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<code class="CONSTANT"></code>.<br>
<br> struct v4l2_queryctrl queryctrl;<br> struct v4l2_control control;<br><br> memset (&queryctrl, 0, sizeof (queryctrl));<br> <a href="http://queryctrl.id">queryctrl.id</a> = V4L2_CID_ZOOM_ABSOLUTE;<br><br>
if (-1 == ioctl (capture_fd_, VIDIOC_QUERYCTRL, &queryctrl)) {<br> if (errno != EINVAL) {<br> perror ("VIDIOC_QUERYCTRL");<br> exit (EXIT_FAILURE);<br> } else {<br> printf ("V4L2_CID_ZOOM_ABSOLUTE is not supported\n");<br>
}<br> } else if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) {<br> printf ("V4L2_CID_ZOOM_ABSOLUTE is not supported\n");<br> } else {<br> memset (&control, 0, sizeof (control));<br> <a href="http://control.id">control.id</a> = V4L2_CID_ZOOM_ABSOLUTE;<br>
control.value = zoom_factor_;<br><br> if (-1 == ioctl (capture_fd_, VIDIOC_S_CTRL, &control)) {<br> perror ("VIDIOC_S_CTRL");<br> exit (EXIT_FAILURE);<br> }<br> }<br><br><br>
<div class="gmail_quote">On Mon, Aug 23, 2010 at 10:01 AM, Ken Tossell <span dir="ltr"><<a href="mailto:ktossell@umd.edu">ktossell@umd.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
You also might want to check out libwebcam and its command-line<br>
configuration utility, uvcdynctrl:<br>
<br>
<a href="http://www.quickcamteam.net/software/libwebcam" target="_blank">http://www.quickcamteam.net/software/libwebcam</a><br>
<br>
$ uvcdynctrl -d /dev/video0 -g 'White Balance Temperature, Auto'<br>
1<br>
$ uvcdynctrl -d /dev/video0 -s 'White Balance Temperature, Auto' 0<br>
$ uvcdynctrl -d /dev/video0 -c<br>
Listing available controls for device /dev/video0:<br>
[...]<br>
Focus (absolute)<br>
Exposure, Auto Priority<br>
Exposure (Absolute)<br>
Exposure, Auto<br>
Backlight Compensation<br>
Sharpness<br>
White Balance Temperature<br>
Power Line Frequency<br>
Gain<br>
White Balance Temperature, Auto<br>
Saturation<br>
Contrast<br>
Brightness<br>
<font color="#888888"><br>
- Ken<br>
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