Re: Video preview proposal: grabPreview

On 10/26/2014 03:59 PM, Martin Thomson wrote:
> I've added a couple of editorial pull requests to the media-capture spec:
> One is not editorial, it's a new proposal:
> >From the PR:
> This adds a new method to MediaDeviceInfo called grabPreview. It
> provides applications with a way of acquiring a preview image for a
> video input device.
> I didn't add the ability to acquire a preview stream, because that is
> totally creepy.

Hmm.... I don't quite get this.

Either you get to capture output from the device, or you don't.

If you don't, and want to, you should ask permission first.
If you get to capture it, you can open it in a getusermedia call.

I don't see the scenario where this is valuable enough to include.


- We're trying to stabilize the spec. This is a new feature.
- It introduces a normative dependency on imagecapture, which still has
some time to go.

One thing that it does as a side effect is to change the type of API of
MediaDeviceInfo from "dictionary" to "interface". If we make this
change, it becomes simple to add that type of functionality in the
future - but at the price of not being able to assure people that "this
is a dictionary".

I'd like comment on that particular aspect.

>  This does risk creeping people out in a similar
> fashion, so I've suggested that access be limited. I think that the
> measures I have described are adequate, particularly because they
> offer the UA quite a bit of flexibility in how often lights come on.
> However, if we can't convince ourselves that they are, then this
> probably isn't a great idea to pursue.
> What I haven't done here is provide information on the aspect ratio of
> the preview image, which will be necessary for the application to
> successfully draw this without distorting it. I'll add that in a
> subsequent commit if this idea sounds appealing.

The idea does not sound appealing to me, but YMMV.


Surveillance is pervasive. Go Dark.

Received on Monday, 27 October 2014 14:27:30 UTC