Post on 02-Jun-2018
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CONTENTS
-T./D0)T/-
!!! 1 23334 566T-7 T86 )8'996-76
ST6PS :/.;'.D
-T./D0)-7 S6)0.T0 @'6S"A
streams# Some cinema processors can be configured to directly accept
digital audio, and digital audio can be converted to analog for legacy
cinema processors# The server also has the ability to command Ghouse
controlsG, i#e#, lights and curtains# -o improvements were made upon
this system until the later half of 233#
STEPS FORWARD
/n July H, 233, a digital cinema milestone was crossed with the
digital premiere of Jurasic Park III in 9os 'ngeles# This particular
presentation was compressed with a version of 5P67 2, as developed
for digital cinema applications by 7rass =alley 7roup# )alled5P67I, 7=7Bs compression was based upon the 5P67 2
decompression standard, making this the first public digital cinema
presentation to use an almoststandard decompression scheme# ;ithin
weeks, a true 5P67 2 presentation was held in -ew urtonBs Planet of te Apes, this time using an 'vica digital cinema
server# Together, these presentations marked the beginning of a new
phase for digital cinema by bringing new components to the scene#
' third server company, 6=S, whose product is also based on
5P67, later $umped in with both 7rass =alley and 'vica to create
interoperable servers# ;hile a noble goal, it did not lead to true
interoperability# 7=7 dropped out of the digital cinema game, and
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6=S and 'vica were not able to demonstrate products that were fully
interoperable#
Security got a little boost during this period, though# T and 7=7
developed a link encr!ption method, called )inelink@tmA for the
protection of the @S5PT6 2!2A digital link between server and
pro$ector# ;hile promoted by the server companies, it was not
implemented in either of the 7=7 or 'vica presentation mentioned
above# 9ink encryption is pictured in the block diagram below#
)inelink@tmA link encryption was introduced by Te%as
nstruments in their 5ark = version of the D9P )inema pro$ector#
9ink encryption encrypts the image data as it is sent to the pro$ector,
offering some security to the system# :ull security, however, re&uired
encryption of the content stored on the server, which had yet to be
introduced#
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This phase began with the promise of file interoperability,
but failed to deliver# t did produce link encryption, however, which
was a step towards addressing the security issue#
INTRODUCING SECURITY
>y early 2332, digital cinema installations were numbered in the
E3Bs# They utili(ed several types of servers, including the Fu>it, 'vica,
and 6=S servers already mentioned, as well as the Technicolor Digital
)inema server designed by Fualcomm# These systems represented
three different compression schemes, and four file formats#
/n 5ay th, 2332, another digital cinema milestone was
crossed with the digital release of Star Wars" Episode II# 'lthough
they didnBt financially contribute to the digital presentation of their
movie, 9ucasfilm heavily promoted that it should be seen as such, and
the heyday increased the digital installation count to over 33# The
movie was released in all four digital formats ++ which proved to be a
challenge all of its own#
6pisode broke ground by being the first digital movie
released employing content encryption# -ot all systems were capable
of supporting content security, but those employed by
>oeing1'vica16=S and Technicolor1Fualcomm certainly was# The
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introduction of fully secure presentation systems was a ma$or step
forward#
5any thought this phase would signal a rollout of digital cinema#
>ut numerous issues remained, the least of which were the many
incompatibilities in data packaging, encryption, key manangement,
and compression# 6%hibitors now had enough e%perience to know thatthey had operational issues, too# To add to the problems, not all
