[mythtv-users] DVB-T Cards - Comparisons or experiences

[Stephen Kitchener]

On Friday 03 Feb 2006 19:05, mike choy wrote:
> Stephen Kitchener wrote:
> > On Friday 03 Feb 2006 16:50, Dan Seddon wrote:
> >> Stephen Kitchener wrote:
> >>> Hi List,
> >>>
> >>> I need some expert advice please.
> >>>
> >>> I am trying to decide as to which DVB-T card to buy, I have a list
> >>> (though there are probably more) to select from, but I need someone who
> >>> has had the experience, to answer a simple question....(the answer
> >>> might not be simple however)
> >>>
> >>> The list is :-
> >>> the list comes from " "http://pvrhw.goldfish.org/tiki-pvrhwdb.php"
> >>>
> >>> Twinhan Visionplus DVB-T
> >>> Wintv Nova-T
> >>> Technotrend Budget DVB-T
> >>> Kworld DVB-T Xpert PCI
> >>>
> >>> (these are the ones that I could identify as DVB-T)
> >>>
> >>> Now I think that the Technotrend Budget DVB-T is the same as the Wintv
> >>> Nova-T, which I already have, and isn't very good at decoding.
> >>>
> >>> The question is, which card is better at reception, I'm not talking
> >>> about speed of tuning, I can compensate for that in the recording
> >>> profiles if needed, what I am asking is which card is more sensitive or
> >>> better at decoding the digital stream ??
> >>
> >> I'm a bit confused here, though you might be answering some questions
> >> which I've wondered. When you mean decoded - I'm guessing you're talking
> >> about turning the recieved transmission in to an Mpeg stream? As, the
> >> actual decoding of the mpeg is done in software or hardware (which ever
> >> you use). So, by saying some cards are better than others at decoding,
> >> do you mean that some a more reliable/faster at converting the signal
> >> (so you have fewer artifacts and quicker channel changes on Live TV) -
> >> as the actual image quality would be determined by the mpeg decoder? I
> >> have 2 Nova-T cards,  as they seem to be the best supported, and
> >> sometimes get freezing and artifacts (which I guess could be down to the
> >> card), but they are definietly very slow at changing channels. You seem
> >> to be saying this varies from card to card - or are you hoping it might
> >> do? I would certainly like my channels to change quicker (though perhaps
> >> that will be improved in 19.0), I hadn't thought of these issues being
> >> card dependent before.
> >
> > Sorry I wasn't specific enough...what I meant was that some cards seem to
> > be better at getting a usable signal from the transmitter before it gets
> > decoded into a digital stream and that is down to the sensitivity of the
> > tuner on the card, its ability to get a signal from the transmitter and
> > not down to the ability of the encoders on the card.
> >
> > If the signal isn't good enough as it leaves the tuner, you will get
> > artifacts and there isn't anything that you can do about it.....Unless
> > someone knows better, I would like to know.
> >
> > As to card switching speeds, I would suggest that is down to the
> > hardware, and not at all down to Mythtv, maybe the firmware, but then
> > that has to talk to the hardware anyway...
> >
> >> Thanks
> >>
> >> Dan
> >>
> >>
> >>
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>
> Off all the cards you have there the K-World is the better card
> it uses the newer conexant chip and seems to produce a cleaner picture.
>
> However you might consider the new Freecom DVB-T USB  it is very very
> sensitive
> and if you are using any sort of amplifier in your house you will
> actually need to add an attenuator.
>
> Have a look here
> http://acaciaclose.co.uk/16253/index.html

Looks ok, wonder if I can run more than one in the same pc......

>
>
> However nothing ever substitutes a high quality aerial, high quality
> downlead when it comes to digital tv.

I have all that, it's just the disparity with the abilities of the set-top 
boxes, where they can get all the channels with no problem and the PCI cards 
where the one that I have at present, the NOVA-T, where it has difficulty in 
resolving the picture. The same antenna system feeds both set-top boxes and 
the PC pci card....

Maybe it's the more hostile environment inside a PC, ie there's more generated 
interference there, that is getting in the way...if there were a way of 
separating the card from the PC somehow, it might be different, but I don't 
see how, so a more sensitive card, one that has a better signal to noise 
ratio, should help, though that might not help as it could just be better at 
receiving the PC noise and not the TV signal :-(, though the PC noise should 
be out of the TV bands.

As you say, a good Antenna and really good aerial downlead is essential. 

It's not the quantity of signal that will fix things its the quality that 
counts. I accept that there must be enough signal, but getting more signal 
though an amplifer won't help, because the amp will amplify the noise floor 
at the same time as it amplifies the signal and the amp will itself add more 
noise to the signal....

Oh well, all I can do in the end is to try one and see I guess...short of 
having some measuring equipment to see what is really happening.

>
> Mike C
>
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