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Repeating/distributing HDTV over coax in our CATV system?

S

spinjector

Hi all,

We're a sports plant with flat panel HD screens in a lot of our studios. Comcast is skewering us big-time for our cable boxes, since we have the NFL package which includes the NFL channel in HD.

The problem is we have more screens than cable boxes, and Comcast now encrypts most of their HD channels, thus making the internal tuner in the flat screens useless.

I was wondering if it's possible to centrally locate one or more cable boxes, keep them set to certain channels, and then "remodulate" that to different channels over the coax, in the same way one might have done with a composite signal & RF modulator back before analog TV died.

I found an HD encoder that would do the job, but it's like $2,000.

Can anyone think of a way to send a "decoded" HD signal back into our CATV system so all the screens can "tune" it with the internal tuner, as described above?

Thanks.
 
I would think that if a cable company can purchase HD modulators for their headends why can't you? The only sticking point would be what the output on the cable box (hdmi?) verses the input to the HD modulator. Of course I'm assuming an HD modulator is an all-on-one product without any external encoder but considering many cable systems have pulled their analog services I would think this would be a somewhat viable option.

The only other thing to factor would be the ROI of building your own headend in comparison to putting up with the nonsense of (yuk!) Comcast. I won't even put their stuff in my house anymore after the way they treated me! I can only imagine how bad they are to work with when you're a commercial client.
 
Do they need to look great, or are they mostly for "decoration"? You could re-modulate to NTSC if you don't need the full-quality HD signal.

I recall something from our local Comcast engineer, about demodulating the encrypted signal down to an un-encrypted transport stream. You could then re-modulate the "in-the-clear' channel to QAM for under $1k, using a digital modulator. You might ask them to have their engineer give you a call.

Also, I remember seeing a Channel Plus "HD Modulator" someplace recently. It requires component input and a DD Bitstream for the audio. I think it was discussed on AVS Forum.
 
Bill DeFelice said:
...The only sticking point would be what the output on the cable box (hdmi?) verses the input to the HD modulator...
Click to expand...

Keep in mind the copy-protection features of HDMI will probably keep this from working...probably have to go component. Running into this problem trying to convert HDMI to HD-SDI.
 
grich said:
Bill DeFelice said:
...The only sticking point would be what the output on the cable box (hdmi?) verses the input to the HD modulator...
Click to expand...

Keep in mind the copy-protection features of HDMI will probably keep this from working...probably have to go component. Running into this problem trying to convert HDMI to HD-SDI.
Click to expand...

Totally slipped my mind. Good catch.
 
Distribute it via HDMI. Google "HDMI over Cat 5 cable" and "HDMI distribution amplifier". Both are quite inexpensive and work well.
 
Cable systems don't use HD modulators. They use quam modulators or edge quam devices. Each 6 meg quam carrier is a path to send data to your tuner or set top box. A typical quam carrier can transport a 38.8 mb/sec stream which can be used for HD, SD, audio only or any combination of the above. The stream can be mpeg2 or mpeg4 depending on the system. 1 HD channel will use 12 -20 mb/sec depending on how much the cable operator compresses it. Statistical Multiplexers are used to compress more data into the 38.8 mb/sec stream. It's not uncommon to see 3 HD channels per quam. HD content is rarely ever in an audio/video format inside a cable head-end and is usually distributed as data in the ASI format, or on TCP/IP networks.
It would be possible to receive on a set top box, re-encode and then modulate the signals into quams, but not really practical or cost effective.
 
I was reading about the HDMI encryption; it's called HDCP. What interested me was that somehow the "key" got leaked online, something like when that 14 year old kid from Finland broke the DVD encryption scheme.

Apparently HDCP causes a lot of compatibility headaches with DVD players & flatscreens.
 
JamieD said:
Cable systems don't use HD modulators. They use quam modulators or edge quam devices....
Click to expand...

Cable head-ends look nothing like they did 30 years ago when my brother became a cable tech...racks of green Scientific-Atlanta stuff and a room full of Sony VO5600 3/4-inch VTR's for commercial insertion.

As to HDMI...I was trying to use a AJA HDMI-to-SDI brick ($500), and if a HD signal attempts to come out the cable box's HDMI out, the DRM kills it. Of course, if you connect a monitor, it works just fine.

Another FYI-HDMI doesn't pass closed-captioning :mad: ...be prepared to deal with that too.
 
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