Working with the Web Audio API

Description

Half-Title Page Series Page Title Page Copyright Page Table of Contents List of Figures List of Code Examples Resources Preface Acknowledgments 1 Introducing the Web Audio API The Web Audio API The audio context What you need to get started Example: Hello World Example: – adding user interaction Interlude – Generating sound with scheduled sources 2 Oscillators A bit of theory OscillatorNode Parameters The oscillator types Example: basic use of the OscillatorNode The PeriodicWave Square wave example Pulse wave example The detune parameter Example: detuning an oscillator Note 3 Audio buffer sources The AudioBuffer Example: creating a buffer source The AudioBufferSourceNode How does playback work? Example: varying playback of an audio buffer Example: wavetable synthesis with audio buffers Example: pausing audio Example: playing audio backwards 4 The constant source node Introducing the constant source Example: DC offset with a ConstantSourceNode Example: using a ConstantSourceNode to affect many parameters Example: grouping audio Interlude – Audio parameters 5 Scheduling and setting parameters Audio parameters Changing audio parameters Methods setValueAtTime(value, startTime) linearRampToValueAtTime(value, endTime) exponentialRampToValueAtTime(value, endTime) setTargetAtTime(target, startTime, timeConstant) setValueCurveAtTime(values, startTime, duration) cancelScheduledValues(cancelTime) cancelAndHoldAtTime(cancelTime) Computation of value Example: beep sound with parameter automation Example: beep sound with custom automation Example: repeating a beep Example: crossfade Example: synthesising a bell sound 6 Connecting audio parameters and modulation Connections revisited Disconnecting nodes Connecting audio parameters Example: FM synthesis Example: AM synthesis Tremolo and vibrato Ring modulation Interlude – Destination and source nodes 7 Analysis and visualization AnalyserNode FFT windowing and smoothing over time Using the AnalyserNode Example: visualizing sound 8 Loading, playing and recording Working with media elements Example: use of an element The MediaElementAudioSourceNode Example: using the MediaElementAudioSourceNode Loading an audio sample What about encodeAudioData? Example: decoding an mp3 file Comparison of media element sources and buffer sources Working with audio streams MediaStreamAudioSource Example: level metering with live audio input Example: MediaStream to AudioBuffer Recording an audio node Note 9 OfflineAudioContext The OfflineAudioContext What the OfflineAudioContext can’t do OfflineAudioContext example OfflineAudioContext example 2 OfflineAudioContext example 3 – suspend and resume Interlude – Audio effects 10 Delay The DelayNode The delay line Delay line interpolation Example: comb filter Example: vibrato simulation with a modulated delay line Example: feedback delay Example: the Karplus-Strong algorithm 11 Filtering Filter definition The BiquadFilterNode Parameters Filter characteristics Methods Example: biquad visualiser Comparison of filter designs IIRFilterNode IIRFilterOptions Methods Example: IIR filter visualizer Stability issues with Web Audio API filters Notes 12 Waveshaper Theory Characteristic curve Hard and soft clipping Input gain Symmetry and rectification Harmonic distortion Intermodulation distortion Aliasing and oversampling Common parameters Tube-sound distortion WaveshaperNode Example: clipping a signal Example: the bit crusher Note 13 Dynamic range compression Introduction Theory A simple dynamic range compressor DynamicsCompressorNode Under the hood of the DynamicsCompressorNode Example: attack and release times Example: compressor parameters Misuse and overuse of dynamic range compression Artifacts Loudness wars The tide is turning 14 Reverberation Theory Direct and reverberant sound fields Why use Reverb? Convolutional reverb Convolution and fast convolution Block-based convolution Overlap and add Physical meaning Convolution implementation Nonuniform partitioned block convolution and other optimizations Convolution engine Multi-channel convolution Channel configurations for input, impulse response and output The convolver node Example: simulating reverb Example: normalizing the impulse response Example: FIR filtering based on convolution Note Interlude – Multichannel audio 15 Mixing audio Up-mixing and down-mixing Computing the number of channels Up-mixing and down-mixing rules Channel merger Channel splitter Example: channel flipper Example: ping-pong delay 16 Stereo panning Theory Panorama StereoPannerNode Example: stereo panning Example: stereo enhancer 17 Spatialized sound Spatial audio in the Web Audio API The coordinate system The AudioListener The PannerNode geometry Directivity Distance models Panning model Azimuth and elevation Panning algorithm Putting it all together Example: moving listener Example: moving source Note Interlude – Audio worklets 18 Working with audio worklets High-level overview An audio worklet Hello World: a noise source The audio worklet processor The audio worklet node Audio worklet Hello World with async await Inputs, outputs and options: the maximum worklet Inputs, outputs and options: the panX worklet Supporting audio parameters: the gain worklet Storing internal variables: smoothing filter worklet processorOptions: first-order filters worklet Messaging: first-order filters worklet 19 The wonders of audio worklets Example: pulse waves and square waves revisited Example: the bit crusher revisited Example: dynamic range compression revisited Example: stereo enhancer revisited Circular buffers and delay lines Example: the Karplus-Strong algorithm revisited Appendix – The Web Audio API interfaces References Index