HTML5 Audio is a subject of the HTML5 draft specification, investigating audio input, playback, synthesis, as well as speech to text in the browser.

<Audio> element format support [edit]

This table documents the current support for audio codecs by the <audio> element.

The adoption of HTML5 audio, as with HTML5 video, has become polarized between proponents of free and patented formats. In 2007, the recommendation to use Vorbis was retracted from the specification by the W3C together with that to use Ogg Theora, citing the lack of a format accepted by all the major browser vendors.

Apple and Microsoft, which between them account for around 39% of the browser market, support the ISO/IEC-defined formats AAC and the older MP3. They cited superior performance,^[ambiguous] and the risk of a submarine patent attack from formats which are believed, but not guaranteed, to be “free”.

Mozilla and Opera, controlling 24% of the market, support the free and open, royalty-free Vorbis codec in Ogg and WebM containers, and criticize the patent-encumbered nature of MP3 and AAC, which are guaranteed to be “non-free”.

Google, controlling 27% of the market, has so far provided support for all common formats.

The result is that for a website to guarantee HTML5 audio for all the above browsers, it has to make two formats available: Vorbis, and either MP3 or AAC.

Gecko-based applications and Safari also support PCM audio in a WAVE container.

In 2012, the free and open royalty-free Opus format was released and standartized by IETF. It is supported by Mozilla’s software since Gecko version 15.

Web Audio APIs [edit]

The Web Audio API specification developed by Google describes a high-level JavaScript API for processing and synthesizing audio in web applications. The primary paradigm is of an audio routing graph, where a number of AudioNode objects are connected together to define the overall audio rendering. The actual processing will primarily take place in the underlying implementation (typically optimized Assembly / C / C++ code), but direct JavaScript processing and synthesis is also supported. Google's Chrome browser implements this API since version 14, released in 2011.

Mozilla's Firefox browser implements a similar Audio Data API extension since version 4, implemented in 2010 and released in 2011, but Mozilla warns it is non-standard and deprecated. Some JavaScript audio processing and synthesis libraries such as Audiolet support both APIs.

The W3C Audio Working Group is also considering the MediaStream Processing API specification developed by Mozilla. In addition to audio mixing and processing, it covers more general media streaming, including synchronization with HTML elements, capture of audio and video streams, and peer-to-peer routing of such media streams.

Speech API [edit]

The Speech API aims to provide an alternative input method for web applications (without using a keyboard). With this API, developers can give web apps the ability to transcribe your voice to text, from your computer's microphone. The recorded audio is sent to speech servers for transcription, after which the text is typed out for you. The API itself is agnostic of the underlying speech recognition implementation and can support both server based as well as embedded recognizers. The HTML Speech Incubator group has proposed the implementation of audio-speech technology in browsers in the form of uniform, cross-platform APIs. The API contains both:

• Speech Input API
• Text to Speech API

Google integrated this feature into Google Chrome on March 2011. Letting its users search the web with their voice with code like:

<script type="application/javascript">
    function startSearch(event) {
        event.target.form.submit();
    }
</script>
<form action="http://www.google.com/search">
  <input type="search" name="q" speech required onspeechchange="startSearch">
</form>

See also [edit]

• Use of Ogg formats in HTML5
• HTML5 in mobile devices

References [edit]

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