nophi-av

Detect and redact PHI/PII in audio/video recordings, built on top of nophi.

nophi-av is an implementation of the MedVidDeID pipeline with nophi as the text PHI-detection engine (in place of philter-ucsf). It exposes the same CLI shape as nophi — nophi-av scan … instead of nophi scan ….

Pipeline

For each input recording:

1. Extract audio — for video, the audio track is demuxed to 16 kHz mono WAV (audio inputs are used directly).
2. Transcribe — WhisperX produces a transcript with word-level timestamps (Whisper + forced alignment).
3. Detect PHI — nophi's text engine (build_analyzer / scan_text) runs over the transcript, so every nophi recognizer (names, drugs, addresses, dates, …) applies automatically.
4. Map spans → time — each detected character span is traced back to the words it covers, yielding a media time interval (see nophi_av/detect.py).
5. Scrub audio — each PHI interval is replaced with a beep (default) or silence (--redact-mode), preserving duration so video stays in sync.
6. Mask faces (video) — every face found by the detector is masked per --mask-mode (box solid fill by default, pixelate, blur, or none to skip), then the scrubbed audio is remuxed back onto the masked video. The detector is swappable via --face-model — YOLO by default, SCRFD as an alternative (see Face detection models).

Outputs per file: the redacted media (<name>_redacted.<ext>), a redacted transcript (<name>_transcript.txt), and a styled Excel findings report with entity type, replacement, and time interval.

Only the audio/transcript path uses nophi. Face masking is a separate visual step that doesn't touch nophi — it masks every detected face (detection, not recognition), the conservative choice for PHI removal.

Supported formats

• Audio: .mp3 .wav .m4a .flac .aac .ogg
• Video: .mp4 .mov .avi .mkv .webm

Install

A single install includes everything — audio scrubbing and video face masking:

pip install -e packages/nophi     # the text engine it depends on
pip install -e packages/nophi-av  # everything: whisperx, torch, pydub, ultralytics, opencv, pyannote

To use the SCRFD face detector (--face-model scrfd), install the optional extra, which adds insightface + onnxruntime:

pip install -e 'packages/nophi-av[scrfd]'

This is a heavy install — torch, ultralytics, and opencv are all pulled in. ffmpeg must also be on your PATH (e.g. brew install ffmpeg).

The first scan downloads model weights (Whisper, the alignment model, nophi's spaCy/scispaCy models, and the YOLO face model). Warm every cache up front with:

nophi-av download-models --whisper-model small

Requirements & caveats

• ffmpeg must be on PATH (e.g. brew install ffmpeg). WhisperX uses it to decode audio, and pydub uses it to encode .mp3/.m4a output. .wav in/out avoids any external ffmpeg dependency.
• Face model — see Face detection models below for the available detectors and how --face-model resolves them. Use --mask-mode none to skip face masking entirely.

Face detection models

Face masking is modular: the pipeline only consumes per-frame bounding boxes, so the detector behind --face-model is swappable. Run nophi-av list-models to see the catalog, or pick from:

How a spec is resolved:

• YOLO — the default backend. Community face weights (yolov{8,10,11,12}{n,s,m,l}-face.pt) aren't official Ultralytics assets, so nophi-av fetches them from the yolo-face release and caches them in Ultralytics' weights dir on first use. You can also pass a local checkpoint path or an official Ultralytics name (e.g. yolov8n.pt, which detects people, not faces). Requires ultralytics>=8.3 for the YOLOv12 architecture (included).
• SCRFD — selected by --face-model scrfd (or scrfd-s). insightface downloads and caches the model pack on first use. Needs the optional extra: pip install 'nophi-av[scrfd]'.

For PHI de-identification, recall matters more than precision (a missed face is a leak; an over-masked box is harmless), so SCRFD is a good upgrade when small or non-frontal faces are being missed.

Adding your own backend: subclass FaceDetector in nophi_av/detectors.py, register it in _BACKENDS, and add a ModelInfo entry to FACE_MODELS so it appears in list-models. Nothing in video.py needs to change — it only calls detector.detect(frame, conf).

Usage

# Audio: bleep spoken PHI, write redacted audio + transcript + report
nophi-av scan interview.mp3 -o ./cleaned

# Audio, mute (instead of beep) PHI, larger Whisper model for accuracy
nophi-av scan interview.wav --redact-mode silence --whisper-model medium -o ./cleaned

# A whole folder; detect only names & dates; report without writing media
nophi-av scan ./recordings -e PERSON,DATE_TIME --dry-run

# Map known participants to stable IDs instead of <PERSON>
nophi-av scan interview.mp3 -m participants.csv -o ./cleaned

# Video: black-box faces + bleep spoken PHI (box is the default)
nophi-av scan visit.mp4 -o ./cleaned   # uses default yolov12s-face (auto-downloaded)

# Video, pixelate faces instead of a solid box
nophi-av scan visit.mp4 --mask-mode pixelate -o ./cleaned

# Video, use the SCRFD detector instead of YOLO (needs the [scrfd] extra)
nophi-av scan visit.mp4 --face-model scrfd -o ./cleaned

# Video, audio scrub + remux only (skip face masking)
nophi-av scan visit.mp4 --mask-mode none -o ./cleaned

# See the available face-detection models
nophi-av list-models

Bare invocation works too: nophi-av interview.mp3 is shorthand for nophi-av scan interview.mp3.

Example

Scanning a ~49s clinical-intake recording with --whisper-model base on CPU:

Entity type    Count   Examples (with timestamps)
-----------    -----   --------------------------
PERSON           2     James Carter (00:17.7), Emily Rivera (00:24.7)
DATE_TIME        1     October 24th, 1999 (00:33.8)
LOCATION/ORG     1     455 University Avenue (00:41.8)

→ cleaned/interview_redacted.mp3 (PHI windows beeped, duration preserved), cleaned/interview_transcript.txt ("My name is Dr. <PERSON> … I live at <ORGANIZATION>, apartment 3B."), and phi_av_report.xlsx.

Key options

Development

The transcript↔time mapping core (nophi_av/detect.py) is ML-free and unit tested without torch/whisperx:

pytest packages/nophi-av/tests