Your video call will only be as good as the quality and speed of your internet connection so you should adjust your video bandwidth to suit your connection speed.
A good connection should use 768kbps (broadband connection of > 5mbps), a slow connection should use as low as 256kbps (connection < 1mbps).
If you're unsure you can test your broadband at a service such as Speedtest.net (www.speedtest.net). The upload and download speed need to be greater than the recommendations above.