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HDTV Dist. Via Modulation?

post #1 of 18
Thread Starter 
I work for a company that installs audio and video into retail stores and with HDTV hitting hard we are need of a way to distribute multiple HDTV sources to multiple HDTV displays. Basically we need to be able to take 2 or more ATSC streams via RG-6 and be able to modulate each stream to a specific UHF or VHF channel frequency, combine the streams and carry them to each TV display via RG-6 and allow each TV's ATSC tuner to tune into the modulated streams. Does anyone know if they make or who makes a frequency agile ATSC modulator that accepts RG-6 and outputs via RG-6. I know that IP TV will take hold in a few years however most of our customers are willing and don't want to rewire their stores.

-isus
post #2 of 18
Huh?!

Sounds like you are saying, you want to receive the OTA Digital TV signal on one channel, and then send it through the system on a different one. Why change their native channels?

If this is what you want, you're talking something similar to an MATV system. You can do that with Digital TV (ATSC) Channel Processors. Some will not work well with adjacent channels, some will. You need to check with the manufacturer's tech support on that part.

Here's one of the ways:
http://206.188.195.56/btl/dhdp.pdf

It's part of this stuff:
http://www.nsccom.com/index.asp?Page...TS&Category=25

There are other manufacturers as well.
But, why not just simply distribute the entire TV spectrum throughout the store, using an antenna and amp?

If you are going more like a full-blown MATV, check out this thread:

http://www.avsforum.com/avs-vb/showthread.php?t=779057
post #3 of 18
Thread Starter 
Basically here is the senerio...

-Say you are building a Hotel and you want to provide 25 HD channels to each of your customers rooms.

-Say you have 500 rooms in your hotel.

-Its much cheaper to purchase 25 cable boxes/sat receivers and 25 RF modulators than it is to purchase 500 cable boxes/sat receivers.

-Basically you just turn cable box 1 to channel x and then run it to modulator 1 and tune it to channel y and so on for each of the 25 channels you want to provide.

-You then combine the RF lines and run it through a distribution amplifer and pull a home run to each room in the hotel.

-Connect your HDTV with ATSC tuner to the RG-6 wall plate and change the channels with the TV remote.

Of course you will not have any 2 way communication with the cable boxes so there will be no EPG but its a hotel, not a home theatre we are talking about.
post #4 of 18
That won't give you any HDTV.

To carry any HDTV, you'll need to decode everything on a channel down to a digital transport stream, then re-modulate it as 8VSB or as QAM. Both are expensive...the last time I looked, it was about $1-2K for a QAM modulator, and about $8K for an 8VSB modulator. You'd still need to demodulate the signal, too.



Here's a site that has "white papers" on some of this stuff:
http://www.rldrake.com/

Also, you'll need to know whether you want to run "OTA mode", which requires ATSC/8VSB, or "Cable TV" mode, which is QAM. Sets won't usually tune them interchangeably.
"OTA" would allow you to easily mix in the local stations. But, you'll only have room for 68 channels...and, maybe only 50 if the manufacturers cut their tuner programming back to the "core channels" (2-51) later on.

"CATV" mode will allow, maybe, 125 total channels, but then everything has to be converted to QAM.

You can mix analog NTSC channels in with the digitals, as long as you set them up on the right channelization, and use the right modulators.

So, you will probably be looking at $2K per channel, minimum, to do a fully-digital system.
post #5 of 18
post #6 of 18
Quote:
Originally Posted by isus View Post

Basically here is the senerio...

-Say you are building a Hotel and you want to provide 25 HD channels to each of your customers rooms.

-Say you have 500 rooms in your hotel.

-Its much cheaper to purchase 25 cable boxes/sat receivers and 25 RF modulators than it is to purchase 500 cable boxes/sat receivers.

-Basically you just turn cable box 1 to channel x and then run it to modulator 1 and tune it to channel y and so on for each of the 25 channels you want to provide.

-You then combine the RF lines and run it through a distribution amplifer and pull a home run to each room in the hotel.

-Connect your HDTV with ATSC tuner to the RG-6 wall plate and change the channels with the TV remote.

Of course you will not have any 2 way communication with the cable boxes so there will be no EPG but its a hotel, not a home theatre we are talking about.

Either
http://www.blondertongue.com/media/p...transcoder.pdf

or
http://www.rldrake.com/digital/sct4860.html will do what you need.
post #7 of 18
Quote:
Originally Posted by isus View Post

Basically here is the senerio...

-Say you are building a Hotel and you want to provide 25 HD channels to each of your customers rooms.

-Say you have 500 rooms in your hotel.

-Its much cheaper to purchase 25 cable boxes/sat receivers and 25 RF modulators than it is to purchase 500 cable boxes/sat receivers.

