Content overview

Replay alternatives

Required servers

Broadcast via HTTP Server only

Version number for server resp. player

Server directories

How to setup a Windows Media Server

Data volumes

Number of users and bandwidth

Question:

Which alternatives exist for the replay of a web document? What advantages/disadvantages do they have?

Solution:

There are 3 alternatives for the replay of audio/video of a web document:

• Local Replay:
  You have local access to the web document. This means that the document is stored on a hard disc of your computer or you have access to another media (e.g CD or network drive) on which the document is stored.
  
  • Advantages:
    

    - Best quality as possible

    - Very short or no preload time

    - Unrestricted scrolling in the document is possible

  • Disadvantages:
    - No fast distribution of the document possible
    - Document can only be replayed if it was produced locally or if it was copied on the computer
    - Document needs hard disc space

     

• Replay via HTTP server:
  The document is stored on an HTTP server. You have access to the document via internet connection.
  
  • Advantages:
    

    - Fast distribution and ease of availability of the document

    - Document does not need local hard disc space

  • Disadvantages:
    

    - Long preload times depending on the available bandwidth

    - Only small bandwidth available for audio/video

    - High loss of audio/video quality

    - Often no replay of video at all

    - Scrolling in the document is not possible

     

• Replay via HTTP and Streaming server:
  The document is stored on an HTTP server and a RealSystem Server resp. Windows Media Server. You have access to the document via internet connection.
  
  • Advantages:
    

    - Fast distribution and ease of availability of the document

    - Document does not need local hard disc space

    - Scrolling in the document is possible

  • Disadvantages:
    

    - Long preload times depending on the available bandwidth 

    - Audio/video quality depends on the available bandwidth

Question:

Which servers are necessary for the accessibility of the documents via the Internet?

Solution:

Three server types are available:

• HTTP-Server:
  During the conversion of your document into the RealMedia resp. WindowsMedia format an HTML document is created, thus an HTTP server is indispensable for the accessibility via the Internet. Since a variety of HTTP servers exist (also due to the different operating systems), we cannot get into detail at this place.
  
  
• RealSystem-Server:
  If your document is converted into the RealMedia format, the use of another server, next to the HTTP server, is expedient. This server takes care of the streaming of the audio resp. video data. You need a RealSystem Server version 6.0 or higher, or the Helix Universal Server by RealNetworks. Free evaluation versions exist of both variants.
  
  
• Windows Media Server:
  If you convert your document into the Windows Media format, it is expedient to use another server, next to the HTTP server. This server care of the streaming of the audio resp. video data. You need WindowsMedia Services (at least version 4.1 or higher) by Microsoft. This server is already included in the program package of Windows 2000 Server. For the Windows NT 4.0 Server the package "WindowsMedia Services 4.1" can be downloaded for free at Microsoft.

WindowsMedia Services can not be installed on a "Standard" platform such as Windows 9x, Windows NT 4.0 Workstation, Windows 2000 or Windows XP. A Windows Server operating system, such as Windows NT 4.0 Server or Windows 2000 Server, is required.

If you select a server in the settings of the LECTURNITY Publisher for the documents, you have to have write permission in the document directory on the respective server.

Question:

Is an HTTP server sufficient for the streaming of documents?

Solution:

Generally, audio and video data can be transmitted by an HTTP server. This, however, is not streaming in the sense of the word, but a download.

Advantages: 

• Apart from the HTTP server, no more servers are necessary.
• When using a firewall only port 80 for HTTP protocol has to be opened. (True Streaming uses more ports.)

Disadvantages:

• There is much loss of quality during the replay of the audio/video data.
• RealMedia:
  Only a narrow bandwidth with a maximum of 32 Kbps can be used even if your Internet connection provides a much higher bandwidth. Consequence:
  
  • Preload time is long and rebuffering appears often.
  • SureStream (dynamic adaption of bit rate) is not supported.
  • In general, the quality of the audio is worse.
  • In the case of video data, only very few frames are displayed.

• Windows Media:
  Similar to RealMedia only a narrow bandwidth can be used. The used bandwidth depends on the selected system profile. Consequence:
  
  • Preload time is long.
  • Often no video is displayed, the video window remains empty (e.g. at a profile for "Multiple Bit Rate Video").
  • Navigation during replay is not possible.

