Vocalburst Locator

⚠️ Two things are easy to get wrong, so they are stated up front:

1. inference.py still auto-downloads model.pt when you do not pass a checkpoint. Pass model_v2.pt explicitly.
2. inference.py's built-in post-processing defaults are still the v1-era values (threshold=0.65, merge_gap=0.3, min_dur=0.5). Pass the v2 values explicitly — they dominate the measured F1 (see below).

Recommended post-processing (v2)

threshold    = 0.50   # was 0.65 in v1
merge_gap    = 0.10   # was 0.30 in v1
min_duration = 0.10   # was 0.50 in v1   <-- the one that matters

Ground-truth bursts have a median duration of ~180 ms. A min_duration of 0.5 s therefore discards ~96 % of real bursts before matching. On one identical checkpoint, only changing post-processing moved event F1 from 0.243 to 0.598 — a larger effect than any training change made for v2. If you read older instructions in this card recommending 0.65 / 0.3 / 0.5, those are the v1 numbers and are not recommended any more.

Copy-pasteable usage

from huggingface_hub import hf_hub_download
from inference import load_model, detect_vocal_bursts   # inference.py from this repo

# 1. Download the recommended checkpoint
ckpt = hf_hub_download("laion/vocalburst-locator", "model_v2.pt")

# 2. Load it (v1 would be loaded if you omit `checkpoint`)
model, fe, device = load_model("cuda", checkpoint=ckpt)   # or "cpu"

# 3. Detect, with the v2 post-processing values
events = detect_vocal_bursts(
    "audio.mp3",
    model=model, fe=fe, device=device,
    threshold=0.50,
    merge_gap=0.10,
    min_dur=0.10,
)

for ev in events:
    print(f"{ev['start']:.2f}s - {ev['end']:.2f}s  (confidence: {ev['confidence']:.2f})")

Command line equivalent:

python inference.py audio.mp3 \
  --checkpoint "$(python -c 'from huggingface_hub import hf_hub_download; print(hf_hub_download("laion/vocalburst-locator","model_v2.pt"))')" \
  --threshold 0.50 --merge-gap 0.10 --min-dur 0.10 --device cuda

Raw state dict (if you build the model yourself — same WhisperSegmenter state dict as v1, 485 tensors, LoRA already merged):

import torch
sd = torch.load("model_v2.pt", map_location="cpu")
model.load_state_dict(sd)     # same keys as model.pt

Why v2 — measured on real audio

Re-measured on a held-out set of 992 real, in-the-wild expressive-speech clips, each checkpoint given a post-processing sweep to find its best possible operating point:

4.0x higher F1 on real audio. Note also how v1 fails: it only reaches usable precision at threshold 0.80, where recall collapses to 0.21 — on real recordings it is very unsure, and buying precision costs it four fifths of the events. v2 operates at 0.50 with recall 0.67.

Which checkpoint to pick

On real audio the two v2 weights are statistically indistinguishable; they differ only on the synthetic-soundscape domain. Both use the same post-processing values above. Details in the model_v2_mixed.pt section.

🔗 Ensemble: pair this detector with the captioner laion/vocalburst-captioning-whisper — locate bursts here, then caption each detected segment with that model. See the threshold study below.

Installation

pip install torch transformers soundfile librosa huggingface_hub

Expected output

Detected 3 vocal burst(s) in audio.mp3:

  1. 2.14s - 3.82s  (duration: 1.68s, confidence: 0.89)
  2. 8.50s - 9.12s  (duration: 0.62s, confidence: 0.74)
  3. 15.30s - 16.94s  (duration: 1.64s, confidence: 0.92)

JSON output (--json):

{
  "file": "audio.mp3",
  "events": [
    {"start": 2.14, "end": 3.82, "confidence": 0.89, "duration": 1.68},
    {"start": 8.5, "end": 9.12, "confidence": 0.74, "duration": 0.62},
    {"start": 15.3, "end": 16.94, "confidence": 0.92, "duration": 1.64}
  ]
}

Model Description

This model performs binary frame-level segmentation on audio: for each 20ms frame in a 30-second audio clip, it predicts whether a vocal burst is occurring. Post-processing then groups these frame-level predictions into discrete events with timestamps and confidence scores.

