All posts by Igor Ridanovic

Digital cinema.

Digital cinema is the practice of digital motion picture distribution and exhibition. As more and more theaters nationwide are adding digital projection capabilities D-cinema is quickly becoming a feasible alternative to the traditional process of 35mm print distribution.

Material shown in digitally capable theaters does not always originate in digital form. Many films are shooting on 35mm negative film only to transition into the digital realm during the DI process.

Digital cinema offers a number of advantages. Digital projection offers superb and consistent sound and image quality which does not suffer from gate weave, scratches and other mechanical damage. Distribution of film on digital media costs a fraction of typical 35mm print shipping cost.

D-cinema

2k Digital Film Scans

Barely larger than HD.

Full aperture 35mm film is usually scanned at 2048×1556 pixels using 10-bit logaritmhic RGB color space.

The area intended for 1.85 aspect ratio projection is smaller than the 35mm full aperture. This projectable area which corresponds to the ground glass marks inside a film camera is 1956 pixels wide [Fig. 1].

A 2k 35mm scan contains much more information than a High Definition frame of video. However for practical purposes a 1.85 projectable area of a 2k scan is smaller and has only a narrow lead over HD video as illustrated in figure 2.

Film – 1956×1057 pixels (1.85 aspect ratio projectable area)

HD – 1920×1080 pixels (1080 HD standards)

D-cinema projectable area is 2048 pixels wide. A film intended for digital presentation is either scaled up from 1956 to 2048 or a wider crop from the original negative scan is used.

full aperture 2k scan

Fig. 1. Full aAperture 2K Scan

1.85 vs. 1080

Fig. 2. Full Aperture 2K Scan

Consumer HD

HDTV Broadcast

Who can see your show in HD? A lucky few.

But the number of HD equipped households is growing rapidly in the U.S. where 13.7% of households were equipped with HDTV gear in 2007 according to Nielsen. The number is projected to grow to beyond 30% in 2008.

European households are slow adopters with projected 3% of households receiving HD broadcasts in 2007.

The U.S. and Japan are leaders in HDTV set penetration accounting for 91% of all HD equipped households worldwide.

HD broadcast in the U.S. is achieved through several means. Stations in larger markets have been broadcasting ATSC compliant digital signal which can be received with an antenna and an HD capable TV set. Digital cable operators and Satellite TV companies offer additional HD channels.

Not all cable networks have HD dedicated channels at the beginning of 2008. This is quickly changing as networks are accumulating enough material to begin HD broadcasting.

Consumer HD, Technical Info

HDTV and HD – The Difference

Practically the same thing.

Strictly speaking High Definition Television (HDTV) is not the same thing as High Definition (HD). However, the difference is insignificant so you will hear the two terms interchanged in everyday use.

HDTV is a subset of Digital Television (DTV). This new standard is mandated to replace the old NTSC analog broadcast in the near future. DTV specification created by ATSC defines a multitude of different frame sizes and frame rates for digital television broadcasts. Several of those are HDTV standards.

HDTV implies “televised” nature of high definition images. It is television delivered to consumers via cable, satellite or terrestrial broadcasts.

HD is high definition in a broader sense. During production and post production high definition video is not television yet. HD becomes HDTV once it is delivered to your home.

Consumer HD

Blu-ray and HD DVD

Blu-ray won the format war.

HD DVD players were the first one to reach the market in April of 2006 and captured the initial market share. However. Blu-ray has prevailed. Although HD DVD lost the format primacy a small amount of titles is still being released on HD DVD in early 2008. The amount of new releases is likely going to dwindle in the near future.

Blu-ray is capable of higher storage (100GB on quad layer discs) which is an important factor when it comes to HD size picture.

While a consumer browsing the menus of the same title on Blue-ray and HD DVD may not see any noticeable difference, the underlining architecture is very different between the two formats. This inherent difference makes it impossible to author a disc for both formats in a single process.

Alternate DVD formats created specifically for HD are VCD HD, HD VMD, EVD, FVD. None of these formats are significant competitors in the United States.

Consumer HD

Copy Protection in HD

Disable unauthorized copying.

Content copy protection in consumer HDTV has another layer of protection previously unavailable in the SD world.

HDCP system scrambles the high definition signal between devices such as HDTV cable box and the monitor. Each device in the chain must be capable to “speak” the same encryption language. If a recording device such as a recordable HD DVD is introduced in the chain it also has to be able to decrypt the signal in order to perform the recording.

In case the device can not decrypt the signal HDCP protocol is intelligent enough to allow the downstream device to receive standard definition downconversion of the signal.

Consumer HD

Consumer HD Monitors

Simple truths.

Many less expensive consumer displays that bear “HD Ready” label are incapable of displaying the full 1920×1080 raster size of the largest HD standard. They internally downconvert larger image to the maximum pixel resolution they can display. On such monitors it may be difficult to discern any visible difference between 1080 and 720 size signals.

Another set of numbers commonly seen on HD monitors is contrast ratio. This ratio describes the maximum dynamic range between darkest black and the brightest white.

Audio

Audio Out of Sync

Proper delay management is crucial.

HD size video takes a good amount of processing power. Almost all devices in signal chain will introduce noticeable video delay. While picture is “held back” the audio is passed without delay resulting in a loss of sync. The effect is cumulative in subsequent passes. Before you know it even a casual observer will report that a sound of a closing door is heard before it is seen.

Most flat screen displays also introduce delay which makes them difficult to use in a professional environment. Proper sync is critical for editing, sound and multi-camera control rooms (trucks).

The issue can be mitigated to some extent by placing proper audio delays to “hold” the audio signal back in line with corresponding video.

Audio

Dolby E and Multiple Tracks

Asked to deliver 8 tracks of audio on HDCAM tape? Tough luck, but there may be a way.

Video tape recorders (VTRs) support different numbers of audio channels based on the format.

HDCAM 4 tracks

HDCAM SR 12 tracks

D5 8 tracks (older ones up to 4 tracks)

DVCPRO HD 8 tracks

VTR formats not listed here are not likely to be requested as delivery formats. Most common mastering format at this time is D5 and 8 channels is adequate although not perfect.

HDCAM’s 4 channels may not be enough in some situations. If you need to deliver 5.1 mix on an HDCAM tape how do you record 6 channels on a 4 channel tape? Dolby E process allows you to squeeze 6 digital audio channels into 2 channels.

Once encoded you can not play such audio back without a Dolby E decoder. The master can not be easily downconverted or run through standards converter while maintaining the integrity of the Dolby E tracks.

Audio

AC-3 File Format

Standard for NTSC DVDs and beyond.

AC-3 (AC3) is a Dolby file format engineered to provide high quality 6 discreet channels of audio. The encoding is compressed in order to maximize limited bandwidth of the delivery media. AC-3 also supports stereo left & right configuration as well as mono configuration.

The system is in widespread use in movie theaters, NTSC DVDs and Digital TV broadcasting.