For a stable audio call a user of your application built on top of QuickBlox services requires Internet connection with speed equal to or more than 200 Kbit/s.
For a video call – up to 2 Mbit/s.
Feel free to check our official documentation for more information that will help you to integrate QuickBlox services into your applications / projects or contact our Support team by submitting a ticket if you have any other questions.