Video Scene Analyzer
Detect scene boundaries in video files and generate structured JSON with content summaries, production tags, and a visual asset library per scene.
Prerequisites
Requires ffmpeg and ffprobe. Verify:
ffmpeg -version && ffprobe -version
If missing, inform the user and stop.
This skill bundles its own videx script at scripts/videx (relative to SKILL.md). Resolve the full path:
VIDEX="$(dirname "$(realpath "<path-to-SKILL.md>")")/scripts/videx"
Workflow Overview
Two-pass process:
- Pass 1 -- Overview: Extract low-res frames, read them all, identify scene boundaries
- Pass 2 -- Deep-dive: Extract high-res frames per scene, generate detailed metadata
- Output: Write
analysis.json + conversation summary
Pass 1: Overview Scan
Step 1: Get video metadata
ffprobe -v error -show_entries format=duration,size -show_entries stream=codec_name,width,height,r_frame_rate -of default=noprint_wrappers=1 <video>
Record duration, resolution, fps for the output JSON.
Step 2: Extract overview frames
Choose interval based on duration:
| Duration |
Interval |
Command |
| < 5 min |
2s |
$VIDEX overview <video> 2 320 0.5 |
| 5-30 min |
5s |
$VIDEX overview <video> 5 320 0.5 |
| > 30 min |
10s |
$VIDEX overview <video> 10 320 0.5 |
Use triplet=0.5 (wider spread) to make transitions visible.
Step 3: Read all overview frames
Read every _b (center) frame chronologically using the Read tool. Read in batches of 20-30 if many frames.
For timestamps where the b frame looks like a transition (blur, blend, fade), also read the a and _c frames.
Step 4: Detect scene boundaries
Compare consecutive _b frames. A scene boundary exists when:
- Hard cut: Completely different content between consecutive frames
- Dissolve/fade: Frame shows blending or fade to/from black/white
- Major change: Same subject but clearly different setting, angle, or composition
Heuristic: when uncertain, prefer splitting. Users can merge; they cannot split what was missed.
Record for each boundary:
- Approximate timestamp (midpoint between the two sample points)
- Transition type (cut, dissolve, fade-to-black, fade-from-black, fade-to-white, fade-from-white, wipe)
The first frame always starts Scene 1. The last sample point ends the final scene (use video duration).
Step 5: Report scene list
Show the user a scene list before proceeding:
Scene 1: 0:00 - 0:04 (cut)
Scene 2: 0:04 - 0:07 (dissolve)
...
Ask if they want to adjust boundaries or proceed.
Pass 2: Scene Deep-Dive
Step 6: Extract scene frames
For each scene, extract at 1280px:
$VIDEX range <video> <start>-<end> --triplet=0.2
Short scenes (< 2s): add --fps=5 Long scenes (> 30s): default 2fps is fine.
Step 7: Analyze each scene
Read all extracted frames for the scene. Determine:
Content summary: 2-4 sentences. Subjects, actions, setting, props, visible text.
Production tags:
| Tag |
Values |
camera_angle |
eye-level, low-angle, high-angle, bird's-eye, dutch-angle, over-the-shoulder, pov |
shot_size |
extreme-wide, wide, medium-wide, medium, medium-close-up, close-up, extreme-close-up |
camera_movement |
static, pan-left, pan-right, tilt-up, tilt-down, zoom-in, zoom-out, dolly-in, dolly-out, tracking, handheld, crane, steadicam |
color_tone |
warm, cool, neutral, desaturated, high-contrast, low-contrast, monochrome, neon, pastel, earth-tones |
lighting |
natural, artificial, high-key, low-key, backlit, side-lit, top-lit, silhouette, mixed |
tempo |
static, slow, moderate, fast, frenetic |
Text overlay:
placement: none, lower-third, centered, top, full-screen, watermarkcontent: actual text visible, or null
Transitions:
in: how scene begins (none for first scene)out: how scene ends (none for last scene)
If a tag changes mid-scene, use the dominant value and note the change in notes.
Step 7b: Build asset library
While analyzing scenes, catalog every distinct visual asset across the entire video. For each asset, record:
| Field |
Description |
id |
Kebab-case unique identifier (e.g., student-summer, logo-brand) |
type |
character, background, icon, ui-screen, photo, product, logo, decoration, text-graphic, effect |
label |
Human-readable one-line description with key visual traits |
style |
anime-illustration, flat-design, realistic-photo, 3d-render, hand-drawn, typography, mixed |
appears_in |
Array of scene numbers where this asset appears |
Guidelines:
- Characters with costume changes get separate entries (e.g.,
student-summer, student-winter)
- Same icon in multiple scenes = one entry with all scene numbers
- Only list distinctive backgrounds (skip generic white/black)
label should be concise but include enough detail to identify the asset (color, pose, size, distinguishing features)
See references/schema.md for the full type reference and examples.
Step 8: Write analysis.json
Assemble the complete JSON per the schema in references/schema.md.
Write to: ./videx-out/<video-name>/analysis.json
Step 9: Conversation summary
After writing JSON, provide:
- Total scenes and video duration
- One-line summary per scene with timestamps
- Asset library summary (total count, type breakdown)
- Notable production patterns across the video
Edge Cases
- < 10 seconds: Use 1-second interval. Single scene is valid.
- > 1 hour: Use 10-second intervals. Read overview frames in batches.
- Static content (slideshow/screencast): Slide changes = scene boundaries. Note
camera_movement: static.
- Ambiguous boundaries: Prefer splitting over merging.
Output Location
./videx-out/<video-name>/
├── overview/ (Pass 1)
├── range_*/ (Pass 2)
└── analysis.json (final output)
