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  1. #1
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    Nov 2011
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    How to properly put camera on stand-by?

    Hi,

    I want to put the camera on stand-by every time when the viewfinder page is inactive.
    But I've noticed that after I call QCamera::stop() and check that it's really stopped with QCamera::status(), my application still consumes energy as if my camera were in active state (~70 mA current).

    Should I do something else besides stopping the camera to avoid battery draining?

    Thanks!

  2. #2
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    Re: How to properly put camera on stand-by?

    QCameraviewfinder does not have any status indicator to react to inactive state. what exactly is the usecase, i mean when do you think that the viewfinder is inactive? sorry i didnt understand your query.

  3. #3
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    Re: How to properly put camera on stand-by?

    No, I meant not the viewfinder itself but the QML page that contains the viewfinder.
    This I easily identify with Page::onStatusChanged event, so this is not actually the problem.

    The question is, how can I force QCamera to consume less energy when it's not needed?
    QCamera::stop() appears insufficient for that.

  4. #4
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    Re: How to properly put camera on stand-by?

    Ok, got it now. But i am not sure of this can be acheived with some QT api. Need to check if backend code handles this case (gstreamer-camera? and how open is that)

    From the documentation -

    QCamera::StandbyStatus 4 The camera is in the power saving standby mode. The camera may come to the standby mode after some time of inactivity in the QCamera::LoadedState state.

    When stop is called it goes to the Loaded state, and standby happens only after sometime of inactivity.

  5. #5
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    Re: How to properly put camera on stand-by?

    OK, then the second question:

    If the camera had been in QCameraFocus::ContinuousFocus mode before it was stopped, does it stop autofocusing in LoadedState? Or should I change the focusing mode to QCameraFocus::ManualFocus before calling stop() to save energy?

  6. #6
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    Jul 2008
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    90

    Re: How to properly put camera on stand-by?

    (I wonder how you would do that... to me, isFocusModeSupported(QCameraFocus::ManualFocus) returns false. )

  7. #7
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    Jan 2012
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    9

    Re: How to properly put camera on stand-by?

    Hi,

    I am suffering a very similar problem with both the N8 and 808. After locking focus and taking a picture, I call QCamera::stop(), after ~40 seconds the camera enters standby mode. At some point in the future, I call QCamera::start() and try to lock focus to take another picture. The camera sits there trying to focus but never achieving it...so I can never take a second picture.

    This was back in March...I put a thread up in the mobility section, and opened a bug with qt. Neither gave a solution :S

    Edit: Here is a link...

    http://www.developer.nokia.com/Commu...-after-standby

  8. #8
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    Nov 2011
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    48

    Re: How to properly put camera on stand-by?

    FYI, if it helps, with my initial question I finished up calling QCamera::unload() instead of stop() because it turned out that (a) the second allocation of resources happens much faster than the initial one and in reasonable time, and (b) it gives user an opportunity to launch another camera-aware application while mine is in background.

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