This may happen if your friend changed his video quality to 'High resolution' and you have a weak CPU or don’t have enough bandwidth. In general, if you're experiencing poor performance, we suggest that you ask your friend to go back to the ‘Standard’ video quality.
Your computer’s CPU
The video and audio quality may be affected if your computer's CPU is not strong enough to process the high video quality. To check your CPU usage, please click CTRL+ALT+DEL. Click 'Task Manager', move to the 'Performance' tab, and look for the CPU usage bar graph. If it's high (90-100%), then this is probably the reason for the poor video.
Available internet bandwidth
Another factor is the available bandwidth; since the high quality video requires more bandwidth, your download bandwidth or your friend's upload bandwidth may not be sufficient for the high quality video.