Digital Cinema FAQs

In spite of the many advantages and the accelerating adoption of Digital Cinema in the Indian film industry, there are still many questions that stakeholders don't have clear answers for. What follows is set of Questions and Answers that can help answer everything you've wanted to know about Digital Cinema.

  1. What is the difference between E-Cinema and D-Cinema?
  2. What is the difference between digital cinema and video projection?
  3. What is picture quality and what shouldn’t you compromise on?
  4. Why should you not use a single chip DLP projector?
  5. What about compatibility with other servers?
  6. How about sound quality in Digital Cinema?
  7. Are you being sold a box or a solution? Does the solution already exist?
  8. Are you assured of the manufacturer’s commitment and future upgrades?
  9. Do the solution providers have experience in dealing with picture and sound?
  10. What should I ask for in a Digital Cinema System?

1. What is the difference between E-Cinema and D-Cinema?

D-Cinema is a minimum standard defined by Digital Cinema Initiatives or DCI, a body setup by the Hollywood Studios to frame a standard for digital cinema that would be as universal as 35 mm film. The DCI Standard requires 2K or 4K resolution projectors with a defined minimum contrast ratio, precise brightness level on screen and a calibrated minimum color gamut. Compression is in the JPEG2000 format at a maximum of 250 Mbits. D-Cinema customers include cinemas that play Hollywood Studio content across the world and multiplexes and popular cinemas in top cities.

E-Cinema is everything else! Being adopted by cinema industries in India, Brazil, China and parts of Europe as well as by independent film exhibitors in the US, E-Cinema typically uses 3-chip DLP projectors, which produce better quality than 35mm film in most situations.

2. What is the difference between digital cinema and mere video projection?

Using just any digital projector doesn’t make your theatre a Digital Cinema Theatre. You have to make sure that your theatre’s picture quality is as good as – or better than – what a good film print gives you. If you don’t ensure that the quality is good, you will be affected by competition from other theatres that upgrade to Digital Cinema using the right equipment. Even if you run new movies in your theatre using a low quality Digital Cinema system, you will not be able to sustain an advantage unless the quality of your picture and sound are fantastic – and that can happen only if you have the right equipment in your theatre.

What makes the picture quality of a theatre better or worse? It is a combination of the digital projector and the digital cinema server.

From our extensive research, we can tell you that the only type of projector that is good enough to match the quality of film and also capable of serving you for many, many years is a 3-chip DLP projector. Single chip DLP projectors are not of sufficient brightness or colour range nor do they give you a long working life. Today’s single chip DLP projectors are used in offices and homes and designed for such environments, not for digital cinema theatres!

Digital Cinema Servers are also a key component of the system and even if you have a 3-chip DLP projector, you need to ensure that the Server can provide sufficient quality. What determines a Digital Cinema Server’s quality? It is the resolution of the images and the compression format used to store the images inside the system. A horizontal resolution of around 1.3K is considered necessary to achieve film quality in a Digital Cinema Theatre. The Qube Cinema Server uses images with a resolution of 1920×1080 or 1.9K and compresses using the standard MPEG-2 compression format at a peak bit rate of 80 Mbits, which is what the Hollywood studios also used until end-2006 for their movies.

In comparison, there are other Digital Cinema Servers in the market that use a low bit rate of only 5 to 8 MBits (a tenth of what Qube Cinema uses!) and some systems use a lower resolution too!

3. What is picture quality and what shouldn’t you compromise on?

When you see a picture on the screen, you can tell by experience if it looks good or doesn’t. But what are the actual factors that determine the picture quality on the screen? The main technical parameters to look at are the brightness of the image, the resolution or sharpness, the colour range and the contrast ratio.

The brightness of an image is easy to see and measure. If you look at the same image from a Digital Projector and a Film Projector, one after the other or side-by-side, anyone can tell which is brighter. It is necessary to attain at least the same brightness as a film projector and have an even illumination across the screen without any drop in the brightness on the edges of the screen.

The resolution of an image is easy to see and also shows in the sharpness of the images on the screen. A film print typically is capable of a resolution of about 750 lines on the screen when projected with a high-quality 35 mm film projector and a relatively new lens so a digital projector that has a resolution of 1,280 lines horizontally is sufficient to produce sharpness that is equal to or better than a typical film print. Projectors that use a lower horizontal resolution cannot produce sharpness that rivals a film print.

The colour gamut of a projector is the range of colours that the projector is capable of producing on the screen. Only 3-chip DLP projectors can produce nearly the full range of colours that a film print can. While LCD projectors can produce reasonably good colours, the quality of an LCD projector drops rapidly with age and only a DLP can guarantee a long life. Single-chip DLP projectors produce very unsaturated colours in comparison with 3-chip DLP projectors.

Contrast is the measure of the range of brightness that a projector produces, from the brightest white to the darkest black. 3-chip DLP Projectors today are typically capable of contrast ratios between 600:1 and 1000:1 and this range is sufficiently similar to a film print’s contrast range. LCD projectors and single chip DLP projectors are not usually capable of such high contrast.

4. Why should you not use a single chip DLP projector?

Today’s single-chip DLP projectors are used in home or office environments while higher-end applications need 3-chip DLP projectors. It is essential to have a high-quality 3-chip projector in order to project images that achieve the contrast range and the colour gamut of a film print.

Cinemas installed with the Qube Digital Cinema System use high-quality, 3-chip DLP projectors based on technology from Texas Instruments. Texas Instruments' DLP technology is used in projectors from numerous manufacturers including Barco, Panasonic and Christie.

