In QuizXpress Director there is a settings page on the Mobile tab:
Here you can configure various options. The important setting here is ‘Server delay’. With this option you basically tell the system to delay all commands sent to the Smart Buzzer app with a certain amount of time (between 0 ... 20 seconds). So when your stream has a 5 second delay (which you can measure by watching your own stream) you set the ‘Server delay’ to 5 seconds and all commands sent to the mobile app on your player’s device will be delayed with 5 seconds, syncing the stream and the app.
However this only fixes part of the issue. When the countdown stops in your studio, the clock on the stream still runs for 5 seconds suggesting the player there is still time to answer. This can be fixed with the ‘Extend answer time…’ option. When enabling this the system will continue to accept response for a certain number of seconds past the countdown making sure your players input is not lost.
You can change these settings even while your quiz is running if you see your latency changes.