cinematographers, studios, and e%hibitors thought the &uality level
was good enough to replace film# 'nd the overriding issue remained4
there wasnBt a sound business model# Studios stood to save
significantly each year by not paying for film distribution, and
e%hibitors stood to pay significantly for the new digital e&uipment#
;hile "rd parties attempted to intermediate as system and service
providers, none were successful# The business partners needed to talk#
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Talking, however, wasnBt a simple task# ' studio collective was
needed to negotiate with e%hibitors# :or this reason, in early 2332,
Digital )inema nitiatives 99) was created# 't first known as -ewco
Digital )inema, D) is a collaboration of the seven ma$or motion
picture studios# 6pisode created a digital cinema bubble, and D)
appeared on the scene $ust as the bubble burst# This led to much unfair
blame placed on D) for the GslowdownG of digital cinema ++ a
slowdown which was inevitable for all of the reasons mentioned
above# Today, in 233", D) is busy sorting out many of the details of
digital cinema, both technical and financial# n the meantime, letBs take
a look at some of the technical issues of digital cinema#
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SYSTEM-LEVEL INTEROPERABILITY
The technology problem imposed by digital cinema is non+trivial#
The goal is to replace a very mature film presentation system, upon
which an entire industry is based, with a not+so+mature digital one#
/bviously, if we want our ticket prices to remain low, we want the
digital system to be not+so+immature upon rollout of the technology#
The technology for pro$ecting digital images onto screens, however,
will not stand still once rollout is begun# Thus, the concept of
GinteroperabilityG is important, as it encapsulates an aspect of system
maturity that can be addressed#
nteroperability can mean different things to different parties# 9etBs
take a look at the practical need for interoperability from an e%hibitorBs
point+of+view#
Digital cinema will not be introduced in the "C,333 cinema
auditoriums that e%ist across the 0S in months, or even in a year# t
will take many years, possibly 3 or more, to build and install a digital
cinema system for every 0S auditorium, and this is not taking into
account the over 33,333 auditoriums around the world# 'n
international rollout of digital cinema could take a very long time#
The long rollout period has significant impact on the concept of
interoperability# :or e%ample, a system installed in
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This could be due to advancements in pro$ection technology, data
storage, networks, and1or the digital link @if anyA between storage and
pro$ector# n addition, we can e%pect there will be clever and
competitive ways of designing and building systems that we have not
yet seen# The progress made by these advances will likely out+pace the
on+going work of standards+making#
/bviously, it is not desirable to impede advances in storage and
pro$ection technology, particularly if they have a beneficial impact on
cost# >ut e&ually so, it is not desirable to obsolete the investment in
digital infrastructure that will be made in the e%hibition booth# To
address this problem, a model for system+level interoperability has
been introduced, originally through work produced by the -ational
'ssociation of Theatre /wners# This model is presented below#
The model reduces the interoperability problem to only three
Presentation System interfaces4 Distribution Package, Theatre
/perations, and )ontent Security# The Distribution Package re&uires a
common file interchange format# Theatre /perations suggests
common 'Ps or protocols for managing the e&uipment in a multiple%
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theatre# Security also re&uires common 'Ps or protocols for the
delivery of security keys to the Presentation System.
