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param-source.js
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param-source.js
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var PseudoAudioParam = require('pseudo-audio-param')
var Event = require('geval')
var extend = require('xtend')
var truncateTypes = ['linearRampToValueAtTime', 'exponentialRampToValueAtTime']
module.exports = ParamSource
function ParamSource (context, defaultValue) {
var result = new PseudoAudioParam(defaultValue)
result.context = context
var insertEvent = result._insertEvent.bind(result)
result.onEvent = Event(function (broadcast) {
result._insertEvent = function (event) {
insertEvent(event)
broadcast(event)
}
result.cancelScheduledValues = function (time) {
cancelScheduledValues(result, time)
broadcast({
type: 'cancelScheduledValues',
time: time,
args: [time]
})
}
result.cancelAndHoldAtTime = function (time) {
var truncatedEvent = null
for (var i = result.events.length - 1; i >= 0; i--) {
if (time <= result.events[i].time) {
truncatedEvent = result.events[i]
} else {
break
}
}
if (truncatedEvent) {
var value = result.getValueAtTime(time)
result.cancelScheduledValues(time)
if (truncatedEvent && truncateTypes.includes(truncatedEvent.type)) {
result[truncatedEvent.type](value, time)
}
result.setValueAtTime(value, time)
}
}
})
return result
}
ParamSource.applyEvents = function (audioContext, source, target, at) {
var maxTime = 0
var currentTime = audioContext.currentTime
at = Math.max(at || currentTime, currentTime)
var number = source.getValueAtTime(at)
var prescheduledTo = at
target.value = number
target.setValueAtTime(number, at)
source.events.filter(e => e.time > at).forEach(event => {
prescheduledTo = Math.max(prescheduledTo, event.time)
handleEvent(event)
})
return source.onEvent(event => {
if (event.time < prescheduledTo) {
// handle live input that lags cycles behind scheduled values
prescheduledTo = event.time
maxTime = event.time
target.cancelScheduledValues(event.time)
}
handleEvent(event)
})
function handleEvent (event) {
var minTime = audioContext.currentTime
var args = event.args
var time = event.time
if (time < minTime) {
time = minTime
}
if (event.type === 'cancelScheduledValues') {
target.cancelScheduledValues(time)
maxTime = event.time
} else {
event.args.slice()
event.args[1] = time
if (event.type === 'setValueAtTime' && time <= minTime) {
target.value = event.value
}
target[event.type].apply(target, args)
}
var sampleTime = event.time
var duration = 0
if (event.type === 'setTargetAtTime') {
duration = event.timeConstant * 8
sampleTime += duration
} else if (event.duration) {
duration = event.duration
}
if (sampleTime < maxTime) {
target.cancelScheduledValues(maxTime)
target.linearRampToValueAtTime(source.getValueAtTime(maxTime), maxTime)
}
if (event.time + duration > maxTime) {
maxTime = event.time + duration
}
}
}
ParamSource.isParam = function (value) {
return value instanceof PseudoAudioParam || value instanceof ReducedParams
}
ParamSource.reduce = function (params, reducer) {
return new ReducedParams(params, reducer)
}
function ReducedParams (params, reducer) {
this.params = params
this.reducer = reducer
this.events = []
this.context = getContext(params)
}
ReducedParams.prototype.onEvent = function (listener) {
var context = this.context
var releases = this.params.map(param => ParamSource.isParam(param) && param.onEvent((event) => {
var duration = 0
var sampleTime = event.time
if (event.type === 'setTargetAtTime') {
duration = event.timeConstant * 8
sampleTime += duration
} else if (event.duration) {
duration = event.duration
}
if (event.type === 'cancelScheduledValues') {
listener(event)
this.events.push(event)
} else {
var value = getValueAt(this.params.filter(p => p !== param).concat(event.value), sampleTime, this.reducer)
var args = event.args.slice()
args[0] = value
listener(extend(event, { args, value }))
this.events.push(event)
}
if (context && context.audio) {
// clean up old events
while (this.events[1] && this.events[1].time < context.audio.currentTime) {
this.events.shift()
}
}
}))
return function () {
while (releases.length) {
var fn = releases.pop()
typeof fn === 'function' && fn()
}
}
// scoped
}
ReducedParams.prototype.getValueAtTime = function (time) {
return getValueAt(this.params, time, this.reducer)
}
function getValueAt (params, at, reducer) {
var paramValues = params.map(p => ParamSource.isParam(p) ? p.getValueAtTime(at) : p)
return reducer(paramValues)
}
function cancelScheduledValues (source, time) {
while (source.events.length && time <= last(source.events).time) {
source.events.pop()
}
if (time < source._prevGotTime) {
source._eventIndex = 0
source._prevGotTime = 0
}
return source
}
function last (array) {
return array[array.length - 1]
}
function getContext (params) {
for (var i = 0; i < params.length; i++) {
if (params[i] && params[i].context) {
return params[i].context
}
}
}