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Discussion Starter · #1 ·
Everybody wants the old Dish 5000+modulator for their PC cards. I just saw one system on ebay for $1500! The modulator can't be that complicated. Has anyone seen a how-to or schematics to roll your own like old NTSC RF modulators?


Let's get some hardware design engineers to design this little baby so we can use any HDTV receiver, take component out and modulate to an ASTC RF channel frequency. Please!
 

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Great idea, those puppies would sell like hot cakes and have the studios running scared. Can it be that hard to make?

Ira


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Ira Solod [email protected]

Pioneer Elite 510, Lexicon DC-1 ver.4 DTS, Parasound 1205A 200W x [email protected] ohms, M&K S150THX LCR, M&K Surround-55 rears, Klipsch PSW-10 sub, Pioneer DV-F727, Quadscan Pro, DTC-100, JVC 7600 SVHS, Camelot Dragon 5.1, Power Wedge Ultra 111, Monster Power 2500, All homemade interconnects made mostly from RG-6QS
 

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Quote:
so we can use any HDTV receiver, take component out and modulate to an ASTC RF channel frequency. Please!
No problem. You can buy one today for a mere $100,000 (just a guess).


What the Dish 5000 modulator does is take an already existing ATSC stream and simply add 8-VSB and RF modulation. Given the right chip (a Zenith T3W41AF), that is fairly easy. But it depends on access to the ATSC data stream.


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So has anyone ever opened up a DTC-100 and IDed the chips to see if you can access the decoded ATSC bitstream? I would think that the satellite bitstream would be de-crypted first, then run through the ATSC demodulator/decoder. Since I'm pretty sure the decoder/demodulator chips don't have on-board satellite decryption, it's logical to assume that there must be a few traces on the PCB responsible for transferring the decrypted ATSC bitstream to decoder.


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So has anyone ever opened up a DTC-100 and IDed the chips to see if you can access the decoded ATSC bitstream?
Here's an idea. Form a company to develop a product that takes the DTC100's ATSC bitstream and ships it out to a recording device via firewire. Perhaps call your company 16by9 or somesuch.


Or see: http://www.avsforum.com/ubb/Forum28/HTML/000234.html



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The idea of cloning or simply copying the Dish modulator has been discussed before.


It's is really not an option. Yes, the circuit can be copied and all the parts are off the shelf. But today's digial circuits are not comprised of discrete logic chips connected together as was in the 70s and 80s. The logic is now designed in software then downloaded into a programmable chip, either when the chip is made or each time the device is powered up. This is not a simple EPROM that can be copied. My inspection of a Dish modulator reveales the logic array is probably loaded from the CPU in the 5000 receiver wioth code that was downloaded from satellite. There is no local NV memory in the modulator. This would be very difficult to capture the data file.


There are a lot of people out there with the sophisicated test equipment and knowqledge to build a modulator and attach it to any satellite receiver. Problem is these people are the deepest nerds and don't watch TV!
 

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"Here's an idea. Form a company to develop a product that takes the DTC100's ATSC bitstream and ships it out to a recording device via firewire. Perhaps call your company 16by9 or somesuch."


Very funny. I'm aware of the 16X9time fiasco - I would have definitely ordered one if they had actually come up with one. Still, I understand that they actually had a prototype working - which proves it's possible.


Adding a firewire board and such is too big an engineering challenge. I'm just wondering whether it's possible to build a simple board that would yield correct voltages for a digitizing board in a computer.


One other possibility is building an 8VSB modulator board from scratch, and directly attaching it through an op-amp to the tapped traces after the satellite demodulation but before ATSC decoding. If so, a Hi-Pix card would be all you'd need.


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At one point there were some prototype PC cards that

could receive the satellite signals directly (plug the

dish right into the card). They needed a port with

a smart card reader so that they could use the proprietary

conditional access features unique to the particular

satellite system (e.g.: to get Dish programming).


For some reason I haven't seen or heard about these

for a while. I wonder why they gave up on them.
 

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Discussion Starter · #10 ·
Okay, but does any of the other Dish/DirecTV receivers provide this stream?


You're right about once it's component video, it's too late - nothing at all like the NTSC modulators because of the compression.
 

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Quote:
Originally posted by dkeller_NC:



Adding a firewire board and such is too big an engineering challenge. I'm just wondering whether it's possible to build a simple board that would yield correct voltages for a digitizing board in a computer.


One other possibility is building an 8VSB modulator board from scratch, and directly attaching it through an op-amp to the tapped traces after the satellite demodulation but before ATSC decoding. If so, a Hi-Pix card would be all you'd need.


Number of problems and assumptions. First and foremost, the satellite signal is not ATSC. That's probably what the Xilinx gate array does before the Zenith 8vsb chip in the 5000 modulator. It must reformat the DVB MPEG stream into an ATSC compliant stream.


As for digitizing, what are you going to digitize? the MPEG transport stream is alredy digitized. If you are talking ablt the analog HD video, that's a big problem. Once the video is de-compressed, we are back at the 160MB (yes, megabytes) per second data rate. No home computer is going to be able to swallow that on a substained basis.

