8-cut

A desktop tool for cutting 8-second clips from video files, designed for building SELVA datasets.

Overview

8-cut lets you scrub through a video, mark a cut point, and export a fixed 8-second clip with one keypress. It tracks every export in a local SQLite database so you can resume a session or switch between resolution variants of the same source without duplicating work.

All clips are exactly 8 seconds — this is a hard constraint of the SELVA format.

Features

• Frame-accurate scrubbing — click or drag the timeline; arrow keys and J/K/L for frame-by-frame stepping
• Keyboard shortcuts — J/L step one frame, Shift+J/L step one second, Space/P play/pause, K pause and return to cursor, E export, M jump to next marker
• Two export formats — H.264/AAC MP4 or lossless WebP image sequence (frames + .wav audio extracted alongside)
• Portrait crop — crop to 9:16, 4:5, or 1:1 before export; adjustable horizontal crop position
• Resize — scale short side to a fixed pixel size (e.g. 256)
• Export history — timeline markers show previously exported clips; fuzzy filename matching detects resolution variants of the same file (e.g. _2160p vs _1080p)
• Mask generation — generate binary foreground masks per-frame using SAM2 (segmentation) or Depth Anything V2 (depth-based), via a bundled venv
• Playlist — drag-and-drop multiple files; duplicates are ignored

Requirements

• Python 3.11+
• ffmpeg in PATH
• PyQt6
• python-mpv (requires libmpv)

pip install -r requirements.txt

For mask generation tools, additional dependencies (PyTorch, transformers, segment-anything-2, opencv) are installed into ~/.8cut/venv/ via the Settings dialog.

Platform notes

Linux — install libmpv via your package manager (apt install libmpv-dev / pacman -S mpv).

macOS — install libmpv via Homebrew: brew install mpv.

Windows — python-mpv requires mpv-2.dll in PATH or in the same directory as main.py. Download it from the mpv Windows builds page (pick the latest mpv-dev-x86_64-*.7z, extract mpv-2.dll). Also ensure ffmpeg.exe is in PATH (e.g. via winget: winget install ffmpeg).

Usage

python main.py

Drop a video onto the playlist or use the file picker. Scrub to your cut point, set the output folder and clip name, then press Export (or E).

Export formats

Format	Output
MP4	<folder>/<name>_NNN.mp4 — H.264 video + AAC audio
WebP sequence	<folder>/<name>_NNN/frame_%04d.webp — lossless WebP frames + <name>_NNN.wav PCM audio

Keyboard shortcuts

Key	Action
← / J	Step back 1 frame
→ / L	Step forward 1 frame
Shift+← / Shift+J	Step back 1 second
Shift+→ / Shift+L	Step forward 1 second
Space / P	Toggle play/pause
K	Pause and snap video to cursor
E	Export clip
M	Jump to next export marker (wraps)

Arrow keys and J/K/L are ignored when a text field has focus.

Mask generation tools

Two standalone scripts live in tools/. They are run by the app via a managed venv but can also be called directly:

python tools/sam_masks.py  --input clip.mp4 --output masks_dir/
python tools/depth_masks.py --input clip.mp4 --output masks_dir/

Both output one binary PNG per frame (frame_0000.png, …) where white = foreground.

• SAM2 (sam_masks.py) — uses facebook/sam2-hiera-large; center-point prompt propagated across all frames
• Depth Anything V2 (depth_masks.py) — uses depth-anything/Depth-Anything-V2-Large-hf; Otsu threshold on the depth map

Database

Export history is stored in ~/.8cut.db (SQLite). The database records filename, start time, and output path for every clip. When you open a file, 8-cut checks whether a similar filename has been processed before (stripping resolution tags like _2160p, _1080p, codec tags, etc.) and pre-populates the timeline with existing markers.

Testing

pytest tests/ -v

38 unit tests covering path builders, ffmpeg command generation, time formatting, and the processed-clips database.