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Tech
Notes
Published by: Larry
Bloomfield & Jim Mendrala
E-mail = HDTVGuy@aol.com
or J.Mendrala@ieee.org
April 6, 2000
Pre-NAB Edition
Tech Note - 054
**********************************************
Talent does what it can, but genius
does what it must!
Our Mission: Sharing
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The Tech Notes are posted and past issues available at:
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and http://www.HDPictures.com.
++++++++++++++++++
From the Publishers:
Both Jim and I will
be at NAB-2000 from Sunday afternoon until Thursday afternoon. We
hope some of you will look us up while there. We are staying at
the Imperial Palace. Jim's schedule is eclectic. I will be at the
LVCC all days save Tuesday, when I'll be at the Sands.
Please call us on
our cell phones if you'd like to touch base: Jim's cell is 661-609-5299
and mine is 408-202-0482.
You can recognize
Jim by his picture on his personal web page: http://home.pacbell.net/Jim_Sue.
You can see my picture
in Broadcast Engineering at the beginning under Beyond the Headlines
or if you see a fat guy in an electric cart, that's probably me.
++++++++++++++++++
Reader Feedback:
From: Matthew Sheby
RE: Tech Note #52
Tell me about it.
I think I was the only non-Napa college guy in the audience. [And
yeah, with the exception of the Firewire guy, the majority of the
speakers were almost as exciting as test tones.]-Matt
++++++++++++++++++
From: Ted Small,
Chief Engineer, KFXK-TV
RE: Tech Note #53
Prior to leaving
for NAB I thought you would be interested in an update on the machine
with so many hours. A few weeks ago Hugh Peavy, my assistant Chief,
and myself went to Dallas to a JVC lunch / demonstration of Upconverting
our 50mbs bit stream to HD using a Leitch decoder/encoder. All I
can say is: WOW!
The Head life of
our BRD-50 is 14,724 Hrs. We are getting a Brand New BRD-50 in exchange
for this one. JVC wants to show it off at NAB. The bad news is today
we pulled the machine off-line to replace the Head cleaning apparatus,
and went to play an older tape and we had a first light indication
of data errors. The tape in the shop had been around the block quite
a few times, so we got a fresh one out of the library and it had
a airable picture, but it to was showing first light data errors
(data errors lights are three in number and go left to right). So
if it were not for the new machine being on the way we would be
installing our first head and drum replacement on this machine.
It will ship out Monday April 3rd so the final number may hit 14,750
after this weekend. I thought you might, might want to pass it along.
Thanks -Ted
++++++++++++++++++
From: C. B. Patel
Re: TECH NOTE #
52 & 53
These two Tech Notes
are very interesting. I have followed this VSB-COFDM debate. We
all read about the VSB receivers failing to perform in test after
test. The Sinclair demo to the several Congressmen is only another
example of it.
So far no one has
bothered to analyze "why the receiver failed to perform." I have
talked to my friend Chris Strolle at the NxtWave, Tianmin Liu at
the Broadcom and Frank Eory at the Motorola. All these companies,
so called the CHIP-Manufacturers are burdened to solve the VSB problems.
I have worked in
the TV design at Sarnoff and then at Samsung since 1974. Unfortunately
currently I am not with any TV design company. I work as consultant
for Samsung but I do not have direct input in their TV designs.
From what I analyze,
the problem is in front-end system design. The chip manufacturers
are no experts in the front-end system design. Yes, they do provide
an Evaluation Board so one can see their chip do equalization and
VSB demodulation. But by no means their implementation is what is
necessary for a good receiver design.
Unfortunately only
that is available for Sinclair, MSTV and others for VSB testing.
No wonder when their implementation is put to tests, it fails miserably.
But still no one is asking them (Motorola, NxtWave) why did your
system failed. No one is bothering to analyze the failure. Rather
massive data is collected in number of sites tested.
If I were the designer,
I need only one, the first site to fail for me. I must camp there,
analyze the received signals, what is being processed in my implementation
and understand thoroughly why it is failing. Failing even at one
site, is one too many.
Do corrections or
come to the conclusion that needed corrections are not possible
before embarking on any more tests. But the Lab & Filed testing
frenzy has gone crazy. The people who supposed to be doing the testing
are not doing the tests. Whether proper design is done is never
questioned. Unfortunately the chip-manufacturers are afraid to admit
that certain area of the front-end design is not their expertise
and want to claim their equalizer could do miracles, which is impossible.
