W3C home > Mailing lists > Public > public-device-apis@w3.org > September 2010

Re: The Media Capture API FPWD

From: Philip Gladstone <pgladstone@cisco.com>
Date: Tue, 21 Sep 2010 13:15:42 -0400
Message-ID: <4C98E83E.10404@cisco.com>
To: Ilkka Oksanen <Ilkka.Oksanen@nokia.com>
CC: ext Dominique Hazael-Massieux <dom@w3.org>, ext Bryan Sullivan <blsaws@gmail.com>, W3C DAP <public-device-apis@w3.org>

On 21-Sep-10 10:27, Ilkka Oksanen wrote:
> 21/09/2010 16:00, ext Dominique Hazael-Massieux kirjoitti:
>> That doesn't seem like a proper outcome — dismissing user’s data 
>> shouldn’t be something we encourage in general. Imagine that the
>> user has been spending a lot of time to get the perfect picture, only
>> to get it randomly trashed by the original invokator.
>> I think once the external app is up and running, canceling a pending 
>> operation should have no direct effect on the external app. It might
>> be OK to cancel the invokation of the callbacks.
> Right. That was the most straightforward approach I could think of. I
> don't see cancel() very useful if it doesn't have any effect on external
> app or callbacks. In such case PendingOp could even be removed from the
> Capture API.
> Deleting the files is probably overkill but I still think that
> cancel() should give the control back to the script. If cancel() is
> included it should in minimum save the possible unfinished recordings,
> close the camera app, and call success callback if there are any files.
> The user is recording content for the app and if the app decides that it
> wants to stop the operation using cancel() and potentially will not
> process the result at all then there is not much point for allowing the
> user to continue?

I think that the files have to be deleted as there is no way for the
webapp to find them in the absence of a success callback (which is the
step that provides the URI). You might argue that there should be a
success callback after each image (or video clip) is recorded, and I
would certainly support that model.

You might ask what the difference between capturing 30 images and
generating 30 success callbacks as one operation, or doing 30 operations
of capture 1 image with 1 success callback each. I think that many of
these camera capture apps will have some sort of startup overhead
(including possibly resetting any preferences, possibly getting user
consent, choosing the camera to use [front or back]) that will make the
second approach less than desirable.


Philip Gladstone
Distinguished Engineer
Product Development
Phone: +1 978-ZEN-TOAD (+1 978 936 8623)
Google: +1 978 800 1010
Ham radio: N1DQ
Blog: http://wwwin-blogs.cisco.com/pgladsto/

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Received on Tuesday, 21 September 2010 17:16:20 UTC

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