Felldude/Wan2.1-Diffusers-HDR-VAE

VAE Reconstruction & Color Expansion Evaluation

Wan2.1 Base VAE vs HDR VAE

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📊 At-a-Glance Summary

Color expansion (HDR VAE vs GT):

• LAB volume: ~+50%
• Saturation: ~+27%
• Unique colors: ~+30%
• Gradient strength: ~+7%

Structural cost:

• SSIM: ~-2%
• MSE: ~+50%

Key takeaway

HDR VAE significantly increases chromatic richness and color diversity,
but reduces structural fidelity and increases reconstruction error relative to Wan2.1 Base VAE.

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🧪 Evaluation Setup

• Task: Image reconstruction (VAE decoding comparison)
• Models:
  • Wan2.1 Base VAE
  • HDR VAE
  • Ground Truth (GT)
• Mode: Deterministic image-to-image reconstruction
• Metrics:
  • Color statistics (HSV / LAB / RGB)
  • Structural metrics (SSIM, MSE, PSNR)
  • Frequency features (edges, gradients)
  • Entropy + color diversity

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📈 Key Findings

🎨 Color behavior

• Wan2.1 Base VAE: slight compression of GT color space
• HDR VAE: strong expansion of color space (+30% to +50%)

🧱 Structure

• Wan2.1 Base VAE: closer to GT, smoother output
• HDR VAE: sharper, more high-frequency artifacts

👁️ Perceptual behavior

• Wan2.1 Base VAE: higher fidelity, lower distortion
• HDR VAE: more vivid but less faithful reconstruction

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📊 Quantitative Results vs GT

Wan2.1 Base VAE

• Brightness: -0.71%
• Contrast: -0.23%
• Saturation: -0.11%
• Entropy: -0.08%
• Dynamic range: -0.46%
• Edge density: -15.35%
• Gradient strength: -5.90%
• LAB color volume: -5.00%
• Quantized colors: -6.60%
• Unique colors: +7.90%
• Sharpness: -45.65%

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HDR VAE

• Brightness: +0.90%
• Contrast: +0.93%
• Saturation: +26.90%
• Entropy: +0.17%
• Dynamic range: -0.07%
• Edge density: +14.98%
• Gradient strength: +7.10%
• LAB color volume: +48.60%
• Quantized colors: +45.60%
• Unique colors: +29.50%
• Sharpness: +32.15%

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🧮 Reconstruction Quality

Wan2.1 Base VAE

• SSIM: 0.822
• PSNR: 25.86
• MSE: 180.88

➡️ Best structural fidelity and lowest reconstruction error

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HDR VAE

• SSIM: 0.806
• PSNR: 24.06
• MSE: 278.08

➡️ Higher distortion but stronger chromatic expansion

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🧠 Interpretation

Color axis → Winner: HDR VAE

• Largest increase in LAB volume, saturation, and color diversity

Structure axis → Winner: Wan2.1 Base VAE

• Closer SSIM and lower MSE

Fidelity axis → Winner: Wan2.1 Base VAE

• More faithful reconstruction of GT distribution

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🏁 Final Conclusion

HDR VAE acts as a chromatic expansion decoder, increasing color space occupancy and high-frequency detail.

Wan2.1 Base VAE remains closer to the ground-truth manifold, prioritizing structural and perceptual fidelity over color amplification.