2. WebAudio with Oscillators

AudioNodes: Processing modules for audio signal

Audio Sources Nodes:

OscillatorNode, AudioBuffer, AudioBufferSourceNode, MediaElecmentAudioSourceNode, MediaStreamAudioSourceNode

Audio Effects Nodes:

BiquadFilterNode, ConvolverNode, DelayNode, DynamicsCompressorNode, GainNode, StereoPannerNode, WaveShaperNode, PeriodicWave

Audio Destinations:

AudioDestinationNode, MediaStreamAudioDestinationNode

Connecting AudioNodes

first create AudioContext to build the audio graph (linkage of AudioNodes)
provide versions for different browsers
var audioContext = new AudioContext(); or var audioContext = new (window.AudioContext || window.webkitAudioContext)();
connecting nodes together: the node that you want to connect is given as the argument of the connect method

eg:

source = audioContext.createMediaStreamSource(stream);
source.connect(analyser);
analyser.connect(distortion);
distortion.connect(biquadFilter);

etc.

OscillatorNode

OscillatorType

Output of AudioNodes

var audioContext = new AudioContext();
var oscillator = audioContext.createOscillator();
oscillator.connect(audioContext.destination);

Parameters

AudioParam interface: an audio-related parameter, usually a parameter of an AudioNode
a list of events
can be set to a specific value or change in value, scheduled to happen at a specific time and following a specific pattern
two kinds of AudioParam: a-rate and k-rate parameters
a-rate AudioParam takes the current audio parameter value for each sample frame of the audio signal
k-rate AudioParam uses the same initial audio parameter value for the whole block processed (128 sample frames)

Attribute 1: frequency

Attribute 2: detune

a-rate:
a detuning value (in Cents) which will offset the frequency by the given amount
default value is 0
k-rate:
parameter to modulate the speed at which the audio stream is rendered
default value is 0
ranges from -1200 to 1200

computedFrequency

both frequency and detune are a-rate parameters, used together to determine a computedFrequency value

One-Shot behaviour

a sound or short audio clip
uses the AudioBuffer interface
used in drum machines, sequencers and 3D games etc
can be played using oscillators (in the form of notes or tunes)
AudioBufferSourceNodes: create a node, attach a buffer, set loop boolean value, connect to a node on the graph that will lead to destination, call noteOn or noteGrainOn, and noteOff

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