9b724f33e3
## New Skill: video-comparer v1.0.0 - Compare original and compressed videos with interactive HTML reports - Calculate quality metrics (PSNR, SSIM) for compression analysis - Generate frame-by-frame visual comparisons (slider, side-by-side, grid) - Extract video metadata (codec, resolution, bitrate, duration) - Multi-platform FFmpeg support with security features ## transcript-fixer Enhancements - Add async AI processor for parallel processing - Add connection pool management for database operations - Add concurrency manager and rate limiter - Add audit log retention and database migrations - Add health check and metrics monitoring - Add comprehensive test suite (8 new test files) - Enhance security with domain and path validators ## Marketplace Updates - Update marketplace version from 1.8.0 to 1.9.0 - Update skills count from 15 to 16 - Update documentation (README.md, CLAUDE.md, CHANGELOG.md) 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
3.4 KiB
3.4 KiB
Video Quality Metrics Reference
Contents
- PSNR (Peak Signal-to-Noise Ratio) - Pixel-level similarity measurement
- SSIM (Structural Similarity Index) - Perceptual quality measurement
- VMAF (Video Multimethod Assessment Fusion) - Machine learning-based quality prediction
- File Size and Bitrate Considerations - Compression targets and guidelines
PSNR (Peak Signal-to-Noise Ratio)
Definition
PSNR measures the ratio between the maximum possible power of a signal and the power of corrupting noise. It's commonly used to measure the quality of reconstruction of lossy compression codecs.
Scale
- Range: Typically 20-50 dB
- Higher is better: More signal, less noise
Quality Interpretation
| PSNR (dB) | Quality Level | Use Case |
|---|---|---|
| < 20 | Poor | Unacceptable for most applications |
| 20-25 | Low | Acceptable for very low-bandwidth scenarios |
| 25-30 | Fair | Basic video streaming |
| 30-35 | Good | Standard streaming quality |
| 35-40 | Very Good | High-quality streaming |
| 40+ | Excellent | Near-lossless quality, archival |
Calculation Formula
PSNR = 10 * log10(MAX_I^2 / MSE)
Where:
- MAX_I = maximum pixel value (255 for 8-bit images)
- MSE = mean squared error
SSIM (Structural Similarity Index)
Definition
SSIM is a perceptual metric that quantifies image quality degradation based on structural information changes rather than pixel-level differences.
Scale
- Range: 0.0 to 1.0
- Higher is better: More structural similarity
Quality Interpretation
| SSIM | Quality Level | Use Case |
|---|---|---|
| < 0.70 | Poor | Visible artifacts, structural damage |
| 0.70-0.80 | Fair | Noticeable quality loss |
| 0.80-0.90 | Good | Acceptable for most streaming |
| 0.90-0.95 | Very Good | High-quality streaming |
| 0.95-0.98 | Excellent | Near-identical perception |
| 0.98+ | Perfect | Indistinguishable from original |
Components
SSIM combines three comparisons:
- Luminance: Local brightness comparisons
- Contrast: Local contrast comparisons
- Structure: Local structure correlations
VMAF (Video Multimethod Assessment Fusion)
Definition
VMAF is a machine learning-based metric that predicts subjective video quality by combining multiple quality metrics.
Scale
- Range: 0-100
- Higher is better: Better perceived quality
Quality Interpretation
| VMAF | Quality Level | Use Case |
|---|---|---|
| < 20 | Poor | Unacceptable |
| 20-40 | Low | Basic streaming |
| 40-60 | Fair | Standard streaming |
| 60-80 | Good | High-quality streaming |
| 80-90 | Very Good | Premium streaming |
| 90+ | Excellent | Reference quality |
File Size and Bitrate Considerations
Compression Targets by Use Case
| Use Case | Size Reduction | PSNR Target | SSIM Target |
|---|---|---|---|
| Social Media | 40-60% | 35-40 dB | 0.95-0.98 |
| Streaming | 50-70% | 30-35 dB | 0.90-0.95 |
| Archival | 20-40% | 40+ dB | 0.98+ |
| Mobile | 60-80% | 25-30 dB | 0.85-0.90 |
Bitrate Guidelines
| Resolution | Target Bitrate (1080p equivalent) |
|---|---|
| 480p | 1-2 Mbps |
| 720p | 2-5 Mbps |
| 1080p | 5-10 Mbps |
| 4K | 20-50 Mbps |