question about "channels"

[korben_dallas]

I have analog cable with standard coax coming out of the wall.

Here is my question:

Is there something inherent in the video & audio being all combined on that one coax cable that gives TV tuner cards the ability to detect and change channels?

Does splitting it into video & audio (s-video + l/r rca, or 3 rca's) strip out some information that the TV tuner needs to detect and change channels?

[stanger89]

It has nothing to do with the audio/video being combined, Coax (RF) and A/V (S-Video L/R audio, etc) are fundamentally different transmisstion methods.

With coax, all the channels are modulated to different frequencies, and the tuner basically picks a specific frequency for the channel you want, tunes it, and demodulates it. Simply, COAX/RF carries all the channels you recieve.

A/V connections carry only one channel at a time, the audio/video is already demodulated/tuned by the time it gets to the A/V connections, and does not pass through the tuner in your TV card, TV, VCR etc. There are no channels on A/V connections.

[korben_dallas]

Is this why it takes 2 individual tuner cards to record two channels simultaneously?

It seems silly to me that a single tuner card can't "split" the channels up internally and make several available at the same time, just like a Y splitter turns 1 coax cable into 2 cables. Or maybe this has something to do with broadcast laws?

[Opus4]

Each encoder card only has a single hardware encoder on it, so it can only encode one channel at a time -- similarly your TV can't do PIP if it only has a single tuner in it. The Hauppauge PVR-500 will be a dual tuner/encoder, but I don't believe it is available anywhere yet. Among other connections, it takes a single coax line & splits it to its 2 tuners/encoders.

- Andy

[kny3twalker]

look here
http://www.buy.com/retail/product.as...386574&loc=273

for cheap too
134.99
cheaper than a pvr 250 dang!!!!!

[Opus4]

Buy.com says they are "On Order", which is probably the case at many stores. Or, did they say they were in stock when you posted that?

- Andy

[kny3twalker]

never really looked just saw the link at HTPCnews

[stanger89]

Originally Posted by kny3twalker

the place that everyone hates has them

I don't hate them, I got my 6800 there. Never had a problem with them. In fact, my mom ordered the wrong thing once (Xmas present) and it was no big deal to return it. But as always YMMV.

I may have to get a 500 just out of curiosity (of course the same could be said of the Plextor )

[ROBinTO]

Originally Posted by korben_dallas

Is this why it takes 2 individual tuner cards to record two channels simultaneously?

It seems silly to me that a single tuner card can't "split" the channels up internally and make several available at the same time, just like a Y splitter turns 1 coax cable into 2 cables. Or maybe this has something to do with broadcast laws?

A tuner can only demodulate one channel at a time. That's why a VCR can't record more then one channel at a time...nothing to do with laws.
A splitter simple splits the signal into two, each less then half the strength of the original single feed.

[jennyfur]

OK well this is the part that confuses me... what about 2 tuner cards when you throw a cable box into the mix? I need my cable box in order to get digital and premium channels. I had it running out to my single tuner HTPC. I controlled the channel changing by a serial cable connected to the cable box, which recently stopped working

So now I just run the cable from the wall directly to the HTPC and it can tune the channels by itself, but since it's not going through the cable box I no longer get the digital and premium channels.

I'd really like to be able to watch one thing while recording another though, and still get all the channels. I was curious how this would work with 2 tuners cards. If you split the cable coming out of the cable box, how do you control the channels separately? Does the cable box stay on channel 4 or something like that and then the tuners just do their own thing? Or is this done an entirely different way?

Please help the clueless newb!

[stanger89]

To record two digital channels you need two cable boxes and two TV cards. The output of your cable box only contains the information from one channel, and bypasses the tuner in the TV cards.

[jennyfur]

What about those new dual tuner cable boxes? I've never seen one so I don't know how setup would work (or even if you can pull it off). The Motorola one is the DCT6400 series I think, but the pics of the back panel on their site make it look like there's no cable out connection so I don't see how that'd work.

[stanger89]

AFAIK, dual tuners are only found on the DVR boxes, and those boxes only have one output, so the extra tuner does you no good in this situation.