# How are hearing-impaired (HI) and visually-impaired narrative (VI-N) audio tracks represented in a DCP, and how do open tools model and check them?

- id: art_01M5MSA3A2VG8KX8WT80FPVBQC
- 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, T13 · tags: none
- updated: 2026-10-23T16:25:38.362Z
- url: https://veyrul.com/articles/art_01M5MSA3A2VG8KX8WT80FPVBQC

In a DCP, hearing-impaired (HI) and visually-impaired narrative (VIN) audio are dedicated channels inside the main sound track, not separate files. SMPTE ST 428-12 defines HI (0Eh) as a dialog-intelligibility channel and VIN (0Fh) as narration describing picture events, and allows several of each for different languages. libdcp maps the MCA ids 'hi' and 'vin'/'vi-n' to its own channel slots, but its verifier has no HI/VIN-specific check. ClairMeta checks only an even channel count. No inspected tool verifies that a VIN channel actually carries narration or is labelled correctly.

In a DCP, hearing-impaired (HI) and visually-impaired narrative (VIN) audio are dedicated channels inside the main sound track, not separate files. SMPTE ST 428-12 defines HI (0Eh) as a dialog-intelligibility channel and VIN (0Fh) as narration describing picture events, and allows several of each for different languages. libdcp maps the MCA ids 'hi' and 'vin'/'vi-n' to its own channel slots, but its verifier has no HI/VIN-specific check. ClairMeta checks only an even channel count. No inspected tool verifies that a VIN channel actually carries narration or is labelled correctly.

Curator qualifications: Standard and code read 2026-10-22; no DCP built or checked. Cinepedia delivery-to-headphones statement carried from producer reading (secondary). ISDCF Doc 04 itself not read.

Limitations: Standard and code read 2026-10-22; no DCP built or checked.

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

```json
{
  "citations": [
    {
      "url": "https://pub.smpte.org/latest/st428-12/st0428-12-2013.pdf",
      "note": "SMPTE ST 428-12:2013 channel table and note; libdcp src/types.h L100-110; libdcp src/main_sound_configuration.cc L175-177; libdcp src/verify.cc (whole-file search); ClairMeta dcp_check_sound.py L47-55"
    },
    {
      "url": "https://cinepedia.com/accessibility/",
      "note": "SMPTE ST 428-12:2013 channel table and note; libdcp src/types.h L100-110; libdcp src/main_sound_configuration.cc L175-177; libdcp src/verify.cc (whole-file search); ClairMeta dcp_check_sound.py L47-55"
    },
    {
      "url": "https://github.com/cth103/libdcp/blob/891facc8ce17cd767948ac5c2eb629bca5288f64/src/verify.cc",
      "note": "SMPTE ST 428-12:2013 channel table and note; libdcp src/types.h L100-110; libdcp src/main_sound_configuration.cc L175-177; libdcp src/verify.cc (whole-file search); ClairMeta dcp_check_sound.py L47-55"
    },
    {
      "url": "https://github.com/cth103/libdcp/blob/891facc8ce17cd767948ac5c2eb629bca5288f64/src/types.h",
      "note": "SMPTE ST 428-12:2013 channel table and note; libdcp src/types.h L100-110; libdcp src/main_sound_configuration.cc L175-177; libdcp src/verify.cc (whole-file search); ClairMeta dcp_check_sound.py L47-55"
    },
    {
      "url": "https://github.com/cth103/libdcp/blob/891facc8ce17cd767948ac5c2eb629bca5288f64/src/main_sound_configuration.cc",
      "note": "SMPTE ST 428-12:2013 channel table and note; libdcp src/types.h L100-110; libdcp src/main_sound_configuration.cc L175-177; libdcp src/verify.cc (whole-file search); ClairMeta dcp_check_sound.py L47-55"
    },
    {
      "url": "https://github.com/Ymagis/ClairMeta/blob/b3b66a024174976ffbde4b6dfff2b599e84e4757/clairmeta/dcp_check_sound.py",
      "note": "SMPTE ST 428-12:2013 channel table and note; libdcp src/types.h L100-110; libdcp src/main_sound_configuration.cc L175-177; libdcp src/verify.cc (whole-file search); ClairMeta dcp_check_sound.py L47-55"
    },
    {
      "url": "https://github.com/Ymagis/ClairMeta/blob/b3b66a024174976ffbde4b6dfff2b599e84e4757/clairmeta/settings.py",
      "note": "SMPTE ST 428-12:2013 channel table and note; libdcp src/types.h L100-110; libdcp src/main_sound_configuration.cc L175-177; libdcp src/verify.cc (whole-file search); ClairMeta dcp_check_sound.py L47-55"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] In a DCP, hearing-impaired (HI) and visually-impaired narrative (VIN) audio are dedicated channels inside the main sound track, not separate files. SMPTE ST 428-12 defines HI (0Eh) as a dialog-intelligibility channel and VIN (0Fh) as narration describing picture events, and allows several of each for different languages. libdcp maps the MCA ids 'hi' and 'vin'/'vi-n' to its own channel slots, but its verifier has no HI/VIN-specific check. ClairMeta checks only an even channel count. No inspected tool verifies that a VIN channel actually carries narration or is labelled correctly. · locator: SMPTE ST 428-12:2013 channel table and note; libdcp src/types.h L100-110; libdcp src/main_sound_configuration.cc L175-177; libdcp src/verify.cc (whole-file search); ClairMeta dcp_check_sound.py L47-55 · source: https://pub.smpte.org/latest/st428-12/st0428-12-2013.pdf

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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