XPost: comp.dsp, sci.crypt, sci.electronics.design   
   From: eric.jacobsen@ieee.org   
      
   On 12/19/2009 12:24 PM, Archimedes' Lever wrote:   
   > On Fri, 18 Dec 2009 19:04:59 -0600, krw  wrote:   
   >   
   >> On Fri, 18 Dec 2009 00:20:47 -0800, Archimedes' Lever   
   >>   wrote:   
   >>   
   >>> On Thu, 17 Dec 2009 20:05:07 -0600, krw  wrote:   
   >>>   
   >>>> On Thu, 17 Dec 2009 17:44:12 -0800 (PST), Mark   
   >>>> wrote:   
   >>>>   
   >>>>>> Passing encrypted video over a satellite network built for unencrypted   
   >>>>>> analog video is not a trivial challenge. As far as I know, there   
   >>>>>> exists no scheme to do this that has not been broken already. The   
   >>>>>> problem is that encryption works partly by diffusing information so   
   >>>>>> that no part of the output looks like any part of the input. The   
   >>>>>> satellite link is filled with errors and distortion that have to be   
   >>>>>> contained to retain adequate video quality.   
   >>>>>>   
   >>>>>> DS   
   >>>>> um,, is that why General Instrument was able to do it did it 15 years   
   >>>>> ago for HBO?   
   >>>> It can obviously be done.  It just requires different, perhaps less   
   >>>> efficient, error correction algorithms which may mean lower S/N   
   >>>> required.   
   >>>   Wrong.  It just requires MORE FEC.   
   >> AlswasWrong is once again wrong.  Surprise everyone!   
   >   
   >   
   >    You're an idiot.  Most digital links can handle up to 10 percent bit   
   > error rate before correction coding fails to fix it.   
      
   Generally not.  Raw BER for BPSK at 0dB is less than 10 percent, and few   
   codes can operate that far down.   Even capacity-approaching codes   
   generally need input error rates higher than that.   
      
   Can you name a code and what code rate would be required to operate with   
   an input BER of 10e-1?  I wouldn't think anyone would use a deep-space   
   code on a satellite because of bandwidth efficiency issues.   
      
   --   
   Eric Jacobsen   
   Minister of Algorithms   
   Abineau Communications   
   http://www.abineau.com   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)