Pairing 2 cameras to 1 remote for 3D stereoscopic shooting?

Discussion in 'SJ7 Star' started by Happy Chappy, Jan 7, 2018.

  1. Happy Chappy

    Happy Chappy New Member

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    Hi,

    I just bought 2 of the SJ7 cameras as a fun experiment to try out doing some 3D stereoscopic shooting.

    Ideally I would like to pair both cameras to a 1 remote so they start recording video at precisely the same time. It would save time and hassle editing because I wouldn't have to synchronise the left and right when creating the side-by-side 3D video.

    I have tried the obvious... putting both cameras into pairing mode simultaneously and pressing the 2 bottom buttons to do the bluetooth pairing... but it only ever pairs with one of the cameras.

    What I can do is pair 2 remotes to 1 camera... the opposite of what I want... but for some reason, I can not pair 2 cameras to 1 remote... so far.

    Perhaps there is some technical reason why this is not possible?... or maybe I just don't know how? If anyone has any ideas, I would welcome suggestions please.

    Loving these little cameras so far... impressed with what little pocket rockets they are. A lot of fun making 3D video too... it would just make so much sense to be able to start and stop both cameras at precisely the same time with a single remote for 3D shooting.

    Thanks!
     
  2. Jason

    Jason Moderator

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    You cant do it. The camera acts as a master and the remote the slave - although multiple slaves can have the same master they can only have one master at a time.

    The way I checked out is the manual way either clicking of fingers, clapping or using a clapper board app. One thing you could look at investigating is a physical button using the FPV controls over the usb connection, as long as you can isolate the power and ground of one camera from the other it should work (e.g. reed switches or IC switches)
     
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  3. RBEmerson

    RBEmerson Humbled by events

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    @Happy Chappy Good idea! The power leads shouldn't been an issue if they're in parallel. Put both hot or (+) leads together and both return or (-) leads together and the worst that happens is the battery with less charge is charged by the other battery - no biggie unless the battery charges are very different.

    Under no circumstances put the batteries in series (Camera1 hot to camera2 return and camera2 hot to camera1 return) - that gives 10V to the circuit. Which will probably let the magic smoke out of some important part. Once the magic smoke comes out, it stops working...
     
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  4. Happy Chappy

    Happy Chappy New Member

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    Thanks a lot guys! Very useful information.

    Physical button is as good as a remote for my purposes, so I'll definitely have a go at that... just for the fun of it.

    Now... just need to find the research resources on the FPV so I know what I'm wiring to what. Time for more searching and reading before I dig the soldering iron out.
     
  5. Jason

    Jason Moderator

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    @Happy Chappy - how are you mounting the cameras -what baseline are you using and are you inverting one to allow shorter baselines?
     
  6. RBEmerson

    RBEmerson Humbled by events

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    Well, you can certainly wire up a shutter remote. Remote... hmmm... two of those wristwatch wanna-be things and there you are without harm to an FPV cable, only damage to your wallet (about $50 worth).

    Jason's right, Put a sharp tone, clapboard bang, or something with a sharp attack curve on the audio, and there's your camera sync. Easy-peasy.
     
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  7. RBEmerson

    RBEmerson Humbled by events

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    Strictly speaking, the further the view, the wider the required baseline. What I want to know, though, is how this stuff gets 3D'ed (as it were).
     
  8. Jason

    Jason Moderator

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    With a baseline the same as an adult human (about 2.5") depth perception of objects will be up to about 30'. Increase the baseline and this distance goes up, but when watching it makes the objects can look smaller (good for shrinking the world). Conversely decreasing the baseline and brining the lenses closer together means you can make 3d videos close up of GIANT CATS for youtube - although I think they've dropped the 3d viewer from their web pages.
     
    Last edited: Jan 8, 2018
  9. RBEmerson

    RBEmerson Humbled by events

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    Agreed - but what's the process to go from two videos to a fabulous 3D experience like no other (until the next one, anyway).
     
  10. Jason

    Jason Moderator

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    It uses parallax - each camera sees a slightly different point of view with subtle shifts in the perspective.
    Try closing one eye and looking ahead with the other. Then keeping your head still swap eyes.

    The image from the left hand camera is shown only to the left eye, the right hand camera shown only to the right eye.

    This cam be done a few ways - anaglyph (the red/blue glasses), VR headset or 3d TV with passive (polarised) or active (Ltd shutter) glasses.

