# How do ITU-T P.800 and P.808 define the MOS scale, listener rules and crowdsourcing controls, and how do the two Recommendations differ?

- id: art_01M5NE2WWQ2S93QX59QAJRWCS2
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T13, T20 · tags: none
- updated: 2026-10-23T22:28:42.511Z
- url: https://veyrul.com/articles/art_01M5NE2WWQ2S93QX59QAJRWCS2

ITU-T P.800 defines the listening-only ACR test whose 5-point mean is the MOS (with a note that older results must be shifted by one to compare) and requires naive listeners (no subjective test in 6 months, no listening-opinion test in a year); P.808 (in force, 2021) adapts ACR/DCR/CCR to crowdsourcing with one gold-standard and one trapping question per 10 stimuli, two-eared headphones and a two-week listening-test gap, and says crowdsourcing complements rather than replaces laboratory tests. Neither defines a TTS-naturalness protocol.

ITU-T P.800 defines the listening-only ACR test whose 5-point mean is the MOS (with a note that older results must be shifted by one to compare) and requires naive listeners (no subjective test in 6 months, no listening-opinion test in a year); P.808 (in force, 2021) adapts ACR/DCR/CCR to crowdsourcing with one gold-standard and one trapping question per 10 stimuli, two-eared headphones and a two-week listening-test gap, and says crowdsourcing complements rather than replaces laboratory tests. Neither defines a TTS-naturalness protocol.

Curator qualifications: Recommendations read 2026-10-22 (PDFs from producer copies); no test run. PDFs verified from producer copies. Minimum ratings per stimulus (producer: at least 8) not located; P.808 note gives 96 votes per condition in one example.

Limitations: Recommendations read 2026-10-22 (PDFs from producer copies); no test run.

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

```json
{
  "citations": [
    {
      "url": "https://www.itu.int/rec/T-REC-P.800-199608-I/en",
      "note": "itu.int/rec/T-REC-P.808-202106-I/en (curator fetch); producer PDFs p800.pdf (562fd1fdb5276...) and p808.pdf (da0e7e96462da...) = pins"
    },
    {
      "url": "https://www.itu.int/rec/T-REC-P.808-202106-I/en",
      "note": "itu.int/rec/T-REC-P.808-202106-I/en (curator fetch); producer PDFs p800.pdf (562fd1fdb5276...) and p808.pdf (da0e7e96462da...) = pins"
    },
    {
      "url": "https://www.itu.int/rec/T-REC-P.800-199608-I/en",
      "note": "itu.int/rec/T-REC-P.808-202106-I/en (curator fetch); producer PDFs p800.pdf (562fd1fdb5276...) and p808.pdf (da0e7e96462da...) = pins"
    },
    {
      "url": "https://www.itu.int/rec/T-REC-P.808-202106-I/en",
      "note": "itu.int/rec/T-REC-P.808-202106-I/en (curator fetch); producer PDFs p800.pdf (562fd1fdb5276...) and p808.pdf (da0e7e96462da...) = pins"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] ITU-T P.800 defines the listening-only ACR test whose 5-point mean is the MOS (with a note that older results must be shifted by one to compare) and requires naive listeners (no subjective test in 6 months, no listening-opinion test in a year); P.808 (in force, 2021) adapts ACR/DCR/CCR to crowdsourcing with one gold-standard and one trapping question per 10 stimuli, two-eared headphones and a two-week listening-test gap, and says crowdsourcing complements rather than replaces laboratory tests. Neither defines a TTS-naturalness protocol. · locator: itu.int/rec/T-REC-P.808-202106-I/en (curator fetch); producer PDFs p800.pdf (562fd1fdb5276...) and p808.pdf (da0e7e96462da...) = pins · source: https://www.itu.int/rec/T-REC-P.800-199608-I/en

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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