Video Conferencing and Streaming Lecture

Internet-Based Desktop Video Conferencing and Streaming

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• http://www.mediacottage.com/vcbasics.html

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Several issues to consider

• The most important is bandwidth. The amount of bandwidth (network capacity) available affects the quality of the conference: the more bandwidth, the better the quality. With less bandwidth, the video is more likely to be jerky and to fall out of synch with the audio.
• Video and audio are compressed (shrunk) prior to transmission, then decompressed prior to display on the receiver's computer. The specific  hardware and software used to do this is called a codec (compression and decompression )
• Number of users: Videoconferences can be between 2 users (point-to-point) or between many users (multipoint). The latter requires more complicated technology and bandwidth.
• Quality: The number of frames per second transmitted affects the quality of the video. The more frames, the higher the quality -- and the higher the bandwidth demands. Usually, Internet videoconferencing transmits 15 frames per second (for comparison, television is 30 frames per second).

Software packages available include

• Netmeeting (Microsoft)
• CU-SeeMe
• ProShare (Intel)
• Sorensen Envision (made in Utah)

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Basic principles of Internet streaming video

Streaming is a technology that allows video/audio files to be transmitted to a client machine as a stream, rather than as a whole file. This means that the file can begin to be displayed before the entire file is downloaded. This is especially useful when large files are involved, as the user does not have to wait a long time.

The key to streaming is buffering. Before beginning to play the video clip, the player will load the first several seconds of the clip. Then, what is stored in the buffer is played to the user.
 

Streaming software	Example	Server platform	Client platform	Development system	Codec
REALPLAYER by Real Networks	Mimi's Lecture, Real Stream (56 kbps) Mimi's Lecture Real Stream (256 kbps)	Linux, Windows, Solaris (Mac not included in latest versions) $8,000+	Any, freeware	Any freeware or $149.95 for pro version.	RealVideo G2 with SVT proprietary codec
WINDOWS MEDIA PLAYER by Microsoft	http://www.msnbc.com/m/v/video_news.asp select from the list of top stories and then choose a connection speed.	Windows NT (no additional cost after NT)	Any, freeware	Windows	Proprietary windows media codec
QUICKTIME by Apple	http://www.apple.com/trailers/ (pick any movie!)	Any (no software needed unless you want to do live streams)	Any, freeware	Any	Sorensen

Internet access affects bandwidth, which affects quality

Several mechanisms are available to access the Internet, each with price and bandwidth implications. The following summarizes typical access methods:

• Internet services provider. Via ISP network and your connection/modem speed. Modem: 56kbps download - 33.6 upload
• ISDN (integrated services data network). Via your phone company: 64-128kbps download - 64-128kbps upload
• Cable modems. Via your cable provider. 384kbps - 4Mbbps up/download
• DSL (digital subscribe line). Carries data at high speeds over standard phone lines. Available via your phone company: 144kbps - 8 Mbps download - 144kbps - 1.7 Mbps
• Wireless. Via cell and satellite telephones. This is a rapidly changing technology sector.

Applications in online education

• Consider how you might use these technologies in online education settings