Flash Audio

Accessible Flash Streaming Audio

by Daryl Croke

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Load and stream an external mp3 file

While versions of Flash previous to Flash MX supported streaming of mp3 compressed sounds within a SWF, they did not support accessibility.  Consequently there is little point in building an accessible audio console that is backward compatible with Flash 4 or 5 because their interaction with a screen reader will at best be a "hit or miss affair" as one user commented.

Instead developers can take advantage of the capability of Flash MX to stream or download native MP3. The advantage being there is no need to take the extra steps of converting MP3 content to sound only SWF. Developers can offer narrated content to users in a common player independent format that is also available to any user of Flash MX.

To load an external file use the following script.

// load audio mp3
function primeSound() {
	mySound = new Sound ();
	mySound.loadSound(current_mp3, true);
}
primeSound();

The file starts streaming and begins to play, current_mp3 is a variable that has the file path assigned to it elsewhere.

current_mp3 = "../assests/mp3/rock2pt44k.mp3";

To mute the sound until a user hits play use mysound.stop(). This stops the playback but still allows the audio to load.

Compatibility Issues

As stated earlier there is little point in attempting to build an accessible player in Flash 4 or 5. To access a Flash MX streaming console users will required a Flash 6 player, r40 or later version. Unfortunately, versions of Flash before 6r40 did not properly support audio streaming. So it is a good idea to detect player version before embedding the player or else some users may experience problems.  Developers can use the Macromedia Flash Deployment kit to detect version and deploy content based upon player version.

Don’t use the standard Macromedia code to embed a Flash movie. This code will force a user with an older player to the Macromedia download site. Instead use the bare minium of code to embed the movie.

<object classid="mymovie" width="160" height="80">
	<param name=movie value="preload.swf">
	<embed src="preload.swf" quality=high type="application/x-shockwave-flash" 
          width="160" height="80"></embed>
</object>

This code will alert users that they require a Flash player but not force them to attempt to install it. Place a link to the latest flash player and users can then manually download the player if they wish. Avoid automatically forcing users to download the latest player. As mentioned earlier some of the target audience use non-flash browsers. They won’t be to happy being forced to download a player they can’t use anyway. Other sections of the audience are sceptical about what benefits Flash, mainly a visual media, has for non-visual users. If it appears that gaining access to the site requires Flash they will understandingly feel excluded and leave.

Conclusion

Developing streaming audio content for the vision impaired is a viable and worthwhile. The American Council of the Blind’s Internet radio station is a brilliant example of what can be achieved. To ensure the widest possible audience place a link to the audio file first. This is the most reliable method of delivers audio across platforms and applications. I would also urge audio develops to download trail versions of screen readers (see links below). We should trail our web sites with the monitor switched off for true useability testing. Macromedia have made steps forward in accessible design with Flash MX. In theory the accessibility features included in Flash MX allow at least a section of visual impaired users access to and interaction with audio content. More needs to be done to make Flash accessible to non-Windows based products.

About the Author

Born 1964 in a small rural town in Australia, Daryl dropped out of High School at 17 and starting playing classical guitar at 18. He worked in a number of blue-collar jobs before studying music at university as a mature age student specializing in composition and audio technology. He completed an honours thesis on using CD-ROM to teach Diatonic Harmony. In 2002 he finished a two-year multimedia course. Formal qualifications: BA Honours in Music, Latrobe University 1997; Graduate Diploma in Music Technology Latrobe University 1995; Advanced Diploma in Electronic Design and Interactive Media, Victoria University, 2002. Email Daryl.

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