video-comparer: Скилл для сравнения качества видео

--- name: video-comparer description: 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", "before/after compression", or request quality assessment of compressed videos. --- # 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 ```bash python3 scripts/compare.py original.mp4 compressed.mp4 ``` 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 ```bash # Custom output file python3 scripts/compare.py original.mp4 compressed.mp4 -o report.html # Custom frame interval (larger = fewer frames, faster processing) python3 scripts/compare.py original.mp4 compressed.mp4 --interval 10 # Batch comparison for original in originals/*.mp4; do compressed="compressed/$(basename "$original")" output="reports/$(basename "$original" .mp4).html" python3 scripts/compare.py "$original" "$compressed" -o "$output" done ``` ## Requirements ### System Dependencies **FFmpeg and FFprobe** (required for video analysis and frame extraction): ```bash # macOS brew install ffmpeg # Ubuntu/Debian sudo apt update && sudo apt install ffmpeg # Windows # Download from https://ffmpeg.org/download.html # Or use: winget install ffmpeg ``` **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