Using the OS-X Video Server
Basic Idea
Apple's video server uses the OS-X operating system. This design provides
two different methods for making digital video available to users on the
Internet. Each has advantages and disadvantages for educators. The legacy
approach uses the HTTP:// Internet protocol. The fastest method uses a
new Internet protocol, RTSP:// which is an Apple invention that, among
other server features, enables Real Time Streaming with thousands of simultaneous
users. This page introduces what must be done on the server and on client
web pages to enable this video reception.
HTTP:// Protocol Setup
This approach will seem very familiar to anyone has posted web pages to
a server. Create a digital video file. Have the server administrator provide
a password protected folder in the "Document" folder for this server.
Also ask for the domain name or Internet protocol number of this server
if no domain name is available. Upload the movie into the assigned account
area. This finishes the chores on the server side.
On an HTML web page create a link to your movie. When you create the
link, use the domain name followed by the account folder space followed
by the movie's file name. The might look like:
http://campusvideoserver.abc.edu/Smith/mymovie.mov
Notice that the folder name Document is not included in this web address.
The server knows to automatically go to the Document folder when it sees
the HTTP protocol.
RTSP:// Protocol Setup
There are many advantages to the RTSP protocol. If your movie is in streaming
format it cannot be copied, reducing the chance of copyright violations
of your compositions. If it is being streamed live, thousands of other
users can watch. However, live streamed video is in a "broadcast" mode
which displays that video from the time the user connects. That is, live
broadcast does not take the user back to the beginning of the video composition.
There is also an archived streaming video procedure which does allow users
to see the stored video from its beginning whenever they connect. RTSP
can also create bandwidth sensitive files. Web browsers cannot link
directly to RTSP protocol files. A separate application such as Quicktime
Player can play the RTSP files without web links.
There is a way though that allows a web page link to a file which in
turn can activate the RTSP files. Creating a link to streamed video starts
procedures that are familiar to HTTP protocol designers. However, the RTSP
uses a special folder for streaming, which by default is called the Movies
folder. The Movies folder contains that real video file. The Document folder
should contain the pointer or alias file which is created with Quicktime
Player to which an HTML link can be made. The HTML link might use an address
like this.
http://campusvideoserver.abc.edu/Smith/mymoviealias.mov
Notice that the folder name Document is not included in this web address.
The server knows to automatically go to the Document folder when it sees
the HTTP protocol, follow the link to the Movies folder, and stream the
video. The filename can be anything; alias does not have to be part of
the filename but is useful to come up with with an extension to the real
movie file name so that you make it clear which is which.
A special procedure is used to teach the alias file in the Document
folder where the actual movie file is located in the Movies folder.
-
Use the RTSP address or URL to open the movie in Quicktime. The address
you enter might look like this:
-
rtsp://campusvideoserver.abc.edu/Smith/mymovie.mov
-
Once the movie is visible and can be played, click File in the menu bar
and select Save As...
-
Two radio-button options present themselves: Save Normally or Make the
Movie Self-Contained. Use the "save normally" option. Create your filename
and save to an easy to reach folder or place on your computer's desktop.
This makes a very small file, about 8K, that holds the Internet location
of the needed file in the Movies folder. Think of this as the pointer file,
pointing to the location of the actual videoclip.
-
Transfer this pointer (alias) file to the Document folder.
-
Create a link to this pointer file in your web page and test the link.
The movie should appear and play in your web page.
There are also disadvantages to the RTSP protocol. This protocol does not
store the movie on the users hard drive in the cache folder, as can be
done in the HTTP protocol. Any replay or advancement to any other point
of the video requires the video to be re-streamed from the server. With
home modems and other situations in which immediate action is important,
the HTTP structure is better to use. Particularly for training purposes
where sections of the movie may need to be played over and over again,
put the movie in the HTTP folder and link it directly.
Trouble Shooting
-
If your pointer or alias file is much larger than 8K, perhaps 60K, recheck
the URL used in opening the file in Quicktime Player. It is likely that
you began the file with HTTP instead of RTSP and are using files in the
Documents folder instead of the Movies folder.
RSHoughton@hotmail.com