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MPEG4 Codec Benefits for High Quality Access Grid Video Conferencing
- 1. 11/11/2004 MPEG4 Codec for Access Grids National Center for High Performance Computing Speaker: Barz Hsu Email: [email_address]
- 24. Thanks for your attendance
Notas do Editor
- Good morning, everybody. I am Barz Hsu, come from Taiwan. Currently, work in National Center for High Performance Computing, abbreviated as NCHC. This talk is entitled to “ MPEG4 Codec for Access Grids.”
- This is the outline. First, we want to give a definition about HDTV Then, give a brief introduction to MPEG4 standard . Then, we would like to demonstrate our contributions to the AG community. Especially, we have incorporated MPEG4-codec to provide high definition and high quality video streaming. However, it is not straightforward to deploy MPEG4 codec into access grid, because it is required much more computational resource and also becomes error-sensitive to pack loss. So, we would pay attention over performance issues and error-resilience capability of MPEG4 codec.
- Mul
- Let review the history of VIC VIC is a video conferencing application developed by the Network Research Group in U.C. Berkeley. This group creates a set of Mbone tools. They are fully used by Access Grid , inSORS, and VRVS community. VIC is based on Real Time Protocol and Real Time Control Protocol to provide real-time video streaming. It supports multicasting transmission to relieve the exponential growth of bandwidth requirement, and also support unicasting. VIC is written by hybrid of Tcl/Tk and C++ languages, and currently supports codec including H.261, H.263, H263++, Motion JPEG, nv, and etc.
- VIC is a critical component for AG, however, there are still many problems. First, it is somewhat hard to maintain owing to it is ten years old and uses mixed languages of Tcl/Tk and C++. The hybrid nature makes VIC hard to trace and debug. LACK OF HIGH-QUALITY VIDEO CODEC Although VIC supports many video codecs, unfortunately, only H.261 is relatively usable, other codecs have some drawbacks such as easy crash, burst bit-rate, and obvious block artifacts. THERE ARE SOME LIMITATIONS ON FRAME RESOLUTION The supported video frame resolutions are only CIF and QCIF or 4CIF However, even using H.261, fast movement can result in degradation and parts of the video feed not being updated for several seconds, depending upon network condition. Also, the viewing windows can only be resized in very limited sizes. Video quality is subjectively good when displayed in medium or small windows but can look pixellated when displayed in a large window. The other serious problem is that VIC lacks of exhaustive optimizations on critical components, for examples, codec, render, grabber, or even the memcpy function. I believe the performance is incredible critical if we want Access Grid to be scalable to accommodate large number of sites.
- Our goal is that we want Access Grid can be broadcasting in television quality, or even in cinema quality. The goal is simple to be understood, however difficult to be realized. Fortunately, we don’t need to reinvent the wheel to do everything. Instead, we leverage with existing open source resources, such as VLC, MPlayer, and FFmpeg, To provide “sense of presence”, first, the video conference should be as real-time as possible. For example If not, you might not realize that your partner was angry until 5 seconds later. Next, we are going to supporting high-definition video source and studio-quality video conferencing by incorporate with up-to-date codecs such as MPEG2, MPEG4, and H.264. Due to advanced codecs designs, in same bit-rate these codecs can provide higher quality and less compression artifacts than H.261’s. Furthermore, error resilience and concealment are essential to maintain quality even when the situation of pack loss and error are heavy. We will detail these in the following.