For the Cinematographer

A Guide to Digital Cinema Mastering

The most critical thing about releasing a movie digitally is how it’s mastered. You must make sure you choose the right mastering company and the right mastering solution. QubeMaster, the digital cinema mastering solution from Qube Cinema conforms to the DCI Specification. It encompasses the encoding, encryption and packaging of content for digital cinema.

What is Mastering?

Mastering is the process of creating the master digital cinema package containing the picture, sound and subtitles as digital files. Encryption is also applied at this stage. When all of the sound, picture and data elements of a production have been completed, they may be assembled into a Digital Cinema Distribution Master (DCDM) which contains all of the digital material needed for the film in its final uncompressed form. The images and sound are then compressed, encrypted, and packaged to form the Digital Cinema Package (DCP). This package of digital files is then ready for duplication onto removable hard disks for distribution or for transfer via satellite or fiber to cinemas.

Here’s how Real Image does it right!

The Mastering Workflow

Real Image, keeping quality in mind, insists on Digital Mastering directly from the Digital Intermediate (DI) data when this is available. QubeMaster is the only digital cinema mastering solution in the world that can go from the DI data directly to a DCP in one easy step. Though this is now rare, where the film has not been through a DI process, the negative or the master positive of the film must be converted to digital form by a telecine or film scanner. During the conversion process, colour grading can be performed and where necessary, Real Image has high quality colour grading systems such as the Digital Vision Film Master available to grade at its premises.

The DI data is processed through a high-quality 3D Lookup Table (LUT) which has been developed by Real Image to emulate a typical film print. Creative control is available to the cinematographer at this stage to tweak the overall look, adding some colour trims, printing down to crush the blacks or creatively handle burn-outs in the picture as desired.

Sound is of course as important a component of a film and the tracks should be delivered as uncompressed 24-bit sound files on a hard drive. The final mix can be delivered as a set of mono WAV files for each reel of the film or as a single multi-channel WAV file. The sound is synced to the picture for each reel using the start and end pops as sync-confirmation.

When mastering for digital cinema, the quality of the monitoring is critical. Real Image has the highest quality screening rooms in India for this purpose. Equipped with 2K D-Cinema projectors as well as 3-chip DLP E-Cinema projectors and 35mm Xenon Film Projectors, high quality micro-perf screens and breathtaking sound, our screening rooms help us ensure that we see every detail in the image and hear every nuance of the sound.

QubeMaster Pro, the Mastering Solution…

QubeMaster Pro, the digital cinema mastering system that is part of the Qube Cinema product line has been very well received worldwide and has been used to not only master hundreds of films in the Indian market but also by several top international post houses to master numerous features worldwide.

QubeMaster incorporates some key capabilities such as the ability to directly encode from the Digital Intermediate created when the film is digitally colour graded. Real Image has years of experience in the digital cinema domain and the company’s expertise coupled with the flexible and high quality mastering possible with QubeMaster makes our masters the best in the Indian market by far.

What about security?

For all feature film content, the digital files are encrypted with the 128-bit AES algorithm to ensure that the content simply cannot be cracked. A specific Key for the target digital cinema server is necessary to decode the content. These Keys are encrypted with an even more secure algorithm, the 2048-bit RSA. These security algorithms are fool-proof and are the same ones that are used by banks to secure their transactions. With the Device Certificate of the target server, the QubeMaster application generates a Key Delivery Messages or KDM that will allow playback of the content on that specific server for a period defined by the user when creating the KDM.

The KDM contains the key(s) required to decrypt the digitized, compressed content. Every movie needs a unique KDM for each server. This means that to play a movie on a given server, one would require the corresponding unique KDM. If the movie files are moved to another server, one would require another KDM for that movie to play from the new server.

At the time of exhibition of the content, the movie files are loaded on a server, along with the KDM specific to that movie and that particular server. However, it must be noted that each KDM comes with a pre-set validity period, which clearly indicates that date from which the Key is valid, and also the date on which this validity expires. Beyond the validity period, one needs to procure a new KDM if the movie is to continue to be screened.

This powerful security mechanism thus provides the distributor or producer, the same level of control that a physical print provides and also gives the Exhibitor the same level of control as with a physical print.