In doing some digging, it also appears that the settings that I am
interested in are also being cached by the driver, so I am not really
getting the right values.
I suspect that for UVC_CT_EXPOSURE_TIME_ABSOLUTE_CONTROL,
UVC_PU_GAIN_CONTROL (at least), I want the UVC_CTRL_FLAG_AUTO_UPDATE
set. This won't (I doubt) improve the exposure of the image, but it will
improve the reporting.
The output from v4l-ctl -l is
brightness (int) : min=0 max=255 step=1 default=128
value=128
contrast (int) : min=0 max=255 step=1 default=32
value=32
saturation (int) : min=0 max=255 step=1 default=32
value=32
white_balance_temperature_auto (bool) : default=1 value=1
gain (int) : min=0 max=255 step=1 default=64
value=64
power_line_frequency (menu) : min=0 max=2 default=2 value=2
white_balance_temperature (int) : min=2800 max=6500 step=1 default=4000
value=4000
sharpness (int) : min=0 max=255 step=1 default=72
value=72
backlight_compensation (int) : min=0 max=1 step=1 default=0 value=0
exposure_auto (menu) : min=0 max=3 default=3 value=3
exposure_absolute (int) : min=3 max=2047 step=1 default=166
value=166
exposure_auto_priority (bool) : default=0 value=1
pan_absolute (int) : min=-36000 max=36000 step=3600
default=0 value=0
tilt_absolute (int) : min=-36000 max=36000 step=3600
default=0 value=0
focus_absolute (int) : min=0 max=255 step=17 default=68
value=68
focus_auto (bool) : default=1 value=1
zoom_absolute (int) : min=1 max=5 step=1 default=1 value=1
Philip
On 12-Aug-11 12:35 AM, Carl Michal wrote:
Hi Philip,
Laurent can correct me if I've got this wrong - but in the latest uvc
driver there are some changes in how the exposure settings are
reported. Before the driver would report settings that the camera
wouldn't support. That is now fixed, but unfortunately the way it
works now seems to confuse a lot of software. Both guvcview and
luvcview are confused by the new driver as well and won't let you
properly turn on or off the auto exposure as well.
In luvcview the fix is trivial, and apparently guvcview has been fixed
upstream. There is some disscussion of this in the list archives a
few weeks ago.
Carl
On Thu, 11 Aug 2011, Philip Gladstone wrote:
I'm running the latest UVC driver and I find that the auto-exposure
doesn't work when I use the UVC driver on linux. The controls (as
reported by fswebcam) are:
Available Controls Current Value Range
------------------ ------------- -----
Brightness 128 (50%) 0 - 255
Contrast 32 (12%) 0 - 255
Saturation 32 (12%) 0 - 255
White Balance Temperature, Auto True True | False
Gain 64 (25%) 0 - 255
Power Line Frequency 60 Hz Disabled | 50 Hz | 60 Hz
White Balance Temperature 4000 (32%) 2800 - 6500
Sharpness 72 (28%) 0 - 255
Backlight Compensation 0 0 - 1
Exposure, Auto Aperture Priority Mode Manual Mode |
Aperture Priority Mode
Exposure (Absolute) 166 (7%) 3 - 2047
Exposure, Auto Priority True True | False
Pan (Absolute) 0 (50%) -36000 - 36000
Tilt (Absolute) 0 (50%) -36000 - 36000
Focus (absolute) 68 (26%) 0 - 255
Focus, Auto True True | False
Zoom, Absolute 1 1 - 5
I'm grabbing images in MJPG format and I wonder if that fact is
confusing the camera. Under windows you can watch it adjust exposure
and gain until the image looks good (when in auto mode).
The values above appear to be the default values after a power cycle
of the camera (plug and unplug the USB).
Does anyone have any idea what is going on? I'd rather not have to
put the camera in the manual exposure mode and then control it in
software.....
Philip
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