Led by Dr Paul Kenyon, University of Plymouth

• View bower_birds_frames_container.htm in a web browser.

• Use the audio controls on the web page to Play, Pause and Stop the commentary. Observe how the page jumps to the picture of the particular bird as the commentary unfolds.

• Click on the names of individual birds listed under 'Audio contents' and observe how the audio stream jumps to describe that species, and how the page moves to a picture of the particular bird

Open the first of these files bower_birds_container.htm in the text-based HTML editor Arachnophilia.

The HTML code sets up three FRAMES that will display the contents of these three files:

• bower_birds.htm
• bower_birds_player.htm
• bower_birds_toc.htm

Screen display

Open the file bower_birds.htm in Arachnophilia.

Locate the <a name ...></a> tags which identify the position on the web page which displays information about each type of bower bird.

The name tag is normally used to write HTML code that enables users to move around a web page.

For example, we could write HTML code such as

which would display in a browser as:

If the user clicked on the blue underlined text they would be shown the area of the page identified with the underlying HTML tag <a name="regent_bower_bird"</a>

The name tag is used by markers in the ASF streaming audio file (bower_birds.asf) to display different parts of the web page as the audio commentary unfolds.

Open the file bower_birds_player.htm in Arachnophilia.

Scroll to the bottom of the file to reveal the HTML code which loads the Windows Media Player into a web page and gives it the name "Media player1"

Parameters passed to Media Player control its appearance and behaviour.

For example:

• <param name="FileName" value="bower_birds.asf"> loads the ASF file bower_birds.asf
• <param name="AutoStart" value="False"> prevents the ASF file playing when it has loaded

The code:

• classid="CLSID:22D6f312-B0F6-11D0-94AB-0080C74C7E95" codebase="http://activex.microsoft.com/activex/controls/mplayer/en/ nsmp2inf.cab#Version=6,4,5,715"

is supplied by Microsoft, and will automatically connect to their web site if the browser detects that the user has not installed Windows Media player. The user is then prompted to download the appropriate browser plugin.

If necessary, open the file bower_birds_player.htm in Arachnophilia.

Scroll to the middle of the file to reveal the function InitializeMarkers (). This code is modified from code contained within the Microsoft Windows Media Software Development Kit (SDK)

The function InitializeMarkers () checks the ASF file (bower_birds.asf) loaded into MediaPlayer1 for any embedded markers. If embedded markers are found the line:

• parent.tocframe.document.write

lists the markers in the frame called tocframe to produce a list of birds

If necessary, open the file bower_birds_player.htm in Arachnophilia.

Scroll to the top of the file to reveal the JavaScript which deals with script commands inserted into the ASF file (bower_birds.asf) by theWindows Media ASF indexer tool

the line:

• <SCRIPT Language="JavaScript" FOR="MediaPlayer1" EVENT="ScriptCommand(bstrtype, bstrparam)">

'listens' to the ASF file as it plays. Several Script Commands have been embedded into the ASF file. Each Script Command passes two parameters (bstrtype, bstrparam) to the MediaPlayer1 event handler . Next we will examine the values of these parameters stored in bower_birds.asf

Open bower_birds.asf in Windows Media ASF Indexer. Hit the Edit Script Commands button

At time 00:00:00.0 bower_birds.asf passes the parameters

• eventnumber1 and blank to

MediaPlayer1 event handler which stores them as

• bstrtype and bstrparam

The actual values may differ in your version of bower_birds.asf

If necessary, open the file bower_birds_player.htm in Arachnophilia.

Locate the line:

• if (bstrtype == eventnumber1"){parent.content.location.href="bower_birds.htm#regent_bower_bird"

This line executes if the MediaPlayer1 event handler receives the the Script Command eventnumber1 in the stream of information from the ASF file bower_birds.asf

The line

• if (bstrtype == eventnumber1"){parent.content.location.href="bower_birds.htm#regent_bower_bird"

displays bower_birds.htm#regent_bower_bird in the frame named 'content'

• parent. content .location.href=" bower_birds.htm#regent_bower_bird "

The 'content' frame name was defined in the HTML file: bower_birds_frame_container.htm

• <FRAME NAME="content" SRC="bower_birds.htm" SCROLLING="auto" FRAMEBORDER="0">

The location 'regent_bower_bird' was defined in the HTML file: bower_birds.htm

• <a name="regent_bower_bird">

These interrelationships are shown in the composite picture below

If necessary, open the file bower_birds_player.htm in Arachnophilia.

Work out what effect the Script Commands:eventnumber2, eventnumber3 and eventnumber4 will have on the information displayed in the frame named 'content'