Media Source Extensions Byte Stream Format Registry

W3C Editor's Draft

More details about this document
This version:
https://w3c.github.io/mse-byte-stream-format-registry/
Latest published version:
https://www.w3.org/TR/mse-byte-stream-format-registry/
Latest editor's draft:
https://w3c.github.io/mse-byte-stream-format-registry/
History:
https://www.w3.org/standards/history/mse-byte-stream-format-registry/
Commit history
Editor:
Chris Needham (British Broadcasting Corporation)
Former editors:
(W3C Invited Expert) (Until February 2024)
Jerry Smith (Microsoft Corporation) (Until September 2017)
Aaron Colwell (Google Inc.) (Until April 2015)
Feedback:
GitHub w3c/mse-byte-stream-format-registry (pull requests, new issue, open issues)
public-media-wg@w3.org with subject line [mse-byte-stream-format-registry] … message topic … (archives)

Abstract

This registry defines the byte stream formats for use with the Media Source Extensions™ specification [MEDIA-SOURCE].

This registry is non-normative.

Status of This Document

This is a preview

Do not attempt to implement this version of the specification. Do not reference this version as authoritative in any way. Instead, see https://w3c.github.io/mse-byte-stream-format-registry/ for the Editor's draft.

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 standards and drafts index.

The working group maintains a list of all bug reports that the editors have not yet tried to address; there may also be related open bugs in the GitHub repository of the Media Source Extensions™ specification.

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 a 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 that 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 18 August 2025 W3C Process Document.

1. Purpose

This registry is intended to enhance interoperability among implementations and users of SourceBuffer objects described in the Media Source Extensions™ specification. In particular, this registry provides the means (1) to identify and avoid MIME-type collisions among byte stream formats, and (2) to disclose information about byte stream formats accepted by MSE implementations to promote interoperability.

2. Organization

The registry maintains a mapping between MIME-type/subtype pairs and byte stream format specifications. The byte stream format specifications describe the structure and semantics of byte streams accepted by SourceBuffer objects created with the associated MIME-type/subtype pair.

This registry is not intended to include any information on whether a byte stream 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 byte stream format.

3. Registration Entry Requirements

To register an entry, file an issue in the Media Source Extensions Byte Stream Format Registry GitHub issue tracker so it can be discussed and evaluated for compliance before being added to the registry.

The Media Working Group may seek expertise from outside the Working Group as part of its evaluation, e.g., from the byte stream format specification editors or relevant standards group. If the byte stream format specification is not publicly available, it must be made available to the Working Group for evaluation. For the entry to be included, there needs to be interest from at least one implementer in the Working Group. If the Media Working Group reaches consensus to accept the candidate, send a pull request (either by editors or by the party requesting the candidate registration) that meets the following requirements:

  1. Each entry must include a unique MIME-type/subtype pair. If the byte stream format is derived-from an existing file format, then it should use the MIME-type/subtype pairs typically used for the file format.
  2. Each entry must include a [[generate timestamps flag]] value that must be used by SourceBuffer when handling the byte stream format.
  3. Each entry must include a link that references a publically 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).
  4. The referenced specification for each entry must comply with all requirements outlined in the Byte Stream Formats section of the Media Source Extensions™ specification [MEDIA-SOURCE].

Once consensus is reached by the Working Group, the registry editors will review and merge the pull request.

If a registration fails to satisfy a mandatory requirement specified above, then it may be removed from the registry (without prejudice). Existing entries cannot be deleted or deprecated otherwise.

Existing entries may be changed after being published through the same process as candidate entries. Possible changes include modification of the link to the publically available specification.

4. Registry

MIME type/subtype Public Specification(s) Generate Timestamps Flag
audio/webm
video/webm
WebM Byte Stream Format [MSE-BYTE-STREAM-FORMAT-WEBM] false
audio/mp4
video/mp4
ISO BMFF Byte Stream Format [MSE-BYTE-STREAM-FORMAT-ISOBMFF] false
audio/mp2t
video/mp2t
MPEG-2 TS Byte Stream Format [MSE-BYTE-STREAM-FORMAT-MP2T] false
audio/mpeg
audio/aac
MPEG Audio Byte Stream Format [MSE-BYTE-STREAM-FORMAT-MPEG-AUDIO] true

A. References

A.1 Informative references

[MEDIA-SOURCE]
Media Source Extensions™. Jean-Yves Avenard; Mark Watson. W3C. 4 November 2025. W3C Working Draft. URL: https://www.w3.org/TR/media-source-2/
[MSE-BYTE-STREAM-FORMAT-ISOBMFF]
ISO BMFF Byte Stream Format. Mark Watson. W3C. 23 July 2024. W3C Working Group Note. URL: https://www.w3.org/TR/mse-byte-stream-format-isobmff/
[MSE-BYTE-STREAM-FORMAT-MP2T]
MPEG-2 TS Byte Stream Format. Mark Watson. W3C. 23 July 2024. W3C Working Group Note. URL: https://www.w3.org/TR/mse-byte-stream-format-mp2t/
[MSE-BYTE-STREAM-FORMAT-MPEG-AUDIO]
MPEG Audio Byte Stream Format. Dale Curtis. W3C. 23 July 2024. W3C Working Group Note. URL: https://www.w3.org/TR/mse-byte-stream-format-mpeg-audio/
[MSE-BYTE-STREAM-FORMAT-WEBM]
WebM Byte Stream Format. Chris Needham. W3C. 23 July 2024. W3C Working Group Note. URL: https://www.w3.org/TR/mse-byte-stream-format-webm/