This skill should be used when comparing two videos to analyze compression results or quality differences. Generates interactive HTML reports with quality metrics (PSNR, SSIM) and frame-by-frame visual comparisons. Triggers when users mention "compare videos", "video quality", "compression analysis"

Video Comparer Overview Compare two videos and generate an interactive HTML report analyzing compression results. The script extracts video metadata, calculates quality metrics (PSNR, SSIM), and creates frame by frame visual comparisons with three viewing modes: slider, side by side, and grid. When to Use This Skill Use this skill when: Comparing original and compressed videos Analyzing video compression quality and efficiency Evaluating codec performance or bitrate reduction impact Users mention "compare videos", "video quality", "compression analysis", or "before/after compression" Core Usage Basic Command Generates comparison.html with: Video parameters (codec, resolution, bitrate, duration, file size) Quality metrics (PSNR, SSIM, size/bitrate reduction percentages) Frame by frame comparison (default: frames at 5s intervals) Command Options Requirements System Dependencies FFmpeg and FFprobe (required for video analysis and frame extraction): Python 3.8+ (uses type hints, f strings, pathlib) Video Specifications Supported formats: .mp4 (recommended), .mov , .avi , .mkv , .webm File size limit: 500MB per video (configurable) Processing time: ~1 2 minutes for typical videos; varies by duration and frame interval Script Behavior Automatic Validation The script automatically validates: FFmpeg/FFprobe installation and availability File existence, extensions, and size limits Path security (prevents directory traversal) Clear error messages with resolution guidance appear when validation fails. Quality Metrics The script calculates two standard quality metrics: PSNR (Peak Signal to Noise Ratio): Pixel level similarity measurement (20 50 dB scale, higher is better) SSIM (Structural Similarity Index): Perceptual similarity measurement (0.0 1.0 scale, higher is better) For detailed interpretation scales and quality thresholds, consult references/video metrics.md . Frame Extraction The script extracts frames at specified intervals (default: 5 seconds), scales them to consistent height (800px) for comparison, and embeds them as base64 data URLs in self contained HTML. Temporary files are automatically cleaned after processing. Output Report The generated HTML report includes: Slider Mode : Drag to reveal original vs compressed (default) Side by Side Mode : Simultaneous display for direct comparison Grid Mode : Compact 2 column layout Zoom Controls : 50% 200% magnification Self contained format (no server required, works offline) Important Implementation Details Security The script implements: Path validation (absolute paths, prevents directory traversal) Command injection prevention (no shell=True , validated arguments) Resource limits (file size, timeouts) Custom exceptions: ValidationError , FFmpegError , VideoComparisonError Common Error Scenarios "FFmpeg not found" : Install FFmpeg via platform package manager (see Requirements section) "File too large" : Compress videos before comparison, or adjust MAX FILE SIZE MB in scripts/compare.py "Operation timed out" : Increase FFMPEG TIMEOUT constant or use larger interval value (processes fewer frames) "Frame count mismatch" : Videos have different durations/frame rates; script auto truncates to minimum frame count and shows warning Configuration The script includes adjustable constants for file size limits, timeouts, frame dimensions, and extraction intervals. To customize behavior, edit the constants at the top of scripts/compare.py . For detailed configuration options and their impacts, consult references/configuration.md . Reference Materials Consult these files for detailed information: references/video metrics.md : Quality metrics interpretation (PSNR/SSIM scales, compression targets, bitrate guidelines) references/ffmpeg commands.md : FFmpeg command reference (metadata extraction, frame extraction, troubleshooting) references/configuration.md : Script configuration options and adjustable constants assets/template.html : HTML report template for customizing viewing modes and styling

video-comparer