-Basically you just turn cable box 1 to channel x and then run it to modulator 1 and tune it to channel y and so on for each of the 25 channels you want to provide.

-You then combine the RF lines and run it through a distribution amplifer and pull a home run to each room in the hotel.

-Connect your HDTV with ATSC tuner to the RG-6 wall plate and change the channels with the TV remote.

Of course you will not have any 2 way communication with the cable boxes so there will be no EPG but its a hotel, not a home theatre we are talking about.

I actually do distribute HD in Hotels, but on a MUCH larger scale (think thousands of rooms) The break even numbers are still not there.

You can't do it easily that way (from a STB) and the suggestions offered in this thread will only work if you have access to the ORIGINAL signals either from the Sat decoder outputting the original QPSK stream (not a consumer STB) with the encryption removed. Just getting the original QAM from Cable or QPSK from Sat signals and remodulating them will also not work because they will have the original CAS or Digicypher encryption schemes in the streams from origination.
If you were to try to use a cable STB to tune an HD channel and take the output of that signal, you need a real time HD encoder into a Multi-Program Transport Stream, a Muxer for the signals you want on each QAM (usually 2 streams / QAM). Individual products are totaling around $20k-$25k per channel for real time encoding. Recently, all in one soultions (encode/mux/QAM output) have come down to around $16k in quantity/ channel if building a complete rack of channels, but could still be problamatic if image constraints are applied to the output of the STB. Even then, you have to license the feeds from the content provider for HD channels.

vegggas
post #8 of 18
Thread Starter 
Thanks for the helpful info. I'll have to do a lot more research on this. My knowledge is like a razors edge on this subject. I know a lot about specific things but not the entire picture.

If I'm getting the info right (For the moment lets only discuss ATSC OTA broadcasts), from what you guys are saying you can't take an OTA signal and modulate it with a regular old modulator correct? From what it sounds like and what I did not think about is the type of modulation that is being used. I'm assuming that a simple RF modulator will modulate the digital signal to what ever channel you want however the way it is interperted by the TV tuner will differ because it is not modulated to any ATSC standard. Will the signal then be picked up by an NTSC tuner but display strangely on the TV?

We are in the process of remodeling the shop and don't have our lab setup yet. We haven't had a chance to test a lot of the new digital TV technology.
post #9 of 18
Thread Starter 
On this same topic, have any of you run into a product that will take a HDMI input and modulate to RF output? The Drake website has a ton of info however the one item I found that would be useful seems to tune into the sat channels and modulate them for you. We really don't want that for our applications. We are looking more for a modulator that will take an HD signal from a sat box and modulate it to be distributed via RG-6 to a TV that has an ATSC/QAM tuner built in.
post #10 of 18
No, you can't use a regular analog modulator with digital signals - Unless you downconvert it to SD 480i over a composite output.
Also, there is no HDMI to modulator conversion possible. You can only modulate the raw mpeg data in an ATSC format with the complete channel build.
Digital modulators require more than just the digital signal in ATSC mpeg format. They also need the "build" of the channel, including the PMT, PAT, PID and other tables that comprise the digital sub-channels within a single RF channel. Most OTA signals have a main channel and a single (or even multiple) subchannels. Any transcoding would have to either demux and rebuild the channel tables or pass along the entire data stream including the subchannels. If you are going from OTA signal to OTA signal, but just want to change the RF carrier the Drake digital De-mod (860) will strip off the RF carrier, and allow you to pass the IF signal to another digiatal modulator at a different frequency.

vegggas
post #11 of 18
As I understand it, the affordable (under $1,000) Blonder-Tongue and Drake QAM and 8VSB modulators need an unencrypted, MPEG data stream to develop an RF channel that is tunable by a conventional TV. As I understand it, the only available unencrypted source of live programming is broadcast TV, which is already modulated to 8VSB, but which can be demodulated and then remodulated to QAM for well under $2,000 per channel. At present, the only reason I see for converting broadcast 8VSB to QAM are to allow it to be distributed at lower frequencies, or to make it compatible with QAM programming froom some other source, presumably franchised cable.

Someone at Drake told me that there are commercial, Motorola receivers that have what I think he called "ASI" outputs that he thought could be modulated to QAM by affordable modulators that his company sells, but that the programmers will not authorize their use by individual properties. Still, I'm skeptical. I don't really know what ASI is, but if it is the initial stage of analog to digital conversion and is uncompressed, then even if a consumer TV tunes it, I don't think it can process it into a picture and sound.

Has vegggas used or evaluated the LG products that can take decrypted/recrypted/heterodyne-downconverted DirecTV and directly tune the subscribed-to programming without using a stand-alone DirecTV receiver?
post #12 of 18
Quote:
Originally Posted by vegggas View Post

Digital modulators require more than just the digital signal in ATSC mpeg format. They also need the "build" of the channel, including the PMT, PAT, PID and other tables that comprise the digital sub-channels within a single RF channel.

