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Conductor Monitor and Latency with Digital

Discussion in 'Multimedia, Projection, and Show Control' started by dumaisaudio, May 3, 2018.

  1. dumaisaudio

    dumaisaudio Member

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    I'll start by acknowledging that there are a lot of scattered threads on this topic. I've been doing a lot of searching here an other places on this topic, and a lot of what I find is several years old or doesn't have much specific info. Most of it points to CRT TV's and analog cameras. While this is obviously a rock solid solution, and why it's still used in many places, the fact is that CRT TV's are old technology. We're currently using an LED LCD TV with an analog camera. There is noticeably latency that actors can see, especially when the conductor is also visible to them in addition to the monitor. We would rather hang a flat panel off the balcony rail then attaching large CRT's only to end up replacing them in the near future for something more current.

    I'm seeing info on OLED TV's that have very low latency, 12ms input lag for instance. Using an HD-SDI camera and needing to convert it to HDMI would introduce some additional latency, though how much I'm not sure. What I'm looking for is anyone that has had good experience with digital conductor camera and monitor setups and can give specifics on what equipment they're using. With all the advances in technology in the last five years, I find it hard to believe that we're still having to rely on old technology for this setup.

    Lastly, when I have seen people mention digital, they usually mention that it's expensive. What I'm looking for is the right solution first, and if that ends up cost $2K or $5K, I can present that proposal and let others decide if the cost is worth it.
     
  2. MNicolai

    MNicolai Well-Known Member Fight Leukemia

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    First things first, turn your existing LED display to "Game" mode and/or go through all the menus and turn all of the special-sauce image processing off. This can have a major impact on the amount of latency you see.

    Most of the better quality HDMI converters you'll find lose 1-2 frames in the A/D or D/A conversion. If you're running 60Hz, that latency per frame is 16ms. At 30Hz, it's 33ms. You want to use a camera, converters, and a display that all handle 60 Hz to minimize the impact of each A/D conversion. Also better if you get a camera that's analog HD-SDI output --- because if you get one that has an HDMI output, now you're waiting 16ms for the camera to convert to HDMI, then another 16ms for HDMI to HD-SDI converter to run the distance back to wherever, and then another 16ms for the HD-SDI to HDMI converter at the display, and 9-12ms for the input lag of the display.

    You can find a lot of info on display input lag here. Think you'll discover 12ms isn't anything amazing, and I wouldn't pay extra for OLED just for that.

    Digital doesn't have to be expensive. Black Magic Design has some suitable HD-SDI / HDMI converters for under $100. What gets expensive is when you need to distribute video out for a remote orchestra pit down a hall and around the corner in addition to stage left, stage right, and a balcony rail. You end up parking a converter at every display and need to use an HD-SDI distribution amp, as well as a lot of wire pull to each destination.

    If you're really picky and need to feed multiple displays distributed around, I like to use an HD-SDI RF modulator to park the conductor camera on Channel 3. If it's a remote pit application, I'll also put the stage camera on Channel 4. Then hook all of the displays up using their coax RF inputs. Now you don't need a converter at every TV. You just need displays that have RF inputs (i.e. not computer monitors).

    To some degree, latency is unavoidable. You take as many reasonable steps as you can to minimize it and then you teach your musicians to anticipate it.

    For reference, here is a video I cut together for what you can expect for impact of latency on musicians and a conductor. The video is at 30 Hz, and shows the frame numbers in the top right corner of each image. You can see how many frames you lose before things get wonky.



     
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  3. dumaisaudio

    dumaisaudio Member

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    These videos are immensely helpful, thanks so much for posting them! So I take it you have been in this situation and were trying to get some real world data. To us, the difference between 0ms and 33ms was pretty small. When staring in the middle of those two images, it was hard to tell the lag, but put a conductor monitor on a balcony rail, and the conductor in the front of the pit, I think you'd be hard pressed to perceive the delay. 67ms was a little more noticeable but not that bad (I'm sure some would disagree though). Everything else was very noticeable.

