apple-audio

Attach each node with engine.attach, connect them with matching AVAudioFormat, then call prepare and start. Chain nodes like AVAudioPlayerNode through AVAudioUnitReverb or AVAudioUnitEQ into engine.mainMixerNode, and schedule buffers or files on the player.

Provide a render block to AVAudioSourceNode that fills the audio buffer list per frame, such as a sine oscillator advancing phase. The block runs on a real-time thread, so pre-allocate all state and never allocate, lock, or log inside it.

Use AVAudioEngine for anything real-time, mixed, or processed, such as effects chains, synthesis, or spatial audio. Use AVAudioPlayer or AVAudioRecorder for simple file playback or recording, which the apple-media skill covers.

The most common cause is a format mismatch on a connect call, so pass an explicit AVAudioFormat matching both nodes. Also verify the node was attached before connecting, the engine was started inside do/catch, and AVAudioSession was configured first on iOS.

Render blocks run on a real-time thread, and any allocation, blocking lock, I/O, or logging causes dropouts. Pre-allocate buffers, pass parameters with atomics or a lock-free ring buffer, and use Accelerate vDSP for vector math.

Add an Audio Unit Extension target hosting an AUAudioUnit subclass, declare the component type like aufx in Info.plist, expose parameters via AUParameterTree, and implement internalRenderBlock for the DSP. Validate with auval and test in hosts like GarageBand or Logic.