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5.4 Background Audio
There
is one other form of inline multimedia generally
available to web surfers audio. Most browsers treat audio
multimedia as separate documents, downloaded and displayed by special
helper applications, applets, or plug-ins.
Internet Explorer, on the other hand,
contains a built-in sound decoder and supports a special tag
(<bgsound>) that lets you integrate with
your document an audio file that plays in the background as a
soundtrack for your page. [Section 12.1] [Section 12.2]
We applaud the developers of Internet Explorer for providing a
mechanism that more cleanly integrates audio into HTML and XHTML
documents. The possibilities with audio are very enticing, but at the
same time, we caution authors that Internet
Explorer's special tags and attributes for audio
don't work with other browsers, and whether this is
the method that the majority of browsers will eventually support is
not at all assured.
5.4.1 The <bgsound> Tag
Use the <bgsound> tag to play a
soundtrack in the background. This tag is for Internet Explorer
documents only. Other browsers ignore the tag. It downloads and plays
an audio file when the host document is first downloaded by the user
and displayed. The background sound file also will replay whenever
the user refreshes the browser display.
<bgsound> |
5.4.1.1 The src attribute
The src
attribute is required for the <bgsound> tag.
Its value references the URL for the related sound file. For example,
when Internet Explorer users first download a document containing the
tag:
<bgsound src=">
they will hear the welcome.wav audio
file perhaps an inviting message play once through their
computers' sound systems.
Currently, Internet Explorer can handle three different sound format
files: wav, the native format for PCs;
au, the native format for most Unix workstations;
and MIDI, a universal music-encoding scheme (see also Table 5-1).
5.4.1.2 The loop attribute
As with Internet Explorer's inline movies, the
loop attribute for the browser's
<bgsound> tag lets you replay a background
soundtrack a certain number of times (or indefinitely), at least
until the user moves on to another page or quits the browser.
The value of the loop attribute is the integer
number of times to replay the audio file, or
infinite, which makes the soundtrack repeat
endlessly.
For example:
<bgsound src=" loop=10>
repeats the ta-dum soundtrack 10 times, whereas:
<bgsound src=" loop=infinite>
continuously plays the noise
soundtrack.
5.4.2 Alternative Audio Support
There are other
ways to include audio in your documents, using more general
mechanisms that support other embedded media as well. The most common
alternative to the <bgsound> tag is the
<embed> tag, originally implemented by Netscape
and supplanted by the <object> tag in the
HTML 4 and XHTML standards. Take a look in Chapter 12 for details.
Ultimately, all background audio, including spoken document content,
should be handled using the various audio extensions defined in the
Cascading Style Sheets 2 (CSS2) standard. While we cover all of these
extensions in Chapter 8, they are not yet supported by any browser.
When such support becomes widely available, all of these early audio
extensions will go the way of the <blink>
and <isindex> tags, early specialized tags
deprecated in favor of more generalized and powerful features.
