Audio stream goes away after turn off camera while put app in background

Below is my requirement.

  1. I am in video call with some one
  2. I put my app in background
  3. As we know that Video stream does not work in background on iOS so I am turning off camera when app goes into background to make call work because if i do not turn off camera then call disconnect after sometime since server is not handling lost Video track right now.
  4. My Camera is being switched off in background but i lost voice i.e audio does not work after that.

Below is code that i am using to turn camera off.

mediaDevices
.getUserMedia({ audio: true, video: false })
.then();

is there any known issue or any solution for this scenario.