This configuration is based on Gopro cameras, goes up to 4K and is desktop-based to allow a SDI output
We use a Freedom360 Broadcaster rig and 6 Gopro cameras: http://www.video-stitch.com/rig-live-360-video-vahana-vr/
We use left-angled HDMI cables because the Gopro have an USB port on the left side. There is the reference: http://www.angledcables.com/left-angle2.html
The acquisition cards are Magewell 4 x HDMI cards. We use two of them.
The computer specs are: Core i7 5930k, GTX 980 Ti Nvidia graphics card, and a mother board with enough PCI slots to install two capture cards.
If you want a SDI output, we use the Decklink SDI 4k
To power the cameras, we recommend to use an external battery adapter. Otherwise the GoPros might overheat quickly and shutdown.
With GoPros, you can order Cam Do for example.
With GoPro 4, remove the internal battery of the GoPro and use the USB to power the camera. The USB hub needs at least 3 Amperes to power all the cameras. We use this one: http://www.amazon.fr/Chargeur-Secteur-USB-Ports-Anker/dp/B00Q4LFQWG/ref=sr_1_1
Note: Do not connect the hub to a computer.
You can of course use other setups, and other cameras if they are compatible with the acquisition card.
Supported input and output cards: http://support.video-stitch.com/hc/en-us/articles/203656986-Supported-video-input-output-cards