Video-Frames Skill

Production-grade video frame extraction with comprehensive quality control, progress tracking, and safety limits.

When to Use

✅ USE this skill when:

• Extracting specific frames from videos at timestamps
• Creating thumbnail grids/contact sheets for video overview
• Generating animated GIFs from video segments
• Batch extracting frames at intervals (e.g., every N seconds)
• Creating video previews or storyboards
• Needing pixel-perfect frame access by index
• Extracting frames at specific quality levels

❌ DON'T use this skill when:

• Simple format conversion → Use ffmpeg-tools
• Video editing (effects) → Use video editor
• Real-time frame capture → Use streaming tools
• Video capture from camera → Use camsnap
• Image generation → Use image-gen

Prerequisites

# Install FFmpeg
brew install ffmpeg        # macOS
sudo apt install ffmpeg    # Ubuntu/Debian

# Optional: Install ImageMagick for better grid generation
brew install imagemagick   # macOS
sudo apt install imagemagick   # Ubuntu

# Verify installation
ffmpeg -version
ffprobe -version

Commands

1. Extract Single Frame

Extract a single frame at a specific time or by frame index.

# Extract frame at timestamp
{baseDir}/video-frames.js frame video.mp4 --time 30 --out frame.jpg
{baseDir}/video-frames.js frame video.mp4 --time 00:02:30 --out frame.jpg
{baseDir}/video-frames.js frame video.mp4 --time 150.5 --out frame.jpg

# Extract by frame index
{baseDir}/video-frames.js frame video.mp4 --index 0 --out first-frame.jpg
{baseDir}/video-frames.js frame video.mp4 --index 1000 --out frame-1000.jpg

# With quality settings
{baseDir}/video-frames.js frame video.mp4 --time 30 --format png --out high-quality.png
{baseDir}/video-frames.js frame video.mp4 --time 30 --quality 1 --out best-quality.jpg
{baseDir}/video-frames.js frame video.mp4 --time 30 --format jpg --quality 2

Time Formats:

Format	Example	Description
Seconds	30	Simple seconds
MM:SS	2:30	Minutes:Seconds
HH:MM:SS	00:02:30	Full timecode
Decimal	90.5	Millisecond precision

Quality Settings (JPEG):

Value	Quality	File Size	Use Case
1	Best	Large	Archival, quality preservation
2-3	High	Medium	Default, good balance
5	Medium	Small	Web, quick preview
10+	Low	Very small	Draft, thumbnail

Supported Formats:

• jpg/jpeg - Web optimized, compression
• png - Lossless, transparency, best quality
• bmp - Uncompressed raw
• tiff - Professional formats
• webp - Next-gen web format

2. Extract Multiple Frames

Batch extract frames at regular intervals.

# Extract 1 frame per second
{baseDir}/video-frames.js frames video.mp4 --fps 1

# Extract specific segment
{baseDir}/video-frames.js frames video.mp4 --fps 1 --start 00:01:00 --duration 60
{baseDir}/video-frames.js frames video.mp4 --fps 5 --start 30 --duration 120

# Higher quality extraction
{baseDir}/video-frames.js frames video.mp4 --fps 1 --quality 1 --prefix keyframe

# Resize during extraction
{baseDir}/video-frames.js frames video.mp4 --fps 1 --width 1920 --quality 1

Frame Rate Options:

Rate	Description	Use Case
--fps 1	1 frame/second	Timeline extraction
--fps 5	5 frames/second	Detailed analysis
--fps 0.1	Every 10 seconds	Overview, storyboard
--fps 0.5	Every 2 seconds	Moderate detail

Output:

/tmp/frames_1234567890/
  ├── frame_00001.jpg
  ├── frame_00002.jpg
  ├── frame_00003.jpg
  └── ...

3. Generate Thumbnail Grid (Contact Sheet)

Create a grid of thumbnails for video overview.

# Basic grid
{baseDir}/video-frames.js grid video.mp4 --output grid.jpg

# Custom size and layout
{baseDir}/video-frames.js grid video.mp4 --count 16 --columns 4 --width 480 --out grid.jpg

# Compact preview
{baseDir}/video-frames.js grid video.mp4 --count 20 --columns 5 --width 320 --out overview.jpg

# High resolution grid
{baseDir}/video-frames.js grid video.mp4 --count 9 --columns 3 --width 640 --format png --out detailed.png

Grid Layout Examples:

Count	Columns	Rows	Best For
4	2	2	Quick preview
9	3	3	Standard overview
12	4	3	Detailed timeline
16	4	4	Comprehensive storyboard
20	5	4	Long videos

Output Format:

+---+---+---+---+
| 1 | 2 | 3 | 4 |    <- 5 seconds into video
+---+---+---+---+
| 5 | 6 | 7 | 8 |    <- 25 seconds into video
+---+---+---+---+
| 9 |10 |11 |12 |    <- 45 seconds into video
+---+---+---+---+

4. Create Animated GIF

Extract video segment as animated GIF.

