[whatwg] Microphone Device API

[Harald Alvestrand]

On 02/17/11 10:30, Jörn Zaefferer wrote:
> Hi,
>
> here at SoundCloud we're interested in an API for recording in the browser
> ( http://blog.soundcloud.com/2010/12/01/record/ ), without Flash and even on
> mobile browsers. The get things moving with the current idea of a device API
> (
> http://www.whatwg.org/specs/web-apps/current-work/multipage/commands.html#devices),
> we put together some draft example markup and JavaScript, based on the
> current proposal and with an alternative approach that could be easier to
> use, based on the style of the geolocation API.
>
> We hope to get a discussion started based on this, while learning how to
> actually get involved in the standards process, and would be happy to help
> with more formal documentation or more example, whatever will help at this
> stage.
I'm interested in seeing how we develop the API for devices; my use case 
is quite different (real time communications), but we do have some of 
the same requirements:

- Let users control access to microphone (whether my app can reach it or 
not)
- Let users turn off and on their microphone

I would very much want to avoid having the "record to file/buffer" be a 
fundamental part of the microphone abstraction, since it's irrelevant to 
my application (if anything should be recorded, it's the conversation, 
not the output from the microphone), so I think we should try to find a 
model where a microphone is an object that provides a data stream, and 
that data stream can be connected to a different object that acts as a 
recorder; if I don't need recording, I should not have to instantiate a 
recorder.

                Harald, RTC-Web activist
> Jörn
>
> The draft:
>
> // Record the microphone input and upload it to the server
> // based on the curent state of device element draft
> //
> http://www.whatwg.org/specs/web-apps/current-work/multipage/commands.html#devices
> // like on http://soundcloud.com/upload (you need to be logged to use
> recording)
> // and more info: http://blog.soundcloud.com/2010/12/01/record/
> // with a short implementation proposal
>
> // show/hide record button depending on the current state
> <button id="start-recording">Record!</button>
> <button id="stop-recording">Stop Recording</button>
>
> // how would we initialize the device in JS?
> // new Device like new Audio? or createElement like with 'video' tag?
> var microphone = document.createElement('device');
>
> // 'media' is quite ambigous, what would it choose - webcam? microphone?
> microphone.type = 'microphone';
>
> var audio = new Audio(),
>      buttonRecord = document.getElementById("start-recording"),
>      buttonStop = document.getElementById("stop-recording"),
>      recorder;
>
> microphone.addEventListener('change', function(stream){
>    // optional: output current input
>    audio.src = stream.url;
>
>    buttonRecord.addEventListener("click", function(event) {
>      recorder = stream.record();
>    }, false);
>
>    buttonStop.addEventListener("click", function(event) {
>      var file = recorder.stop();
>      upload(file);
>    }, false);
>
> }, false);
>
> // alternative version, modelled after geolocation api
>
> function success(stream){
>    // optional: output current input
>    audio.src = stream.url;
>    recorder = stream.record();
> }
>
> function error(e){
>    alert(e.message);
> }
>
> buttonRecord.addEventListener("click", function(event) {
>    microphone.openStream(success, error);
> }, false);
>
> buttonStop.addEventListener("click", function(event) {
>    var file = recorder.stop();
>    upload(file);
> }, false);
>