@moqtap/codec

MoQT (Media over QUIC Transport) wire-format codec and session state machine for JavaScript/TypeScript.

• Multi-draft support (drafts 07 through 17)
• Stateless encode/decode of all MoQT control messages and data streams
• Protocol session state machine with FSM-based validation per draft
• Zero runtime dependencies
• Works in Node.js, Bun, and browsers
• Full TypeScript types with discriminated unions

Install

npm install @moqtap/codec

Quick Start

MoQT is pre-RFC, so a draft version must always be specified. Use draft-scoped imports for the best experience:

import { createDraft07Codec, DRAFT_VERSION } from '@moqtap/codec/draft07'

const codec = createDraft07Codec()

// Decode a message from bytes
const result = codec.decodeMessage(bytes)
if (result.ok) {
  console.log(result.value.type) // e.g. 'subscribe'
}

// Encode a message to bytes
const encoded = codec.encodeMessage({
  type: 'client_setup',
  supportedVersions: [DRAFT_VERSION],
  parameters: new Map(),
})

Or use the factory if your application supports multiple drafts:

import { createCodec, DRAFT_VERSIONS } from '@moqtap/codec'

const codec = createCodec({ draft: '17' }) // '07' through '17'

// DRAFT_VERSIONS provides wire version numbers under short aliases:
//   DRAFT_VERSIONS['07'] — 0xff000007n

Subpath Exports

Each draft is available as a subpath import with its own codec and session state machine:

| Import path | Description | | -------------------------------- | ------------------------------------------------- | | @moqtap/codec | Factory + shared types (createCodec({ draft })) | | @moqtap/codec/draft07 | Draft-07 codec | | @moqtap/codec/draft08 | Draft-08 codec | | @moqtap/codec/draft09 | Draft-09 codec | | @moqtap/codec/draft10 | Draft-10 codec | | @moqtap/codec/draft11 | Draft-11 codec | | @moqtap/codec/draft12 | Draft-12 codec | | @moqtap/codec/draft13 | Draft-13 codec | | @moqtap/codec/draft14 | Draft-14 codec | | @moqtap/codec/draft15 | Draft-15 codec | | @moqtap/codec/draft16 | Draft-16 codec | | @moqtap/codec/draft17 | Draft-17 codec | | @moqtap/codec/draft{N}/session | Session state machine for draft N |

Note: A default (versionless) codec will be available once the MoQT specification reaches RFC status. Until then, always specify a draft version.

Draft-Specific Imports

For applications targeting a single draft version:

import { createDraft17Codec } from '@moqtap/codec/draft17'
import { createDraft17SessionState } from '@moqtap/codec/draft17/session'

Session State Machine

Validate protocol message sequences without transport coupling:

import { createDraft17SessionState } from '@moqtap/codec/draft17/session'

const session = createDraft17SessionState('client')

const result = session.receive(incomingMessage)
if (!result.ok) {
  console.error('Protocol violation:', result.violation)
}

License

MIT