PLEASE NOTE: This draft of the charter was for review only. Please see the final charter in place at:

Audio Working Group Charter

DRAFT: for review only.

The mission of the Audio Working Group, part of the Rich Web Client Activity, is to define a client-side script API adding more advanced audio capabilities than are currently offered by audio elements. The API will support the features required by advanced interactive applications including the ability to process and synthesize audio streams directly in script.

The HTML5 specification introduces the <audio> and <video> media elements, including an API to play back prerecorded audio and video files and to get limited information about the media, such as duration. The Audio Working Group will build upon and expand that basic functionality.

Join the Audio Working Group.

End date 28 February 2013
Confidentiality Proceedings are public
Initial Chairs Alistair MacDonald (Invited Expert)
Initial Team Contacts
(FTE %: 20)
Doug Schepers, Thierry Michel
Usual Meeting Schedule Teleconferences: topic-specific calls may be held
Face-to-face: we will meet during the W3C's annual Technical Plenary week; an additional face-to-face meeting may be scheduled by consent of the participants


The audio API will provide methods to read audio samples, write audio data, create sounds, and perform client-side audio processing and synthesis with minimal latency. It will also add programmatic access to the PCM audio stream for low-level manipulation directly in script. This API can be used for interactive applications, games, 3D environments, musical applications, educational applications, and for the purposes of accessibility. It includes the ability to synchronize, visualize, or enhance sound information when used in conjunction with graphics APIs. Sound synthesis can be used to enhance user interfaces, or produce music. The addition of advanced audio capabilities to user agents will present new options to Web developers and designers, and has many accessibility opportunities and challenges that this working group will keep in mind.

Two existing experimental audio APIs are currently being developed in different browsers. The Mozilla Firefox browser provides simple read-write access to the audio stream, relying on script to perform real-time audio algorithms; the WebKit implementation in Apple Safari and Google Chrome provides an additional higher-level graph-based API, which performs some common functions in the native browser implementation. This charter does not dictate which approach the Audio Working Group will follow. In order to satisfy both approaches, the group is encouraged to define a two-layer API, with the high-level functionality as an additional layer on top of a low-level, simpler API; this may also encourage wider implementation.

This working group is a result of deliberation by the W3C Audio Incubator Group which preceded it, and will address the use cases and requirements developed by that incubator group, which are currently under final development.

The scope of this working group includes:

This working group will take into account common work-flows for sound creators, including considerations for common audio formats. This group will also liaise with other groups for direct connection to audio inputs, such as microphones.

This working group is expected to collaborate with other groups, such as the HTML Working Group, Device APIs and Policy Working Group, Web Real-Time Communications Working Group, or their successors, to define an API for accessing system devices such as microphones, speakers, and audio processors and channels. If work does not proceed elsewhere in a timely fashion, this group may define an API for audio device access.

Real-time communication is an important and related topic, so this group will work closely with the proposed Web Real-Time Communications Working Group to ensure interoperability of the deliverables.

Success Criteria

In order to advance beyond Candidate Recommendation, each specification is expected to have at least two independent implementations of each of feature defined in the specification, with preference toward at least two desktop browsers and one mobile browser.

Out of Scope

This group will not work on audio representation markup during this charter period; discussions of music notation formats will continue in the Audio Incubator Group.

The audio API is intended to operate on local and remote sources including synthesis, files, and sound-capture sources. APIs for implementing interactive audio streaming directly between users is not in scope. This group will coordinate with the other groups working in this area, such as the proposed Web Real-Time Communications WG, to discuss the interactive streaming use case and its interaction with the Audio WG APIs.

Specific functionality for speech synthesis is out of the direct scope of this group, though discussions and collaborations may occur with groups chartered to do such work, to ensure broad compatibility.


The working group will deliver at least the following:

Web Audio API
This specification defines a client-side script interface to allow web applications to read and write raw audio data, to modify audio streams, and to synthesize sound. This specification may be a single API, or a set of modular APIs with increasing levels of capability.

