Pipeline

Pipelines define how audio data flows through the Amplimix processing system before reaching the audio device. Using a node-graph architecture, pipelines allow you to chain together various processing nodes to create custom audio rendering paths.

Pipeline Architecture¶

A pipeline is a directed acyclic graph (DAG) of processing nodes. Audio data enters through an Input node, flows through various processing nodes, and exits through an Output node.

flowchart LR
    Input --> Attenuation
    Attenuation --> Occlusion
    Occlusion --> StereoPanning
    Occlusion --> NearFieldEffect
    StereoPanning --> StereoMixer
    NearFieldEffect --> StereoMixer
    StereoMixer --> Output

Each sound source in your game gets its own pipeline instance, allowing per-sound processing with unique spatial properties.

Pipeline Definition¶

Pipelines are defined as JSON files in your project's pipelines/ directory and compiled to .ampipeline binary assets when building your project. Each pipeline contains:

• id — Unique identifier for the pipeline
• name — Human-readable name
• nodes — Array of node definitions

Node Definition¶

Each node in the pipeline has:

• id — Unique node ID within this pipeline
• name — The registered node type name
• consume — Array of node IDs this node receives input from
• parameters — Optional array of float parameters for node configuration

Available Nodes¶

Amplitude provides a comprehensive set of built-in pipeline nodes:

Input/Output Nodes¶

Mixer Nodes¶

Mixer nodes combine multiple audio streams into one.

Spatial Processing Nodes¶

These nodes handle 3D audio positioning and spatialization.

Environmental Processing Nodes¶

These nodes simulate acoustic environments.

Obstruction/Occlusion Nodes¶

These nodes simulate sound passing through obstacles.

Dynamics/Limiting Nodes¶

These nodes control signal levels.

Node Types¶

Pipeline nodes fall into three categories based on how they handle audio:

Producer Nodes¶

Producer nodes generate or receive audio data and don't consume input from other nodes.

• Input — The only built-in producer node

Consumer Nodes¶

Consumer nodes receive input from exactly one other node and produce output.

• All processing nodes (Attenuation, StereoPanning, Reverb, etc.)
• Output — The terminal consumer node

Mixer Nodes¶

Mixer nodes can receive input from multiple nodes and combine them.

• StereoMixer
• AmbisonicMixer

Pipeline Rules¶

When designing pipelines, follow these rules:

1. One Input, One Output — Every pipeline must have exactly one Input node and one Output node
2. Connected Graph — All nodes must be connected; no orphaned nodes
3. No Cycles — The graph must be acyclic (no circular dependencies)
4. No Self-Consumption — A node cannot consume its own output
5. Single Consumer Input — Consumer nodes (non-mixers) can only consume from one source
6. Valid Node Names — All node names must be registered in the engine

Example Pipelines¶

Simple Stereo Pipeline¶

A basic stereo pipeline suitable for games that don't need Ambisonic processing:

{
  "id": 3,
  "name": "stereo",
  "nodes": [
    { "id": 1, "name": "Input", "consume": [] },
    { "id": 2, "name": "Attenuation", "consume": [1] },
    { "id": 3, "name": "Occlusion", "consume": [2] },
    { "id": 4, "name": "StereoPanning", "consume": [3] },
    { "id": 6, "name": "NearFieldEffect", "consume": [3] },
    { "id": 8, "name": "StereoMixer", "consume": [4, 6] },
    { "id": 9, "name": "Output", "consume": [8] }
  ]
}

This pipeline:

1. Takes audio input
2. Applies distance-based attenuation
3. Applies occlusion filtering
4. Branches into stereo panning and near-field effect processing
5. Mixes both branches together
6. Outputs the final stereo signal

Full-Featured Pipeline¶

A comprehensive pipeline with all spatial and environmental processing:

{
  "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": "StereoPanning", "consume": [17] },
    { "id": 5, "name": "AmbisonicPanning", "consume": [3] },
    { "id": 6, "name": "NearFieldEffect", "consume": [3] },
    { "id": 7, "name": "AmbisonicMixer", "consume": [18] },
    { "id": 8, "name": "StereoMixer", "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": "StereoMixer", "consume": [15, 16] },
    { "id": 18, "name": "AmbisonicRotator", "consume": [5] },
    { "id": 9, "name": "Output", "consume": [13] }
  ]
}

This pipeline includes:

• Distance attenuation and occlusion
• Both stereo and Ambisonic spatial paths
• Obstruction and environment effects
• Room reverb and early reflections
• Near-field HRTF processing
• Binaural decoding for headphone output
• Final hard clipping for safety

Minimal Music Pipeline¶

A simple pipeline for background music that doesn't need spatial processing:

{
  "id": 100,
  "name": "music",
  "nodes": [
    { "id": 1, "name": "Input", "consume": [] },
    { "id": 2, "name": "Limiter", "consume": [1] },
    { "id": 3, "name": "Output", "consume": [2] }
  ]
}

This applies only limiting to prevent clipping—ideal for pre-mixed audio content.

Performance Considerations¶

Pipeline complexity directly affects CPU usage:

• More nodes = more processing — Each node adds computational overhead
• Ambisonic processing — Higher order Ambisonics require more CPU
• Room simulation — Reverb and reflections are computationally expensive
• Per-sound instances — Each playing sound has its own pipeline instance

For mobile or CPU-constrained platforms, consider:

• Using simpler pipelines with fewer nodes
• Disabling binaural processing when not using headphones
• Limiting the number of simultaneous sounds