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General Information About Streaming Media
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Streaming Media doesn't work with dialup connections
All Streaming Media codec developers are putting major efforts
in optimizing their codecs for sub-100Kbit/s connections. Depending
on the type and quality of the original content, and the quality
of the encoding and delivery processes, even a 40Kbit/s stream
can be a great experience. Note that you should choose content
that is encoded at a maximum of 80% of your maximum dialup bitrate.
If you still have problems with viewing streaming content through
your personal dialup connection, please contact your ISP.
Streaming Media and Your Internet connection
First, welcome to the Digital Age! Upgrade your Internet connection.
More and more business information is exclusively made available
through Streaming Media. You shouldn't deny your employees access
to this type of content. Second, Streaming is more bandwidth
efficient than downloading or emailing the same media.
What are RTSP, PNM/PNA and MMS?
RTSP (Real Time Streaming Protocol) is an Open Standard protocol
for streaming media, used by the majority of streaming vendors,
including Apple. MMS is Microsoft's own solution, but Microsoft
will replace MMS with RTSP in future releases. PNA and PNM are
RealNetworks' legacy streaming protocols and are not
used anymore. It is important for network administrators not
to block RTSP protocols and connections in their firewalls.
Downloading vs Streaming Content
Multimedia content downloaded from the Internet, or received
by email can indeed contain a virus, therefore you should install
Anti-Virus software on your mail servers and firewalls. Streaming
Media on the other hand, is the opposite of downloading: content
is streamed directly to the Player, and is not placed on your
harddrive. There are no known viruses that can distribute nor
activate themselves using Streaming Media content, servers or
players. There are some minor and major known vulnerabilities
in Windows Media Player, please use Windows Update to patch
these, and please read the EULA for all players carefully.
What is the difference between downloading and streaming?
Downloading is exactly what it says: you load a copy of a file
from a server to your local computer. Basic error correction
technology built in TCP makes sure that you receive every bit
and byte. The error correction is bad for audiovisual content
since it requires a large overhead in the connection. Another
problem is that you have to wait until the complete file is
on your computer before you can use it. Some players fake streaming
by measuring how fast a file is downloaded and start playing
it during the download, this is called "Fast Start". This results
in those annoying hickups. Another problem is that webservers
aren't capable of sending a lot of simultaneous audio and video
files.
A streaming server only sends streaming data right to the streaming
client. No data is saved to the harddisk in this process. The
rtsp and mms protocols uses UDP which has no error correction.
(The player and server use better error correction technology
which prevents data loss as far as possible but don't require
a large amount of overhead). The stream is buffered at the client
side so possible dips can be overcome. This is just an example
of the smart technology used in streaming software. Since server
and player software are optimized for realtime content distribution,
the overall experience using streaming is *far superior* opposed
to downloading. Note: streaming servers can tunnel mms/rtsp
streams through HTTP, so content still can't easily be downloaded,
but will still get through firewalls. Some other servers (Icecast)
fake a stream and do send a regular file over HTTP (progressive
download).
What are Multirate Files? Windows Media Technology
Multi-bitrate streams can contain several video tracks and one
audio track to allow viewers with different internet connection
speeds to view the encoded media as best as can be available
to them. The Windows Media Player determines the best connection
rate with the Windows Media server, and then streams at the
best bit rate available to that connection speed. Multicast
normally only sends data to a client without receiving any from
a client, there is no way for the player and server to negotiate
bandwidth. Therefore, the server only transmits the highest
bit rate stream from the stream. Multirate technology requires
you to use streaming server software.
QuickTime uses another similar solution but with another technology.
You encode multiple streaming files in several bitrates and
sizes. You also produce a reference movie. This reference movie
looks at the technical details of the system configuration of
the end-user (like system power, network connection, software
version, etc) and selects the appropriate streaming file. This
technology gives you the most control over the content but also
has a downside, because a player can't automatically switch
between bitrates during playback.
Content from streaming servers can't be downloaded
First, optimized streaming servers don't run http services such
as Apache or IIS. When streaming content to a player, no data
is written to the harddisk, so no copy is placed on the users'
PC. So yes, your content is safer on a streaming server than
on a regular webserver. But, several rtsp and mms recorders
are available that pretend to be a media player and try to rebuild
a media file from a stream. These rebuilt files aren't exact
clones of the original file and always have some level of degradation.
Another way to capture a stream is to connect the PC to a VCR,
tapedeck or digital recording device. But in order to redistribute
the content, one has to re-encode the captured file again, resulting
in huge quality losses. A third way is to write virtual drivers
or virtual audio and video cards, and then save the stream to
a file. This workaround is also used to bypass DRM security.
Our conclusion: content is never 100% safe, but you shouldn't
worry too much about (and invest too much in!) a minority of
some smart kids that get a kick out of ripping some streams.
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