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The Test-Player is written in JavaScript and works as follows:

When playback starts, a starting-time is set, which is used to compute the running time (the position in the text). The time for text playback is synchronous with the system time on the computer.

In regular intervals (10th of a second) the time which passed since playback started will be determined. If a timestamp for a text is reached or exceeded the text will be updated. The areas for »Speaker«, »Info«, »Text« and »Time« have unique »ID« attributes each in the HTML source. Using the JavaScript method »getElementById« the current text element is addressed and changing the property »nodeValue« the current text value is inserted dynamically.

When continuing (after pausing), or skipping in the Text (next, previous, enter a time), the starting-time will be set anew because the running time is computed as a difference to this value.

The following issues are checked and verified when testing the Player-Script

• running-time and texts change dynamically
• dynamic buttons: change after clicking or on »MouseOver«
• control functions (Start, Stop, Pause), skipping and custon time input work
• no other kinds of JavaScript errors occur

The JavaScript Text-Player was successfully tested on the following platforms and browsers

• Windows 98: Netscape 7.2, Opera 8.54, MS-Internet Explorer 5.5, 6.0
• Windows XP: MS Internet Explorer 6.0 MS Internet Explorer 7.0, Firefox
  
• Linux i686: Netscape 7.2, Konqueror 3.3 & 3,5, Firefox 1.0.4, Mozilla 1.7.12
• Mac OS:Firefox, Safari

Audio-Plugins

Audio-Plugins, enable browser to playback MP3 Files, but make things even more complicated. Not always is a suitable plugin installed, it is not always possible to determine installed plugins, and comtrols and height of embedded audio players vary. Some plugins can be controlled using JavaScript but most do not fully support this

As an alternative to plugins, we also thought about playing back the audio using Java or Flash, but after some investigation we learned that this is not possible as easily as we thought.

Finally we decided to optimze our program for Quicktime, since it is available for Windows and Apple systems, and audio can be controlled by JavaScript. This way text and audio can easily be played back synchronous.