[mythtv-users] DVB cards and encoding

Jon Dye jon at pecorous.co.uk
Tue Dec 9 07:13:10 EST 2003


Christian Hack wrote:
>>I've been looking at Myth TV for a while and I'm trying to 
>>decide what 
>>hardware to buy.  I would like to buy an EPIA M10000 
>>motherboard and I 
>>know that they aren't very powerful for encoding.  I am therefore 
>>thinking about getting a PVR250 or PVR350 card to put in it 
>>to do MPEG 
>>encoding.
>>
>>I have also been looking at DVB cards, specifically the 
>>Nova-T and I was 
>>wondering if the output from this card (into the computer) is 
>>MPEG(2?) 
>>and if so does that mean that recording from this card 
>>requires little 
>>CPU power or does the data from this card need encoding in some way?
> 
> It doesn't need encoding as such. It needs "processing" though. DVB
> streams can have more than one audio and video stream embedded in them.
> So the software needs to strip out the unwanted streams. Since it's
> essentially throwing data away, it takes very little CPU. I think some
> cards can even do this themselves. Can they? I might have made this last
> bit up.
> 
> On my XP2400+ nForce 1 board I can't really see it even use the CPU.
> Maybe a few percent every now and again.

That's the answer I was looking for.  I knew that the data came in to 
the card as MPEG in some form but didn't know whether this was useable 
by Myth without conversion.  I guess the answer is that it can use the 
encoded stream wihout conversion but it needs to extract it from the 
rest of the data from the card.

I am thinking of getting a Nova-T card for recieving digital terestrial 
TV (UK) and putting it on a M10000 EPIA Mini-ITX board.  Therefore the 
card will give me MPEG(2?) with little CPU usage and the stream can be 
played back through the CLE266 chip on the motherboard (as the Nova-T 
does not have the decoder on it) again with little CPU.

Anyone see any problems with this plan (other than newness of the CLE266 
support)?

JD



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