Web Audio Editor

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Der Web Audio Editor ist neu in Firefox 32.

With the Web Audio API, developers create an audio context. Within that context they then construct a number of audio nodes, including:

Each node has zero or more AudioParam properties that configure its operation. For example, the GainNode has a single gain property, while the OscillatorNode has frequency and detune properties.

The developer connects the nodes in a graph, and the complete graph defines the behavior of the audio stream.

The Web Audio Editor examines an audio context constructed in the page and provides a visualization of its graph. This gives you a high-level view of its operation, and enables you to ensure that all the nodes are connected in the way you expect. You can then examine and edit the AudioParam properties for each node in the graph. Some non-AudioParam properties, like an OscillatorNode's type property, are displayed, and you can edit these as well.

This tool is still experimental. If you find bugs, we'd love it if you filed them in Bugzilla. If you have feedback or suggestions for new features, ffdevtools.uservoice.com or Twitter are great places to register them.

Den Web Audio Editor öffnen

Der Web Audio Editor ist nicht in Firefox 32 nicht automatisch aktiviert. Um ihn zu aktivieren, öffne die Developer Tool Einstellungen und mach ein Häckchen bei  "Web Audio". Nun sollte es einen extra Reiter in der Toolbox toolbar mit der Überschrift "Web Audio" geben. Klicke auf den Reiter und öffne eine Seite die einen Audiokontext definiert hat. Dies sind zwei gute Demos:

  • der Voice-change-O-Matic, kann verschieden Effekte auf einen Mikrofoneingang anwenden und die Ergebnisse visualisieren.
  • das Violent Theremin, das Höhe und Lautstärke einer Sinuswelle per Mausbewegung ändern lässt.

Visualizing the graph

The Web Audio Editor will now display the graph for the loaded audio context. Here's the graph for the Violent Theremin demo:

You can see that it uses three nodes: an OscillatorNode as the source, a GainNode to control the volume, and an GainNode as the destination.

Connections to AudioParams

Displaying connections to AudioParams is new in Firefox 34.

Connections between nodes are displayed as solid lines. If, instead, you've connected a node to an AudioParam in another node, then the connection is shown as a dashed line between the nodes, and is labeled with the name of the AudioParam:

Inspecting and modifying AudioNodes

If you click on a node, it's highlighted and you get a node inspector on the right hand side. This list the values of that node's AudioParam properties. For example, here's what the OscillatorNode looks like:

With the Violent Theremin demo, the frequency parameter is modified as the user moves the mouse left and right, and you can see this reflected in the node inspector. However, the value isn't updated in real time: you have to click the node again to see the updated value.

If you click on a value in the node inspector you can modify it: press Enter or Tab and the new value takes effect immediately.