How to Stream Stand Out
Streaming VR games is a little bit trickier than your average game. This is compounded a little by the fact that the desktop mirror is only from your left eye, so if you aim a scoped weapon with your right eye you will not be able to capture the view down the scope.
Fortunately the fix is not that complicated. See the below sections for some specifics to Vive/Rift.
Beware: Streaming VR games, or non-VR video games, can increase CPU utilization by a considerable amount if you do not use GPU encoding. This might lead to lower FPS than the 90FPS to maintain an optimal experience, and when your FPS drop below 90FPS you experienced reduced movement speed and other issues.
Increasing the process priority of StandOut.exe to High can prevent this from negatively impacting your gameplay performance. If you have and some GPU headroom and the ability to use a hardware encoder, this is advisable over the software one as it will take a lot of the load from the CPU for the capture.
Configuring the Source for Capture
SteamVR Display Mirror
In the SteamVR settings (the dropdown from the desktop monitor window) enable the Display Mirror option, and then in the Display Mirror window you can change the view to the right eye. Using your broadcasting/recording application of choice select the SteamVR mirror window and you should be set!
Note that the SteamVR display mirror has somewhat poor visual quality. No SS is applied, in addition there is an interpolation "mask" that causes additional jaggies. Complaining on the SteamVR discussion hub might help get someone to improve this particular problem! (so far it has not.)
The native aspect ratio of one eye in a Vive/Rift is 1080x1200, which is very unusual to say the least. The SteamVR mirror outputs in this aspect ratio, so you will want to manipulate your OBS Studio canvas/output to capture a 16x9 aspect ratio (1280x720) for your stream/recording. This does end up cropping a lot of the SteamVR mirror so it cannot be seen, however, the SteamVR fov is such that much of the display output cannot be seen in your HMD, so it ends up being kind of a wash. To do so shrink the SteamVR mirror source in OBS until it fills the window side to side and then experiment with adjusting the height slightly until you find a good center.
Note that I need some supporting comments from a Vive owner for the above section, I only have experience with doing the same thing for a Rift.
OBS OpenVR Plugin
A very, very excellent OBS-Studio plugin was released on 7-8-2017 and is both easier to use, more customizable and provides superior image quality to the SteamVR Display Mirror. You can download it here, along with some installation tips. https://obsproject.com/forum/resources/openvr-input-plugin.534/
Note, the native '16x9' presets for the OpenVR plugin do not appear to fill a 16x9 canvas properly. Try the following settings:
Capture right eye: Checked
Crop preset: none
Crop top: 0.18
Crop bottom: 0.65
Crop left: 0.00
Crop right: 1.00
The Oculus Mirror application is a CLI process that is located in the Oculus Diagnostics folder. The fov / aspect ratio of the Oculus Mirror is fixed, so while you can (as of 1.15) change the Height and Width of the mirror, the aspect ratio remains the same. The aspect ratio seems to be made for 16x9 output, with variances in a 16x9 resolution in the settings just stretching/cropping that aspect ratio. However, the aspect ratio provided is great for streaming AND it is a high quality output!
Navigate to your Oculus Diagnostics folder, under c:\program files\oculus\support\oculus-diagnostics\, right click OculusMirror.exe and select Send-To->Deskto(Create Shortcut).
Then navigate to the desktop, go to properties on the OculusMirror target, and change the Target to look something like this:
"C:\Program Files\Oculus\Support\oculus-diagnostics\OculusMirror.exe" --RightEyeOnly --Size 1920 1080"
The Oculus mirror outputs in a fixed 16x9 aspect ratio at a fixed fov, which is a little lower than what can bee seen in the HMD. However, considering you would have to morph the resulting window for OBS/etc to pick up, its kind of a wash. The greatly increased output quality make this a much better option for a capture source than using SteamVR Display Mirror if you are an Rift owner, though many would still recommend the OpenVR plugin.