How to change the frame rate in Vive pro

[lily_iniad]

Hello.

I'm a Japanese student researching whether VR sickness can be improved by adjusting the frame rate.

I'm sorry for my poor English, I'm running it through a translator.

 

Let's cut to the chase.

Using unity, I was able to successfully change the FPS on my PC screen using the following method.

void Start () { 
Application.targetFrameRate=30; //30fps 
QualitySettings.vSyncCount = 0; //This line works without it.
}

and the vSyncCount setting in unity has also been changed to "Don't Sync".

 

However, when I connected it to the Vive pro, it automatically did this

Application.targetFrameRate＝-1

The value of -1 seems to be an automatic adjustment.　As a result, FPS will be 90, which is Vive pro's refresh rate value.

But, I want the FPS value to vary between 10~90.

 

Is there any way to prevent Application.targetFrameRate = -1?

I would appreciate your advice.