 

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Discussion Starter · #12 ·
Remember the first DirecTV receivers with the "high bandwidth port". I'll bet you there is such a tap in the HD receivers where one could latch onto the stream after decryption and before expansion. Designers always make an intermediate stream available on the outside of the chip - for testing if nothing else.


Modulate this output on the standard 3.5MHz RF to send to my HiPix.
 

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"Number of problems and assumptions. First and foremost, the satellite signal is not ATSC. That's probably what the Xilinx gate array does before the Zenith 8vsb chip in the 5000 modulator. It must reformat the DVB MPEG stream into an ATSC compliant stream.


As for digitizing, what are you going to digitize? the MPEG transport stream is alredy digitized. If you are talking ablt the analog HD video, that's a big problem. Once the video is de-compressed, we are back at the 160MB (yes, megabytes) per second data rate. No home computer is going to be able to swallow that on a substained basis."



Sorry, didn't make myself clear. Yes, I know that the satellite bitstreams are not ATSC, which is why I was speculating on opening up the case of a DTC-100 to "tap" the ATSC bitstream after satellite decryption but before ATSC decoding.


Once you have access to the bitstream, you need a way to get it into the computer. That's where a digitizing board comes in - all "digital" signals are a series of rapidly switching analog voltages, and you need the digitizing board to capture these and output it as a digital file in the computer that can then be read by playback software. Otherwise, how would you get the tapped voltages off of the back of the satellite decryption circuit into the computer?


And, yeah, I'm aware of the difficulty of re-compressing the analog HD output, which is why capturing the ATSC bitstream is a lot more effective. Stevemac's last post has the general idea.




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>> Sorry, didn't make myself clear. Yes, I know that the

>> satellite bitstreams are not ATSC, which is why I was

>> speculating on opening up the case of a DTC-100 to

>> "tap" the ATSC bitstream after satellite decryption

>> but before ATSC decoding.


It sounds like you didn't get the message. The bitstream from the satellite is probably MPEG2/DVB without any ATSC wrapper at all. So even if you could "tap in" right after satellite "decryption" you probably wouldn't have an ATSC signal to send to an ATSC receiver.


Using CBS on Dish as an example, I bet the flow goes something like this:


CBS-HD-Satellite (high datarate) ->

CBS network channel (KCBS/LA or WCBS/NYC) ->

(ATSC encoded 19.2mbit broadcast) ->

Dish uplink center (ATSC/8VSB receiver) ->

Dish Sattelite (61.5 or 148) as MPEG2/DVB (NO ATSC)->

Dish receiver (received as MPEG2/DVB) ->

Dish HDTV modulator (if using Dish 5000 receiver) ->

ATSC ouput to TV or HiPix.


So dish stripped off the ATSC wrapper when they received

the signal from CBS, and you don't get to see ATSC again

unless you happen to have a Dish5000 with an HDTV (8VSB/ATSC) modulator card.


In the case of DirecTV the HD-HBO channel probably has no ATSC wrapper involved anywhere you could see. They probably broadcast the basic MPEG2 stream through the satellite and none of the DirecTV receivers attempt to add an ATSC wrapper.


You could be confused by the fact that all the OTA signals are wrapped in the ATSC/8VSB standard so the DirecTV receivers and Dish 6000 can process incoming ATSC streams, but that applies to OTA only not to Satellite broadcasts.

(If someone knows otherwise please jump in now and debunk all my "theories").


>> Once you have access to the bitstream, you need a

>> way to get it into the computer. That's where

>> a digitizing board comes in

>> - all "digital" signals are a series of rapidly

>> switching analog voltages, and you need the

>> digitizing board to capture these and output it as

>> a digital file in the computer that can then be read by

>> playback software. Otherwise, how would you get

>> the tapped voltages off of the back of the satellite

>> decryption circuit into the computer?


Generally you DO NOT want to attempt to record digital

representations of analog voltage levels to record HDTV!

PC cards like HiPix and accessDTV accept the analog

ATSC/8VSB signal and "decode" (not decrypt) the digital

portion of the signal and then save _that_ to hard disk.

The "decoded" digital data has not been "processed" yet -

it is still in the "ATSC" spec which includes the ability

to have multiple seperate (not yet decoded) MPEG2 streams in different

ATSC spec HDTV resolutions but it does not attempt to

store information about the analog carrier that was

used to deliver the signal to you.


>> And, yeah, I'm aware of the difficulty of

>> re-compressing the analog HD output,

>> which is why capturing the

>> ATSC bitstream is a lot more effective.


Well, yeah - I guess you sortof understand this aspect.

You do not want to have to re-MPEG the program since

you would need _ALOT_ of CPU power to do it and you

would be introducing all sorts of extra picture artifacts

and analog generational loss by doing this.


I think you may have a bit more to learn about how the

ATSC signal is sent on top of an analog carrier and then

how it is received, decoded, and processed.
 

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Hay, is that a new HDTV PCI (AND USB)!!! card hiding in there!!! It says 8VSB decoding at 6mhz, and even mentions HDTV in the specs. Is this thing being made over seas? and what is the cost?
 
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