Encrypted Media Extensions Initialization Data Format Registry

W3C Editor's Draft

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Joey Parrish (Google Inc.)
Greg Freedman (Netflix Inc.)
Former editors:
Mark Watson (Netflix Inc.) (Until September 2019)
David Dorwin (Google Inc.) (Until September 2017)
Jerry Smith (Microsoft Corporation) (Until September 2017)
Adrian Bateman (Microsoft Corporation) (Until May 2014)
GitHub w3c/encrypted-media (pull requests, new issue, open issues)
public-media-wg@w3.org with subject line [eme-initdata-registry] … message topic … (archives)


This specification defines the initialization data formats for use with the Encrypted Media Extensions [ENCRYPTED-MEDIA].

Some formats may be extracted from media data as defined in the Encrypted Media Extensions Stream Format Registry [EME-STREAM-REGISTRY]. All may be provided separately, such as via a manifest or other application data.

This registry is non-normative.

Status of This Document

This section describes the status of this document at the time of its publication. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at https://www.w3.org/TR/.

This document was published by the Media Working Group as an Editor's Draft.

Publication as an Editor's Draft does not imply endorsement by W3C and its Members.

This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

This document was produced by a group operating under the W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

This document is governed by the 03 November 2023 W3C Process Document.

1. Purpose

This registry is intended to enhance interoperability among implementations and users of encrypted media streams with the Encrypted Media Extensions (EME) specification [ENCRYPTED-MEDIA]. In particular, this registry provides the means (1) to identify and avoid collisions among initialization data type strings, and (2) to disclose information about initialization data formats accepted by EME implementations to promote interoperability.

2. Organization

The registry maintains a mapping between initialization data type strings and format specifications, which describe the structure and semantics of initialization data. The strings are those used for initDataType values provided by and to Encrypted Media Extensions [ENCRYPTED-MEDIA] APIs.

This registry is not intended to include any information on whether a format is encumbered by intellectual property claims. Implementors and users are advised to seek appropriate legal counsel in this matter if they intend to implement or use a specific format.

3. Registration Entry Requirements

  1. Each entry must include a unique initialization data type string.

  2. Each entry must include a link that references a publicly available specification. It is recommended that such a specification be made available without cost (other than reasonable shipping and handling if not available by online means).

  3. Candidate entries must be announced by filing an issue in the Encrypted Media Extensions GitHub issue tracker so they can be discussed and evaluated for compliance before being added to the registry.

  4. Per the Encrypted Media Extensions specification, entries must be fully specified and support common formats such that instances of the format can be processed in a fully specified and compatible way.

  5. Existing entries cannot be deleted or deprecated.

4. Registry

Initialization Data Type Public Specification(s)
cenc "cenc" Initialization Data Format [EME-INITDATA-CENC]
keyids "keyids" Initialization Data Format [EME-INITDATA-KEYIDS]
webm "webm" Initialization Data Format [EME-INITDATA-WEBM]

A. References

A.1 Informative references

"cenc" Initialization Data Format. David Dorwin; Adrian Bateman; Mark Watson; Jerry Smith. W3C. 15 September 2016. W3C Working Group Note. URL: https://www.w3.org/TR/eme-initdata-cenc/
"keyids" Initialization Data Format. David Dorwin; Adrian Bateman; Mark Watson. W3C. 15 September 2016. W3C Working Group Note. URL: https://www.w3.org/TR/eme-initdata-keyids/
"webm" Initialization Data Format. David Dorwin; Adrian Bateman; Mark Watson. W3C. 15 September 2016. W3C Working Group Note. URL: https://www.w3.org/TR/eme-initdata-webm/
Encrypted Media Extensions Stream Format Registry. David Dorwin; Adrian Bateman; Mark Watson. W3C. 15 September 2016. W3C Working Group Note. URL: https://www.w3.org/TR/eme-stream-registry/
Encrypted Media Extensions. David Dorwin; Jerry Smith; Mark Watson; Adrian Bateman. W3C. 18 September 2017. W3C Recommendation. URL: https://www.w3.org/TR/encrypted-media/
HTML Standard. Anne van Kesteren; Domenic Denicola; Ian Hickson; Philip Jägenstedt; Simon Pieters. WHATWG. Living Standard. URL: https://html.spec.whatwg.org/multipage/