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Archive-name: Satellite-TV/TVRO/part4
Posting-Frequency: 15 Days Disclaimer: Approval for *.answers is based on form, not content. See reader questions & answers on this topic! - Help others by sharing your knowledge 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. User Contributions: |
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