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

From: Jan-Ivar Bruaroey via GitHub <sysbot+gh@w3.org>
Date: Mon, 16 Dec 2019 21:46:20 +0000
To: public-webrtc-logs@w3.org
Message-ID: <issue_comment.created-566258416-1576532778-sysbot+gh@w3.org>
> The source in that case is audio output to headphones or speakers, correct?

"That case" being the special "Monitor" audio input device in Firefox on Linux? Sure.

However, this is achieved at the OS/device driver level—Specs generally can't, nor should they, attempt to restrict what an OS or user agent can provide as audio input in the form of virtual devices.

Importantly, the existence of such a device, in no way changes the fact that no general mechanism for capturing system audio output exists in this spec.

> The point ... 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",

I think the spec is clear: "Sinks" never become "sources" in this model. They're entirely separate devices from the viewpoint of this API. Any real-world connection between browser-provided devices in this API exists outside of this spec. E.g. there's no constraint or property for this.¹

> make it clear that is not possible per this specification, so that users who have that requirement can abandon all hope

This spec is written with extension specs in mind, so it rarely rules things out, only in. As such, if something isn't mentioned in this spec, it isn't covered by this spec.

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<sub>1. The only relationship between exposed "devices" in this spec is [`groupId`](https://w3c.github.io/mediacapture-main/getusermedia.html#def-mediadeviceinfo-groupId), but I would even hesitate using that here. That's because its stated use case is the headset (with mic and speakers). I.e. the assumption is users might want to use these together. I don't think the same holds for a speaker and the monitor of said speaker, because using them together would feedback.</sub>

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Received on Monday, 16 December 2019 21:46:22 UTC

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