# Audio Fft Sanity

> FFT-based sanity check for audio output files — verifies fundamental frequency, THD, SNR, clipping, and silence. Use after offline C tests or WASM OfflineAudioContext captures to confirm a signal chain is producing correct output.

- **Type:** Skill
- **Install:** `agentstack add skill-gertsylvest-meta-team-audio-fft-sanity`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [gertsylvest](https://agentstack.voostack.com/s/gertsylvest)
- **Installs:** 0
- **Category:** [Content & Media](https://agentstack.voostack.com/c/content-and-media)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [gertsylvest](https://github.com/gertsylvest)
- **Source:** https://github.com/gertsylvest/meta-team/tree/main/library/skills/audio-fft-sanity

## Install

```sh
agentstack add skill-gertsylvest-meta-team-audio-fft-sanity
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Audio FFT Sanity Check

Run a suite of FFT-based assertions on an audio output file to confirm a signal chain is behaving correctly. Suitable for both offline C test output and WASM `OfflineAudioContext` captures.

## Requirements

- Python 3.8+
- `numpy` and `scipy`: `pip install numpy scipy`

## Instructions

Arguments are in `$ARGUMENTS`. Pass them directly to the analysis script:

```bash
python3 "$(dirname "$0")/analyse.py" $ARGUMENTS
```

## Checks performed

| Check | What it detects |
|---|---|
| `CLIPPING` | Any sample magnitude > 0.99 — indicates gain staging problem or overflow |
| `SILENCE` | RMS below -60 dBFS — catches zero-output bugs (uninitialised buffer, wrong pointer) |
| `FUNDAMENTAL` | Detected peak frequency vs `--freq` (if given) — verifies oscillator/filter tuning |
| `THD` | Total harmonic distortion (harmonics 2–5 vs fundamental) — catches nonlinear distortion or aliasing |
| `SNR` | Signal-to-noise ratio estimate — catches noise floor issues or quantisation problems |

## Exit codes

- `0` — all checks passed
- `1` — one or more checks failed

## Examples

```bash
# Basic smoke test — check for clipping, silence, SNR, THD with defaults
python3 analyse.py output.wav

# Verify a 440 Hz sine from a synth, strict THD limit
python3 analyse.py output.wav --freq 440 --thd-max 1.0 --snr-min 60

# Raw float32 file at 48 kHz, stereo interleaved (uses first channel)
python3 analyse.py output.f32 --sr 48000 --channels 2 --freq 1000
```

## Typical usage patterns

**Synthesizer test:** Run the synth at a known pitch (e.g. MIDI A4 = 440 Hz), render N frames to a float32 file, then:
```bash
python3 analyse.py synth_output.wav --freq 440 --thd-max 2.0 --snr-min 50
```

**Effect processor test (e.g. filter, EQ):** Feed a broadband noise or sweep, capture output — omit `--freq` and check only for clipping and SNR:
```bash
python3 analyse.py filtered_output.wav --snr-min 30
```

**Impulse response capture:** Feed a single-sample impulse, check output is non-silent and not clipping:
```bash
python3 analyse.py ir_output.wav
```

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [gertsylvest](https://github.com/gertsylvest)
- **Source:** [gertsylvest/meta-team](https://github.com/gertsylvest/meta-team)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-gertsylvest-meta-team-audio-fft-sanity
- Seller: https://agentstack.voostack.com/s/gertsylvest
- Browse the marketplace: https://agentstack.voostack.com/browse

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