Au review
Modular Markdown-based audio skills for AI agents and developers, covering signal processing, synthesis, effects, analysis, and spatial audio.
npx -y skills add kunitoki/sonic-skills --skill au-reviewAssembled from the repository path, not quoted from the project. Check it against their README if it does not work.
One thing to look at
- 14 stars14 stars. Stars are a popularity signal and not a quality one, but at this level it is likely that nobody has read this closely except its author, and you would be relying on your own review.
What its author says it does
Copied from the file, not written here
Reviews AudioUnit v2/v3 plugin implementations for spec compliance, thread safety, and correctness. Use when the user asks to review an AudioUnit plugin, check an AUv3 app extension, audit property or parameter handling, or asks "is my AUComponent thread-safe?" or "why does my AU crash in Logic?". Trigger on phrases like "review my AudioUnit", "check my AUv3", "is my render block safe?", or when you see AURenderCallback, internalRenderBlock, kAudioUnitProperty_*, or AUAudioUnit in the code.
SKILL.md
5.5 KB, as published. Nobody here has run it
AudioUnit (AUv2 / AUv3) Review
AUv2 runs in-process inside the host; AUv3 runs in a sandboxed XPC extension. Both share the same realtime-callback constraints, but AUv3 adds ObjC/Swift runtime exposure and app-extension lifecycle rules that introduce a distinct class of violations.
Step 0 — Run universal checks first
Invoke audio-dsp-review and audio-numerics-review before this skill. This skill adds
AU-specific checks on top; it does not replace realtime-safety or numerics reviews.
Step 1 — Identify AU version and structure
Determine which AU variant is under review:
| Variant | Entry point | Render surface |
|---|---|---|
| AUv2 (Component Manager) | AudioComponentRegister / AUMIDIEffectFactory | AURenderCallback |
| AUv3 (App Extension) | AUAudioUnit subclass, NSExtensionPrincipalClass | internalRenderBlock |
Locate: the render callback / render block, allocateRenderResourcesAndReturnError:,
deallocateRenderResources, supportedViewConfigurations, and all
kAudioUnitProperty_* / AUParameter access sites.
Step 2 — Scan for AU-specific violations
| Violation | Where to look | Risk |
|---|---|---|
ObjC message send ([obj msg] / .property) in render callback | AURenderCallback body, internalRenderBlock capture body | ObjC runtime uses locks and may allocate; not realtime-safe |
Render block calls through self, weak references, Swift closures, or ObjC properties | AUv3 render block | Runtime calls and weak-reference loads are not realtime-safe |
kAudioUnitProperty_* read/written from render thread | Any render-path property access | AudioUnitGetProperty / SetProperty are not thread-safe |
| Parameter ramps not applied sample-accurately | AUParameterEvent handling, AUv2 renderProc | Parameter jumps produce zipper noise on DAW automation |
Tail time not reported via kAudioUnitProperty_TailTime | Reverb, delay, convolution AUs | Host silences the AU before tail has decayed |
AUv3 extension missing com.apple.security.app-sandbox entitlement | Xcode target entitlements | App Store / Notarisation rejection; Logic refuses to load |
NSFileManager, NSUserDefaults, or UserDefaults accessed from render block | AUv3 internalRenderBlock | Main-thread-only / file-I/O APIs; realtime violation and potential deadlock |
AUAudioUnit subclass not calling super in allocateRenderResources | allocateRenderResourcesAndReturnError: override | Resources for format negotiation never initialised; silent misrender |
Format negotiation not honouring outputBusses[n].format before allocating | allocateRenderResources | Mismatch between agreed and actual format; distortion or crash |
auval failures not addressed | Overall AU implementation | Plugin rejected or silently disabled by Logic, GarageBand, and MainStage |
Step 3 — Write the review
Same format as audio-dsp-review / audio-numerics-review:
Verdict · Critical Violations (category, file:line, Why, Fix) · Warnings · What's Done Well · Recommended Fixes (priority order)
Prefix the header with AudioUnit Review: [file / class].
auval checklist
Run auval -a to list registered AUs; validate with type/subtype/manufacturer codes:
auval -v aufx MYFX MFGR (effect) · auval -v aumu MYSY MFGR (instrument)
| Common auval failure | Cause | Fix |
|---|---|---|
AU does not support kAudioUnitProperty_CocoaUI | Missing NSView-based UI factory | Implement AUCocoaViewInfo + property handler |
Render returned error | Non-zero OSStatus from render callback | Validate stream format; guard every render call |
TailTime not set | Reverb/delay returns 0 tail time | Return duration from kAudioUnitProperty_TailTime |
Latency reported as 0 | Plugin adds latency but reports none | Return correct samples from kAudioUnitProperty_Latency |
Parameter not in range | Default value outside AUParameterInfo min/max | Clamp default inside declared range |
Quick fix table
| Violation | Fix |
|---|---|
| ObjC call in render block | Cache plain C/C++ DSP objects, buffers, and atomics before returning the block; call ObjC only outside callback |
self / weak-self use in render block | Capture raw C++ kernel pointers or __unsafe_unretained ivars once; do not load weak refs or call properties per render |
| Property access from render thread | Use std::atomic<> or lock-free FIFO; read/write properties only from main/audio-graph thread |
| No sample-accurate parameter ramps | Process AUParameterEvent list per-sample; use a one-pole smoother for missing events |
| Missing tail time | AUv2: implement kAudioUnitProperty_TailTime; AUv3: override tailTime in seconds |
| Sandbox entitlement missing | Enable the AUv3 app-extension sandbox; add file/network entitlements only when the extension actually needs them |
NSUserDefaults in render block | Store params via AUParameter tree; load defaults only in init / allocateRenderResources |