But they do not seem to understand the limitations.
What I am saying
is "it is not the VSB that is failing, its (poor) implementation
is failing." And if the results are properly analyzed or even looked
at, it could be very easy to see that. But the issue is now politicized.
I am not saying
that the COFDM is not better. But if the designer understands what
a COFDM receiver does in their front-end so it does demodulate properly
even in multipaths, and compare if any such "care" is taken in a
VSB receiver design, it is not hard to understand why the VSB receivers
perform the way they are performing.
You said that NBC/RCA
came up with the needed correct solution about Color TV when needed.
(Something like that). Unfortunately today, there is no such R&D
Lab like Sarnoff of those days. Today's Sarnoff is not the same.
Where is the General
when we need him? C. B. Patel
++++++++++++++++++
From: THOMAS LENTO,
Sarnoff Labs
Subj: Re: TECH NOTE
#53
I'm not getting
involved in the 8VSB wars other than to point to our position paper
on our web site.
But here's a thought
for you on another of your points: the commercial justification
for DTV.
In 2 to 4 Mbps of
bandwidth you can push a raft of info and entertainment (read: music
and TV-quality video) services through the air. Our WaveXpress venture
is just one of the companies expecting to give broadcasters a whole
new revenue stream that we think makes the DTV transition a good
commercial move.
Naturally we think
WaveXpress is the leader here, with their open business model and
turnkey service.
By the way, at 2
to 4 Mbps for these datacasting services you still have room in
a 6 MHz channel for an HDTV program or multiple SDTV programs using
8VSB. It's quite a bit tighter with COFDM.
Check out WaveXpress
at NAB. Let me know if you want to talk to them and I'll see what
I can arrange.
Also, on 1080i vs.
720p: Why don't people look at the ATSC standard? There is a "1080p"
format built in, at 24 fps (native movie speed, no pull-down necessary).
That's "true HD" with a 2 Megapixel picture no matter who's looking
at it.
As for 1080i, though
I'm not technical, I like to think of it as a placeholder for progressive-scan
30fps until compression technology improves. The ATSC standard is
extensible, and there's no reason that can't be added when it's
technically feasible. So locking into 720p for production and broadcast
may not play so well, say, 5 years from now.
Tom
+++++++++++++++++++++++
Subject: Encryption
Systems for Digital Cinema
by Jim Mendrala
Digital cinema being
discussed mainly in Hollywood seems to always bring up the subject
of security otherwise known as encryption and de-encryption. It
seems like a great amount of time and effort is being spent on security
issues that have no real impact on the quality of the presentation.
Any encryption system used in digital cinema would be transparent
to the images and sound but would not sacrifice the security of
the copyrighted material.
Based on the use
of strong encryption systems and by the general inaccessibility
of the entertainment content to the general public, pirated copying
could result in movies being put on DVD-R. Standard Definition Television
(SDTV) video versions of the copyrighted material could also be
distributed on VHS or even on the Internet in violation of copyrights.
The attributes of
an appropriate digital cinema encryption systems need to be explained
however to the content owners, producers, studios, distributors
and stakeholders. Even though sufficiently strong encryption is
readily available today, the limited breaking of the DVD CSS (which
was intended only to protect against casual copying) and the well-publicized
hacker attacks on the Internet give the impression that encrypted
content is vulnerable to code cracking. The reality is that essentially
unbreakable content protection ciphers are available, and that secure
access management systems can be assembled from thoroughly tested
components. These statements remain true; even though logos and
trailers may give crackers plain text versions of the cipher text
they would attack. Security of protected digital cinema content
will be far superior to that of today's 35mm film, but the problems
of employee trust and physical security of the exhibition environment
will still remain as points of vulnerability. Security experts understand
that compromising modern encryption systems is impractical without
accomplices among trusted personnel.
From the standpoint
of digital cinema, the encryption systems are envisioned to have
certain characteristics, including:
* A store-and-forward
means of distributing the protected property.
This means that
entertainment material will be stored and transferred between storage
locations outside of the physical control of content owners (as
it is with 35mm film) and there may be multiple stages of store-and-forward.
* The storage and
distribution of the protected property will take place in hostile
environments, which have no security by trusted personnel.
This implies a requirement
for physical security of the digital cinema equipment, e.g., anti
tampering provisions. Un-trusted personnel who may not be technically
sophisticated will manage the exhibition of protected property.