So what will be the "building blocks" of a digital, consumer TV surveillance camera channel? Do some cheap CCD cameras have digital non-compressed outputs? Could someone then integrate a chip containing whatever a consumer ATSC TV needs to see to recognize it as a channel.

Might the solution be for the TV industry to include a "dumb" D/A converter that can process low resolution, non-compressed ASI signals?
post #13 of 18
Quote:
Originally Posted by AntAltMike View Post

Someone at Drake told me that there are commercial, Motorola receivers that have what I think he called "ASI" outputs that he thought could be modulated to QAM by affordable modulators that his company sells, but that the programmers will not authorize their use by individual properties. Still, I'm skeptical. I don't really know what ASI is, but if it is the initial stage of analog to digital conversion and is uncompressed, then even if a consumer TV tunes it, I don't think it can process it into a picture and sound.

ASI ia the Asynchronous Serial Interface. For a demodulator output it would be the demodulated data with all PSIP tables, MPEG video, and audio data for as many sub channels as are present in the broadcast. You need an MPEG decoder to get video and audio from ASI.
post #14 of 18
These guys carry Digital IRDs that can have ASI outputs:

http://www.standardcom.com/products.asp

Wish I had the funds to really test some of this out, though .

veggas....have you dropped in on the "MATV Thread"?
post #15 of 18
I just got an e-mail from NACE, introducing a new line of Blonder Tongue products that apparently can take one to four SD digital or analog data streams or even one HD and two SD data streams and MPEG-encode them into a single data stream that can be modulated into one QAM channel. The catch here is probably that unencrypted HD data streams are not normally available other than from broadcast television, but for my purposes, it looks like what I have been looking for.

http://www.blondertongue.com/media/p...esentation.pdf

I'll probably call BT tomorrow to confirm the capabilities of this product and feel them out for price and availablilty, but it sure looks like there is about to be an affordable way to develop a digital house message or lobby camera channel, and even to develop a digital distribution system since I think it can take the analog outputs of four DirecTV or DISH receivers and combine them into one clear QAM channel.
post #16 of 18
Bad news. The dealer list price, when it becomes available shortly, will be around $14,000
post #17 of 18
I am sure this guy did it a little cheaper than that. http://www.computerforidiot.com/vide...rom-n6qqq.html
He got the modulator from Germany.
John
post #18 of 18
Quote:
Originally Posted by AntAltMike View Post

...Someone at Drake told me that there are commercial, Motorola receivers that have what I think he called "ASI" outputs that he thought could be modulated to QAM by affordable modulators that his company sells, but that the programmers will not authorize their use by individual properties. Still, I'm skeptical. I don't really know what ASI is, but if it is the initial stage of analog to digital conversion and is uncompressed, then even if a consumer TV tunes it, I don't think it can process it into a picture and sound...

ASI, or Asynchronous Serial Interface, is basically a wrapper, a way of encapsulating transport streams without decoding or actually manipulating the encoded/compressed bitstream. It allows baseband single or multiple-program transport streams a method of being piped around broadcast facilities over simple 75-ohm cable similar to that used for SDI or analog video (such as Belden 1694A). Quite often digital sat signals are demodulated directly to ASI format for further processing, and yes, it can be used to feed a QAM modulator, but the ASI wrapper is stripped just before modulation (and the signal remains compressed and encoded). Many stations keep signals in ASI format up until final conversion to SMPTE310 just before the transmitter exciter. Others may make that conversion earlier (if the equipment demands it) or may demodulate to baseband for local switching and later convert back to either ASI or (more likely) directly to 310.

There is really no practical way to MATV HD OTA signals on anything other than a small scale, unless significant equipment and maintenance is applied. If the signals are essentially received at the same level, then they can be distributed just like any other RF signal. If the levels are quite variable, then it becomes problematic, as post amplification depends upon signals all being within a particular window of operation. There are some methods of filtering at the headend that can equalize signal levels to an extent, but atmospheric changes can thwart this at times.

The good news is that unlike analog RF signals, digital RF (8VSB or QAM) signals can be distributed over a MATV system with a larger window of operation. They are not as susceptible to noise issues, and you can theoretically send them at much lower levels, as well as at the same higher levels as analog, without system noise degrading the picture quality. As long as signals are 15 dB above the noise floor (rather than 45-50 above for analog), you can achieve digital lock. For this to be consistent, I recommend design that allows 20 dB above noise, as otherwise you may have incidental issues with reception. This ability makes utilization quite forgiving and can greatly offset the problems of incoming signal levels being quite divergent or changing dynamically due to atmospheric conditions, but it still is best to have very good original reception and process each signal individually with AGC to conform them all to a workable level, which is essentially the same method used by analog cable systems for decades.
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