Manifest Box Validation

The Manifest Box method embeds a full C2PA manifest directly into each media segment, as defined in section 19.3 of the C2PA specification. Each segment is self-contained with its own COSE signature, so no init segment or session keys are needed.

Continuity between segments is verified through manifest ID chaining: each segment declares the manifest ID of the previous segment, forming a verifiable chain.

Overview

Unlike the VSI/EMSG method, the Manifest Box method does not require a separate init segment validation step. Instead, a single function — validateC2paManifestBoxSegment — handles everything: manifest parsing, signature verification, BMFF hash validation, and continuity checks.

Two pieces of state are threaded between calls:

• lastManifestId — the manifest ID from the previous segment, used for continuity verification
• state — a ManifestBoxValidationState object that tracks lastStreamId and lastSequenceNumber

Validating Segments

import { validateC2paManifestBoxSegment } from '@svta/cml-c2pa'
import type { ManifestBoxValidationState } from '@svta/cml-c2pa'

let lastManifestId: string | null = null
let state: ManifestBoxValidationState | undefined

for (const segmentUrl of segmentUrls) {
  const bytes = new Uint8Array(await fetch(segmentUrl).then(r => r.arrayBuffer()))

  const { result, nextManifestId, nextState } = await validateC2paManifestBoxSegment(
    bytes,
    lastManifestId,
    state,
  )
  lastManifestId = nextManifestId
  state = nextState

  if (result.isValid) {
    console.log(`Segment ${result.sequenceNumber}: valid`)
  } else {
    console.error(`Segment ${result.sequenceNumber}: failed`, result.errorCodes)
  }
}
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The function returns an object with:

• result — a ManifestBoxValidationResult with the validation outcome
• nextManifestId — the manifest ID to pass into the next call
• nextState — the updated state to pass into the next call

Complete Example

import { validateC2paManifestBoxSegment, LiveVideoStatusCode } from '@svta/cml-c2pa'
import type { ManifestBoxValidationState } from '@svta/cml-c2pa'

async function validateStream(segmentUrls: string[]) {
  let lastManifestId: string | null = null
  let state: ManifestBoxValidationState | undefined

  for (const segmentUrl of segmentUrls) {
    const bytes = new Uint8Array(await fetch(segmentUrl).then(r => r.arrayBuffer()))

    const { result, nextManifestId, nextState } = await validateC2paManifestBoxSegment(
      bytes,
      lastManifestId,
      state,
    )
    lastManifestId = nextManifestId
    state = nextState

    if (result.isValid) {
      console.log(
        `Segment ${result.sequenceNumber}: valid` +
        ` (stream: ${result.streamId}, issuer: ${result.issuer})`,
      )
    } else {
      for (const code of result.errorCodes) {
        switch (code) {
          case LiveVideoStatusCode.CONTINUITY_METHOD_INVALID:
            console.error('Continuity chain broken')
            break
          case LiveVideoStatusCode.ASSERTION_INVALID:
            console.error('Assertion field mismatch (sequenceNumber or streamId)')
            break
          default:
            console.error('Validation failure:', code)
        }
      }
    }

    // Access the full manifest when needed
    if (result.manifest) {
      console.log('Claim generator:', result.manifest.claimGenerator)
      console.log('Assertions:', result.manifest.assertions.length)
    }
  }
}
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State Management

The ManifestBoxValidationState object carries inter-segment state for continuity checks:

The function is pure — it does not mutate any external state. The caller is responsible for persisting nextManifestId and nextState between calls.

When state is omitted or undefined, the function skips streamId consistency and sequence number monotonicity checks (suitable for the first segment).

Manifest ID Chaining

Each segment's c2pa.livevideo.segment assertion includes a previousManifestId field that must match the manifest ID of the preceding segment. This creates a verifiable chain:

Segment 1: manifestId = "abc-123", previousManifestId = "initial-manifest"
Segment 2: manifestId = "def-456", previousManifestId = "abc-123"  // must match segment 1
Segment 3: manifestId = "ghi-789", previousManifestId = "def-456"  // must match segment 2
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The continuityMethod field indicates how continuity is verified. The currently supported method is c2pa.manifestId.

When the chain is broken (the previousManifestId does not match the previous segment's manifest ID), the result includes LiveVideoStatusCode.CONTINUITY_METHOD_INVALID.

Result Fields

The ManifestBoxValidationResult contains: