Hi Martijn,
On Tuesday 18 December 2007, Martijn Houtman wrote:
> Hello list,
>
> I am creating an application where I need a webcam to have a static
> exposure time per frame so it does no try to compensate the lighting
> situation and I can control the lighting myself.
>
> I am using the mjpeg-streamer application to grab images over HTTP,
> which works fine btw, very handy tool! I added a few lines in the
> input_uvc module so as to turn off auto-exposure, gain and
> whitebalance, but no combination of this seems to work.
>
> The following code:
> printf("Auto whitebalance: %d\n", v4l2SetControl(vd,
> V4L2_CID_WHITE_BALANCE_TEMPERATURE_AUTO, 0));
> printf("Auto exposure: %d\n", v4l2SetControl(vd,
> V4L2_CID_EXPOSURE_AUTO, 0));
> printf("Auto gain: %d\n", v4l2SetControl(vd, V4L2_CID_AUTOGAIN,
> 0));
>
> results in:
> contol White Balance Temperature, Auto unsupported
> Auto whitebalance: -1
I don't know why this fails. Could you try modifying auto white balance only
and check the kernel log for error messages ? You can set the trace level to
4 for additional control-related information.
> Auto exposure: 0
No problem there.
> Auto gain: -1
Auto gain is not supported by your camera, so this is expected.
>
> dmesg output:
> uvcvideo: Failed to query (1) UVC control 2 (unit 2) : -32 (exp.
> 2).
Have you tried modifying the brightness ? control 2/unit 2 is the brightness
control.
> uvc module revision 156, device id 046d:08ce,
>
> Am I missing something?
Except the fact that auto gain is not supported by the device, you haven't
missed anything obvious.
Best regards,
Laurent Pinchart
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