Audio-Node-Suite

Web Audio API AudioNode Suite

About

Audio-Node-Suite is a JavaScript library, for use in the Browser with the Web Audio API, which provides a suite of Web Audio API compatible AudioNode classes:

AudioNodeComposite: this is a convenient class for creating a custom composite/wrapping AudioNode class. It is used internally and can be also used for creating your own custom composite/wrapping AudioNode. As an additional goodie, the class provides a useful "by-pass" functionality for temporarily by-passing the effect of the underlying AudioNode instances.
AudioNodeNoise: this is a white or pink noise generator which can be used for testing purposes.
AudioNodeMute: this is a simple node for muting the audio stream.
AudioNodeGain, AudioNodeCompressor, AudioNodeLimiter: these are just convenient wrappers for the regular functionality provided by the Web Audio API GainNode and DynamicsCompressorNode classes, providing the bypass() functionality and some opinionated parameter defaults.
AudioNodeEqualizer: this is based on the Web Audio API BiquadFilterNode class and provides a convenient parametric multi-band equalizer AudioNode.
AudioNodeMeter: this is based on the Web Audio API AnalyzerNode class and continuously tracks and measures the overall volume in decibel of the audio stream. It is also the internal base building block for the AudioNodeGate, AudioNodeAmplitude and AudioNodeSpectrum classes.
AudioNodeGate: this is based on the Web Audio API GainNode class and measures the volume in decibel of the audio stream and drains the volume if it drops below a certain decibel threshold. It is intended to act as a Noise Gate.
AudioNodeAmplitude: this is based on AudioNodeMeter and hence the Web Audio API AnalyzerNode class to analyze the volume level of the audio stream and continuously render it into a Canvas element in the DOM.
AudioNodeSpectrum: this is based on AudioNodeMeter and hence the Web Audio API AnalyzerNode class to analyze the frequency/decibel spectrum of the audio stream and continuously render it in a (linear or logarithmic) scale to a Canvas element in the DOM.
AudioNodeVoice: this is based on AudioNodeMute, AudioNodeEqualizer, AudioNodeGate, AudioNodeCompressor, AudioNodeGain and AudioNodeLimiter to provide a convenient single AudioNode which acts as a reasonable filter chain for voice. Its opinionated parameters are intentionally hard-coded and are just based on experiences of the author.

Installation

$ npm install audio-node-suite

Usage

See the TypeScript definition for details on the provided Application Programming Interface (API).

Implementation Notice

Audio-Node-Suite is written in TypeScript 4 (ECMAScript 2022) and is transpiled to plain JavaScript (ECMAScript 2022) and this way runs in all current (as of 2023/Q1) JavaScript environments, of course. To support different loader environment, the transpiled output is provided in the three distinct variants ESM (ECMAScript 2022), CommonJS (Node) and UMD (Legacy Browser).

License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

`dBFS` calculation issue, perhaps.

It has been decades since I was in a signal processing class, so I am certainly not a subject matter expert. As such, I am opening this issue more out of curiosity as to your opinion on the specification.

Referring to your dBFS calculation here, I see this computation used in a myriad of other projects:

dbfs_value = 20 * Math.log10(rms(signal))

However, you do not "offset" the dBFS calculation by +3dB as described here:

value_dBFS = 20*log10(rms(signal) * sqrt(2)) 
   = 20*log10(rms(signal)) + 3.0103

The explanation for the offset given here seems fairly compelling:

The reason for the sqrt(2) is that the definition of dBFS is explicitly designed such that the dBFS value of a full-scale sine wave equals 0. Since the RMS of the full-scale sine wave is 1/sqrt(2), multiplying rms(signal) by sqrt(2) ensures that the formula evaluates to 0 when signal is a full-scale sine wave.

There even seems to be some confusion about this in the industry, listing a few DAWs that differ on their calculation of 0 dBFS.

Searching through GitHub, I did find one project that uses this 3dB normalization factor:

// Normalised RMS - this value is normalised to a 997 Hz Sine Wave at 0dbFS
// More info: https://en.wikipedia.org/wiki/DBFS
const normalisationFactor = 3.01
const RMSPowerDecibels =
  20 * Math.log10(Math.sqrt(sumOfSquares / waveFormValue.length)) + normalisationFactor

I would appreciate hearing your thoughts on this. Thanks.

rse / audio-node-suite Goto Github PK

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`dBFS` calculation issue, perhaps.

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