# How to Implement Custom Cut Padding Strategies in video-use: Handling Scribe Timestamp Drift

> Handle Scribe timestamp drift by implementing custom cut padding strategies in video-use. Modify EDL timestamps 30-200ms to prevent audio pops and ensure smooth playback.

- Repository: [Browser Use/video-use](https://github.com/browser-use/video-use)
- Tags: how-to-guide
- Published: 2026-07-04

---

**Implement custom cut padding strategies within the 30–200ms window by modifying EDL timestamps before rendering, clamping values between 30ms and 200ms to absorb ElevenLabs Scribe's 50–100ms timestamp drift while preventing audio pops.**

The `browser-use/video-use` repository enforces strict padding requirements to compensate for word-level timestamp inaccuracies in ElevenLabs Scribe transcripts. When building automated video editing pipelines, you must pad every cut edge by 30–200ms to handle the typical 50–100ms drift while maintaining the hard rules defined in [`SKILL.md`](https://github.com/browser-use/video-use/blob/main/SKILL.md). This guide shows you how to implement a custom padding strategy that respects these architectural constraints without modifying the core rendering engine.

## Why the 30–200ms Window Matters

The video-use skill defines a hard rule that every cut edge must be padded to absorb timestamp drift and prevent audio artifacts.

**Scribe timestamp drift** creates the primary requirement. According to [`SKILL.md`](https://github.com/browser-use/video-use/blob/main/SKILL.md) (lines 27–29), the word-level timestamps returned by ElevenLabs Scribe can deviate by approximately 50ms, with extremes reaching 100ms. Hard Rule 7 mandates a working window of 30–200ms to absorb this drift without cutting into adjacent words.

**Audio pops** enforce the minimum boundary. The per-segment extractor in [`helpers/render.py`](https://github.com/browser-use/video-use/blob/main/helpers/render.py) (lines 87–90) automatically inserts a 30ms fade-in/out using FFmpeg's `afade` filter. Without at least 30ms of padding, these fades would clip into the actual content, creating audible clicks at cut points.

## Where to Apply Padding in the Pipeline

Cuts are represented in the **EDL** (Edit Decision List) JSON file, structured as an array of ranges with `start` and `end` timestamps. This structure is defined at the end of [`helpers/render.py`](https://github.com/browser-use/video-use/blob/main/helpers/render.py) (lines 66–75).

You must modify these timestamps **before** they reach the `extract_segment` function, which performs the actual FFmpeg extraction. The padding values are added to raw word timestamps, then clamped to the allowed 30–200ms range. This approach keeps the core rendering logic unchanged while allowing flexible pre-processing.

## Implementing the Padding Algorithm

Create a helper function that adjusts EDL timestamps while respecting neighbor boundaries. The algorithm must clamp padding to the allowed window, prevent segment overlap, and ensure minimum durations.

```python
from copy import deepcopy

def apply_padding(edl: dict, padding_ms: int = 80) -> dict:
    """
    Adjust every cut edge in an EDL by `padding_ms` (default 80ms).
    
    - Guarantees a minimum of 30ms and a maximum of 200ms.
    - Never overlaps the neighboring cut (keeps segment order intact).
    - Works on both start and end times.
    """
    MIN_PAD = 30      # ms

    MAX_PAD = 200     # ms

    padded = deepcopy(edl)
    for i, r in enumerate(padded["ranges"]):
        # 1. Compute raw padding (clamp to allowed window)

        pad = max(MIN_PAD, min(padding_ms, MAX_PAD)) / 1000.0   # seconds

        # 2. Pad start – but never before the previous segment's end

        if i > 0:
            prev_end = padded["ranges"][i-1]["end"]
            r["start"] = max(prev_end, r["start"] - pad)
        else:
            r["start"] = max(0.0, r["start"] - pad)

        # 3. Pad end – but never after the next segment's start

        if i < len(padded["ranges"]) - 1:
            next_start = padded["ranges"][i+1]["start"]
            r["end"] = min(next_start, r["end"] + pad)
        else:
            # No following segment → just add padding

            r["end"] = r["end"] + pad

        # 4. Guard against negative duration (fallback to minimum 0.02s)

        if r["end"] - r["start"] < 0.02:
            r["end"] = r["start"] + 0.02
            
    return padded

```

Key implementation details:
- **Clamp** the requested padding to the 30–200ms window using `max(MIN_PAD, min(padding_ms, MAX_PAD))`.
- **Never cross** into neighboring segments by comparing against `prev_end` and `next_start`.
- **Preserve order** by working on a deep copy of the EDL dictionary.