To meet the requirements
of presentation, the exhibition of protected property will be scheduled
in combination with other protected or unprotected material by the
exhibitor. The exhibition of protected property may be stopped for
various reasons, and must be able to be re-started in a reasonable
way.
Time based requirements
for protecting property -- Owners of property to be protected are
concerned about security breaches that compromise day and date releases
(worldwide). Upon public exhibition, entertainment material is subject
to copying by camcorders of various levels of sophistication. This
form of copying takes place outside the encryption system, except
for watermarking and fingerprinting protections, which imply legal
protection sanctions.
The nature of the
protected property contains image, audio, and metadata. It may also
contain various other data, which might be essential for its presentation.
Protected property
may also refer to information concerning the exhibition of the entertainment
content itself. The ownership of such data is determined by the
contractual agreements between property owners and stakeholders.
Functional requirements
of the encryption systems for protected property owners and stake
holders -- Stake holders are those parties who do not actually own
the property but who have an interest in protecting it, at least
in part. The encryption system must embody the contractual relationships
between stakeholders and owners of the protected property.
Security -- Security
is the first concern of the encryption system. It includes confidentiality,
meaning the concealment of protected property from all but parties
authorized to reveal, transport, or sub authorize other parties,
according to their contracts with protected property owners. Security
may also include means of tracking security breaches within or outside
of the encryption system.
Authentication --
The parties using the protected property must be assured of the
true identity of other transacting parties or equipment.
Data integrity --
The parties using the protected property must be assured that unauthorized
parties have not modified the protected property.
Non-repudiation
-- Transacting parties must be able to demonstrate that the sender
and receiver did actually send and receive the claimed components
of the transaction.
Availability --
The encryption system must ensure a quality of service that meets
the contractual obligations of the parties. In addition to a reference
to delivering exhibition, this requirement includes the ability
to service equipment or maintain the encryption system with minimal
impact on security or exhibition.
Specifics -- The
encryption system must include among its protections authorizations,
which apply to place, time, and exhibition equipment.
Renewability --
In the event that security is breached, the encryption system must
be able to revoke compromised trust relationships (with hardware,
software, or humans), report the security breach to responsible
parties, and maintain security and functionality of the un-compromised
components of the greater encryption system.
Co-existence --
Digital cinema encryption systems, like other elements of digital
cinema, will co-exist for many years with the systems that now support
35mm film projection. Such legacy systems include the physical environment
and personnel, existing automation systems, existing theatre management
systems, and existing box office systems.
Press, employee,
and test screenings -- Producers as well as exhibitors require presentations
prior to opening day public screenings. The content protection system
must apply to these screenings as well. One possibility for additional
protection would be the inclusion of an obvious watermark, perhaps
similar to watermarks as used by television stations, for these
screenings. This watermark would not appear if certain access keys
were used, and these keys could be time enabled.
Small market size
-- The market size for digital cinema systems, certainly at first,
is small compared to the size of encryption systems such in DirecTV
or the Dish Network, for example. This suggests that the components
of digital cinema encryption systems should be selected from existing,
standardized hardware and software in order to keep costs manageable.
To add to the complexity
producers and exhibitors so far have expressed the desire for the
choice of hardware, software, and services to be open and competitive.
This implies that the elements of the encryption system must be
modular and interchangeable to some degree. It also implies the
standardization of the interfaces between the various elements of
the encryption systems. SMPTE is studying these issues in the digital
cinema DC28 Study Group.
These are some of
the concerns surrounding digital cinema. In the beginning back in
June of 1999, George Lucas released "Star Wars - The Phantom Menace"
to 4 theaters in the United States. At that time the only security
used was a security guard in each of the projection booths. That
was a humble start but security issues discussions have come a long
way since then.
Jim
++++++++++++++++++
Subj: The following
is in response to a letter from Robin Rowe, a new subscriber.
By: Larry Bloomfield
Re: Tech Note #53
I'm more than happy
to answer your questions. When I said: "Although the ATSC technically
classifies 720 lines as high definition, true HDTV is 1080 lines,"
I was referring to the international definition of HDTV and the
ATSC. Tony (can't remember his last name) at ABC is heading the
US International delegation to get 720P accepted internationally
as HDTV. I've heard no word on the progress.
