Questionable spec language: "MUST attempt"

[eladalon1983]

The spec reads:

When own audio restriction is applied, the user agent MUST attempt to remove any audio from the audio being captured

The combination of "MUST" and "attempt" seems unusual. Presumably this was a conscious choice?

(Btw, since this was never implemented in any browser, maybe we should move it to the -extensions spec.)

[eladalon1983]

Another way to communicate the same intention is:

Let the document that called getDisplayMedia() be "the capturing document". When own audio restriction is applied, the user agent MUST remove from the captured audio any audio that originated from the capturing document.

• The user agent SHOULD remove this by avoiding capture of such audio to begin with.
• Barring that option, the user agent SHOULD remove this audio via processing.
• Barring these two options, the user agent MUST exclude as much audio from the capture, of which the capturing document's audio is a subset, until the capturing document's audio is completely excluded from the capture. This MUST be done even if it requires that no audio be captured at all, in which case, the user agent MUST keep the track muted until it is able to capture audio again.