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Interview with Jiang Li, Researcher/Project Leader: Microsoft Research


Dr. Jiang Li joined Microsoft Research, Asia as Researcher in January 1999. His research interests include video compression, image processing, video broadcast and communication, peer-to-peer networking, realistic image synthesis and image based rendering. Before joining Microsoft, Dr. Li was an associate professor at Zhejiang University. Dr. Li received his Ph.D in Applied Mathematics from the State Key Laboratory of Computer Aided Design and Computer Graphics, Zhejiang University in 1998. After obtaining his M.S. degree in Optics from Zhejiang University in 1992, Dr. Li joined the university's faculty and built copper vapor lasers and researched on laser-tissue interaction for Photodynamic Therapy. Dr. Li received B.S. degrees in both Applied Physics and Applied Mathematics from Tsinghua University in 1989. He completed a 3-year National Natural Science Foundation project "Wave-Based Illumination Models for Computer Graphics" in the end of 1999. He received the Best Paper Award at Chinagraph 1996 and Chinagraph 1998. Dr. Li is leading Microsoft Portrait project. What exactly does Microsoft Portrait do?

Jiang Li: Microsoft Portrait is a research prototype for mobile video communication. It supports .NET Messenger Service, Session Initiation Protocol and Internet Locator Service on PCs, Pocket PCs and Handheld PCs. It runs on local area networks, dialup networks and even wireless networks with bandwidths as low as 9.6 kilobits/second. Microsoft Portrait delivers portrait-like video if users are in low bandwidths and displays full-color video if users are in broadband. In low bandwidths, portrait video possesses clearer shape, smoother motion, shorter latency and much cheaper computational cost than do conventional video technologies. Microsoft Portrait pursues providing presence notification, chat/voice/video functions anytime, anywhere, on any device. What do you like most about Portrait?

Jiang Li: Microsoft Portrait is the first software in the world that provides two-way video communication on Pocket PC. Two-way video communication on Pocket PC means you can not only receive and display video on your Pocket PC, but also capture and send video on your Pocket PC in real-time. The later feature is much more difficult than the former. Usually mobile devices such as Pocket PC and Smartphone possess only limited computational power and low connection bandwidth. Microsoft Portrait can enable two-way video communication on Pocket PC because the video technologies behind Microsoft Portrait possess two advantages: low computational complexity and low bandwidth requirement. Can we expect more changes/updates in the near future?

Jiang Li: As I have said in the answer to the first question. We pursue providing presence notification, chat/voice/video functions anytime, anywhere, on any device. Let's wait to see what's going on. How long was Microsoft Portrait in development, and how many people were involved?

Jiang Li: As you can see from the What's New page on Microsoft Portrait web site, the first version was posted in July 2001. The start day of the development is about one year earlier than that. After the first release, we updated it version by version according to users' feedback and our research progress. Many people involved in the project, and the number varied in different periods, some periods a dozen and some periods just a couple. It's interesting that we have visiting students joining us since we are also a research institute. What was the most difficult aspect of the development process?

Jiang Li: It's how to reach low bitrate target at the beginning of development process. The motivation of the project came from the observation that current video communication software is still not suitable to dialup users who have only about 56 Kbps bandwidth (the actual available bandwidth is bout 80% of it) and exist in most areas of the world. So we want to develop a codec that works at 10-20 Kbps, therefore can provide two-way video communication for dialup users. Since it seems that there are no more rooms in the improvement of conventional DCT based coding, we consider using line drawings in video communication in which expressions are the most important and scenes are relatively fixed.

We tried edge detection algorithms in order to extracting the outlines of face, eyes, eyebrows, mouth, etc., but the results are not very robust. In addition, the visual effects are also not satisfactory since if you only write the outlines with black lines, you will see that the hair areas are white - the color of the background. In order to avoid this situation, we consider combining the outline image with a binary image that is converted from a gray scale image by a threshold. In this case, hair areas are always black and the visual quality improved significantly. Although the visual quality becomes better, the compression ratio cannot be higher due to the existence of lines and dots from the outlines. We considered what would happen if we just used the binary image that was converted from a gray scale image by a threshold and did not use any outline information. It is surprising that the visual effects are even better. This is exactly what the current black/white video form is.

The remaining problem is how to compress these binary image sequences. You know there are international standards JPEG for still full-color image, MPEG for motion full-color images and JBIG for still binary image, but no any standard for motion binary images. By analyzing the temporal correlation between successive frames and flexibilities in the scene presentation using bi-level images, we achieved very high ratios in bi-level video compression. The decription would be long, I have to stop here. Please refer to our papers, listed at for details. It's interesting. During the development of this product was there any hilarious or outlandish moments that stick out in your mind?

Jiang Li: I don't think there was any hilarious or outlandish moment that stuck out in my mind during the development of the research prototype. I would say that the development process was smooth. A characteristic of the development process that may be worth noting is that this is a development process that software goes ahead of hardware. What I mean is that cameras for Pocket PCs were just released in recent months, but our video coding algorithm for enabling the video capture function using Pocket PC cameras were ready over one year ago. This is also why we can so quickly release new versions that enabled two-way video communications when Pocket PC cameras are available. As a researcher, I feel this is really amazing. What do you foresee as the future of mobile communications?

Jiang Li: In my opinion, video communication would be reachable anytime, anywhere on any device. You may know that the business model of video phone failed in the past. But if video feature is integrated with many other features in a device, not only one single feature in the device, it will be more acceptable. The current mobile phones help people to remotely access via voice, the future mobile devices will help people to sense visually. We can also imagine that more other human feelings such as touch and smell will be enabled remotely in the future. What is the bandwidth requirement for full color video?

Jiang Li: About 50 Kbps for a QCIF size (176x144) video at an acceptable frame rate. Do you have anything else to add?

Jiang Li: I would like to take this opportunity to express my sincere appreciations to hundreds of thousands of users who sent us bug reports, suggestions and warm encouragement, and also to hundreds of web sites that reported, linked or reviewed Microsoft Portrait. It's these active responses that make us feel our research is valuable and useful to people. Finally I want to thank my colleagues Keman Yu and Gang Chen, who made the greatest contributions to the project.

Additional Information:

Microsoft Project Website

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