Audio Working Group Charter draft

Scope

The audio API provides methods to read audio samples, write audio data, create sounds, and perform client-side audio processing and synthesis with minimal latency. It also adds 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 presents new options to Web developers and designers, and has many accessibility opportunities and challenges that this working group will keep in mind.

The group has integrated the best features from two existing proposal for audio APIs: the Web Audio API, describing the WebKit implementation in Google Chrome and Apple Safari, which provides an additional higher-level graph-based API to perform common functions natively; and the MediaStream Processing API which extends HTML Streams to provide audio mixing and effects processing, which has been published as a Working Group Note.

This working group is guided by the use cases and requirements it has developed in collaboration with other groups and the wider community.

In addition to an audio processing API, this group has received feedback from the audio and music community and industry, who wish to Web-enable their MIDI-capable devices. MIDI is an electronic device interface, developed by the musical instrument industry, that includes communication protocols for two-way connection and control of a wide variety of devices, including digital musical instruments, digital audio workstations, lighting sytems, game controllers, and many other systems. The MIDI specification has wide adoption and interoperable deployment across devices and computer operating systems, and to extend this existing infrastructure, the Audio Working Group will also develop a specification to create a bridge between the browser and existing system-level MIDI APIs, to make musical instruments first-class citizens of the Web.

The scope of this working group includes:

• Developing a client-side script API for processing and synthesizing PCM audio streams, including direct scripted solutions.
• Access to audio devices, such as for microphones or other audio inputs, and multi-channel speakers or other audio outputs.
• APIs and advanced functionality regarding audio cache management and audio capability information.
• Defining a client-side script API for accessing and manipulating MIDI-capable devices available on the users' systems.

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, Sensors and Devices 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 Web Real-Time Communications Working Group to ensure interoperability of the deliverables.

Because the specifications defined by this group carry potential security, privacy, and accessibility concerns, this group will seek guidance from the appropriate groups to ensure technical review. In particular, these APIs are intended to be executed in a browser context, and access to system resources or I/O devices must be defined in a manner consistent with user awareness and control.