When it comes to video conferencing the primary determinant of picture and sound quality is the capacity of the "pipe" that joins the two sites.
A commonly quoted magic number is a capacity of > 384 kb/s (kilo bits per second) in each direction, with more being better. So if you have a 2 Mb/s (Mega bits per second) ADSL line you should be right? Right?
Perhaps. ADSL stands for Asymmetric Digital Subscriber Line. The asymmetry refers to the fact that the download speed is much faster than the upload speed. Most of the time this does not matter as we do a lot more downloading than uploading, however for video conferencing upload speed is critical, because it is upload speed that determines how good the picture will be at the other end of the connection.
You can test your connection using one of these speed testers:
You need an upload speed of ~400 kbps (0.4 Mbps) for good video conferencing. More is better. Note that an upload speed of 750-800 kbps is about as good as it gets in Australia using ADSL. Fortunately this is adequate to support a single video conference at a time.