You said: "Under
your theory neither 1080i or 720p would qualify as HDTV, although
you later state that 1080i is HDTV." The actual frame resolution
of 1080i is only half of that, or 540 lines at 60 fields. Granted
it's a different 540 lines on alternate fields, but as I recall
subjective viewers differ on whether 1080i or 720p is actually sharper.
There are no fields with 720p as it is progressive.
In theory, I agree
with your statement. I have been a proponent of 720P asking the
question, "how can you take two different pictures from different
points in time and expect them to look as good as a progressively
scanned picture."
And yes, both formats
have approximately the same bit rate. I have seen both 1080i and
720p side by side, and they both look good. If I was forced to choose,
I opt for the 720p because of my bias. It is interesting to note
that a new company is on the news front, iBeam and the group owners
of the stations who subscribe and support it will go to 720p irrespective
of their network affiliation - NBC or CBS.
When you said: "Motion
picture resolution isn't just pixels," I agree. I used a Kodak statement
in the SMPTE journal as my source for the comparison, which is their
info.
I even went further
then saying that HDTV provides wide-screen picture quality similar
to 35mm film. I said that the D-Cinema in use to day is lesser quality
than the broadcasters are transmitting. The TI system puts about
1.3 Megapixels on the screen. You do the math: 1920 x 1080.
That wasn't going
too far. There are too many who say that is just fine and don't
wish to push the limits to what we could have in the electronic
motion picture technology. I saw Toy Story 2 all in digital from
start to finish, never on film, in San Francisco as part of the
Feb. 2000 SMPTE conference. I was impressed. There are many points,
which made it better than a 35mm film presentation, but it is not
the best we could have today. There are no standards establish,
as yet, for D-Cinema. I hope and pray those who are establishing
them at this time don't settle for anything but the best. We have
the technology; let's use it.
As for my roll and
interest in all this, I suggest you check out my bio at http://www.hdpicutres.com.
Mendrala's is there also. If you have any questions after that,
I'd be more than happy to answer them. As for what I do, I know
write and am a consultant to several firms. I had an accident several
years ago that will only permit me to do that now. I've been doing
Beyond the Headlines for Broadcast Engineering for nearly 2½
years. The folks at BE saw some of my early work in the Tech Notes
and like it. The rest is history. In addition to this, I like to
stir the pot. It never hurts to have a protagonist who is not afraid
to take the bit in their teeth and get people to thinking. I know
doing that, sometime, upsets people, but oh well. A person gets
sore when they don't use mussels, which haven't been used for a
while. The same is true of the brain. I'm never afraid to answer
questions, as that tends to either make me rethink issues and either
come up with a better way/answer or confirm my thinking. My best
regards, Larry
++++++++++++++++++
Subj: ATM and video
From: Ralph P. Manfredo
(Ed Note: Manfredo
is the President & CEO of BroadBand Networks Company in Santa
Clara, CA. Manfredo is also in the process of writing a book on
this very topic.)
What are these new
terms or acronyms used in the digital television industry:
CBR, VBR, ABR, VPIVCI,
VDSL, FSAN,
DSLAM, HFC, FTTC,
AATM and ATM25?
These acronyms are
not Italian and I will try to explain them to you:
CBR - Constant (or
Continuous) Bit Rate. This is one of the ATM service types offered
in which a virtual circuit is configured to support a fixed (constant)
amount of end system traffic for the duration of the connection.
These services guarantee a fixed rate of communications
VBR - Variable Bit
Rate. This is one of the ATM service types offered in which a virtual
circuit is configured to supports the transport of "bursty" type
of traffic as opposed to CBR traffic. VBR is characterized by an
average SCR (Sustainable Cell Rate) and PCR (Peak Cell Rate).
ABR - Available
Bit Rate. This is one of the ATM service types offered in which
a virtual circuit is configured to provide a minimum bit rate for
user transmission and allows a higher bit rate, up to PCR (Peak
Cell Rate) if the capacity is available.
VPI/VCI - Virtual
Path Identifier/Virtual Channel Identifier. The combination of VPI
and VCI used to identify a specific segment of an end-to-end ATM
virtual circuit (VC) between two ATM devices and to switch cells
in an ATM network. (See VPI and VCI below.)
VPI - Virtual Path
Identifier. A value in an ATM cell header that identifies the virtual
path (VP) to which the cell belongs. This field is 8-bits in cells
traversing a UNI (User-Network Interface) and 12-bits in cells traversing
network circuits.
