Here is some sample code that I use to set the "Zoom, Absolute" control in
v4l2. You could replace V4L2_CID_ZOOM_ABSOLUTE with
V4L2_CID_AUTO_WHITE_BALANCE to enable/disable auto white-balance.
struct v4l2_queryctrl queryctrl;
struct v4l2_control control;
memset (&queryctrl, 0, sizeof (queryctrl));
queryctrl.id = V4L2_CID_ZOOM_ABSOLUTE;
if (-1 == ioctl (capture_fd_, VIDIOC_QUERYCTRL, &queryctrl)) {
if (errno != EINVAL) {
perror ("VIDIOC_QUERYCTRL");
exit (EXIT_FAILURE);
} else {
printf ("V4L2_CID_ZOOM_ABSOLUTE is not supported\n");
}
} else if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) {
printf ("V4L2_CID_ZOOM_ABSOLUTE is not supported\n");
} else {
memset (&control, 0, sizeof (control));
control.id = V4L2_CID_ZOOM_ABSOLUTE;
control.value = zoom_factor_;
if (-1 == ioctl (capture_fd_, VIDIOC_S_CTRL, &control)) {
perror ("VIDIOC_S_CTRL");
exit (EXIT_FAILURE);
}
}
On Mon, Aug 23, 2010 at 10:01 AM, Ken Tossell <
ktossell@umd.edu> wrote:
> You also might want to check out libwebcam and its command-line
> configuration utility, uvcdynctrl:
>
> http://www.quickcamteam.net/software/libwebcam
>
> $ uvcdynctrl -d /dev/video0 -g 'White Balance Temperature, Auto'
> 1
> $ uvcdynctrl -d /dev/video0 -s 'White Balance Temperature, Auto' 0
> $ uvcdynctrl -d /dev/video0 -c
> Listing available controls for device /dev/video0:
> [...]
> Focus (absolute)
> Exposure, Auto Priority
> Exposure (Absolute)
> Exposure, Auto
> Backlight Compensation
> Sharpness
> White Balance Temperature
> Power Line Frequency
> Gain
> White Balance Temperature, Auto
> Saturation
> Contrast
> Brightness
>
> - Ken
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>
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