DLP systems use a digital, solid-state Digital Micro-mirror Device or DMD to reflect light from the projector lamp onto the screen through a high-quality lens. In a 3-chip DLP projector, a prism and fixed colour filters break up the light into basic Red, Green and Blue components, which are then handled by three individual DMD devices before being recombined to produce the final full-colour image on the screen.

In a singe-chip DLP projector, a colour-wheel allows the single DMD to produce the images for Red, Green and Blue one-after-the-other. The human eye integrates such a quick succession of images of different colours into one complete image. One serious problem with single-chip DLP projectors is this colour wheel, which is a moving part and liable to break down in the heat and dust of a theatre environment.

Obviously, a 3-chip projector can also produce brighter images that have much better colour saturation. This is because there are three DMDs reflecting light compared to a single DMD. Each DMD can only handle a certain amount of light and heat so three units can produce three times the brightness compared to a single unit. Most importantly, many 3-chip projectors are also designed for industrial use and they have sealed optics that can handle difficult environments for years of service without any visible degradation in performance.

Other alternative technologies for digital projection such as LCD exist but such systems do not have the contrast range or colour fidelity of a DLP. What is worse, LCD systems usually have a fairly limited operational life and often suffer progressive degradation in colour fidelity over time. In fact, bluntly put, LCD systems will degrade in quality and their images will end-up looking like an old film print in just 12 to 18 months of constant use in a movie theatre!

5. What about compatibility with other servers?

Everyone in the film industry is aware of the confusion that was caused by multiple digital sound formats in the mid-90's. With DTS, Dolby Digital and SDDS being three incompatible formats, some theatres were forced to buy two or even three different sound processors for their theatre!

When Digital Cinema was in its early days worldwide, the same situation prevailed with no manufacturer’s systems being compatible with any other… fortunately, good sense prevailed and the Hollywood Studios set up the body called Digital Cinema Initiatives or DCI to arrive at a common standard that everyone would follow so that any digital print could play on anyone’s digital system.

While DCI arrived at a common specification, several of the key manufacturers of Digital Cinema Servers worldwide got together to make a common standard for Servers broadly based on the DCI specifications but with some modifications. This standard is called the MPEG MXF Interop and all of the DCI Compliant digital cinema servers on the market also support the MPEG MXF Interop standard including Dolby, Doremi, Kodak, GDC, XDC and of course Qube.

Every film released on Qube Cinema in Real Image’s Indian rollout has been in this MPEG MXF Interop format and today’s films are made available in the DCI JPEG2000 format.

6. How about sound quality in Digital Cinema?

As far as sound is concerned, the minimum that we think is acceptable for Digital Cinema is 6-channel surround sound, which is equal to or better than what theatres have today. Qube Cinema actually has 8 channels of 24-bit 48KHz or 96KHz sound and best of all, this sound is uncompressed so it is even better than DTS and Dolby Digital!

Using a Dolby Digital (otherwise called AC-3) sound track or an MP3 or AAC sound track in the server is definitely not considered sufficient quality. Even Dolby Laboratories who make their own Digital Cinema Server do not use Dolby Digital sound on their Server! And MP3 and AAC are the formats used on consumer music players such as the popular iPod! Surely, you wouldn’t consider it sufficient quality for your cinema -- but that's sadly what some Digital Cinema systems in India use!

7. Are you being sold a box or a solution? Does the solution already exist?

The Qube Cinema System is a complete end-to-end system – including mastering, encoding, encryption and delivery of content via satellite, playback, monitoring, network management and media management on the Server. All of these technologies and capabilities are built in-house to global standards by Real Image.

While you may hear other system sellers claiming to have end-to-end solutions, the specifications of their products may not be as per international standards. As you can imagine, not following international standards will likely mean that you will have problems procuring films in the future primarily because film producers and directors will not accept a non-standard format or quality in the coming years.

8. Are you assured of the manufacturer’s commitment and future upgrades?

For Real Image, future upgrades are just a software upgrade – most other systems may require expensive hardware components to incorporate a change and such upgrades will obviously come at a high cost. Most of the other systems being sold in India are older non-compatible models that will require major upgrades to become compatible with international standards.

Since Qube Cinema is Real Image’s own technology, any future upgrade made to the system for the global market will automatically be carried out for all the existing installations as well – a commitment that most other manufacturers will find difficult to deliver on, let alone their distribution partners in India.

9. Do the solution providers have experience in dealing with picture and sound?

Digital Cinema is a very new area for most people in the film industry. Since Digital Cinema involves a thorough knowledge of picture, sound and computers as well as an understanding of the current practices and quality requirements of the film industry, there are very few companies worldwide that have the experience required to build, operate and support a Digital Cinema system.

Real Image is uniquely positioned with an in-depth knowledge of picture and sound through their long association with Avid editing systems and DTS Cinema Sound, respectively. Real Image worked to implement these two revolutionary technologies in India and ensured that these revolutions came to the country not long after they were available internationally.

So when it was time to bring the ultimate revolution to Indian cinema, Real Image utilized Indian software talent, which is now recognized for being amongst the best in the world, and built a system that would be ideal for India -- and the world.

10. What should I ask for in a Digital Cinema System?

When someone wants to sell you a Digital Cinema system, ask them if they will give you a 3-chip DLP Projector and if they will give you a Digital Cinema Server with a resolution of 1920×1080, which uses high bit-rate image compression along with uncompressed 6-channel sound.

And most important of all, ensure that you have a Digital Cinema Server that uses either a DCI compliant standard or the MPEG MXF Interop format so that you can receive digital prints from anyone who follows this standard and are not stuck with only one supplier of digital films!