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Low-latency IP cameras

Discussion in 'Multimedia, Projection, and Show Control' started by Sparks & Light, May 17, 2019.

  1. Sparks & Light

    Sparks & Light Member

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    Have a situation where we want to set up an IP camera on the director in the pit and a display for singers backstage. I've tried security cameras but the ones I've looked at have a delay of at least 200-300 milliseconds, sometimes more depending on the codec settings.

    I'd like to use a networked camera to avoid the hassle and expense of cabling. Are there any cameras out there that provide a more real-time feed?
     
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  2. ruinexplorer

    ruinexplorer Sherpa CB Mods Premium Member Fight Leukemia

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    If you are on a tight budget and require very low latency, you are going to want to look at older analog cameras/display. You will be using composite signal over co-axial cables.

    If you are requiring a networked camera, you are going to get latency due to the processing of the signal. If you already have Cat-6 cables run and you can avoid network switches (i.e. dry lines or patch bay), then you might consider a HDBase-T system.
     
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  3. AlexDonkle

    AlexDonkle Active Member

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    With the technology today, I think you'll be better off with HDbaseT (over Cat6 STP) or SDI (over coax) rather than a true IP camera. Marshall POV cameras are pretty popular for this. The broadcast industry is in a slow process of switching over to IP at the moment, so you'll likely start seeing better small, low latency IP camera options in the next few years, but I haven't seen any good IP conductor camera options yet.

    If you want to go the IP route though, I'd suggest taking a look at this, just to confirm your current camera is the issue, as IP video systems have several possible sources of latency: https://www.axis.com/files/whitepaper/wp_latency_live_netvid_63380_external_en_1504_lo.pdf
     
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  4. Jay Ashworth

    Jay Ashworth Well-Known Member

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    Everyone else is being polite. I'll be (in the immortal words of Tina Turner) .. rough.

    No. There is no possible way you'll get conductor-level latency out of a IP camera. 300ms is *fantastic* for that, it can often get up close to a second. Even hardware MPEG encoding is slow by comparison to frame rates.

    Analog all the way to an analog CRT is the only 100% reliable way to get microsecond latency.

    *Most* SDI and *some* HDMI cameras can stay down around 1-2 frames, and *some* monitors can lock to that, or at worst, lose only another frame in conversion. But it's going to take some experimentation to get it right.
     
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  5. Scenemaster60

    Scenemaster60 Active Member

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    Again, depending on your budget, I've had good results using the Magenta Multiview technology for transmitting video over cat 5e cabling.
    While this technology still works perfectly well, I think it is more or less sunsetting as a "go-to" for video transmission with the nearly universal adoption of HDBase-T for 4K video over cat 6 cable.

    When purchased new, these units were quite expensive ($800-$1000), but you can often find transmitters and receivers on ebay for pennies on the dollar. From my look this morning, you could probably score a transmitter and receiver for well under $100.

    The entry level units transmit and receive a VGA signal over up to 500' of cat 5e cable. Other than a video camera itself, you will also need a convertor to change either a 480i composite video or HDMI video to VGA. On the receiving end you just use a large computer monitor with a VGA input (and we all have some of those lying around...)

    I used a Multiview 500A/S transmitter and Multiview 500A receiver in this capacity as a live monitor for the organ console at a large church in Minneapolis for about 3 years. I won't say there is no latency in it (I'm guessing it's less than 10ms) but the organist never complained that it was a problem when accompanying choirs and orchestras via the monitor.

    Also, if you're using building data cabling, you'll obviously need access to the switch room so that you can remove both data runs from the switch and simply jumper them together. That's what I did at the church and it worked just fine.

    Here's the brochure of the Magenta Multiview product line from a while back:
     

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  6. Sparks & Light

    Sparks & Light Member

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    Thank you all for the replies. I had hoped for something IP based, and I see that I'm out of luck. As @Scenemaster60 notes, I would have to have access to the wiring closet to repatch the cat5/cat6 to run HDBase-T.

    I shall, as we so often do, figure something else out.
     
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  7. Sparks & Light

    Sparks & Light Member

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    I know we're both just geeking out here at this point, but remember that with analog the display is, on the average, half a frame behind, because of the nature of the scan; we perceive the older part image due to a combination of persistence of the phosphor and persistence of vision until the electron beam again reaches it. So about 17 mS.

    A more interesting question is what is acceptable for the application. I would guess around 50 mS would be good enough.
     
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  8. Jay Ashworth

    Jay Ashworth Well-Known Member

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    Yeah; I quoted this recently (somewhere) as a minimum perception time of about 120ms; that was wrong -- it includes the *response* time. The actual minimum perception time is apparently around 17ms; half a frame.

    It is, I think, theoretically possible to keep the chain delay around 3 frames, and I suspect that would work, it's just damned expensive. :-}

    And of course, it depends on the material.

    Bolero? Just fine. Bumblebee... yeah, no.
     
  9. Ancient Engineer

    Ancient Engineer Well-Known Member

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    I use the Marshall cameras here over HD-SDI with excellent results. About a frame or less of latency from camera to destination.

    Your mileage may vary...
     
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  10. MNicolai

    MNicolai Well-Known Member Fight Leukemia

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    I tend to like the Marshall's as well via HD-SDI. With the interchangeable lenses you can get a lens that matches the view you need for your stage.

    Key thing to remember is that with projectors and cameras, you almost always want to be on the wide end of the lens. Just because you can 30x zoom doesn't mean you should -- you're throwing away 40-80% of your brightness by zooming all the way in. Get the right lens for the view your need.
     

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