# Basic GIF (5 seconds from start)
{baseDir}/video-frames.js gif video.mp4 --output clip.gif

# Specific time and duration
{baseDir}/video-frames.js gif video.mp4 --start 00:01:30 --duration 5 --out highlight.gif
{baseDir}/video-frames.js gif video.mp4 --start 30 --duration 10 --out segment.gif

# Quality presets
{baseDir}/video-frames.js gif video.mp4 --start 60 --duration 3 --preset fast --out quick.gif
{baseDir}/video-frames.js gif video.mp4 --start 60 --duration 3 --preset quality --out smooth.gif
{baseDir}/video-frames.js gif video.mp4 --start 60 --duration 3 --preset cinematic --out cinema.gif

# Custom parameters
{baseDir}/video-frames.js gif video.mp4 --start 30 --duration 5 --fps 30 --width 720 --out preview.gif

GIF Presets:

Preset	FPS	Width	Colors	Size	Best For
fast	15	480px	128	Small	Quick generation
balanced	20	640px	256	Medium	Default
quality	24	720px	512	Large	Smooth motion
cinematic	30	1080px	1024	Very large	Maximum quality

Max Duration: 300 frames (~10 seconds at 30fps)

5. Get Video Information

Display detailed video metadata.

{baseDir}/video-frames.js info video.mp4

Output:

{
  "stats": { "size": 1234567890, "mtime": "..." },
  "duration": 3665,
  "width": 1920,
  "height": 1080,
  "fps": 29.97,
  "totalFrames": 109785,
  "info": { ... }  // Full ffprobe output
}

Progress Tracking

Operations display real-time progress:

⏳ Extracting frames: 15/30 (50.0%) | Elapsed: 12.3s
⏳ Generating thumbnails: 8/12 (66.7%) | Elapsed: 5.2s

Safety Features

Limits

Limit	Value	Description
Max Video Size	50 GB	Input file size limit
Max Duration	4 hours	Video length limit
Max Frames	1,000	Batch frame extraction
Max Grid Size	60 thumbnails	Contact sheet limit
Max GIF Frames	300	Animated GIF limit
Timeout	30 minutes	Default operation timeout

Video Validation

Before processing, the skill validates:

• File exists and is readable
• File size within limits
• Valid video format
• Duration within limits
• Contains video stream
• Not corrupted

Error Handling

Error Codes

Code	Name	Description
0	SUCCESS	Operation completed
1	INVALID_INPUT	Missing/invalid parameters
2	FILE_NOT_FOUND	Video not found
3	INVALID_FORMAT	Unsupported format
4	INVALID_TIME_RANGE	Invalid timestamp
5	FFMPEG_ERROR	FFmpeg execution failed
6	OUT_OF_MEMORY	Memory limit exceeded
7	TIMEOUT	Operation timed out
8	INTERRUPTED	User interrupted
9	PERMISSION_DENIED	Cannot read/write
10	VALIDATION_FAILED	Video validation failed
99	UNKNOWN	Unexpected error

Common Scenarios

Frame Index Out of Range:

{baseDir}/video-frames.js frame video.mp4 --index 999999
# ❌ ERROR: Frame index 999999 out of range (0-109784)

Timestamp Beyond Video:

{baseDir}/video-frames.js frame video.mp4 --time 10000
# ❌ ERROR: Timestamp 02:46:40 out of range (0-01:01:05)

Too Many Frames:

{baseDir}/video-frames.js frames video.mp4 --fps 100
# ❌ ERROR: Too many frames requested: 366500 (max: 1000)

Large GIF Request:

{baseDir}/video-frames.js gif video.mp4 --duration 60 --fps 60
# ❌ ERROR: GIF too long: 3600 frames (max: 300)

Technical Details

Frame Extraction Methods

1. Segment Seek (-ss before -i)

   • Fast frame access
   • Use for --time option
   • Slight accuracy trade-off at start

2. Frame Selection (-vf select)

   • Precise frame index extraction
   • Slower but frame-accurate
   • Use for --index option

3. Extract at Interval (fps filter)

   • Efficient batch extraction
   • Frame-rate conversion
   • Use for batch operations

Quality Settings

JPEG Quality (CRF - Constant Rate Factor):

