If you are making a custom dual camera rig for shooting video in stereoscopic 3D format, then you’ve probably ran yourself with some issues in actually getting a live 3D preview in order to setup the cameras correctly for the subject you are going to shoot and even if you just want to properly align the two cameras. Of course the two cameras/camcorders must be the same make and model, but even that does not guarantee you that they will be perfectly aligned with each other, so you might have to do a little bit of additional tweaking in order to get the proper vertical alignment of the two lenses. Here I’m using two Sony HDR-SR11E HD camcorders (on the photo above) and as you can see I’ve connected the video out cable to each other, something that is not so convenient on this model. The closest interocular distance I could get with the SR11Es was about 8 centimeters in a parallel configuration, but with the video out cables connected the minimum distance goes to about 10-11 centimeters which is not very useful for filming close objects in 3D. However it has worked very nicely helping me properly align vertically the two cameras, because they’ve had a bit of an offset as you’ll see on the photos below…
The solution I’m describing here is for SD quality preview and good enough for alignment of the cameras, it is not intended to provide a Full HD quality and resolution with the idea of the whole setup to be very affordable and mobile. Not that you cannot go for a better quality solution, but you might have to sacrifice some of the mobility you get or purchase much more expensive hardware to be able to do that, and if you go for Full HD preview quality you might as well go for directly capturing from the cameras and not recording the footage on their HDDs. What I’m using here is a pair of Easy Cap USB video capture adapters, because these provide quite good SD quality and come very cheap – you can get them for even under $10 USD each. So these get connected to a laptop to get everything mobile, for portability you might get them connected to a smaller netbook should you need that, or if mobility is not needed you can use a portable nettop or even a normal desktop PC. If you are going for a Full HD preview then you need a suitable HDMI capture card and these are of course available, but you’ll have to get around $200 USD for each. I’m talking about the more affordable Blackmagic Design’s Intensity Pro and Intensity Shuttle products. With the Intensity Pro being a PCI Express based add-in card that needs to be inserted in a motherboard and the Intensity Shuttle using USB 3.0 interface which makes it possible to be used with a compatible laptop and not just a desktop PC. You can of course even go for the Blackmagic Design DeckLink HD Extreme 3D add-in card that is stereo 3D ready and has HDMI and SDI inputs for capture, but you’ll have to prepare $900+ USD for it and that makes it quite a bit more expensive, although it offers more options and additional features.
So up to here we have the two cameras/camcorders with their video out cables connected and then in turn the video out cables connected to the USB capture cards plugged in a PC or a laptop. So now we have the ability to preview and/or capture single streams coming from each of the cameras or camcorders with pretty much any software that supports video capture functionality. However we need a special software that will have to combine the two separate video streams coming from each camera into a single stream that can be in turn previewed or captured in a compatible stereoscopic 3D video player. There are a few such programs available, but here I’m using Peter Wimmer’s Stereoscopic Multiplexer and after that we’ll also need the Stereoscopic Player from the same author for the 3D preview part. Both programs are commercial, meaning that you need to purchase a license, but there are also free evaluation versions that allow you to try them and purchase a license should you decide they do the job you need them to.
After you install and run the Stereoscopic Multiplexer you need to go over a few simple steps in order to setup the two capture devices, with the first one being to actually select the right capture device for the left and for the right camera. You need to be careful here as when using the came capture devices they both have the same name, but if you make a mistake you can get back and correct it at this point. Also be careful not to select other capture devices available in your system, other than the ones you are using that are connected to the cameras. The Easy Cap USD capture adapters are being recognized as Syntek STK1150, but the name here might be a different one even you you get the same cheap video capture adapters.
The second step from the Setup process is to choose the resolution and mode you are going to be capturing in. As I’ve already mentioned here SD capture adapters are used, so the mode to select is either 720×576 PAL or 720×480 NTSC. You can test if everything works as it should when selecting the mode, it should be the same for both capture devices, by pressing the test buttons for the left and for the right video devices. If everything is working fine, then you may proceed with further setting up the Stereoscopic Multiplexer.
The next step offers you to do some additional adjustments, such as to set a specific frame rate for the capture. This is good if you have the camera/camcorder working at a specific framerate like 24, 25, 30 fps and you need to make sure that the preview will also be at the same framerate. Below the framerate option you have some checkboxes in order to rotate the image should you have any of the recording cameras rotated in some way. Having one of the cameras upside down for example is not so uncommon when you are making a custom stereoscopic 3D rig, so these option can be very helpful in providing the right video input so that the left and right video can be properly displayed.
A few more additional options in the next Setup step, probably you will not have to change anything here. Just a word of caution regarding the Deinterlace mode, you should probably stay away from it, unless you know what you are doing. This is because if you activate the Deinterlace mode you are actually getting the odd fields dropped (removed from the image being shown), so you better leave that unchecked (not selected).
Now, you are finished with the setup and you’ll be able to see some preview in the Stereoscopic Multiplexer as well as an option to record the video footage you are getting. However this part of the software’s functionality is not very advanced and you don’t have a lot of options, so you should consider using the Stereoscopic Multiplexer together with the Stereoscopic Player. In order to do that you can start the player, open the File menu, go to the Live Video and select the Stereoscopic Multiplexer as the source from the menu (you don’t need the Stereoscopic Multiplexer running at the background if you plan on using it from within another software like the Stereoscopic Player or VirtualDub). Now you’ll be able to preview the content in pretty much any output format supported by the Stereoscopic Player, like for example anaglyph that will work with any display or do a direct preview on 3D Vision-capable laptop or desktop PC. What the Stereoscopic Multiplexer does is to create a DirectShow filter that contains both left and right views in a Side by Side configuration and the good news is that you can use that filter as a capture source in other programs too, like for example use the capture mode of the free Virtual Dub video editor if you need to capture any of the footage coming from the cameras in stereo 3D format.
Using the anaglyph output format with a pair of paper red-cyan glasses provides great flexibility as it is practically useful on any kind of display and does not require any specific hardware, so you can go with pretty much any laptop or desktop PC. This will help you get a portable and mobile preview station to go along with your two cameras or camcorders without having to go and buy a new laptop with a 3D-capable display – pervasively polarized or with active shutter glasses. By using the anaglyph mode you can also quite easily spot vertical misalignment of the two cameras and do the needed fixes, so that you will not have to do any fixes for that in post production of the video after you’ve already shot it. As you can see on the screenshot above my two Sony SR11E camcorders did have some vertical misalignment that I was already aware of even before working out the live preview procedure, after recording and previewing some test 3D footage. However with the live preview I was able to easily fix the issue in no time, by doing some modifications on the metal bar holding the two cameras together by being able to see in real time the alignment after the modifications to perfectly match the two cameras.
I hope this guide is helpful to all of you who are recording stereoscopic 3D video with custom dual camera setups and I’d be glad is you also share some ideas and/or methods you are using as well as what custom camera/camcorder setups do you use for recording…