## Integrating into the Rendering Pipeline

Wire the padding helper into a pre-processing script that runs before [`render.py`](https://github.com/browser-use/video-use/blob/main/render.py). This keeps the mandatory 30ms audio fade (handled automatically by `extract_segment`) separate from your custom time-window padding.

```python

# helpers/prepare_edl.py

import json
import argparse
from pathlib import Path
from copy import deepcopy

def apply_padding(edl: dict, padding_ms: int = 80) -> dict:
    MIN_PAD = 30
    MAX_PAD = 200
    padded = deepcopy(edl)
    
    for i, r in enumerate(padded["ranges"]):
        pad = max(MIN_PAD, min(padding_ms, MAX_PAD)) / 1000.0
        
        if i > 0:
            prev_end = padded["ranges"][i-1]["end"]
            r["start"] = max(prev_end, r["start"] - pad)
        else:
            r["start"] = max(0.0, r["start"] - pad)
            
        if i < len(padded["ranges"]) - 1:
            next_start = padded["ranges"][i+1]["start"]
            r["end"] = min(next_start, r["end"] + pad)
        else:
            r["end"] = r["end"] + pad
            
        if r["end"] - r["start"] < 0.02:
            r["end"] = r["start"] + 0.02
            
    return padded

def main(edl_path: Path, out_path: Path, pad_ms: int = 80):
    edl = json.loads(edl_path.read_text())
    padded_edl = apply_padding(edl, padding_ms=pad_ms)
    
    out_path.write_text(json.dumps(padded_edl, indent=2))
    print(f"Padded EDL written to {out_path}")

if __name__ == "__main__":
    ap = argparse.ArgumentParser()
    ap.add_argument("edl", type=Path)
    ap.add_argument("-o", "--output", type=Path, required=True)
    ap.add_argument("--pad-ms", type=int, default=80,
                    help="Desired padding in milliseconds (30-200)")
    args = ap.parse_args()
    main(args.edl, args.output, args.pad_ms)

```

Execute the pipeline in two stages:

```bash
python helpers/prepare_edl.py edit/edl.json -o edit/edl_padded.json --pad-ms 80
python helpers/render.py edit/edl_padded.json -o final.mp4

```

The render step automatically applies the mandatory 30ms audio fade via `afade` in [`helpers/render.py`](https://github.com/browser-use/video-use/blob/main/helpers/render.py), so you only manage the time-window padding in your custom logic.

## Testing and Verification

Validate your padding implementation using [`timeline_view.py`](https://github.com/browser-use/video-use/blob/main/timeline_view.py) to visualize cut points against the waveform:

```bash
python helpers/timeline_view.py video.mp4 1.2 2.5 -o verify/cut_01.png --transcript edit/transcripts/video.json

```

Inspect the generated PNG: the cut line should appear **slightly before** the first kept word (pre-padding) and **slightly after** the last kept word (post-padding). The distance between the cut line and the nearest word must fall within the 30–200ms range when measured against the waveform.

## Customizing Your Strategy

Adapt the padding values to match your content's pacing requirements:

- **Faster-paced cuts** (montages, quick dialog): Use `--pad-ms 40` (still ≥30ms) to maintain tight timing while respecting the minimum fade requirements.
- **Cinematic, slower pacing**: Use `--pad-ms 150` to create more breathing room around cuts, staying well under the 200ms maximum.
- **Dynamic per-segment padding**: Pass a dictionary mapping `{segment_index: padding_ms}` to `apply_padding` and adjust individual ranges based on speaker-change markers or pause detection in the transcript.

Because the helper works on a copy of the EDL, you can implement bespoke logic—such as inferring padding from transcript confidence scores—without touching the core rendering code in [`helpers/render.py`](https://github.com/browser-use/video-use/blob/main/helpers/render.py).

## Summary

- **Clamp padding values** to the 30–200ms window defined in [`SKILL.md`](https://github.com/browser-use/video-use/blob/main/SKILL.md) (lines 27–29) to handle Scribe's 50–100ms timestamp drift.
- **Modify EDL timestamps** before they reach `extract_segment` in [`helpers/render.py`](https://github.com/browser-use/video-use/blob/main/helpers/render.py) (lines 87–90), which handles the mandatory 30ms audio fade separately.
- **Prevent overlap** by checking neighboring segment boundaries when adjusting start and end times.
- **Verify visually** using [`timeline_view.py`](https://github.com/browser-use/video-use/blob/main/timeline_view.py) to ensure cut points maintain proper distance from word boundaries.
- **Keep core helpers untouched** by implementing padding logic in a pre-processing script like [`helpers/prepare_edl.py`](https://github.com/browser-use/video-use/blob/main/helpers/prepare_edl.py).

## Frequently Asked Questions

### What happens if I use less than 30ms of padding?

Using less than 30ms violates Hard Rule 7 in [`SKILL.md`](https://github.com/browser-use/video-use/blob/main/SKILL.md) and risks audio pops. The `extract_segment` function in [`helpers/render.py`](https://github.com/browser-use/video-use/blob/main/helpers/render.py) always applies a 30ms `afade` filter; without sufficient padding, these fades clip into the actual speech content, creating audible clicks at cut points.

### Can I exceed the 200ms maximum padding window?

Exceeding 200ms is not recommended as it may cause visible pauses or overlap with adjacent segments. The 200ms upper bound in [`SKILL.md`](https://github.com/browser-use/video-use/blob/main/SKILL.md) represents the maximum safe margin for Scribe drift while maintaining tight editing pacing. The `apply_padding` function automatically clamps values to 200ms to enforce this constraint.

### Why modify the EDL instead of changing render.py directly?

Modifying the EDL before rendering keeps the architecture clean and maintainable. The [`helpers/render.py`](https://github.com/browser-use/video-use/blob/main/helpers/render.py) file handles low-level FFmpeg extraction with specific audio fade requirements; by pre-processing the EDL, you separate timestamp adjustment logic from media processing logic. This allows the rendering engine to remain unchanged while supporting multiple padding strategies across different projects.

### How do I handle the first and last segments differently?

The `apply_padding` algorithm automatically handles edge cases: for the first segment (`i == 0`), it clamps the start time to `0.0` instead of a previous segment's end. For the last segment, it adds padding without checking a next segment's start time. You can extend this logic to apply different padding values to opening/closing segments by checking `i == 0` or `i == len(ranges) - 1` in your custom implementation.