问题
This question is very similar to V4L2 absolute exposure setting has (almost) not effect
I have a UVC
compliant camera that I am running on a Raspberry Pi CM3+
module. It appears as video0
.
Using the tools/drivers v4l2-ctl
, qv4l2
or guvcview
the absolute exposure
cannot be controlled, yet it can be controlled when using Amcap
on Windows 10.
The camera has two exposure modes manual
and aperature controlled
. When in aperature controlled
the exposure levels in the image change dynamically, however, when switched to manual
mode the image becomes very dark and does not change whether at the upper or lower limit of the range which can be selected.
When running v4l2-ctl
the range min
is stated to be 5
and the max
is 2500
. Yet in windows it is between -2
and -11
and the exposure of the image changes proportionally as you would expect.
Parameter range from v4l2
:
exposure_auto 0x009a0901 (menu) : min=0 max=3 default=3 value=1
exposure_absolute 0x009a0902 (int) : min=5 max=2500 step=1 default=156 value=1659
Parameter range from Amcap
on Windows 10:
If I do v4l2-ctl -d0 -all
here is what I get:
pi@raspberrypi:~ $ v4l2-ctl -d0 --all
Driver Info:
Driver name : uvcvideo
Card type : HD USB CAMERA: HD USB CAMERA
Bus info : usb-0000:01:00.0-1.3
Driver version : 5.4.79
Capabilities : 0x84a00001
Video Capture
Metadata Capture
Streaming
Extended Pix Format
Device Capabilities
Device Caps : 0x04200001
Video Capture
Streaming
Extended Pix Format
Media Driver Info:
Driver name : uvcvideo
Model : HD USB CAMERA: HD USB CAMERA
Serial : 01.00.00
Bus info : usb-0000:01:00.0-1.3
Media version : 5.4.79
Hardware revision: 0x00000224 (548)
Driver version : 5.4.79
Interface Info:
ID : 0x03000002
Type : V4L Video
Entity Info:
ID : 0x00000001 (1)
Name : HD USB CAMERA: HD USB CAMERA
Function : V4L2 I/O
Flags : default
Pad 0x01000007 : 0: Sink
Link 0x02000013: from remote pad 0x100000a of entity 'Extension 4': Data, Enabled, Immutable
Priority: 2
Video input : 0 (Camera 1: ok)
Format Video Capture:
Width/Height : 640/480
Pixel Format : 'YUYV' (YUYV 4:2:2)
Field : None
Bytes per Line : 1280
Size Image : 614400
Colorspace : sRGB
Transfer Function : Default (maps to sRGB)
YCbCr/HSV Encoding: Default (maps to ITU-R 601)
Quantization : Default (maps to Limited Range)
Flags :
Crop Capability Video Capture:
Bounds : Left 0, Top 0, Width 640, Height 480
Default : Left 0, Top 0, Width 640, Height 480
Pixel Aspect: 1/1
Selection: crop_default, Left 0, Top 0, Width 640, Height 480, Flags:
Selection: crop_bounds, Left 0, Top 0, Width 640, Height 480, Flags:
Streaming Parameters Video Capture:
Capabilities : timeperframe
Frames per second: 30.000 (30/1)
Read buffers : 0
brightness 0x00980900 (int) : min=-64 max=64 step=1 default=0 value=-6
contrast 0x00980901 (int) : min=0 max=95 step=1 default=1 value=6
saturation 0x00980902 (int) : min=0 max=100 step=1 default=52 value=22
hue 0x00980903 (int) : min=-2000 max=2000 step=1 default=0 value=0
white_balance_temperature_auto 0x0098090c (bool) : default=1 value=0
gamma 0x00980910 (int) : min=100 max=300 step=1 default=115 value=115
power_line_frequency 0x00980918 (menu) : min=0 max=2 default=1 value=1
white_balance_temperature 0x0098091a (int) : min=2800 max=6500 step=1 default=4600 value=4600
sharpness 0x0098091b (int) : min=0 max=7 step=1 default=0 value=0
backlight_compensation 0x0098091c (int) : min=36 max=160 step=1 default=54 value=36
exposure_auto 0x009a0901 (menu) : min=0 max=3 default=3 value=1
exposure_absolute 0x009a0902 (int) : min=5 max=2500 step=1 default=156 value=1659
error 22 getting ext_ctrl Pan (Absolute)
error 22 getting ext_ctrl Tilt (Absolute)
focus_absolute 0x009a090a (int) : min=0 max=1023 step=1 default=0 value=355
focus_auto 0x009a090c (bool) : default=1 value=0
error 22 getting ext_ctrl Zoom, Absolute
I have tried changing the format between MJPEG
and YUYV
without any change.
I am assuming that it a driver issue or some setting that I am overlooking?
回答1:
Amcap (Windows) in my case has 5 discrete exposure levels [-6,-5,-4,-3,-2]
.
Linux (guvcview
and v4l2
) has a continuous range from [5 to 2500]
(as can be seen in the OP using v4l2-ctl
.
I have manually set the exposure levels in Amcap and then read them using Linux (guvcview
):
[-6 = 156; -5 = 312; -4 = 625; -3 = 1250; -2 = 2500]
When I set the exposure
to any of these levels it works as expected. HOWEVER if I set any other values, for example, 2499 or 157, just one digit off I get nearly complete black!
I am sure there is some mathematical reason that will show this, however, I have found this misleading since the Linux drivers report a continuous range which suggests that the exposure range is linear, but it is not and is discrete!
来源:https://stackoverflow.com/questions/65595380/v4l2-manual-exposure-not-working-compared-to-windows-10