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by
Chris Muriel |
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What is Digital Satellite Television |
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All Pace receivers up to late 1997 seem to suffer from this and, according to a recent French magazine report, so do Sagem boxes sold for the French TPS (Television Par Satellit) bouquet. You also need the relevant Conditional Access Module (CAM) for any subscription channel along with appropriate smartcard (which could include a pirate card - these started to appear in summer 1997 although many were knocked out via ECM's from the operators). There are several different conditional access schemes in use by the different operators & each system needs the relevant CAM (as well as the smartcard for subscription channels). IRDETO was the commonest in Europe but now SECA seems to have overtaken it. *** See diagram of a generic CA (conditional access) system as used in an IRD ***
Just to explain a some of the acronyms used in the diagram:- ACS
=
Access Control System DVB-CI was a "cop-out" in that they could have specified that all DVB receivers used the same form of conditional access. Instead they paralled the situation that occurs in analogue satellite transmissions i.e. many different systems co-exist. This kept the status quo with the operators (& Hollywood) but runs totally against EU open market policy.Only the CAM interface is covered by the DVB spec. -so they can use their own proprietary encryption system. In Spain the 3 digital satellite operators were each going to use different encryption methods. However,the Spanish authorities stepped in tried to force them all to use compatible systems. This promotes healthy competition ,allowing the Spanish consumer to buy one digital receiver & choose to take 1 ,2 or 3 subscriptions (involving 1,2 or 3 smartcards) but they will all work on the one receiver & CAM. If
you want to complain, I suggest those in Europe write to their Euro
MP IRDETO - used by Kirch/DF1,Nethold/Multichoice,Telepiu, M-Net (C-band) SECA
- French. Used by Canal Plus/CSN (Canal
Satellite Numerique). VIACCESS - Used by TPS (Television Par Satellit), French Bouquet which can be found on Hotbird 2 (13 degrees east). Also AB-Sat on the same satellite. I believe rights are owned by France Telecomm as it was developed in their CCETT research centre. CRYPTOWORKS - Used by RTL (Austria/Switzerland). Cryptoworks is a trademark of Philips. CONAX - Used by Canal Plus for Scandinavian packages. Conax is a Telenor company. VIDEOGUARD (NDC) - To be used by Sky Digital in UK. Proprietary encryption system with no CAM used - the CAM function is built into the motherboard and is non-removeable. NagraVision - Used by the Spanish Via Digital multiplex. Normal CAM modules use PCMCIA connections - a technology borrowed from laptop computers. This should allow you to unplug one module & insert another to switch from, for example, IRDETO to Viaccess. However this isn't a simple 5-minute task & the internal software isn't guaranteed to support the change!! Add to that the difficulty in easily obtaining CAM modules other than the one supplied within the IRD, so this isn't going to be an easy option for many people. Of course, it gets easier with receivers that have 2 CI CAM slots. There is a group known as OKAPI trying to cut through the Conditional Access mess! OKAPI = Open Kernel for Access to Protected Interoperable interactive services). They consider:
Multicrypt and Simulcrypt Multicrypt transmissions allow two different encryption systems to co-exist in the same receiver.The MPEG transport stream is sent sequentially through different modules that are inserted into the CI & each CAM will receive its entitlement messages. Simulcrypt, on the other hand,allows different decoders with different CAMs (not necessarily CI compatible) to decrypt valid entitled channels (i.e. channels for which a valid smartcard is present in the CAM). This adds complexity to the service provider's equipment but allows the use of existing receivers without modification.Any individual IRD selects the entitlement information it requires whilst ignoring entitlement messages that are destined for other IRDs that use a different decryption system.Therefore,a CI compatible IRD is NOT required.However,global security is necessarily weaker. At this time of writing (January 1999) CI CAMs are available for Conax,Nagravision,Seca, Viacess and Cryptoworks. The long overdue CI version of Irdeto CAMs is expected in spring 1999. DiSEqC This stands for DIgital Satellite EQuipment Controller. DiSEqC was an idea dreamed up by the Eutelsat satellite team in order to make it easier for users in Europe to watch multiple satellites. In particular, they wanted more people to watch the Hotbird group of satellites at 13 degrees east whilst, at that time, Astra at 19.2 degrees east had the largest audience. Many people used 1 dish & 2 LNBs carefully positioned at the dish feed; this worked and required some form of LNB switch at the dish end but controlled from indoors. Otherwise 2 separate lengths of IF cable were needed to run from the dish to the indoor receiver. So Eutelsat, based in Paris, successfully demonstrated the DiSEqc system. Normally the receiver acts as the DiSEqC controller sending commands to switches or even intelligent LNBs via the same coaxial cable that provides LNB power and acts as the IF downlead. It was a logical progression as Universal LNBs using the absence or presence of a 22KHz tone to select between 2 local oscillators were already proving a great commercial success. DiSeqC modulates the (existing) 22KHz tone with digital code words; in other words, the coaxial feed is used as a digital communication bus with DiSEqC commands superimposed on the tone. The idea was presented by Eutelsat in 1996 & test units shipped to interested manufacturers that year. A low cost microcontroller was used and a UK firm built the original evaluation boards as well as providing technical support to triallists. The hardware cost of designing DiSEqC into a receiver turned out to be minimal - about 1 US dollar. Simple Master/Slave implementation does not even need full 2-way communication as this uses a simple "receive only" LNB or switcher at the dish end. Some flavours of DiSEqC are : Mini
DiSEqC
- for simple control of block LNBs. Eventually, the self-installing intelligent LNB could become a reality using DiSEqC 2.x. There's more information and specifications on Eutelsat's website (www.eutelsat.org) as well as some on Philips Semiconductor website concerning compatible ICs. |