    In our previous setup, were using a Vizio 42". In doing more research now, it seems these are known for having a lot of input lag, though I'm not finding specific numbers. We had put it in gaming mode and turned off all the extra stuff on the tv that might have introduced more latency. I think the issue was just that it wasn't that great of a tv and we hadn't really considered latency when purchasing it, because we didn't know it would be a problem (this was 8 years ago or so).

    What you're describing seems to be what we've settled upon. We're looking at an HD-SDI camera and the converter at the display end to get to HDMI. We seem to have found a 32" computer monitor that is pretty fast, so at the very least, it will be faster than what we have. The monitor isn't too expensive, so if it doesn't work, our TD has a new display for his drafting setup.

    In our setup, it's more about the actors on stage (and in the wings) having an accurate shot of the conductor. We have put a monitor in the pit for the drummer before, and not had problems with complaints about delay. Those were different monitors anyway, so maybe they were better with the delay. Your suggestion of an HD-SDI RF modulator is a good one, as we'll probably need to distribute the camera to at least 4 or 5 different displays in the future.

    Thanks again for the advice. I hope others will chime in to contribute and find this info helpful.
     
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  4. Jay Ashworth

    Jay Ashworth Well-Known Member

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    Go to a $(BIGTVSTORE).

    Look at The Wall.

    What you will likely see is that half the TVs showing the Single Demo DVD/BD output video are a frame behind the rest on cuts. (You'll also notice there aren't many cuts in those demo videos anymore, for precisely this reason. :) )

    The ones that are behind are the 720p sets that have to downsample.

    But yes, 1-2 frames is pretty hard to spot, for most people.
     
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  5. AlexDavila

    AlexDavila Member

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    Can you recommend a specific HD-SDI RF Modulator? I’m spec’ing a system for a small theatre that’s adding latecomer monitors in their lobby and I want to give them flexibility to add dressing room/backstage monitors in the future.
     
  6. Plady

    Plady Member

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    We just installed a video monitor on the balcony rail so large casts can see the conductor (I know, welcome to the game right?) but after the initial excitement it became clear that there was a millisecond lag and so the director and music director said they didn't want it. Rather than give up after one rehearsal does anyone have any ideas how to fix the millisecond lag time? We are using coaxial cable to run directly from the camera to the TV. The camera is a tiny little thing made by Ansice (?- the website on it doesn't seem to exist, ansice.net) and the monitor is an LG smart tv.
    Anyone have any ideas?
     
  7. RonHebbard

    RonHebbard Well-Known Member Premium Member

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    @Plady A large, repertory, Shakespearean Festival I used to work at solved this problem by skipping TV's and computer monitors and going with two displays built in their in-house electronics shop. The displays contained a minimal number of raw LED's. I'm now blind and retired and thus never saw the actual displays but from what I was told here's what I think I'm remembering. Envision a vertical column of red LED's with a a couple of amber near the top followed by a green LED at the very top. Envision the same sequence and quantities of colors at the bottom of the vertical column. Envision the same idea as a horizontal row. They built two identical displays, one smaller and more compact that lived next to their conductor and an identical, larger, display for the face of their balcony. The conductor had easily manipulated rudimentary controls for speed / tempo and start / stop and noted appropriate settings and start / stop points in his score. Essentially zero lags, only LED's firing at the speed of light and electricity. The same theater, a thrust seating approximately 2,000 did a similar LED display on the front of their balcony to coordinate the side to side swaying of their cast when they were supposed to all be swaying in synchronization on the deck of a large cruise ship during the performances of a musical.
    Toodleoo!
    Ron Hebbard.
     
  8. ruinexplorer

    ruinexplorer Minion CB Mods Premium Member Fight Leukemia

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    You need to make the monitor as "dumb" as possible by turning off anything that will process the signal. Just the default settings will likely add delay as they are trying to optimize the signal. So anything in the menu that says auto or enhanced or something like that will be potentially slowing it down.
     
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  9. Plady

    Plady Member

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    We dumbed it all down by removing the flat screen, building a shelf and installing a 1991 vintage CRT tv. Voila. No more latency. Tonight's choruses better end with some crisp cutoffs.
     
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