audio-buffer-list

audio-buffer-list

Extension of BufferList for AudioBuffers. Handy and performant to deal with (possibly long) sequence of audio buffers − accumulate, read, stream, modify, delete etc. It provides interfaces of both AudioBuffer and BufferList, as well as bunch of other useful methods.

Usage

const AudioBufferList = require('audio-buffer-list')
const AudioBuffer = require('audio-buffer')

let abl = new AudioBufferList(new AudioBuffer(1, [0, .1, .2, .3]), new AudioBuffer(1, 100))

abl.append(new AudioBuffer(1, 100))

abl.length // 204
abl.slice() // <AudioBuffer 0, .1, .2, .3, 0...>

API

new AudioBufferList(source, options?)

Creates new audio buffer list instance, new is not strictly required.

source can be AudioBuffer, AudioBuffer array, AudioBufferList, AudioBufferList array or callback.

options may provide numberOfChannels, context for web audio API context and sampleRate.

list.insert(buffer, offset=0)

Put new AudioBuffer, AudioBufferList or array of them at the offset.

list.delete(count, offset=0)

Delete number of samples starting at the offset. count can possibly be negative, then items are deleted on the left side from the offset. offset can also be negative, meaning to start from the end.

list.repeat(count)

Repeats contents of the list specified number of times. Modifies list in-place.

list.map((buffer, index, offset) => buffer|bool?, from=0, to=-0)

Create new list by mapping every buffer. Optionally pass offsets from and to to map only buffers covering the subset, keeping the rest unchanged. If no buffer returned from the mapper function then the old buffer will be preserved. If null returned then the buffer will be discarded. offset tracks buffer offset in new list, index reflects buffer count.

list = list.map((buf, idx, offset) => {
	for (let c = 0; c < channels; c++) {
		let data = buf.getChannelData(channel)

		//start buffer from the subset may start earlier than the subset
		//end buffer from the subset may end later than the subset
		for (let i = Math.max(from - offset, 0),
					l = Math.min(to - offset, buf.length);
					i < l; i++) {
			data[i] = process(data[i])
		}
	}
}, from, to)

list.each((buffer, index, offset) => {}, from=0, to=-0, {reversed}?)

Iterate over buffers from the indicated range. Buffers can be modified in-place during the iterating. Return false to break loop. Pass {reversed: true} as the last argument to iterate in reverse order.

AudioBuffer properties & methods

list.duration

Total duration of the audio list, i.e. sum of buffers durations.

list.numberOfChannels

Detected from the buffer with max number of channels in the list. Can be set by options.

list.sampleRate

Just for convenience with AudioBuffer interface

list.getChannelData(channel)

Return FloatArray with merged data for the channel.

list.copyFromChannel(destination, channel, startInChannel=0)

Put data from the channel to destination FloatArray. Optional startInChannel defines offset in the channel to start from.

list.copyToChannel(source, channel, startInChannel=0)

Put data from the source FloatArray into channel, optionally starting at startInChannel offset.

BufferList properties and methods

list.length

Total length of list in samples, i.e. sum of inner buffer lengths.

list.append(buffer)

Insert new AudioBuffer, AudioBufferList or array of them to the end.

list.slice(start=0, end=-0)

Return merged AudioBuffer representing indicated interval.

list.shallowSlice(start=0, end=-0)

Return sublist — a handle for the data of the indicated interval.

list.get(idx, channel)

Get single sample value at the coordinate.

list.duplicate()

Create new AudioBufferList consisting of the same AudioBuffers as the initial list.

list.copy(dest, destStart?, srcStart?, srcEnd?)

Put data into destination AudioBuffer.

list.consume(length)

Delete data from the beginning.

Stream methods

See also

• audio — high-level class for audio
• audio-buffer — audio buffer class for nodejs and browser
• audio-buffer-utils — toolset for audio buffers
• buffer-list — canonical BufferList implementation