Big improvements made in getting the message through

As broadband becomes more widely available, real-time video conferencing is becoming more widely used.  At the University of Waikato we are working on techniques to improve the quality of video conferencing.

When computers use a network like the Internet, information passes through multiple conceptual layers. Video conferencing programs such as Skype or MSN Messenger (also called Windows Live Messenger) work at what is known as the application layer.  They pass information to a lower layer known as the transport layer, which takes over the responsibility of sending the information to the remote computer.

These lower layers operate in a simplistic manner -- they send information in the order they are passed it and do so with little inter-layer communication.  In our research, we are looking at improving video conferencing by improving the communication between layers.  As part of this we are passing down to the transport layer what time the information should reach the other end by, and what type of information it is (audio or video).

In the transport layer, the traditional rules are that you send information in the order you are given it, and that if you run out of space to store information you throw away the most recent information.  With video conferencing, our research has shown that this does not give the best results and we have come up with a scheme called "Send the Best Packet Next".

Previous studies have shown that audio is more important than video in a video conference. If you think about this it makes sense - if you can see the person but can't hear them then the message is not imparted. On the other hand if you can hear them but not see them you can still communicate, even if it is not optimal. In our research we send the audio before the video which means it has a better chance of getting through.

The optimal time for live conversation to reach the other end is considered to be within 150 milliseconds. As the time starts to increase beyond this it gets harder to communicate. With a computer network it is known approximately how long it will take information to get to the other end. With our scheme the computer looks at the current time, looks at the expiry time for the information and then checks if there is enough time for the information to get there. If there is not the computer discards the expired information so that newer information has a chance to get through.

When network conditions are not perfect we are seeing around 20% improvement in the audio getting through with virtually no change to video, which will lead to a better video conference experience for the user.

As published in the Waikato Times 1st August 2007

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Last updated: 1st August 2007