f the focus for interoperability is placed on these three areas of
theatre system infrastructure, then the Presentation System is free to
evolve, as it naturally will# This concept can simplify the immediate
work of standards committees, but more importantly, it can allow
differentiation in the design of the presentation system and still gain
the confidence of the system investor# t also sets the stage for
manufacturers of complete digital cinema presentation systems, much
as there are manufacturers of platter and "Cmm pro$ector presentation
systems today# >uilding from this concept of system+level
interoperability, weBll e%plore some of the issues behind each point of
interoperability4 Presentation, Theatre /perations, Security, and
Distribution Package#
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PRESENTATION SYSTEM:
THE BROADCAST SERVER MODEL
There are two models for the secure storage and play out of digital
cinema content4 the >roadcast Server model, and the Data Server
model# ;ithin the realm of the Presentation System, there is no need
find a winning model ++ the market place is very efficient for
determining winners and losers# @;hich leads us back to the
importance of interoperabilit! as described#A
The >roadcast Server model is based on broadcast+style
servers, where image content leaves the server as a decompressed,
real+time stream# The server must decrypt the content sent by the
studio, decompress it, and stream it to the pro$ector# -aturally, link
encryption is needed to make the link between server and pro$ector
secure# :ocusing on the image and audio paths, the block diagram
below depicts the >roadcast Server model#
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The player is the device that accepts digital data and produces a
synchronous stream of video and audio#
The Lpro$ector* also has its own speciali(ation, it is entirely
different from conventional pro$ector#
n the broadcast model of digital cinema, a synchroni(ed image
stream leaves the broadcast+style server and goes to the pro$ector,
while a synchroni(ed audio stream goes to the audio processor# See thefigure given below#
THE DATA SERVER MODEL
The >roadcast Server model for digital cinema systems is
realistic but does not take advantage of 5ooreBs 9aw# ' more efficient
design is possible that utili(es e%isting standards in the data industry#
'gain focusing on only image and audio paths, the Data Server model
is presented in the block diagram below#
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The Data Server model distinguishes itself from the >roadcast
Server model by using the server only for asynchronous data transfer#
n fact, the GserverG is really nothing more than storage# 's with the
>roadcast Server model, the stored content is strongly encrypted#
0nlike the >roadcast Server model, data is only served from the
storage array upon the re&uest of the pro$ector# Thus, the Data Server
model pro$ector GpullsG data from storage, a ma$or distinction from the
>roadcast Server model server, which GpushesG data to the pro$ector#
Since the storage array does not decrypt the strongly encrypted
data, it is not part of the security system, so does not re&uire physical
protection# :urther, the link between server and pro$ector also does not
re&uire protection, since the data traveling across it retains the original
strong encryption provided by the studios# Thus, link encryption is not
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needed# The system becomes simpler, while also inherently more
secure#
5ost importantly, the link between the server and the pro$ector
can now be a standard link from the S'- @Storage 'rea -etworkA
industry# The storage can also be shared among different screen
systems# n the block diagram above, :iber )hannel is shown# :iber)hannel currently supports bandwidths up to 7b1sec, but a standard
is in process that will support 37b1sec# 8owever, 7b1sec can be
sufficient, since the transported data remains both encrypted and
compressed# 2? image data, at 2Efps @frame per secondA, with a very
conservative 3M compression and +bit words per color, re&uires a
bandwidth of 2C3 5b1sec# E? image data, again with a conservative
3M compression and +bit words per color, re&uires a bandwidth of
7b1sec#
The use of shared standards+based S'- networks can be a plus
for those e%hibitors who want the ability to instantly move shows from
screen+to+screen# Since no physical movement of data is re&uired,
multiple screens can be scheduled from a single unit of shared storage,
up to the bandwidth limitations of the S'-# S'-s also offer a degree
of scalability, allowing the storage system to grow as the number of
digital screens grows#
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Shared S'- storage may not be for everyone, though# The cost
of a S'-s network must be weighed against the benefits gained#
8owever, the Data Server model is not limited to a S'-s
implementation, and some vendors are pursuing Data Server designs
that utili(e low+cost storage @but not necessarily shared storageA#
'nd, with the data model of digital system architecture, the server
