Publishing
Once the video
is edited it is time to publish. There are four basic video publishing
outlets in order of increasing quality (and file size): web download,
web streaming, CD, and DVD. Three factors to consider in deciding which
to use are (1) how viewers will access the movie (online or via a disc),
(2) the length of the video, and (3) if online, what speed will viewers
be able to access the movie. If viewers will use a CD or DVD, then the
file size or length of the movie is really the only consideration. CDs
hold about 700 MB and DVDs hold about 4.7 GB.
Choosing to make a video available online allows viewers to download the entire movie before viewing. This can be time consuming, but if the video is being used in the classroom it can be downloaded ahead of time and viewers will not need to rely on the speed and availability of an Internet connection. On the other hand, streaming video is played directly off of the server on which it resides. The online limitation here is the viewer's Internet connection speed or bandwidth capacity. This allows download of longer movies without taxing computer file space. Streaming is an option but it does require special server software.
A decision must be made about
the type of player viewers will use, and therefore the file type of
the video. The most common are RealMedia (http://www.real.com),
QuickTime (www.apple.com/quicktime/),
WindowsMedia (www.windowsmedia.com/
) and Mpeg4 , which is compatible with the previous three.
The choice of video editor may limit the choice of player. For example,
iMovie only allows export as a QuickTime file, although
there are numerous programs available that will convert between formats.
For a detailed discussion of the different players visit http://www.clickandgovideo.ac.uk/players.htm.
In order to get a movie down
to a reasonable size for publishing to the web, to a CD, or to DVD it
must be compressed. Video is compressed using a codec. The word codec
is a combination of coder and decoder. There are numerous codecs available
that use an algorithm to reduce the memory file size by eliminating
unnecessary audio and video data (Click and Go Video, 2002).
For example, if the video includes a still shot for 20 frames, the codec
reduces the memory needed for those 20 frames to one frame repeated
20 times so that about 19 frames worth of memory are eliminated.
When compressing video be sure to balance file size with quality so that the best quality version is accessible to viewers. For streaming video consider how your viewers will access the movie: via dial-up modem, cable, DSL, or a T1 line. A typical dial-up modem has a speed of 56 kbps (kilobits per second). That means that one minute of video can take no more than 420 kbps of memory (there are 8 bits in a byte). However, a viewer using a cable or DSL line can handle 255 kbps so one minute of video can take up to 1.9 MB. It is important that the video size not exceed these limits as it will appear jerky and out of sync.
There are three ways to control video file size: image compression, frame rate, and pixel dimension. Image compression depends on the type of codec. There are numerous codecs available and many editing software packages allow for codec choice. Some are more common than others but the best way to choose is to try several and see which looks best.
Frame rate is the number of frames shown per second. Your video was most likely recorded at 30 frames/second, however for viewing, 15 frames/second is often more than adequate. Again, it is best to try several different frame rates to see which works best.
Adjusting pixel dimension or window size is the most obvious method for reducing file size. DVD or CD will probably want a larger window size, such as 640 x 480, since download speed or memory is not an issue. For streaming or download off the Internet, 320 x 240 is quite acceptable. For short video with lots of detail a larger window size may work best. Again, try out several sizes to see which is most appropriate.
Once the video has been edited and encoded in a suitable format it is ready to publish. At this point the video can be burned to a CD or DVD or uploaded to the web for download or streaming, depending on the available publishing resources.
Conclusion
Whether teachers and students choose to create their own videos or simply show videos in class as a means to stimulate discussion or bring distant and difficult concepts to life, video is undeniably a powerful medium. Even the most technology-challenged teachers can use video to help integrate technology in their curriculum as mandated by the No Child Left Behind (NCLB) legislation and the National Education Technology Standards (NETS) using the strategies described above. Access to video on the Internet and new, affordable tools for creating video open up a whole new world of visual learning compared to the filmstrips of fifty years ago. Teachers have only to take advantage of these video resources to improve and enhance student learning.
About the Author
Elizabeth Snoke Harris is an
outreach coordinator for The Science House (http://www.science-house.org/
) at North Carolina State University. She has her M.Ed. in Instructional
Technology, is a former editor of Meridian, and recently published
her first book First Place Science Fair Projects for Inquisitive
Kids .
Email: beth_harris@ncsu.edu
Send correspondence to:
NCSU Box 8211
Raleigh, NC 27695
Phone 919.513.7521
Fax 919.515.7545
Appendix: Free Video Resources Online
Annenberg/CPB
http://www.learner.org/view_programs/view.programs.html
Apple iLife - videos created by students
http://education.apple.com/education/ilife/
Apple Learning Exchange - includes video from a variety of sources including NASA http://ali.apple.com/
Atomic Learning's Video Storytelling Guide - includes the video examples used in this article. http://www.atomiclearning.com/storytellingindex.shtml
Educscapes - a collection of links to streaming video and other online resources
http://www.eduscapes.com/seeds/stream.html
eScreening Room - free, full length, documentaries
http://escreeningroom.com/
Internet Movie Archive
http://www.archive.org/details/movies
Real Guide News
http://news.guide.real.com/
United Streaming - requires a subscription but has a free 30 day trial
http://www.unitedstreaming.com/
Video Placement Worldwide
http://www.vpw.com/educational/
YouTube - watch and share video online
http://www.youtube.com/
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