FreeSync and G-Sync are technologies that reduce tearing while maintaining low latency. They use an adaptive refresh rate to accomplish this. The way the work, however, can sometimes have a negative impact on the streaming performance of Parsec. If you are hosting a session on a gaming PC with FreeSync or G-Sync and the other latency saving techniques mentioned here do not help you, you can try disabling FreeSync or G-Sync.