You have a point,... but not about the backplane or Ethernet speeds... Modern Ethernet connections/devices can handle the data throughput, and wireless n comes close. On the recording end,... an Intel Dual Core with 4 GB RAM can handle most of what you would throw at it... up to about 6 inputs at least (provided it wasn't doing double duty as a front end too).

Remember,... analog sources are going to be limited to 480p resolution, nobody broadcasts in more than 1080i for the most part, and a lot of the devices do their own decoding, including the HTPC front ends... And that said, the recording is largely going to be done on one machine (from hardware decoding capable input devices),... not a ton of calcs happening, just a need for cached writes to storage, and a tad of processing muscle...

Your good point is about the number of input devices. But that's mostly from a "why'd'ya need so many?" perspective. The simple point is that for a system that can handle 12 inputs, you'll likely have two servers doing the heavy lifting, and your going to be servicing a user environment that can afford the hardware (think 1%-ers)... That kind of system to install, along with some simple home automation, comes in at a minimum price tag of probably $12,000 or more (much more if you went for proprietary solutions). Plus, with 4+ inputs, you likely have enough for most use cases for a family of 4-6... At least in this era... the Future?!?! Who knows...

My system can currently handle all 4 inputs simultaneously, with no noticeable bottleneck or lag in performance. My server is a Dual Core with 4GB RAM, the tuners are 2 HDhomeruns, and there are 3 HTPCs besides the server (two dual cores, one lackluster Atom machine). Eventually, the server will go headless (freeing processing resources), and I will add probably 3 more HTPCs and at least 2 more HDhomeruns. But, I rapidly forsee a day when the HTPCs can be replaced by the successor systems to things like the Rasberry PI and/or the Ouya. And,... I haven't even touched on control systems like Android tablets and phones acting as remotes... (even a Nintendo DSi can serve that role... )...

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I am in an area where these channels are not broadcasting currently and I need to listen to them. The recording system (tuners, streaming server) will be installed in the area where the signal of the channels can be recorded and then the recorded file is streamed over Internet. In this way I can listen to these channels everywhere where I am via Internet without being in the area of broadcasting. I don't forget the copyright issues but now I am more interested to solve the technological aspect.These channels are available over Internet now. This is why I come to this forum to look for a reliable technology which can work 24/7. Thank you very much for your help.

For radio,... on the cheap,... You might want to look into using cheap USB tuners and SDR software (Software Defined Radio) ...

http://www.thepowerbase.com/2012/06/...-with-rtl-sdr/

(Card based multichannel FM Radio tuners can run into the thousands of dollars ... And I don't know of any Linux software drivers for them...)

And,... Also,... maybe look into setting up a squeezebox server:

http://wiki.slimdevices.com/index.php/Squeezebox_Server

I don't know anything about squeezebox software though.

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Jasp, I can say for sure that trying to record 6 HD tv shows in any format will exceed the limits of a common desktop.

I think that you only need to use a single channel at once. There seems to be no reason for having all 12 available at one time. You can remotely tune to your choices.

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6 simultaneous recordings maxing out the PC?!?!
You realize that when you record digital TV, it's just capturing the data stream to disk, right? If you were transcoding the video while recording it, that'd be one thing,... But if your not, the limit is just the IO throughput of the system... So, 6 digital recordings are nothing, especially if one or more are on the same channel (i.e.: 106.1, 106.2, 106.5, etc.).

Some quad tuner cards can handle 24 recordings at once (6 per channel)... If you had two of those, that's potentially 48 simultaneous recordings,... the only issue would be bus speed and hard drive IO.

Now trying to watch 6 channels at once... on the same machine... Now you'd be 100% right.

As for having 12 available at one time,... when watching live TV through MythTV, it's recording what you're watching, allowing you to do things like pause, rewind, and skip ahead (watching live TV is actually like a slight "tape delay"). If you want to be watching on 3 sets and recording 9 other things... you'd need 12 tuners (assuming the programs are on different channels). When would you need that? Well,... sports,... plus a movie the kids want, plus the Mrs. favorite show,... get the picture (excuse the pun)?

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[These channels are available over Internet now.[/QUOTE]
Sorry for the mistake, I would like to say the channels are NOT available currently over Internet. Thank you to all of you for the help.

You were asking for a hardware solution, so I just shrugged that one off...

I think that the OP wants to somehow have a device in some city. He then wants every channel available to stream to some remote location or more likely many locations all at once in near real time.

Not sure I get the way a quad tuner could record or tune to any more than 4 channels at one time.

The OP should look at the SDR stuff from my post above (#18), and some kind of server, like the squeezebox solution I indicated... Something like that could be on 24/7. With ssh or a web server with protected SSL logins ought to give him near real-time access.

As for recording more than one channel at a time,...
http://www.mythtv.org/wiki/Record_mu..._one_multiplex
You're dealing with the multiplex nature of digital broadcasts.