Hi Halil,
On Tuesday 15 July 2008, Halil Demirezen wrote:
> Hello,
>
> I am using Logitech Quickcam pro for Notebooks as input device for my
> mastership thesis with the topict "constructing an autonomous tracker
> of a certain shape". For example red circle on white A4 paper.
>
> Anyway, I could manage to set AUTO_EXPOSURE mode to OFF by
> calling like
>
> control.id = V4L2_CID_EXPOSURE_AUTO;
> control.value = 1; // value 8 sets the auto exposure
>
> ioctl(vd->fd, VIDIOC_S_CTRL, &control);
The auto-exposure control supports the following values:
0: Manual Mode
1: Auto Mode
2: Shutter Priority Mode
3: Aperture Priority Mode
Instead of hard-coding the value, use the v4l2_exposure_auto_type enum defined
in linux/videodev2.h (Linux 2.6.26 or newer).
enum v4l2_exposure_auto_type {
V4L2_EXPOSURE_AUTO = 0,
V4L2_EXPOSURE_MANUAL = 1,
V4L2_EXPOSURE_SHUTTER_PRIORITY = 2,
V4L2_EXPOSURE_APERTURE_PRIORITY = 3
};
> and setting a certain exposure value by
>
> control.id = V4L2_CID_EXPOSURE_ABSOLUTE
> control.value = 350;
>
> ioctl(vd->fd, VIDIOC_S_CTRL, &control);
>
>
> Under dark light conditions the camera display is so dark that I
> make an extra call to ioctl to set V4L2_CID_BRIGHTNESS to a
> certain value such as
>
> control.id = V4L2_CID_BRIGHTNESS
> control.value = 90;
>
> ioctl(vd->fd, VIDIOC_S_CTRL, &control);
>
>
> These are the only ioctl manipulations done on camera, however, even though
> I set the exposure to absolute which in the past auto exposure caused
> delays in the display, and set the brightness to support bright display
> under short exposure time, i am still getting delayed stream display
> sometimes. I could not get the logic behind when it will stream slow or
> normal. Is there any control which may lead to slow streaming that i should
> set?
Best regards,
Laurent Pinchart
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