Re: [mediacapture-screen-share] Provide a means to select only part of a screen to capture (#105)

@youennf Crop constraints at `getDisplayMedia()` call makes sense from perspective here. Yes, similar to the linked document, though, again the requirement for this user is to capture video from an `HTMLVideoElement`, which is essentially the output of the browsers' respective Web Media Player implementation; described in more detail at,,, and `HTMLMediaElement.captureStream()` and `MediaRecorder` currently do not provide a means to capture multiple video media sources when the `<video>` `src` attribute is changed. `replaceTrack()` and `getDisplayMedia()` is the closest have arrived at meeting the requirement at both Chromium and Firefox. Chromium crashes the tab when `MediaSource` is captured using `captureStream()`; `canvas.captureStream()` with `AudioContext.createMediaStreamDestination()` has noticeable lack of quality ("pixelation") at closing image frames; `replaceTrack()` mutes a minimal though noticeable portion of the last 1 second of audio; `getDisplayMedia()` has the issue of having to perform _two_ user gestures _and_ use CSS to remove portions of the screen other than the `<video>`; and other bugs found during the process of trying to compose code for both Chromium and Firefox; still not sure why `MediaRecorder` is specified to stop recording if a `MediaStreamTrack` is added or removed from the `MediaStream`.

If the `<video>` element could be listed as a "device", e.g., `"videoouput"` at `enumerateDevices()`; or `<video>` could be selected as an _application_ or `window`, or `MediaRecorder` could be modified to not be specified to stop recording when the underlying media resource of a `<video>` is changed at `src` attribute, then that might lead to resolution of the requirement. 

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Received on Monday, 29 April 2019 22:02:22 UTC