I am a regular user of imo. I used it for audio call, video call also for group call which is may restricted to 4 of people.
I saw that many users gives Negative review that video quality is poor but I know the main reason behind that.
The video quality is Poor because of your slow Internet connection. As I use WhatsApp also for video calling but some times due to slow network I have to just back and WhatsApp stop the and message appears slow connection.
But in case of imo, imo reduce the video quality as per your network speed so that it will not affect the conversation going on through out the call.
So it’s a good thing not take it as a negative.