[linux-dvb] Re: Recommended DVB-T card for UK use please

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

On Sat, Mar 29, 2003 at 08:31:40AM -0000, Edward Wildgoose wrote:

> So just to be sure about this.  If I get the full and extremely expensive
> non-budget card (in particular the TT-DVB-T  card), then I will get a V4L
> interface that I could plug xawtv into without any bother?  

Yes.

> And presumably I get another /dev/dsp device to get sound from? 

I would expect so - I only have a Nova-T so can't be sure on this.

> Channel changing is also automatic by the V4L interface?

No, I wouldn't expect so. The tuning would be via the DVB API, 
although there may be support for changing channels via V4L, I 
wouldn't bet on it..

> My original plan was to setup a box for mythtv and a bt878 tuner for normal
> terestrial TV.  However, digital tv looks like it might provide a higher
> quality input than normal analogue TV. 

It's a bit horses-for-courses... The MPEG2 streams will be perfectly 
sized and interlacing will always work properly, and features such as 
16:9 / 4:3 can be set automatically, and the EPG is integrated and 
non-reliant on crazy Perl scripts to parse web-based TV guides.

On the other hand, the bitrate on many DVB-T channels is quite low and 
in high-movement scenes and fades to/from black the macroblocking 
artefacts are quite visible and rather annoying.

However, the alternative is to use analogue input which means you'll 
need a stronger TV signal, and it can be tricky to ensure A/V sync is 
maintained, given the audio comes via a soundcard and the video comes 
via a seperate PCI V4L card.

Also, mythtv will need to do some software de-interlacing on the 
incoming picture data, or you'll end up with one of 3 things:

1) maximum vertical resolution of 288 pixels
2) full 756 pixel height, but you are able to see the previous field.
3) 'tearing' of the image as the timings don't match up

> Obviously I am wasting CPU power by decoding and re-encoding the MPEG
> channel,

Not to mention image-quality :)

> few advantages such as adjustable encoding bit rate, and epg program
> information for the future, rather than just now/next.

I expect the full 7-day guide to re-appear on DVB-T at some point... I 
wouldn't like to say when, though.. I had hoped the launch of Freeview 
would be the perfect time..

There are the same shaky Perl-scripts to import Web guides into VDR as 
mythtv :)

> However, mythtv is v4l only and doesn't take mpeg input directly
> (shame)

Yes, analogue is a dying breed, it seems a little short-sighted to 
choose an analogue solution this late in the game.

I think Klaus has the best mix for UK users - DVB for everything except 
the Sky Digibox which he uses a Kfir MPEG2 encoder card for.  There's 
also a V4L 'analogtv' plugin for VDR on the go - I saw a recent 
announcement of a new version - it might be worth checking that out..
 
> unless you own a DVB card, I can't get it to fire up and run without one...
> There are a limited number of screen shots as well. 

VDR's interface is very minimal, no full-screen pretty gradient-fill 
pictures, etc. because it's limited to the On-Screen Display 
capabilities of the AV7110 chip on the full-featured cards. That's 
why screenshots are both scarce and fairly irrelevant :)

If 'pretty' is important, mythtv or Freevo might be better choices.

> The point is that I am
> not in any way against using vdr, its just that I don't know much about it.

If you want to 'have a tinker' - I think the best thing you can do is 
get a Creative Dxr3 or Sigma Designs 'Hollywood+' MPEG2 card from eBay 
(about £25)... they're decent cards, and VDR will quite happily run on 
one and let you have a play with the analogue plugins before you commit 
to a DVB card.

Don't forget that once you have the Dxr3/H+, you don't need the 
full-feature card - a cheaper Nova-T will do.

> Myth I know and is working for me very well so I would like to plug a
> TT DVB card into it first and work from there)

On the other slant, it might be better to lobby the mythtv author for 
digital support, it being The Future! and all that..
 
> Thanks for any further confirmation

Cheers,
Gavin.



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