# How should upscaled footage be judged: what do primary sources say about full-reference versus no-reference metrics and their limits?

- id: art_01M5MTXH6HN52FB185VESXGDQB
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T10, T12, T20 · tags: none
- updated: 2026-10-23T16:53:43.755Z
- url: https://veyrul.com/articles/art_01M5MTXH6HN52FB185VESXGDQB

Blau and Michaeli prove that lower distortion (full-reference measures such as PSNR/SSIM) and better perceptual quality are at odds for any distortion measure, which is why GAN-based upscalers can score worse on PSNR while looking better. Real-ESRGAN reports only the no-reference NIQE and warns such metrics do not track human preference. The VMAF docs describe a full-reference metric trained on subjective data for stated viewing conditions, say it captures gains from enhancement operations, and provide a NEG mode that disables enhancement gain for codec comparisons; its FAQ shows upscaling the distorted clip before comparison. No inspected source states a validated protocol for judging AI-upscaled finishing footage; broadcaster specs require QC but no metric thresholds in the passages read.

Blau and Michaeli prove that lower distortion (full-reference measures such as PSNR/SSIM) and better perceptual quality are at odds for any distortion measure, which is why GAN-based upscalers can score worse on PSNR while looking better. Real-ESRGAN reports only the no-reference NIQE and warns such metrics do not track human preference. The VMAF docs describe a full-reference metric trained on subjective data for stated viewing conditions, say it captures gains from enhancement operations, and provide a NEG mode that disables enhancement gain for codec comparisons; its FAQ shows upscaling the distorted clip before comparison. No inspected source states a validated protocol for judging AI-upscaled finishing footage; broadcaster specs require QC but no metric thresholds in the passages read.

Curator qualifications: Excerpted evidence located (one excerpt-less row); perception-distortion trade-off (Blau & Michaeli); VMAF tracking subjective quality vs rewarding enhancement kept (use-scope difference).

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://arxiv.org/abs/1711.06077v4",
      "note": "candidate evidence excerpts"
    },
    {
      "url": "https://github.com/Netflix/vmaf/blob/272c5967701017b90a0ebcff24205e59dbba6421/resource/doc/models_v0.md",
      "note": "candidate evidence excerpts"
    },
    {
      "url": "https://github.com/Netflix/vmaf/blob/272c5967701017b90a0ebcff24205e59dbba6421/resource/doc/faq.md",
      "note": "candidate evidence excerpts"
    },
    {
      "url": "https://github.com/Netflix/vmaf/blob/272c5967701017b90a0ebcff24205e59dbba6421/resource/doc/models_v1.md",
      "note": "candidate evidence excerpts"
    },
    {
      "url": "https://arxiv.org/abs/2107.10833v2",
      "note": "candidate evidence excerpts"
    },
    {
      "url": "https://github.com/hzwer/Practical-RIFE/blob/bbfd2ea90910789a860ea3e2b32a240cd577b75e/README.md",
      "note": "candidate evidence excerpts"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] Blau and Michaeli prove that lower distortion (full-reference measures such as PSNR/SSIM) and better perceptual quality are at odds for any distortion measure, which is why GAN-based upscalers can score worse on PSNR while looking better. Real-ESRGAN reports only the no-reference NIQE and warns such metrics do not track human preference. The VMAF docs describe a full-reference metric trained on subjective data for stated viewing conditions, say it captures gains from enhancement operations, and provide a NEG mode that disables enhancement gain for codec comparisons; its FAQ shows upscaling the distorted clip before comparison. No inspected source states a validated protocol for judging AI-upscaled finishing footage; broadcaster specs require QC but no metric thresholds in the passages read. · locator: candidate evidence excerpts · source: https://arxiv.org/abs/1711.06077v4

Rights:
- documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources.

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