does not include the player# nstead, the player is located at thereceiver end, typically in the pro$ector as given in the figure below#
The data server will produce a stream but unlike it is synchronous# '
data server in a digital cinema system will not work with an ordinary
video pro$ector# ' pro$ector with an internal or outboard player is
re&uired#
SECURITY
Security is perhaps both the most important and least
understood aspect of digital cinema# )ertainly, the encryption and
decryption of content is not a ma$or challenge# There is general
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agreement that movies will be symmetrically encrypted using a strong,
public encryption algorithm such as '6S @'dvanced 6ncryption
StandardA with very large keys# >ut there are as many ways of getting
that symmetrical key securely to the theatre as there are security
vendors# This is where things get difficult#
The simplest approach for managing keys is for the decryptiondevice inside the theatre to have a secret private key, whose public key
is held by a trusted certificate authority, sort of a Gpublic key bankG#
The content key is encrypted with the decryption deviceBs public key,
which can only be decoded using the private key held securely within
the device#
'nother method employed does not rely on a trusted certificate
authority, and instead destroys the key used to encrypt the symmetrical
movie key immediately upon encryption# The key is later
reconstructed using a proprietary method at the theatre, allowing the
movie key to be decrypted only by authori(ed devices#
;hile not absolutely re&uired, good practice generally re&uires
that a "rd party is employed to manage the keys# Thus, the technology
used by the "rd party key manager defines the security technology
used in the theatre# n a competitive environment where multiple
security vendors co+e%ist, interoperability becomes a concern#
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Solutions for interoperability have been proposed, most notably
within the S5PT6 D)2K Digital )inema )ontent Security ;orking
7roup# 'mong the solutions offered is the introduction of a Security
5anager device within the theatre environment# n one concept, the
Security 5anager employs a proprietary means uni&ue to the security
vendor for receiving and handling keys, while using a link+encryption
method for transmitting keys to the decryption device# /ther concepts
are also being considered#
>oth content owners and e%hibitors have business re&uirements to
impose on security systems# )ontent owners want to know that only
authori(ed devices have successfully retrieved keys, and thus have a
need to track key usage# 6%hibitors, in turn, re&uire the ability to freely
move e&uipment around per maintenance and business re&uirements#
They do not want the movement of a decryption device to prevent the
playing of a movie, and likewise, they do not want the movement of
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the movie to a different screen within their comple% to prevent the
playing of the movie# 0ltimately, if the movie doesnBt play, neither
studio nor e%hibitor makes money# Thus, fle%ibility in the management
of the security system is important to both studio and e%hibitor#
The challenge that lies ahead is to allow the desired fle%ibility
while maintaining the desired level of security# 0ltimately, this is both
a technology issue and a business issue, for which a satisfactory
solution has yet to be agreed upon#
THEATRE OPERATIONS
Theatre operations in the film world are fairly straight+forward# '
show is made up by $oining policy trailers, ads, movie trailers, and the
feature movie together on a single platter# This operation is called
Gmake+upG# The platter, in turn, feeds the "Cmm pro$ector with a
contiguous show# 'utomation cues, such as those needed to control
house lights, move curtains and1or screen masking are physically
tagged to the print and read by the automation system# Thus, once a
show is Gmade+upG, its platter can be physically moved to any
pro$ector in the house for presentation to an audience#
n the digital world, it is necessary to maintain the same level of
functionality as provided by modern+day film systems# /ther features
are also possible, however, which should not be overlooked# These
features can affect how the theatre of the future is operated, right down
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to the systems used for booking content# 6%hibitors have asked for
basic features of their digital theatre operations systems4
Show Scheduling
Show G5ake+0pG
'sset @)ontentA 5anagement
Show 9ogs
6&uipment 5onitoring
Software is already being discussed by at least one vendor thatwill combine the booking of ads, trailers, and movies with the ability
to create system play lists at the time the content is booked# n this
way, the creation of play lists becomes centrali(ed, and can be
downloaded by the e%hibitor to the theatre for operational use#
9ikewise, system management software can log the play of the
content, so that the e%hibitorBs central office can efficiently oversee
operations# This capability is compelling, and it is not available today#
