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Thread: SDI video distribution vs RGBHV

  1. #1

    SDI video distribution vs RGBHV

    I've been asked to comment on a new theatre installation. The theatre consultants proposed an SDI video distribution system for show video (i.e. to be used between Catalyst and projectors in various places). I kind of balked at this and said Catalyst output is DVI and then to RGBHV via Triple Head-2-Go.

    Maybe I'm confused, but is there any situation in the next 10-30 years where an SDI distribution system is going to be useful for Catalyst output to projectors/LED walls/etc? I told them a 5-core copper solution terminated on BNCs for RGBHV would be more appropriate. Am I wrong? Should we be looking at fibre? This building is going to be our flagship for the next 30 years, it just feels as if 5 core analog RGBHV is not future proof. But maybe it is?

    Someone suggested that CAT5 distribution systems are the way forward, but I've read about transmission rates not being high enough and other problems with systems that use digital switches. There is already two CAT5 ports in every location that the show video port will be, so I don't feel the need to go that route. or maybe i do and need to use a special kind of cat5 cable?

    Any help appreciated,
    Kevin Carson
    Lighting & Video Technician
    Royal Shakespeare Company

  2. #2
    Join Date
    Feb 2004
    Location
    Melbourne, Australia
    Posts
    163
    I would suggest using fiber. You can then use different encoders and decoders to get the signal you want.

    www.thinklogical.com for example

    Many companies have devices for distributing all types of signal over fiber. It would seem to be the most "futureproof" solution. Lots of bandwidth.

    The biggest problem I have experienced with permanently installed RGBHV is that is very hard to stop interference from power cabling and other devices.

    Cheers

    Toby

  3. There is a DVI over CAT5 solution from TVOne coming out in the next month or so, very affordable

    Nev.
    Nev Bull
    Pixels Plus Limited
    Digital Video Services

    Catalyst Software - Upgrades - Server Hardware - Accessories - Training - Support

    t: +44 (0)1494 858151
    skype: nevillebull
    e: nev@pixelsplus.co.uk
    w: www.pixelsplus.co.uk

  4. #4
    'sdi' is only standard definition 720x576PAL 720x486 NTSC.

    Can you find out what the cable spec is for HD-SDI?
    And how far it goes?

    Its going to be much shorter as the bandwidth is 6x greater.

    So you will be unlikely to be able to use any sdi cables to go long distances with hd-sdi.

    I suspect the short distance hdsdi cables go - mean people then consider having to use fibre and dvi.

    The technology life cycles these days are between 18months and 3 years max.

    Bettting on any technology outside this timeframe is not going to be a winning strategy.

    Richard

  5. #5
    Quote Originally Posted by NevBull View Post
    There is a DVI over CAT5 solution from TVOne coming out in the next month or so, very affordable

    Nev.
    cat5 cable is not screened?
    Does it use 'special' cat5?

    fibre is more resilient to electrical interference.

    As you know even unscreened DMX can be a problem in installations.

  6. #6
    Quote Originally Posted by tharding View Post
    Many companies have devices for distributing all types of signal over fiber. It would seem to be the most "futureproof" solution.

    Toby
    ...the future is getting closer all the time...

    i dont believe much technology at our level lasts longer than 3 years at the moment.

  7. CAT5 UTP cable is not screened, but CAT5 STP is. But you know that.These adapters are designed to be good for runs up to 250m. But obviously they can be affected by 'atmospherics' as can any signal cable

    Nev.
    Nev Bull
    Pixels Plus Limited
    Digital Video Services

    Catalyst Software - Upgrades - Server Hardware - Accessories - Training - Support

    t: +44 (0)1494 858151
    skype: nevillebull
    e: nev@pixelsplus.co.uk
    w: www.pixelsplus.co.uk

  8. #8
    Quote Originally Posted by NevBull View Post
    CAT5 UTP cable is not screened, but CAT5 STP is. But you know that.These adapters are designed to be good for runs up to 250m. But obviously they can be affected by 'atmospherics' as can any signal cable

    Nev.
    there are many levels of things that need to be checked -
    there is the signal, the protocol, the connector, the cable.

    For example you cannot run cat5 Gigabit 1000BASE-T ethernet to 250m- whatever kindof cable - because of the way ethernet works - not the cable.
    its the time delay associated with packets.
    that's not a transmission line problem.

  9. #9
    I would also highly suggest getting fiber installed. Especially where it's an installation and you don't have to worry about the fiber getting broken, etc.

    With fiber, you can get whatever transmitters/receivers you want. So, you can go SDI, HD-SDI, DVI, Analogue, etc.

    RGBHV is very much NOT the way to go I would say. Hum, more prone to failure on a single connector, etc.

    The video over cat 5 boxes have the problem that they are just using cat 5 cable, they are NOT doing this over ethernet, so it will not work with ethernet devices (hubs, switches, repeaters, etc) Though I don't know of the new one Nev mentioned, as of yet I have not seen one capable of using ethernet for transmission. The other caveat with these boxes is that while they say they can do up to 1920x1080 (example) resolution, their distance at that resolution is much shorter than what they say is their max distance. The max distance on the product listed is normally at the lowest res the box can run at.

    One of the benefits to SDI/HD-SDI is that since it is a broadcast standard, the equipment is going to be around for a while. Unlike computer technology, which is in a constant state of flux, the broadcast world stays much more stable, as the level of investment, etc is much higher. People don't change out $100,000 switchers every couple of years. Computers on the other hand change very frequently. It was HD-15/RGBHV, then DVI, now we have HDMI as well, and now the new "Display Connector" is starting to appear.

    That is why fiber gives you the most flexibility. Its probably cheaper to install than the SDI route would have cost. And since it is just the transmission medium, you can make it send and receive whatever it is that you need. You can even change it based on the needs of the show coming in.

  10. #10
    OK, lots of stuff to think about. Thanks. However, nobody has answered the question about the usefulness of SDI/HD-SDI with Catalyst. Is it possible and/ or desirable to output SDI from Catalyst in a theatre environment? Is the quality better/worse than DVI via RGBHV and Triple Head-2-Go?

    Also, can HD-SDI be transmitted over the same cable as SDI? From what Richard says above, it sounds like HD-SDI will require a different cable and won't transmit nearly as far.

    Sounds like fibre is my best option. Any drawbacks to permanently installed fibre that I should know about? Is the cost of the DVI to fibre codecs significantly more expensive than RGBHV DAs?

    Just heard back that they are now proposing a RGBHV network and also pulling some fibre to a few key points, similar to what is happening with the Sound install. I'm just wondering if we need RGBHV at all now. Esp considering the manual patch bay will be RGBHV. Why not just make a fibre patch bay and be done with it? Or, if we can afford it, a digital fibre switching matrix.

    Thanks again,
    Kevin Carson
    Lighting & Video Technician
    Royal Shakespeare Company

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