[linux-dvb] Re: QAM Satellite Feeds

[Salvatore Domenick Desiano <sal@email.arc.nasa.gov>]

I had thought that DVB-S was capable of time-division multiplexing on a
single signal, whereas DVB-C was not. Which would mean that the DVB-C in
the Motorola box is doing something odd to demultiplex the QPSK-QAM
translated signal that another DVB-C might not know to do. And then
there's the question of when the CAM is accessed... Any insight?

Incidentally, I ask these by way of preparation. If I have a reasonable
amount of confidence that this could possibly work, I'll get started
hacking code with y'all.

-- Sal
smile.



On Fri, 22 Nov 2002, Johannes Stezenbach wrote:

o On Fri, Nov 22, 2002 at 12:02:15AM -0500, Salvatore Domenick Desiano wrote:
o > A DVB-C works with cable and a DVB-S works with satellite. And the DVB-C
o > uses QAM demodulation. But what about the MDU set-top boxes (Motorola's
o > DSR470 and EchoStar's 3750) -- they use cable wiring and frequencies and
o > QAM demodulation, but use each 6 Mhz channel as though it was a 30 Mhz
o > satellite channel, and behave just like the low-end satellite set-top
o > boxes.
o >
o > So, the question: is there a DVB card that can handle this odd ball
o > QAM/Satellite arrangement? It's common in MDU setups.
o
o Judging from http://broadband.motorola.com/catalog/productdetail.asp?ProductID=162
o the DSR470 is a DVB-C box with additional analog cable capabilities.
o IMHO any DVB-C card which is capable of the specific QAM-modulation
o and symbolrate of your network should do. No guarantees, though.
o
o The special thing about cable networks fed from a satellite feed
o is that the NIT (network information table) is invalid and cannot
o be used for a service scan (unless the DVB-S to DVB-C converter
o replaces it with a new, valid one). But that's a software issue.
o
o
o Johannes
o

--------------
  Salvatore Domenick Desiano
    Research Scientist
      NASA Ames Research Center (QSS Group, Inc.)



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