# What do primary sources fix for AmbiX (ACN/SN3D), YouTube spatial-audio uploads and Opus ambisonics, and what breaks if FuMa material is mislabelled?

- id: art_01M5M8CT7B06HQ5VTVYP1NYT6G
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T14, T19 · tags: none
- updated: 2026-10-23T11:30:01.574Z
- url: https://veyrul.com/articles/art_01M5M8CT7B06HQ5VTVYP1NYT6G

YouTube's spatial-audio help requires AmbiX (ACN ordering, SN3D normalisation) with first-order audio as a single 4-channel W, Y, Z, X track at 48 kHz (PCM in MOV, AAC at 256 kbps or more, or Opus family 2 at 512 kbps or more in MP4), plus a 6-channel head-locked variant; Google's SA3D box declares ordering and normalisation and uses channel_map to describe a track's order (W,X,Y,Z input -> 0,2,3,1); RFC 8486 Opus family 2 carries ACN-ordered, SN3D-normalised channels with optional non-diegetic stereo.

YouTube's spatial-audio help requires AmbiX (ACN ordering, SN3D normalisation) with first-order audio as a single 4-channel W, Y, Z, X track at 48 kHz (PCM in MOV, AAC at 256 kbps or more, or Opus family 2 at 512 kbps or more in MP4), plus a 6-channel head-locked variant; Google's SA3D box declares ordering and normalisation and uses channel_map to describe a track's order (W,X,Y,Z input -> 0,2,3,1); RFC 8486 Opus family 2 carries ACN-ordered, SN3D-normalised channels with optional non-diegetic stereo.

Curator qualifications: Audible effect of FuMa material labelled as AmbiX (F2) rests on a secondary guide (ambisonics.ch, S26) and was not measured or reinspected. YouTube Help page is live and unversioned; recheck before citing. Documentation reading only; no audio encoded, injected or uploaded.

Limitations: Vendor help page plus an IETF RFC and a vendor RFC document.

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

```json
{
  "citations": [
    {
      "url": "https://support.google.com/youtube/answer/6395969",
      "note": "support.google.com/youtube/answer/6395969 (hl=en, fetched 2026-10-22), requirements; spatial-media docs/spatial-audio-rfc.md at 2308497c (SA3D fields); RFC 8486 section 3.1 (txt lines ~139-177); spatial-media LICENSE"
    },
    {
      "url": "https://github.com/google/spatial-media/blob/2308497c39bb604a7c3ba56ac17e302f2b1b6a96/docs/spatial-audio-rfc.md",
      "note": "support.google.com/youtube/answer/6395969 (hl=en, fetched 2026-10-22), requirements; spatial-media docs/spatial-audio-rfc.md at 2308497c (SA3D fields); RFC 8486 section 3.1 (txt lines ~139-177); spatial-media LICENSE"
    },
    {
      "url": "https://www.rfc-editor.org/rfc/rfc8486.txt",
      "note": "support.google.com/youtube/answer/6395969 (hl=en, fetched 2026-10-22), requirements; spatial-media docs/spatial-audio-rfc.md at 2308497c (SA3D fields); RFC 8486 section 3.1 (txt lines ~139-177); spatial-media LICENSE"
    },
    {
      "url": "https://ambisonics.ch/ambisonics-101/formats/",
      "note": "support.google.com/youtube/answer/6395969 (hl=en, fetched 2026-10-22), requirements; spatial-media docs/spatial-audio-rfc.md at 2308497c (SA3D fields); RFC 8486 section 3.1 (txt lines ~139-177); spatial-media LICENSE"
    },
    {
      "url": "https://github.com/google/spatial-media/blob/2308497c39bb604a7c3ba56ac17e302f2b1b6a96/LICENSE",
      "note": "support.google.com/youtube/answer/6395969 (hl=en, fetched 2026-10-22), requirements; spatial-media docs/spatial-audio-rfc.md at 2308497c (SA3D fields); RFC 8486 section 3.1 (txt lines ~139-177); spatial-media LICENSE"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] YouTube's spatial-audio help requires AmbiX (ACN ordering, SN3D normalisation) with first-order audio as a single 4-channel W, Y, Z, X track at 48 kHz (PCM in MOV, AAC at 256 kbps or more, or Opus family 2 at 512 kbps or more in MP4), plus a 6-channel head-locked variant; Google's SA3D box declares ordering and normalisation and uses channel_map to describe a track's order (W,X,Y,Z input -> 0,2,3,1); RFC 8486 Opus family 2 carries ACN-ordered, SN3D-normalised channels with optional non-diegetic stereo. · locator: support.google.com/youtube/answer/6395969 (hl=en, fetched 2026-10-22), requirements; spatial-media docs/spatial-audio-rfc.md at 2308497c (SA3D fields); RFC 8486 section 3.1 (txt lines ~139-177); spatial-media LICENSE · source: https://support.google.com/youtube/answer/6395969

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

Use this evidence:
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