VCI - Virtual Channel
Identifier. A 16-bit value in the ATM cell header that provides
a unique identifier for the virtual channel (VC) within a virtual
path (VP) on a given virtual circuit that carries that particular
cell.
DSL - Digital Subscriber
Line. General name for several specifications supporting digital
customer local loops. See ADSL and VDSL below.
ADSL - Asymmetric
Digital Subscriber Line. An ANSI standard that provides for voice
plus a data connection on the same customer local loops that currently
only support one analog voice connection. The data connection supports
from 384Kbps up to 8Mbps downstream (to the customer) and 64Kbps
up to 1.5Mbps upstream (from the customer to the network).
VDSL - Very high-bit-rate
Digital Subscriber Line. A new and emerging specification to provide
connectivity and broadband services to residential customers. VDSL
supports from 27Mbps up to 52Mbps downstream (to the customer) and
up to 3Mbps upstream (from the customer to the network).
FSAN - Full Service
Access Network. This is a new and emerging standard being developed
by the major telephone companies in the world. This standard will
define how new DSL services will be distributed to the residence.
There is an organization called FSAN and among its members are:
Bell Canada, British Telecom, Deutch Telecom, French Telecom, GTE,
Korea Telecom, SwissCom, Telstra & Telecom Italia (CSELT), SigTel
(Singapore Telecom), SBC Communications, Bell South, U.S. West and
GTE.
DSLAM - DSL Access
Multiplexer. The network half of the DSL system. It can reside either
in the central office (CO) or on the street. It concentrates multiple
subscribers and provides access to the appropriate data services
such as Internet Service Providers (ISP).
HFC - Hybrid Fiber
Coax. A residential access technology to provide broadband services
over the cable TV infrastructure with fiber to the curb and coax
to the residence. Connectivity supports data rates of 27Mbps downstream
and up to 1.5Mbps upstream.
FTTC - Fiber To
The Curb. A residential access technology to provide broadband services
over fiber optic cable directly to the home. This connectivity supports
data rates of up to 622Mbps.
ATM - Asynchronous
Transfer Mode. A broadband switching and multiplexing technology
used for transferring video, data and voice information. ATM is
a connection-oriented high-performance integrated technology that
supports Broadband Integrated Services Digital Network (B-ISDN)
services under specified Quality of Service (QoS) guarantees. Since
capacity is allocated on demand with no clocking control between
end points, is called asynchronous. Information is transmitted a
very high rates using a fixed cell size. Each ATM cell is 53-octet
(byte) packet comprised of a 5-octet header and 48-octet payload.
ATM provides for different QoS Classes, allowing for traffic streams
to be distinguished, based on Class of Service.
ATM25 - A version
of ATM that uses CAT3 or CAT5 UTP (unshielded twisted pair) cable
for use inside a building. The typical interface supports 25Mbps
and uses the ATM protocol. The FSAN VDSL protocol appears to be
leaning towards the ATM protocol because current VDSL products that
are non-proprietary in nature are using ATM as the protocol. The
set top boxes we used in both Korea and Canada had ATM VPI/VCI addressing.
Hope this helps.
Ralph
++++++++++++++++++
(Ed Note: The
Editors and Publishers of the Tech Notes wish to thank Des Chaskelson,
Research Director of SCRI International for his generosity in posting
the Tech Notes on the SCRI web site. http://WWW.SCRI.com).
SUBJECT: NAB2000
and SCRI Research News
FROM: Des Chaskelson,
Director, SCRI International
NAB2000 exhibitor
listing and press release site - free access at: http://www.scri.com/nabindex00.html
-- includes over 600 NAB2000 exhibitor listings and news releases!
Contact info@scri.com for details. SCRI Research News:
US TV Station Migration
to H/DTV -- System Specification
http://www.scri.com/sc_hdtv_2000trends.html
SCRI's New - 2002
Broadcast | Pro Video Trends Survey Now Online - Facilities only
- Get FREE Access to Online Insider Report: http://www.scri.com/sc_sur.html
New HDTV Marketplace
Trends Report: 2000 - 2004
http://www.scri.com/sc_hdtv_2000trends.html
++++++++++++++++++
The Tech Notes are
published for broadcast professionals, and others, who are interested
in DTV, HDTV, Electronic Cinema, etc., by Larry Bloomfield and Jim
Mendrala. We can be reached by either e-mail or land lines (408)
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