Manifest Box Validation

The Manifest Box method embeds a full C2PA manifest in each media segment, as section 19.3 of the C2PA specification defines. Each segment is self-contained, with its own COSE signature, so it needs no init segment and no session keys.

Manifest ID chaining verifies the continuity between segments. See Manifest ID Chaining below.

Overview

Unlike the VSI/EMSG method, the Manifest Box method needs no separate init segment validation step. One function, validateC2paManifestBoxSegment, does everything: manifest parsing, signature verification, BMFF hash validation, and continuity checks.

Two pieces of state pass from one call to the next:

• lastManifestId: the manifest ID from the previous segment, used for the continuity check
• 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 contains the state between segments for the continuity checks:

Field	Type	Description
lastStreamId	string | null	Stream ID from the previous segment
lastSequenceNumber	number | null	Sequence number from the previous segment

The function is pure. It does not mutate any external state. The caller must keep nextManifestId and nextState between calls.

When state is omitted or undefined, the function skips the checks for a consistent stream ID and for increasing sequence numbers.

Manifest ID Chaining

The c2pa.livevideo.segment assertion of each segment includes a previousManifestId field. That field must match the manifest ID of the previous segment, which 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 states how continuity is verified. The only built-in method is c2pa.manifestId, which the specification defines (C2PA §19.3.2).

When the chain is broken, because previousManifestId does not match the manifest ID of the previous segment, the result includes LiveVideoStatusCode.SEGMENT_INVALID.

Custom continuity methods

The specification allows implementers to define their own continuity methods (§19.3.2), identified by a custom label such as com.example.anchor-chain. Their semantics are implementation-specific, so this library cannot validate them by default. Segments that declare an unrecognized method fail with LiveVideoStatusCode.CONTINUITY_METHOD_INVALID, as §19.7.2 requires. They also get LiveVideoStatusCode.CONTINUITY_METHOD_UNSUPPORTED, which lets consumers tell an unverifiable method from a broken chain.

To validate a custom method, register a validator for its label in the options parameter. A stream uses one continuity method, so one validator is registered at a time:

const { result } = await validateC2paManifestBoxSegment(bytes, lastManifestId, state, {
  continuityValidator: {
    method: 'com.example.anchor-chain',
    validate: (liveVideoAssertion, manifest) => {
      // method-specific fields are available on liveVideoAssertion
      return verifyAnchorChain(liveVideoAssertion['anchorToken'], manifest.instanceId)
    },
  },
})
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The validator receives the full decoded c2pa.livevideo.segment assertion, including method-specific fields, and the parsed manifest of the segment. Anything else the method needs, such as lastManifestId, which the caller already has, can be captured in the closure of the callback. Returning false or throwing reports LiveVideoStatusCode.SEGMENT_INVALID. The built-in c2pa.manifestId method cannot be overridden.

Result Fields

The ManifestBoxValidationResult contains:

Field	Type	Description
manifest	C2paManifest | null	Parsed manifest, or null on parse failure
issuer	string | null	Certificate issuer from the signature
sequenceNumber	number | null	From the c2pa.livevideo.segment assertion
previousManifestId	string | null	From the c2pa.livevideo.segment assertion
streamId	string | null	From the c2pa.livevideo.segment assertion
continuityMethod	string | null	From the c2pa.livevideo.segment assertion
bmffHashHex	string | null	Hex-encoded BMFF content hash
isValid	boolean	All checks passed
errorCodes	readonly (LiveVideoStatusCode | C2paStatusCode)[]	Failure codes (empty when valid)