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Built-in Pipeline Nodes

This reference documents every built-in pipeline node in the Amplitude Audio SDK. Pipeline nodes are the building blocks of the audio processing graph executed by Amplimix each frame.

Node Categories

All nodes fall into one of four categories:

Category Description
Input Marks the entry point of audio into the pipeline.
Output Marks the exit point of processed audio.
Processor Transforms audio in-place (single input, single output).
Mixer Combines multiple inputs into one output.

Input / Output

InputNode

Marks the start of the pipeline. Receives audio from the sound source.

{ "id": 1, "name": "Input", "consume": [] }

OutputNode

Marks the end of the pipeline. Sends audio to the audio device.

{ "id": 99, "name": "Output", "consume": [98] }

Spatial Nodes

AttenuationNode

Applies distance-based gain attenuation using the sound's assigned attenuation model.

Parameter Type Description
attenuation float Output gain after applying the curve (read-only). 
{ "id": 2, "name": "Attenuation", "consume": [1] }

SpeakerPanningNode

Pans a source to the pipeline's output speaker layout (stereo, quad, 5.1 or 7.1) using constant-power panning, placing each of the source's channels as a virtual emitter around its direction.

{ "id": 3, "name": "SpeakerPanning", "consume": [2] }

Panning is constant-power: a centred mono source reaches each side at -3.01 dB. A multichannel source plays at its spread width, at unity on its own channels.

AmbisonicPanningNode

Encodes a mono source into Ambisonic B-Format channels based on 3D position.

{ "id": 4, "name": "AmbisonicPanning", "consume": [2] }

AmbisonicRotatorNode

Rotates the Ambisonic sound field to match listener orientation.

{ "id": 5, "name": "AmbisonicRotator", "consume": [4] }

AmbisonicBinauralDecoderNode

Decodes Ambisonic B-Format to binaural stereo using HRIR convolution.

{ "id": 6, "name": "AmbisonicBinauralDecoder", "consume": [5] }

AmbisonicMixerNode

Mixes multiple Ambisonic streams together.

{ "id": 7, "name": "AmbisonicMixer", "consume": [5, 10] }

MixerNode

Mixes multiple streams of the pipeline's output channel layout together.

{ "id": 8, "name": "Mixer", "consume": [3, 6] }

Effect Nodes

EnvironmentEffectNode

Applies the environment's assigned effect to sounds inside the zone.

{ "id": 9, "name": "EnvironmentEffect", "consume": [2] }

NearFieldEffectNode

Simulates near-field pressure effects for very close sources.

{ "id": 10, "name": "NearFieldEffect", "consume": [2] }

ReflectionsNode

Computes early reflections based on room geometry.

{ "id": 11, "name": "Reflections", "consume": [1] }

ReverbNode

Applies late reverberation based on room materials and dimensions, through a pluggable reverb algorithm. The room's surface areas and volume set the algorithm's normalized room-size parameter, and its wall materials' absorption coefficients, averaged, set the absorption parameter.

{ "id": 12, "name": "Reverb", "consume": [1] }

The node name selects the algorithm: Reverb uses Freeverb; Freeverb, Dattorro, and RoomReverb select that algorithm explicitly.

{ "id": 12, "name": "Dattorro", "consume": [1] }

See the Custom Reverb Tutorial to register your own.

Occlusion / Obstruction

OcclusionNode

Applies frequency-dependent low-pass filtering based on the entity's occlusion value.

{ "id": 13, "name": "Occlusion", "consume": [2] }

ObstructionNode

Applies low-pass filtering based on the entity's obstruction value.

{ "id": 14, "name": "Obstruction", "consume": [2] }

Dynamics Nodes

LimiterNode

Prevents clipping by limiting peak amplitude.

Parameter Type Description
threshold dB Level above which limiting begins.
attack ms Time to respond to peaks.
release ms Time to return to unity gain. 
{ "id": 15, "name": "Limiter", "consume": [8] }

ClampNode

Hard-clips samples to a maximum amplitude.

{ "id": 16, "name": "Clamp", "consume": [15] }

HardClipNode

Applies aggressive hard clipping (distortion).

{ "id": 17, "name": "HardClip", "consume": [15] }

RoundoffClipNode

Applies softer roundoff clipping.

{ "id": 18, "name": "RoundoffClip", "consume": [15] }

Default Pipeline

The default pipeline shipped with Amplitude combines most of these nodes:

{
  "id": 1,
  "name": "default",
  "nodes": [
    { "id": 1, "name": "Input", "consume": [] },
    { "id": 2, "name": "Attenuation", "consume": [1] },
    { "id": 3, "name": "Occlusion", "consume": [2] },
    { "id": 4, "name": "SpeakerPanning", "consume": [17] },
    { "id": 5, "name": "AmbisonicPanning", "consume": [3] },
    { "id": 6, "name": "NearFieldEffect", "consume": [3] },
    { "id": 7, "name": "AmbisonicMixer", "consume": [18] },
    { "id": 8, "name": "Mixer", "consume": [4, 6, 10, 12, 14] },
    { "id": 10, "name": "AmbisonicBinauralDecoder", "consume": [7] },
    { "id": 11, "name": "Reflections", "consume": [1] },
    { "id": 12, "name": "AmbisonicBinauralDecoder", "consume": [11] },
    { "id": 13, "name": "HardClip", "consume": [8] },
    { "id": 14, "name": "Reverb", "consume": [1] },
    { "id": 15, "name": "Obstruction", "consume": [3] },
    { "id": 16, "name": "EnvironmentEffect", "consume": [3] },
    { "id": 17, "name": "Mixer", "consume": [15, 16] },
    { "id": 18, "name": "AmbisonicRotator", "consume": [5] },
    { "id": 9, "name": "Output", "consume": [13] }
  ]
}

Custom Nodes

You can implement custom pipeline nodes by subclassing Node and NodeInstance. See the Custom Pipeline Node Tutorial for details.

Next Steps