Question:

Which versions of server and player for RealMedia resp. WindowsMedia should be selected in the LECTURNITY Publisher?

Solution:

RealMedia:

Here, the principle of the "lowest common denominator" is true. Therefore, for the conversion of your document the lowest version number of server resp. Player Plugin is decisive since different codecs are used according to the selected version.

Example: If you use a RealSystem Server version 6.0 and a RealPlayer version 8.0, then consider the settings on the dialog "Version selection" in the LECTURNITY Publisher. Under "RealServer" select the entry "Version 6.0 (G2)". A RealSystem Server version 6.0 cannot stream RealMedia data which was created with the Codec for version 8.0! 

Windows Media:

Here, the version of the used WindowsMedia Player for the replay is decisive, the version of thw Windows Media Server is of minor importance. I.e. the Server "WindowsMedia Services 4.1" can stream WindowsMedia data that was created with the codec for the WindowsMedia Player 9.

Special case with Windows 98 and Windows NT 4.0: For these two systems, only the WindowsMedia Player up to version 6.4 is available so far, higher versions of the WindowsMedia Player are not supported!

Example: If you want to support the replay of your document on platforms under Windows NT 4.0, you should select standard codecs for the WindowsMedia Player 6.4 in the dialog "Settings" in the LECTURNITY Publisher.

Question:

In which directories do the servers store streaming data of RealMedia resp. WindowsMedia?

Solution:

RealSystem Server:

Under Windows, the RealNetworks server usually creates a subdirectory with the name "Content". (in a standard installation it is C:\Program files\Real\RealServer\Content). There, any further subdirectories with streaming data can be created.

Example: In the LECTURNITY Publisher, you can enter the following in the dialog window "Target Selection (2)" under "Target directory on the Real server":

C:\Program files\Real\RealServer\Content\My_Presentation

Windows Media Server:

The WindowsMedia Services server usually creates a subdirectory with the name "ASFRoot". (in a standard installation it is C:\ASFRoot). There, any further subdirectories with streaming data can be created.

Example: In the LECTURNITY Publisher, you can enter the following in the dialog window "Target selection (2)" under "Target directory on the Windows Media Server":
C:\ASFRoot\My_Presentation

Question:
What must be considered when setting up a Windows Media Server?

Solution:

For the setup of a Windows Media Server the use of Windows Media Services (version 4.1 or higher) is required (see also "Required Servers"). The following instructions is based on the operating system "Windows 2000 Server".

The Windows Media Server can be administrated by "Start" ==> "Control Panel" ==> "Administrative Tools" ==> "Server configuration" ==> "Web/Media Server" ==> "Windows Mediaserver" ==> "Adminstration". 

Used Ports:

The "Windows Media Unicast Service" must run as a service("Start" ==> "Control Panel" ==> "Administrative Tools" ==> "Services"). Probably the service must be started manually.

Windows Media files are stored in the "ASFRoot" directory. It is best to create a subdirectory for every single document. The default "ASFRoot" directory is "C:\ASFRoot". 

The Windows Media Server can be administrated and configured with the tool "Windows Media Administrator" (C:\WINNT\system32\Windows Media\Server\nsadmin.exe).

Under "Configure Server" ==> "Server properties" ==> tab "Protocolls" the creation of logfiles can be activated. Default directory for logfiles is C:\WINNT\system32\LogFiles.)

Question:

Which amount of data are produced during the export of audio/video data into a streaming format?

Solution:

On the one hand the produced data volumes depend on the media type (audio, video, Screengrabbing clip). On the other hand they depend on the settings for the bandwidth (RealMedia) resp. system profiles (Windows Media) in the Publisher. The more bandwidth one selects the more data volume is produced.

• Produced data volume depending on the media type:
  The following table shows typical ranges for the data volumes:
  
  
  
  
  
  
  The data volume for Screengrabbing clips depends on their resolution. Screengrabbing clips in Windws Media format require much less memory compared to the RealMedia format if a special "screen capture" codec with high data compression is used.
  
  
• Streamed data volumes depending on the used bandwidth:
  The following table shows the streamed data volumes for a showcase recording of 30 minutes. They are compared with a LECTURNITY Presentation Document.
  
  

Question:

How many users can have access to a Windows Media server at the same time and with which bandwidth?

Solution:

The following table gives a guideline for the number of users at different bandwidths. We presume a maximum workload of 50 % of the available network bandwidth: