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?

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.

{
  "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"
    }
  ]
}