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PART FOUR - Compression, Encryption and Encoding Methods

* What Television Broadcast Standards are compatible with BUDs?

All television distribution uses some set of technological standards
incorporated to allow specific types of reception. This is mainly important in
terms of the type of TV set you use and what part of the world you are in.
Satellite television, generally speaking, is compatible with all standards of
television broadcasting; the only necessary information needed is whether or not
a particular model/type of receiver will work with your television set and what
country a satellite transmission is intended to be viewed in.

(This FAQ is not meant to be a comprehensive technical guide to how television
itself works. It is only meant to distinguish between different technological
standards so that they can be recognized and differentiated as simply as
possible.)

1. NTSC - NTSC, which stands for National Television System Committee, was
established in 1941 as the original standard for television broadcasting. It
primarily exists in North America and Japan. In the simplest terms, NTSC has a
525-line screen image delivered at 60 half-frames per second. Your television
(if you live in North America or Japan) is probably an NTSC compliant
television.

2. PAL and SECAM - These are standards that are not used in North America. PAL,
or Phase Alternating Line, is the standard for television in most of Europe and,
for that matter, is the most used television standard in the world. Unlike NTSC,
PAL has 625-line screen image delivery delivered at 50 half-frames per second.
The primary difference between NTSC and PAL is that the phase of the color
components is reversed from line to line and the color difference signals are of
a different type. SECAM is a third standard used in France, Russia, and a few
other places in the world. Both PAL and SECAM are considered to have superior
horizontal resolution than NTSC.

NTSC, PAL, and SECAM refer to general low-definition television viewing
standards and do not address the issue of compression of broadcast bandwidth.

* What Compression Schemes are used with BUDs?

Digital compression allows for more than one video and/or audio channel per
satellite transponder.

1. DigiCipher II - DigiCipher II (DC2) is a digital encoding and encryption
format developed by General Instruments (now part of Motorola) that is used for
many American digital TVRO transmissions. In order to view DC2 channels, a
special receiver called 4DTV is required. DC2 is a proprietary standard based
upon MPEG-2. DC2 technology can be licensed to other companies, but no other
companies have requested a license. Only Motorola manufactures 4DTV receivers.
Those made for consumer BUD use cost around $400-$800 suggested retail, but are
typically available at discounts that at times can be quite deep.

2. DVB/MPEG-2 - MPEG-2 is a general encoding scheme used for many differing
digital technologies; DVB, which stands for Digital Video Broadcasting, is the
satellite television-specific variety of the MPEG-2 standard. This is not so
much a competing digital standard as it is an OPEN standard. This standard is
used in most of the world outside of the U.S. for digital TVRO broadcasts. Many
international and non-traditional programming is found using DVB/MPEG-2. Many
U.S. DVB feeds are free to air and are receivable with a DVB/MPEG-2 FTA digital
satellite receiver. Channels using this standard may or may not choose to stay
free-to-air indefinitely; once a network disappears, it may or may not be gone
forever to consumer TVRO viewers.

For more complete information about DVB/MPEG-2, see the MPEG-2/DVB (Satellite)
FAQ written by the Delphi DVB Hobbyists. It is located at:

 http://dvbwave.com/faq

And Rod Hewitt's "North American MPEG-2 Information" at:

 http://www.coolstf.com/mpeg/index.html

* What Encryption Methods are used with BUDs?

The type of encryption depends on whether the transmission is analog or digital.
In North America, there are still encrypted analog channels, although more and
more channels are switching to digital compression and the encryption methods
used with digital channels.

The only important remaining analog encryption method is VideoCipher II+
Renewable Security, or VC-II RS for short. VC-II RS was developed by General
Instruments. The original VideoCipher I was developed in the mid-1980's by
M/A-Com (who was later bought out by GI) when satellite encryption was just
beginning. VideoCipher I was short-lived and was replaced by VideoCipher II, and
later VideoCipher II+. VC-II RS is the last version of this encryption scheme
that will probably ever be developed as more and more channels use digital
encryption methods. All modern IRDs have VC-II RS decoding capability.

Besides VC-II RS, the other common form of analog encryption still used is
Leitch. This is used primarily by networks such as ABC and ESPN. The other
notable types of analog encryption are Oak Orion and BMAC. Oak Orion was a
standard used by Canadian satellite transmissions until most Canadian
subscription channels moved to Bell ExpressVu (DBS) and StarChoice (DigiCipher
II). Oak Orion is no longer used. BMAC was a third analog encryption scheme but
is no longer used much anymore.

More importantly these days are digital encryption methods. Here is a
description of these methods:

1. DigiCipher II - DigiCipher II (DC2) is the defacto American standard for
digital TVRO encryption. The only hybrid digital/analog IRD is Motorola/GI's
4DTV receiver. With the introduction of the Motorola/GI 4DTV sidecar receiver in
2001, you no longer need to replace your older analog IRD to enable DC2
reception. There are no third-party DC2 receivers, unlike analog TVRO IRD's. No
third-party companies have requested a license, so Motorola/GI never has
licensed the technology. Canadian StarChoice is transmitted in DC2, and
StarChoice receivers are manufactured by Motorola/GI.

(The following are DVB/MPEG-2 encryption methods.)

2. PowerVu - used by AFRTS, NBA TV, RDS - Roseau des Sports, Musique Plus,
MusiMax, Le Canal Nouvelles TVA; others

    This is a standard developed by Scientific Atlanta. You need either the
    Scientific Atlanta PowerVu 9223 receiver, which runs about $1600, or
    the Scientific Atlanta PowerVu 9234 receiver, which runs about $750.
    The 9223 is designed for cable companies to allow them to receive
    MPEG-2 signals that are uplinked for their benefit. Consequently, its
    user interface is very complex and is not designed for channel surfing.
    The 9234 "Business Satellite Receiver"  is a little more user friendly.

3. Irdeto  -  used by ABS-CBN International, Lakbay TV, Channel D; others

    This is a standard developed by Irdeto Access.

4. Nagravision  -  used by Caliber Learning Network, other private networks

    This is a standard developed by Kudelski.

5. Viaccess  -  used by some programming on Telstar 5 satellite

    This is a standard developed by France Telecom.

6. Wegener  -  used by Empire Sports Network, Televisa, XEW - Canal 2, XHGC -
Canal 5;  XEQ - Canal 9; others

    This is a standard developed by Wegener Communications.

Note: There is no consumer receiver that can receive both DigiCipher II/VC-II RS
*and* DVB/MPEG-2 programming and there probably won't be one available anytime
soon. General Instruments produces a commercial grade receiver (DSR-4800) that
will receive both Digicipher II and DVB/MPEG-2.

A WORD ABOUT 4:2:2 SCREEN PIXEL RATIO

Most DVB/MPEG-2 receivers receive what is called 4:2:0 screen ratio for picture
resolution. But certain DVB/MPEG-2 channels, usually network and/or studio
feeds, use what is called 4:2:2 screen ratio. This involves the ratio of video
data to vertical pixel and horizontal pixel color. 4:2:2 is NOT part of the
standard DVB specifications but is used mainly by studios that need better
picture quality than standard DVB offers. This is the standard currently used
for in-the-clear reception of NBC, as well as Warner Brothers and Fox network
feeds. Most consumer FTA receivers cannot receive signals with the 4:2:2 ratio;
a more expensive receiver is required. Note that 4:2:2 is NOT a type of
encryption; however, like certain types of encryption, it does force the TVRO
viewer to make certain considerations when purchasing receiving equipment.