Architecture

Audio (16kHz, 30s) → Whisper-small Encoder (LoRA rank-8 merged) → 1500 frame embeddings
    → Linear(768→384) + GELU + Dropout
    → Conv1d(384, kernel=7) + GELU + Dropout   (temporal smoothing)
    → Linear(384→1) → sigmoid → 1500 probabilities
    → Post-processing → [(start, end, confidence), ...]

The model uses OpenAI's Whisper-small encoder as the audio feature backbone. During training, the encoder was adapted using LoRA (rank 8, alpha 16) on the q_proj and v_proj attention matrices. The LoRA weights have been merged into the base weights, so no adapter library is needed at inference time. All three checkpoints (model.pt, model_v2.pt, model_v2_mixed.pt) share this architecture and load with identical code.

Files

Inference Parameters

The "built-in default" column is what the script uses if you pass nothing; it has been left at the v1 values for backwards compatibility. Pass the recommended column explicitly.

Understanding Precision, Recall, and the Threshold Trade-off

Imagine the model is a security guard watching for vocal bursts. It has to make a decision for every moment of audio: "Is this a vocal burst, or not?"

There are four possible outcomes:

                        REALITY
                   Vocal Burst    Not a VB
                 ┌─────────────┬─────────────┐
  MODEL    Yes   │ True Pos ✓  │ False Pos ✗ │  ← "False alarm"
  SAYS:          │ (correct!)  │ (oops)      │
                 ├─────────────┼─────────────┤
           No    │ False Neg ✗ │ True Neg ✓  │  ← "Missed it"
                 │ (missed!)   │ (correct!)  │
                 └─────────────┴─────────────┘

• Precision = Of everything the model flagged, how many were real? TP / (TP + FP)

  • High precision → when the model says "vocal burst!", it's almost always right
  • Low precision → lots of false alarms (the model is trigger-happy)

• Recall = Of all real vocal bursts, how many did the model catch? TP / (TP + FN)

  • High recall → the model rarely misses a real event
  • Low recall → the model is too conservative, missing real events

• F1 Score = The harmonic mean of precision and recall — balances both into one number.

How Each Parameter Affects Results

threshold — The confidence cutoff

The model outputs a confidence score (0 to 1) for every 20ms frame. The threshold decides: "How confident must the model be before we call it a vocal burst?"

low threshold   →  Model flags almost everything
                   ✓ High recall (catches most VBs)
                   ✗ Low precision (many false alarms)
                   Think: paranoid security guard

high threshold  →  Model only flags when very sure
                   ✓ High precision (almost no false alarms)
                   ✗ Low recall (misses quieter/ambiguous VBs)
                   Think: lazy security guard

For model_v2.pt the swept best operating point on real audio is 0.50. (For v1 on synthetic data it was 0.65; for v1 on real audio it was 0.80, where recall collapses — see Previous version.)

min_dur — Minimum event duration

After grouping confident frames into events, discard any event shorter than min_dur.

min_dur = 0.1s  →  Recommended for v2 on real audio
                   ✓ Keeps short coughs/gasps and the ~180 ms median real burst
                   ✗ Slightly more short false positives

min_dur = 0.5s  →  The old v1 default
                   ✓ Filters noise spikes in synthetic soundscapes
                   ✗ Discards ~96 % of real bursts

min_dur = 1.0s  →  Only keeps long events
                   ✗ Misses almost everything on real audio

This is the single most impactful knob. On synthetic soundscapes, mixed-in bursts are long (0.5–3 s) and a large min_dur cheaply removes false positives — which is why v1 shipped 0.5. On real recordings the ground-truth median burst is ~180 ms, so the same setting throws away the majority of true events.

merge_gap — Gap tolerance for merging

If two detected segments are separated by less than merge_gap, merge them into one event.

merge_gap = 0.0s  →  No merging. A laugh with a brief pause becomes 2 events.
                     Result: Over-counting (more events than expected)

merge_gap = 0.1s  →  Recommended for v2. Bridges frame-level dropouts without
                     swallowing neighbouring bursts.

merge_gap = 1.0s  →  Even 1-second gaps get bridged....

pt · 927 MB · SHA-256 3b8b2fef6976…7e3d · Hugging Face