Audio Document: Why .filters expects BiquadFilterNodes not AudioNode?

[takahirox]

Description of the problem

Audio Document mentions that in Audio.filters

.filters : Array
Represents an array of BiquadFilterNodes.

but why .filters expects BiquadFilterNodes array, not generic AudioNode array?

Audio.setFilters looks just composing a chain of array elements with this.filters[ i - 1 ].connect( this.filters[ i ] );. Then I think we don't need to limit filters to BiquadFilterNodes and we may accept generic AudioNode.

Actually I set AnalyserNode as filters in my project and it works. (Because of a certain reason, I want to insert AnalyserNode right after audio source then I couldn't use THREE.AudioAnalyser.)

So, I'd like to suggest to replace BiquadFilterNodes with AudioNode for filters in Audio document unless there is a strong reason why it limits to BiquadFilterNodes.

Three.js version

• Dev
• r119
• ...

Browser

• All of them
• Chrome
• Firefox
• Internet Explorer

OS

• All of them
• Windows
• macOS
• Linux
• Android
• iOS

Hardware Requirements (graphics card, VR Device, ...)

[Mugen87]

I guess it was limited to BiquadFilterNode since nobody was aware of different use cases.

TBH, I still don't get the reason why you are passing an AnalyzerNode to setFilters(). Do you mind explaining in more detail? In any event, I'm not sure it's worth to update the documentation if most users don't understand the purpose of passing AudioNode to setFilters(). Enhancing the docs in that regard is maybe more confusing than anything else.

[takahirox]

Do you mind explaining in more detail?

I want to insert Analyzer Node and a certain Audio Node (I call Effector here) right after audio source.

Audio.source - Analyzer - Effector - Audio.gain (Audio output)

In my case Audio.gain.gain.value can be changed by other modules or end-user UI. I want Analyzer to analyze "raw" audio source data and Effector to apply certain effect depending on analyzed result (Limiter, Compressor, adjusting volume level, or so on).

I want to handle raw audio source data then I couldn't use THREE.AudioListener.filter or THREE.AudioAnalyzer (which connects to Audio output). And I want to let THREE.AudioListener regard audio applied effect by Analyzer and Effector as original audio source.

I couldn't find any other places to handle raw audio source data other than THREE.Audio.filters in Three.

I found now that AudioListener.filter is typed as AudioNode, not BiquadFilterNode in the document. Does this mean that applying effect other than BiquadFilter should be done in THREE.AudioListener side, not THREE.Audio side, in Three?

Off topic: Why THREE.AudioListener.filter, not THREE.AudioListener.filters (array)? Any special reasons? I think THREE.AudioListener.filters (array) would be more useful because it can compose filter chain as THREE.Audio.filters does.

[Mugen87]

I found now that AudioListener.filter is typed as AudioNode, not BiquadFilterNode in the document. Does this mean that applying effect other than BiquadFilter should be done in THREE.AudioListener side, not THREE.Audio side, in Three?

I guess this is a mistake. It should be BiquadFilterNode. However, if this done was one purpose, I have no objections no use AudioNode for Audio.filters, too.

Why THREE.AudioListener.filter, not THREE.AudioListener.filters (array)? Any special reasons?

TBH, no. I guess the idea was to keep it simple and just use a single filter for listeners.

[takahirox]

It should be BiquadFilterNode.

Then audio connection will be

Audio source - Audio.filters (BiquadFilterNode array, optional) - Audio.gain (Audio output) - AudioListener.gain (Audio input) - Audio.filter (BiquadFilterNode, optional) - destination

How can we apply audio effect with non-BiquadFilterNode like DynamicsCompressorNode or ConvolverNode? Or they shouldn't be used in Three Audio (because we think they are useless effects)?

(Sorry if my question and suggestion are stupid, I'm still new to (Web)Audio).