Check Video

Check Video Screencast

Extract frames from screencast videos, analyze visual content, and execute instructions based on the video.

When This Skill is Invoked

Claude uses this skill when:

• User runs /check-video [N] <instruction>
• User wants to analyze a recorded screencast
• User needs to verify UI changes shown in a video
• User wants to document features from a screen recording

Usage

/check-video [N] <instruction>

• N (optional): Which video to use (1 = latest, 2 = second latest, etc.). Default: 1
• instruction: What to do after analyzing the video content

Process

1. Locate the Video File

Find the latest (or N-th latest) video file in ~/ビデオ/スクリーンキャスト/:

# Get the N-th latest video file (default N=1)
VIDEO_FILE=$(ls -t ~/ビデオ/スクリーンキャスト/*.{mp4,webm,mkv,avi,mov} 2>/dev/null | sed -n '${N}p')

# Example for latest (N=1):
VIDEO_FILE=$(ls -t ~/ビデオ/スクリーンキャスト/*.{mp4,webm,mkv,avi,mov} 2>/dev/null | head -1)

2. Extract Frames with ffmpeg

Extract key frames at regular intervals (e.g., every 3 seconds):

# Create temporary directory for frames
FRAME_DIR=$(mktemp -d)

# Extract frames every 3 seconds
ffmpeg -i "$VIDEO_FILE" -vf "fps=1/3" "$FRAME_DIR/frame_%04d.png"

# Or extract specific number of frames evenly distributed
DURATION=$(ffmpeg -i "$VIDEO_FILE" 2>&1 | grep "Duration" | awk '{print $2}' | tr -d ,)
# Calculate interval for N frames (e.g., 10 frames)
ffmpeg -i "$VIDEO_FILE" -vf "select='not(mod(n\,30))'" -vsync vfr "$FRAME_DIR/frame_%04d.png"

3. Read and Analyze Frames

Use the Read tool to view each extracted frame:

# List all extracted frames
ls "$FRAME_DIR"/*.png

Then read each frame with the Read tool to analyze the visual content:

• UI elements and their states
• Text content visible in the UI
• Error messages or dialogs
• Visual bugs or layout issues
• Feature demonstrations

4. Execute the Instruction

Based on the analyzed video content, execute the user's instruction:

• Fix UI bugs identified in the video
• Update documentation with screenshots from the video
• Verify that features work as shown
• Implement missing features observed in the video
• Compare actual behavior with expected behavior

5. Cleanup

# Remove temporary frames
rm -rf "$FRAME_DIR"

Frame Extraction Strategies

Strategy 1: Time-based (Every N seconds)

# Every 3 seconds
ffmpeg -i "$VIDEO_FILE" -vf "fps=1/3" "$FRAME_DIR/frame_%04d.png"

Strategy 2: Fixed Number of Frames

# Extract exactly 10 evenly-distributed frames
ffmpeg -i "$VIDEO_FILE" -vf "select='not(mod(n\,$(ffprobe -v error -count_frames -select_streams v:0 -show_entries stream=nb_read_frames -of default=nokey=1:noprint_wrappers=1 "$VIDEO_FILE" | awk '{print int($1/10)}'))'" -vsync vfr "$FRAME_DIR/frame_%04d.png"

Strategy 3: Scene Changes (Key Frames Only)

# Extract frames only when scene changes significantly
ffmpeg -i "$VIDEO_FILE" -vf "select='gt(scene,0.3)'" -vsync vfr "$FRAME_DIR/frame_%04d.png"

Common Use Cases

Use Case 1: UI Bug Verification

/check-video 1 Verify if the alignment issue in PhotoTags tab is fixed

Use Case 2: Documentation

/check-video 1 Create screenshots for the S3 backup feature documentation

Use Case 3: Feature Implementation

/check-video 1 Implement the emoji icons shown in the maintenance tab

Use Case 4: Regression Testing

/check-video 2 Compare this video with the previous one to check for regressions

Tips

1. Frame Rate: Adjust fps based on video length

   • Short videos (< 1 min): Extract every 2 seconds (fps=1/2)
   • Medium videos (1-5 min): Extract every 3-5 seconds (fps=1/3 or fps=1/5)
   • Long videos (> 5 min): Extract every 10 seconds (fps=1/10)

2. Video Format: ffmpeg supports most formats (mp4, webm, mkv, avi, mov)

3. Frame Quality: Use PNG for lossless quality when analyzing UI details

4. Focus on Key Moments: Use scene detection to capture only important changes

5. Temporary Storage: Always use mktemp -d for frame storage and clean up afterwards

Error Handling

• Video not found: Verify the path ~/ビデオ/スクリーンキャスト/ exists and contains video files
• ffmpeg not installed: Install with sudo apt install ffmpeg (Linux) or brew install ffmpeg (Mac)
• Permission errors: Check file permissions on the video directory
• Out of disk space: Clean up old frames from previous runs

Integration with PhotoClove Development

This skill is particularly useful for:

• Verifying UI alignment and styling issues
• Documenting new features with visual examples
• Reproducing bugs shown in screen recordings
• Comparing before/after states during refactoring
• Creating visual test cases for regression testing

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