[linux-dvb] Re: Differences in DVB-C and DVB-T

[Gavin Hamill <gdh@acentral.co.uk>]

On Sun, Aug 10, 2003 at 08:17:56PM +0300, Lauri Tischler wrote:

> Good question, maybe somebody wise can also explain why the two,
> T and C, are different in the first place.

From what I've been able to glean from Google (yes, OK, I should have
done this before the original posting...) it seems that DVB-T is
actually more difficult to deal with than DVB-C.

DVB-T uses COFDM to eliminate things like signal ghosting and provide 
facility for Single-Frequency Networks ideal for mobile DVB (in the same 
way that DAB does for digital radio). Once the core signal is extracted,
there are the usual options of QAM and FEC settings.

Google searching seems to suggest that because a high-quality 
signal is already available via a dedicated cable, DVB-C does not 
perform any COFDM processing, and instead starts immediately with QAM in 
any value from 16 right up to 256, since the signal quality should be 
there to deal with such intensity...

So it would seem that using a DVB-T card on a DVB-C network may require 
bypassing the COFDM section of the signal processing. I'm guessing there 
may also be an issue with voltage across the input provided by the cable 
company that would not exist on a standard rooftop aerial...

Perhaps I've answered my own question, but I'd still be interested to 
hear more informed opinion!

Cheers,
Gavin.


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