinema System Specification v1.0, July 20, 2005 |
| Description | The DCDM is a set of uncompressed and unencrypted files that represent moving image content optimized for the electronic playback in theaters. The specification embraces not only theatrical feature films but is also intended for content like trailers and advertisements; the full range of works are called compositions in the specification. The DCDM's files or tracks contain images (high resolution representations of motion picture frames, often produced by scanning film), audio, subpictures and/or timed text (mainly subtitles and/or captions), and auxiliary data (which includes such things as data to control room lights and curtains in a theater). A Composition Playlist synchronizes the playback of these files. The overall Digital Cinema Initiative (DCI) system specification defines a life cycle in which content exists in a succession of states: • DSM. Content originates as a Digital Source Master; format selected by producer, not specified. • DCDM_1_0. Content is shaped into a Digital Cinema Distribution Master, covered by the specification • DCP. Content is compressed and encrypted for transport to the theater as a Digital Cinema Package, covered by the specification • DCDM (again). Content is unpackaged, decrypted, and decompressed at the theater for exhibition. Content is divided into reels, segments of picture and sound analogous to the film reels (typically 22 minutes in duration) that are distributed to theaters. DCDM employs a hierarchical structure that provides imagery at both 2K (2048x1080 pixels) and 4K (4096x2160 pixels) resolution, in order to serve projectors with different capabilities. The overall system specification devotes considerable space to the required capabilities for playback and projection systems in theaters, and regarding security and content protection. |
| Production phase | Final-state for use in a distribution chain; may also serve as a middle-state format for archiving. |
| Relationship to other formats | |
| May contain | MXF_UNC, MXF File with Uncompressed Images in Generic Container DCDM's image track(s) |
| May contain | WAVE_LPCM_BWF, Broadcast WAVE Audio File Format DCDM's sound track(s) |
| May contain | PNG, Portable Network Graphics Format (PNG) DCDM's subpicture track(s) |
| May contain | XML, XML (eXtensible Markup Language) DCDM's subpicture navigation file(s) and timed text track(s) |
| May contain | Auxiliary data file(s) conforming to SMPTE specification 12M, not documented at this time |
| [Has transport format] | DCP_1_0, Digital Cinema Initiative Package (DCP), Version 1.0 |
| Has earlier versions | Draft versions of overall specification; see Format specifications below; not documented at this Web site. |
| LC experience or existing holdings | None |
| LC preference | None |
| Disclosure | Fully disclosed. Developed by the Digital Cinema Initiatives. [See Notes below for information on the relationship of the DCI to the SMPTE DC28 standards-development process.] |
| Documentation | The DCDM is one element defined in the Digital Cinema System Specification v5.2, June 2005. The specification is accessible at the Digital Cinema Initiatives Web site. |
| Adoption | This format and the overall system was introduced in July 2005, and adoption will begin during the following years. |
| Licensing and patent claims | None identified. The specification includes a disclaimer: "Compliance with this document may require use of one or more features covered by proprietary rights . . . no position is taken by DCI with respect to the validity of any patent of other proprietary right." (p. vii) |
| Transparency | The bundling structure and some other elements will be encoded in XML, which is very transparent. The essence wrappers, e.g., MXF, are generally transparent. The DCDM essences will be as transparent as their underlying encodings. |
| Self-documentation | Metadata to describe the content and to manage the playback process and security protections is a part of the specification. |
| External dependencies | Depends upon specialized projectors and other playback systems in theaters, including the use of a surround sound infrastructure and systems for curtains and lighting that respond to data in the DCDM, etc. |
| Technical protection considerations | Not fully investigated at this time. In the 161-page draft specification, 78 pages are devoted to security. A public-private key, signature based system is specified. |
| Video elements | |
| Normal rendering for video | DCDM files will play in special authoring or theater systems. |
| Clarity (support for high image resolution) | Although the DCDM is uncompressed by definition, image files are compressed for movement to theaters in the DCP, using lossy JPEG 2000 with a maximum data rate of 250 Mb/s, which will yield excellent quality when decompressed. Quality when projected will vary dependending upon picture size (2K vs. 4K; see Description above). |
| Functionality beyond normal video rendering | Extensive; not documented at this time. |
| Sound elements | |
| Normal rendering for sound | DCDM files will play in special authoring or theater systems. |
| Fidelity (support for high audio resolution) | Excellent; sound track files can have sampling rates as high as 96 kHz; bit depth is specified as 24 bits per sample. |
| Support for multiple sound channels | Intended for use in surround-type environments; 16 channels are possible and specified mappings for 8- and 6-channel systems are specified. Each channel will be represented by a separate sound file or track. |
| Functionality beyond sound normal rendering | Not investigated at this time. |
| Tag type | Value | Note |
| Filename Extension | Not applicable | |
| Internet Media Type | Not applicable | |
| Magic numbers | Not applicable |
| General | In the DCDM, the image track consists of uncompressed data mapped to the MXF Generic Container in accord with SMPTE standard 384M, using the frame wrapping method. In the DCP_1_0, the image track consists of lossy JPEG 2000 data mapped to the MXF Generic Container in accord with SMPTE standard 422M, and using JPEG 2000 codestreams conforming to J2K_C_Profile_3 (for 2K) and J2K_C_Profile_4 (for 4K). |
| History | From the Digital Cinema Initiatives Web site: "Digital Cinema Initiatives, LLC (DCI) was created in March 2002, as a joint venture of Disney, Fox, MGM, Paramount, Sony Pictures Entertainment, Universal and Warner Bros. Studios. DCI's primary purpose is to establish and document voluntary specifications for an open architecture for digital cinema that ensures a uniform and high level of technical performance, reliability and quality control. DCI will also facilitate the development of business plans and strategies to help spur deployment of digital cinema systems in movie theaters." During 2004, DCI and others applied considerable effort to image quality testing, examining image-creation methodology, encoding, and projection systems. The testing used Standardised Evaluation Material (StEM) created through a collaborative effort of the American Society of Cinematographers (ASC) and DCI. The formal standardization of DCI specifications is being overseen by the SMPTE technology committee DC28, made up of four working groups preparing more than 20 separate items. The relationship of this to the Digital Cinema Initiative (and a European counterpart) was articulated in 2006 by the European Federation of Cinematographers: "The establishment of a new standard for the future digital cinema projection copy has been delegated to the SMPTE [DC28 technology committee]. Both DCI (Digital Cinema Initiatives) and EDCF-T (European Digital Cinema Forum - Technical Module) are input bodies towards SMPTE DC28. . . . Now that the DCI published their specifications it is to expect that the standardisation work at SMPTE will accelerate and it is possible that SMPTE may finalize the standard in less than a year from now." |
URLs
• Specification (http://dcimovies.com/DCI_Digital_Cinema_System_Spec_v1.pdf)
• For members, Digital Cinema Initiatives Web site offers online access to the following draft documents:
• Digital Cinema System Specification v5.2, June 2005
• Digital Cinema System Specification v5.1, April 2005
• Digital Cinema System Specification v5.0, March 2005
• Digital Cinema System Specification v4.3, December 2004
• Digital Cinema System Specification v4.2, August 2004
Print
URLs
• Digital Cinema Initiatives Web site (http://www.dcimovies.com/).
• European Federation of Cinematographers (http://www.imago.org/main/public_html/_htm_digital/)
Print
• Swartz, Charles S., editor. Understanding Digital Cinema: A Professional Handbook. Amsterdam; Boston: Focal Press, 2005. LCCN: 2004021603; ISBN: 0240806174.
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