t demonstrates the importance of defining interfaces for theatre
operations that empower the use of new business tools#
The ability to monitor the health of e&uipment, particularly from
remote locations, is an important tool for maintenance crews# ;hile
remote monitoring is not uncommon in the T world, there is nothing
like it today in the cinema# 9ike the T world, S-5P has become the
most widely discussed protocol for use in system monitoring#
DISTRIBUTION PACKAGING
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Distribution packaging is the means for enabling a common
interchange format for content# ;hile this can be thought of as the
GD=DG of the cinema world, it is far more comple% in nature# The
basic re&uirements of a packaging method are4
'llow any make of system to read the packaged content,
'llow defective files to be replaced by segment, without
replacing the entire movie,
Provide a fle%ible means for including additional language
sound tracks, subtitles, etc#,
Provide a means to communicate the synchroni(ation of files#
Through work in the S5PT6 D)2K Packaging ad hoc group, the
schematic of a packaging scheme has been outlined and circulated
among industry participants, n early 233", it was the recommendation
of the D)2K ad hoc group that 5N: @5aterial 6%change :ormatA be
employed as the packaging technology for digital cinema# 5N: is a
technology originally proposed by the Pro+5P67 group, and currently
in process for standardi(ation within the S5PT6 ;2C Technology
)ommittee for broadcast applications# ' digital cinema Goperational
patternG has yet to be proposed for standardi(ation at the time of this
writing#
PUTTING IT ALL TOGETHER
f youBve gotten this far, youBre either employed in the industry or
youBre a very interested person# Just to show in terms of a block
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diagram how a real system might look, the block diagram is given
below#
;e havenBt said much about audio, and it deserves a little
attention# G-IG audio channels are shown in the diagram, a simple
way of saying that - channels is never enough# f youBre familiar with
the history of film sound, -I says it all#
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0nfortunately, itBs not possible to achieve -I with '6S"#
;hile a popular serial transmission method, '6S" is pair limited, with
two audio channels per pair# 5'D @'6S3A is a standardi(ed serial
format that supports C channels of digital audio# @9etBs hope that C
are greater than -I#A :ortunately, S5PT6 D)2K has discussed
grouping audio in blocks of channels, making it easy to place on
6thernet, even when using !?h( sampling and 2E+bit audio# Several
6thernet audio methods e%ist, including 5agic and )obranet#
Some new blocks are shown in the diagram above# ' Theatre
5anagement System and a Security 5anager are included# The
Theatre 5anagement System is a central place for operations+related
software# The Security 5anager is discussed earlier#
DTS, for Digital Theatre System, was introduced by Steven
Speilberg with the release of Jurrassic Park in !!"# So far, this
standard applies more to the big screen than private home# The sound
is coded over si% channels as in Dolby Digital# There are now many
DTS+compatible systems available# So surround systems, like sound
cards, can decode the standard via software# 8owever, while the
e%cellent &uality of DTS undeniable, and even a bit higher than Dolby,
remember that there are no movies available in DTS alone, and that
Dolby is considered to be the digital sound standard and DTS is not#
The main feature of DTS is that its coding system favors sound
&uality over disc space# So a DTS sound band codes in 2E bits instead
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of the K bits with Dolby# )ompression uses a dynamic process where
the compression rate varies with the amount of sound to encode# This
rate ranges from 4 to 4E3 and generally results in better sound
&uality than Dolby Digital with an average rate of #C 5b1s# The main
draw back is obviously that the sound band takes up much more space
@about " times as muchA than Dolby# So D=Ds coded in DTS can only
have one language and a limited number of bonuses# >ecause it is
optional as a sound standard, there are not many D=Ds with DTS on
the market, through the number is growing#
The main advantages of the DTS are video piracy# That is, only
authori(ed people can get the data# There is no problem of physical
transportation because of the server system# The most attractive
advantage is that preservation of films or archival of films#
CONCLUSION
's you might e%pect, thereBs more to the digital cinema story than
we have covered here# Digital cinema is not television ++ it is much
more comple%, fle%ible, and &uality+oriented# ;hile not always visibleto the public, there are a lot of people working to move this
technology forward# n time, youBll be able to en$oy the fruits of their
laborO
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BIBILIOGRAPHY
# www#mkpe#com
2# DTS ' retrospective, by .eward :leming#
"# Theatre system architectures for Digital cinema, by Streven '# 5orely
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2!