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CHAPTER NINETEEN
- REAL AUDIO/REAL VIDEO
NOTE:
We no longer support RealAudio and RealVideo. However, if you
know how to install it yourself you are more than welcome to do
so. It is very easy to install and you can obtain full instructions
on downloading it and implementing it at Real
Networks Site. We have provided the following information
as a courtesy.
RealAudio and RealVideo technology utilizes an interactive system
between the RealVideo Server and the RealPlayer to enable real-time
audio and video delivery over the Internet. When the user clicks
on a link on a Web page, the clip buffers and then begins to play,
all within a few seconds. This gives the deceiving impression
that the file is linked directly to the Web page. In reality,
information is passing between the Web server supporting the Web
page, the RealVideo Server supporting the file, and the RealPlayer.
How does streaming audio/video
work?
The file itself is not linked through the web page, contrary to
general belief. Information actually passes between the web server,
the RealServer, and the RealPlayer. RealAudio and Video can only
be retreived by the RealPlayer. If you have a link to the actual
file on your server, the file will be downloaded completely before
it can be played by the RealPlayer. There needs to be a go between
between the web server and the Real Server. This go between is
a metafile. This metafile provides the URL of the file to be played
to the RealPlayer.
What is a Metafile and how does
it work?
Metafiles are text files which contain the URL location of a RealAudio
or RealVideo file. Remember that RealAudio and RealVideo files
cannot be referenced directly by the Web page because this would
cause them to be downloaded in their entirety before playback.
In order for the files to be played in real-time, they must be
played through a RealPlayer, and served by a RealVideo Server.
Therefore there must be a link between the Web server and the
RealVideo Server. The link is contained in the metafile.
I've got RealAudio installed on
my site, but it's not streaming. It's downloading the file and
then playing it. I didn't want it to do this!
You need to have a metafile call the file itself.
How do I make a metafile?
Let's say you want to play the RealAudio file that is named hello.rm
You make a text file with the following line:
pnm://servername/username/domain-www/file.rm
and save the file as hello.ram
(Email
if you do not know your servername and we will provide you with
this information).
You then call the hello.ram in your HTML code as you would any
html document.
Where can I get more information
about creating Real Audio/Video files?
You can find this information at Real
Networks Site. .
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