Re: [mediacapture-main] Update getusermedia.html (#651)

> The `device.kind` of the `"Monitor of Built-in Audio Analog Stereo"` device here in Firefox is `"audioinput"`—a virtual audio input that Firefox (or the underlying Linux OS) has chosen to expose as a **_source_**.
> The spec allows us to do this, saying _"User Agents MAY allow users to use any media source, including pre-recorded media files."_

> This supports having devices that are only sinks, only sources, and both. Makes sense?

The source in that case is audio output to headphones or speakers, correct?

Your attempt to clarify the capabilities described in the specification does provide clarity to some extent.

The point of this PR and linked issue is to make it unambiguously clear that it is possible to capture audio output, as a "source", to speakers or headphones using the methods defined in this specification, that is, precisely under which cases a "sink" becomes a "source", with accompanying canonical code example to do so added to the specification - or, make it clear that is not possible per this specification, so that users who have that requirement can abandon all hope of achieving that requirement using `enumerateDevices()` and `getUserMedia()`. That requirement is possible given certain prerequisites, e.g., certain *nix OS's and Firefox. If clearly specified, should be possible by default at all implementations of the specification, so that implementers are not able to state "the specification does not provide for that functionality" or like statement when the use case and spec are referenced. Currently, there appears to be room for different interpretations of whether it is specified or not if and when a "sink" _can_ become a source, per this specification.

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Received on Thursday, 12 December 2019 22:07:12 UTC