There is currently no option to change quality settings from the Viki app. The strength of your internet connection will dictate the quality of the video. Simply put, as your connection fluctuates, so will your video quality.
The Roku app uses HLS or Adaptive Streaming, which is a protocol that detects your bandwidth and CPU capacity in real time and adjusts the quality of a video stream accordingly.
This means that Roku will automatically choose the best video resolution, depending on your internet connection.
If your video looks blurry, is slow or has a very low resolution, please reset your internet connection, get the Roku device closer to your wireless modem, and try again.
For more help on troubleshooting video issues, please visit: Helpful steps to troubleshoot video issues