-q:v 1  -> 100% quality (best, largest)
-q:v 2  -> ~95% quality (default)
-q:v 5  -> ~85% quality (web)
-q:v 10 -> ~70% quality (low)
-q:v 31 -> ~10% quality (minimum)

PNG Output:

• Always lossless
• Larger file sizes
• Best for archival
• Transparent backgrounds supported

Scaling (Lanczos):

-vf scale=320:-2:flags=lanczos

• Lanczos resampling for best quality
• -2 ensures even dimensions (encoding requirement)
• Maintains aspect ratio

GIF Optimization

Palette Generation:

1. Parse video segment
2. Generate optimal 256-color palette
3. Apply palette to all frames
4. Dithering for smooth gradients

File Size Optimization:

• Fixed frame rate
• Limited color palette
• Resizing before encoding
• Optimized encoding settings

Examples

Video Storyboard Creation

#!/bin/bash
VIDEO="movie.mp4"
OUTDIR="storyboard"

mkdir -p $OUTDIR

# Create overview grid
echo "Creating overview grid..."
{baseDir}/video-frames.js grid "$VIDEO" --count 20 --columns 5 --width 480 --out "$OUTDIR/overview.jpg"

# Extract key frames every minute
echo "Extracting key frames..."
{baseDir}/video-frames.js frames "$VIDEO" --fps 0.0167 --prefix key --out "$OUTDIR/"

# Create chapter thumbnails
echo "Creating chapter thumbnails..."
for time in 0:00 10:00 20:00 30:00; do
  {baseDir}/video-frames.js frame "$VIDEO" --time $time --quality 1 --out "$OUTDIR/chapter_${time//:/}.png"
done

echo "Storyboard complete in $OUTDIR/"

Video Preview Gallery

#!/bin/bash
for video in *.mp4; do
  echo "Processing: $video"
  
  # Create 3x3 grid
  {baseDir}/video-frames.js grid "$video" --count 9 --columns 3 --width 640 --out "${video%.*}-grid.jpg"
  
  # Create 5-second preview GIF
  {baseDir}/video-frames.js gif "$video" --start 30 --duration 5 --preset balanced --out "${video%.*}-preview.gif"
  
done

Extract Frames Every N Seconds

# Extract frame at beginning of every minute
for i in {0..60}; do
  {baseDir}/video-frames.js frame video.mp4 --time $((i*60)) --out "frames/minute_${i}.jpg"
done

# Shell script for batch extraction
extract_frames() {
  local video="$1"
  local interval="${2:-10}"  # default 10 seconds
  local duration
  duration=$(ffprobe -v error -show_entries format=duration -of csv=p=0 "$video")
  
  for ((t=0; t<duration; t+=interval)); do
    {baseDir}/video-frames.js frame "$video" --time $t --out "frames/frame_${t}.jpg"
  done
}

High-Quality Thumbnail Generation

# Best quality single frame
{baseDir}/video-frames.js frame video.mp4 \
  --time 10 \
  --format png \
  --width 1920 \
  --out thumbnail.png

# Best quality grid
{baseDir}/video-frames.js grid video.mp4 \
  --count 9 \
  --columns 3 \
  --width 640 \
  --format png \
  --out grid.png

Performance Tips

1. Use JPEG for Speed

JPEG encoding is faster than PNG:

{baseDir}/video-frames.js frame video.mp4 --format jpg  # Faster
{baseDir}/video-frames.js frame video.mp4 --format png  # Better quality, slower

2. Lower Quality for Drafts

# Quick preview
{baseDir}/video-frames.js grid video.mp4 --count 9 --width 320  # Small, fast

# Final quality
{baseDir}/video-frames.js grid video.mp4 --count 16 --width 640  # Higher detail

3. Parallel Processing

# Process multiple videos in parallel
{baseDir}/video-frames.js grid video1.mp4 --out g1.jpg &
{baseDir}/video-frames.js grid video2.mp4 --out g2.jpg &
{baseDir}/video-frames.js grid video3.mp4 --out g3.jpg &
wait

4. Resize During Extraction

Better than extracting full size then scaling:

# Good
{baseDir}/video-frames.js frame video.mp4 --width 320 --out thumb.jpg

# Less efficient
{baseDir}/video-frames.js frame video.mp4 --out full.jpg
# Then resize externally

Notes

• Grid generation uses ImageMagick when available (better quality), FFmpeg tile filter otherwise
• Frame index 0 is always the first frame of the video
• Timestamps are rounded to nearest frame based on video FPS
• GIFs are optimized with 256-color palette for balance of quality and size
• PNG transparency is preserved (useful for overlays)
• All operations clean up temporary files automatically
• JSON output enables programmatic integration
• Grid thumbnails include timestamps at video intervals