[mythtv] dvb-t confusion

Nigel Pearson nigel at ind.tansu.com.au
Thu Jul 8 21:44:52 EDT 2004

> Some observations and questions about installing a dvb-t card into 
> mythtv.
> It's a long and boring story of unending failure, sorry for wasting 
> your
> bandwidth.

	Jukka, I feel your pain. I have taken a long time getting all
this nearly working, too.

> Then it asks me about channels. I got to where it asks me about channel
> number "(just like xawtv)" ... now what exactly do I answer there if 
> I'm
> using a dvb-t card? It doesn't really have channels like analogue cards
> had

	In Australia it does. There is a separate DVB transponder for each
network in the region, and the DVB channels transmit the same material
as the analogue channels do, so for now the same Video Sources and
Channel Numbers apply.

	Note that I think the Program Guide uses the channel numbers.
When I had none, the guide was always empty, even though there was
programme data in the database.

	Entering all the DVB parameters (FEC, hierarchy, bandwidth, etc)
is fairly complicated. A few months ago, Malcolm Smith posted a perl
script to the list that makes this a little bit easier if you have
compiled and used scan from the linuxtv-dvb-apps package.

(I made some modifications for mythtv 0.15 compatibility,
  but it needs a lot of improvement work e.g. to cope with
  multiple DVB channels per source. If anyone wants the
  modded version, email me. I will try and provide detailed
  instructions on how to used it)

> How good a signal strength or signal/noise ratio should I have for the
> stream to be usable? At present looking at the setup programs "Card
> verification wizard" I seem to be getting 32% signal strength and 
> 20-35%
> signal/noise. Bit error rate and uncorrected blocks stay at zero which 
> of
> course can't be right. But anyone have a clue on how high should the
> numbers go?

	I can only comment on my current card, an AverTV DVB-T.
The wizard reports 100% signal strength and around 60% signal
to noise, and that seems to not be enough for reliable operation.
(e.g. the backend spits out about 30 stream errors per second,
       and I have only succeeded in recording 15minutes before
       the backend silently dies)

Nigel Pearson, nigel at ind.tansu.com.au | "Now the world has gone to bed,
Telstra BI&D, Sydney, Australia       |  Darkness won't engulf my head,
Office: 8255 4222    Fax:  8255 3153  |  I can see by infrared,
Mobile: 0408 664435  Home: 9792 6998  |  How I hate the night." -Marvin

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