Other Deliverables

This group may define audio device access APIs (e.g. microphone and speaker access), in coordination with other groups working on related deliverables.

Other non-normative documents may be created such as:

  • Use case and requirement documents;
  • Test suites for each specification;
  • Primer or Best Practice documents to support web developers.


Note: The group will document significant changes from this initial schedule on the group home page.
Specification FPWD LC CR PR Rec
Web Audio API Q2 2011 Q1 2012 Q4 2011 Q1 2012 Q3 2012

Dependencies and Liaisons

W3C Groups

HTML Working Group
Ensure that the audio APIs are compatible with the relevant HTML elements
Protocols and Formats Working Group
Ensure that use cases and requirements include and meet accessibility needs
User Agent Accessibility Guidelines Working Group (UAWG)
Ensure that user agent accessibility requirements for audio features and controls are supported
Voice Browser Working Group
Coordinate on issues involving voice control and speech synthesis
Device APIs and Policy Working Group
Supply use cases, requirements, and review of specifications related to audio, including microphone access and speaker output
Web Real-Time Communications Working Group
Supply use cases, requirements, and review of specifications related to audio, including real-time communications
Web Applications Working Group
Review by the Web Applications Working Group will help guide this group. This group is likely to use the WebIDL specification, developed in the WebApps WG, to define its interfaces.

External Groups

MIDI Manufacturers Association
Coordinate on the relationship between the audio API and the Musical Instrument Digital Interface protocol
Khronos Group
Coordinate with on the relationship between the audio API and the OpenSL ES API


To be successful, the Audio Working Group is expected to have 10 or more active participants for its duration. The Chairs and specification Editors are expected to contribute one day per week towards the Working Group. There is no minimum requirement for other Participants.

The Audio Working Group will also allocate the necessary resources for building Test Suites for each specification.

The group encourages questions and comments on its public mailing lists, as described in Communication.

The group also welcomes non-Members to contribute technical submissions for consideration, with the agreement from each participant to Royalty-Free licensing of those submissions under the W3C Patent Policy.


Most Audio Working Group teleconferences will focus on discussion of particular specifications, and will be conducted on an as-needed basis.

This group primarily conducts its work on the public mailing list public-audio@w3.org (archive). The public is invited to post messages to this list.

Information about the group (deliverables, participants, teleconferences, etc.) is available from the Audio Working Group home page.

The group will use a Member-confidential mailing list for administrative purposes and, at the discretion of the Chairs and members of the group, for member-only discussions in special cases when a participant requests such a discussion.

Information about the group (for example, details about deliverables, issues, actions, status, participants) will be available from the Audio Working Group home page.

Decision Policy

As explained in the W3C Process Document (section 3.3), this group will seek to make decisions when there is consensus and with due process. The expectation is that typically, an editor or other participant makes an initial proposal, which is then refined in discussion with members of the group and other reviewers, and consensus emerges with little formal voting being required. However, if a decision is necessary for timely progress, but consensus is not achieved after careful consideration of the range of views presented, the Chairs should put a question out for voting within the group (allowing for remote asynchronous participation -- using, for example, email and/or web-based survey techniques) and record a decision, along with any objections. The matter should then be considered resolved unless and until new information becomes available.

This charter is written in accordance with Section 3.4, Votes of the W3C Process Document and includes no voting procedures beyond what the Process Document requires.

Patent Policy

This Working Group operates under the W3C Patent Policy (5 February 2004 Version). To promote the widest adoption of Web standards, W3C seeks to issue Recommendations that can be implemented, according to this policy, on a Royalty-Free basis.

For more information about disclosure obligations for this group, please see the W3C Patent Policy Implementation.

About this Charter

This charter for the Audio Working Group has been created according to section 6.2 of the Process Document. In the event of a conflict between this document or the provisions of any charter and the W3C Process, the W3C Process shall take precedence.

Doug Schepers

$Date: 2011/03/26 17:26:57 $