Short answer
Digital cinema is the system in which films are distributed as digital packages (DCPs) instead of 35 mm prints and shown on digital projectors that meet the DCI specification. The film reaches the cinema encrypted, is unlocked with a key issued for that hall's device (KDM), decrypted in the media block and sent to the projector; in multiplexes the whole process is managed with a TMS.
The digital cinema chain
- Mastering: the film is turned into a DCP that meets the DCI specification.
- Distribution: the DCP reaches the cinema on disk, by satellite or over the internet.
- Key: the distributor sends a KDM specific to the hall's device and play dates.
- Ingest and validation: the DCP is loaded onto the server and checked for integrity.
- Playback: the media block decrypts the film, the projector puts it on screen, and the processor distributes sound.
Terms
- DCI (Digital Cinema Initiatives)
- Joint venture formed by the major studios in 2002. It publishes the system specification (DCSS) for image, sound, encryption and security in digital cinema.
- DCI-compliant
- Equipment that meets the test and security requirements of the DCI specification. Encrypted commercial films can only be played on such equipment.
- DCP (Digital Cinema Package)
- The digital package of a film prepared for cinema playback: picture, sound, subtitles and descriptor files. More: DCP and KDM guide.
- KDM (Key Delivery Message)
- Key file that unlocks an encrypted DCP on a specific device within a set date and time window. Defined in SMPTE ST 430-1.
- CPL (Composition Playlist)
- File in a DCP defining which picture, sound and subtitle files play in which order. KDMs are issued for a specific CPL.
- IMB (Integrated Media Block)
- Secure unit that decrypts content and feeds the image to the projector. Usually fitted inside the projector; its security certificate is the device identity KDMs are issued for.
- Server / SMS
- System that stores films and manages playback in a single hall (Screen Management System).
- TMS (Theatre Management System)
- Software that manages content, KDMs, playlists and automation for every hall centrally. More: TMS guide.
- 2K / 4K
- The two DCI image resolutions: 2048 × 1080 and 4096 × 2160 pixels.
- HFR (High Frame Rate)
- Presentation at frame rates above the standard 24 frames per second, such as 48 fps.
- Foot-lambert (fL)
- Unit of screen luminance. The 2D reference is 14 fL (48 cd/m²).
- Laser phosphor / RGB laser
- The two main light-source architectures of laser projectors. More: xenon to laser.
- Flat and scope
- The two main cinema aspect ratios: 1.85:1 (flat) and 2.39:1 (scope). Screen masking is set to match.
- Immersive audio
- Formats using overhead speakers and object-based sound, such as Dolby Atmos and DTS:X. More: sound guide.
- PLF (Premium Large Format)
- Premium auditorium formats with large screens, high brightness and enhanced sound.
- Interop and SMPTE DCP
- Two DCP formats. Interop is the older, transitional format; SMPTE DCP is the current format fully aligned with SMPTE standards.
Frequently asked questions
What is the difference between digital cinema and 35 mm film?
With 35 mm, films are distributed as physical prints and played from reels. In digital cinema, films are distributed as encrypted digital packages (DCPs), played from a server and shown on a DCI-compliant digital projector.
What is DCI?
DCI is a joint venture formed by the major Hollywood studios in 2002 that publishes the technical specification for digital cinema.
Why does the IMB matter?
The IMB is the secure unit that decrypts the film; KDMs are issued for its certificate. When the IMB is replaced, distributors must be sent the new certificate.
AHA DCS installs, operates and reports on the cinema side of the chain: installation, content and KDM management, monitoring.
Digital cinema solutions