Hi,
Thank for your posting this. Sometimes it can be difficult to pinpoint the problem as there could be a variety of causes.
During a video call can you see a clear picture of your video? In this case, since your video works well with some people and poorly with others, it sounds like a network problem (maybe some friends have a poor internet connection or are using the internet to download files at the same time, have weak computers, etc.). As a first step, please click here to read a knowledgebase article.
From experience, I can tell you that one time the other person's webcam was out of focus and all he had to do was manually adjust it 
. This probably isn’t the case but it’s a good idea to ask if the other person has the same problem with other calls.
If this doesn't help, I suggest that you open a support request and attach logs. Click here for more information.
Thanks for using ooVoo,
ooVoo Marv