Antti Kupila

Personal Blog, Portfolio and Online playground

View over the green room at Sid Lee, Montreal

SoundFX, out-of-the-box audio filters with actionscript 3

We had a project where we would have needed to apply something like a lowpass filter in real time on an audio track. Doing some research for this quickly triggered even further interest in audio programming. I also realized it’s not as scary as it first seems and a whole lot of fun. We deployed on Flash player 9 so we ended up going with another approach. Still, this is what came out of that.

While all the audio stuff isn’t as hard as it looks when reading the docs it can still be intimidating to a lot of developers. Hopefully this post will help out those guys. The key focus here was to keep the syntax as similar to the one we’re familiar with from display objects, the SoundFX class does all the heavy lifting. Take a look at the following syntax:

[as]
var sound : SoundFX = new SoundFX( new URLRequest( “music.mp3″ ) );
sound.filters = [ new CutoffFilter( 12000 ) ];
sound.play( );
[/as]

When you don’t have to worry so much about the nitty gritty stuff of making it work you can focus on the fun creative part. You can do basically anything you can do with display object filters, animate the properties etc. It’s a lot of fun ;)

A simple demo of how this works (flash player 10 required):

Go crazy with the filters :)
A couple small shortcuts will help you too:

  • Double click: default value
  • Shift + double click: maximum value
  • Command/ctrl + double click: minimum value
  • Shift + command/ctrl + double click: middle value
  • Click on visualizer to pause/resume playback (pretty cool if you’ve added some echo)
  • Double click visualizer to randomize all knobs

An added bonus here is added control over audio streaming. As with NetStreams you can specify how many seconds should be loaded before playback starts.

Source (includes SoundFX and the demo)

The filters are currently ported from C source at musicdsp.com (awesome resource!). Once i look a bit more into the math & magic behind the effects i’ll try to post new effects. Of course i’m more than happy to include any other people’s effects too, creating new effects is pretty simple.