    You can also take into account convergence where you angle the cameras slightly so they are both pointing directly to the same point. This is the plane that ends up on the screen, anything infront will pop out of the screen, anything behind will drop back into the screen - but that can be faked in software
     
  11. RBEmerson

    RBEmerson Humbled by events

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    Anaglyphs I know about first hand. The results aren't very good for a full color experience. I'm aware of the other techniques. Turning the two cameras' video into an anaglyph is fairly straightforward. It's the other two techniques I'm wondering about.
     
  12. Jason

    Jason Moderator

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    easiest way to encode a video is make a TAB (top and bottom) or SBS (side by side) where the image contains both eyes either one over the other or side by side. Often the images for each eye is half the height / width of a normal frame so that together they still take up the same space as for a full frame.

    The Digital TV then parses these videos into the two separate eyes. For passive glasses one eye is horizontally polarised and the other vertically polarised, for the active glasses there's LCD filters built into the glasses which are synchronised to the TY via bluetooth - one eye black out when the image for the other eye is displayed.

    shot0001.jpg
     
  13. RBEmerson

    RBEmerson Humbled by events

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    Gotit - TNX
     
  14. Happy Chappy

    Happy Chappy New Member

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    With one of these. A Neewer Dual Camera Tripod Mount Bracket for 3D Stereo Photography... £6 from Amazon.

    Neewer 20.3 cm Dual Camera Mount Tripod Bracket for 3D Stereo Stereoscopic Photography.jpg

    Which looks like this with Cameras mounted just using parts that came with the camera and mounting bracket
    SJ7 Cams mounted2.jpg

    Baseline. I have done experiments from 2.5" in increments all the way up to the almost 7" max of the bracket. I hadn't thought of inverting one to have them closer. It's a good idea so I'll have a play with that too.
     
  15. Happy Chappy

    Happy Chappy New Member

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    I tried the 2 remotes to 1 camera and it wouldn't work... Jason explained why earlier in the thread.

    I hadn't thought of using a clapperboard being so new to working with 3D and it was a great idea and made the synch much easier. I was just letting a ruler come into view from above... it worked, but the clapperboard is simpler.

    But, I can still get half-frame differences even at 60fps. So I'm still very interested in the idea of a physical button for perfect synch in the first place at the recording. A half frame difference at 60fps does not seem noticeable to my eyes, but even so... if I can have it perfect and save the time synching in editing for the price of a couple of FPV cables and a button, I would still like to make one anyway. It's useful and a fun little project for me to learn something new.

    After much searching I found the wiring pinout for the SJ7 on a forum provided by
    sjcamhd
    SJCAM Official Site

    https://www.rcgroups.com/forums/showpost.php?p=37855874&postcount=505


    SJ6 SJ7 USB PINS.png

    Now I need to figure out how I go from having this information, to creating a working physical button with the parallel splitter leads to the cameras.

    So far I've found out that the PWM pin is the one for the shutter, but in all honesty my electrical wiring knowledge is not sufficient go from what I've learned so far, to creating the button/cable that I need to make this work.

    I can see I'm likely going to be buying 2 of the FPV cables... and wiring those in parallel to make a splitter cable is easy enough for me to understand. It's how to wire up a button to that splitter part that I need to find out next. Any help in acheiving a solution would be greatly appreciated. Thank you!
     
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  16. RBEmerson

    RBEmerson Humbled by events

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    Full marks for your work! Yea! Hurray! Cheers!
     
  17. Jason

    Jason Moderator

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    It seems that PWM is on pin 6 - which is also pulled low when the external mic is connected. Perhaps it needs to be pulled high for the shutter release (or held high for video) or the FPV setting changes the way that pin 6 is used. Either way, it would seem that you wont be able to use external mics if using the FPV shutter

    Maybe @Troy or @TonySosa can shed some light on how the FPV works.
     
  18. RBEmerson

    RBEmerson Humbled by events

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    Sigh... this means we're back to

    @TonySosa , @Troy We really need the pinout specs for the SJ7 USB connector This request has been up for weeks. So far... crickets. If SJCam views this as proprietary information, please say so. But at least have the courtesy to acknowledge the request.
     
  19. Jason

    Jason Moderator

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    Or they could just tell us how to use the PWM part of the official SJCAM FPV cable which as its a product that's they should be marketing I'd assume they have the info some where.
     
  20. RBEmerson

    RBEmerson Humbled by events

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    Why not the full spec instead one pin? "In for a penny, in for a pound" and all that. And I really am not amused that SJCam won't respond. Sena did much the same thing. Not A Wise Move.
     

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