[linux-uvc-devel] uvcvideo exposure bias (V4L2_CID_AUTO_EXPOSURE_BIAS) support

[Michael B. Darling]

Hello,

I am new to the UVC Developer's mailing list and have a question about support for auto exposure bias in the uvcvideo driver. For my master's thesis, which aims to demonstrate vision-based formation flight of two small robotic aircraft, it would be very helpful if I could bias the exposure to be slightly underexposed. (I am trying to detect very high intensity LEDs affixed to the lead aircraft. An underexposed image would prevent large areas of the image from becoming saturated and allow the LEDs to better stand out.)

Does the uvcvideo driver currently support the V4L2_CID_AUTO_EXPOSURE_BIAS control, or is support of that feature specific to the model of webcam I am using? Auto-exposure bias does not appear when I query the device capabilities, but I was wondering if there might be a newer version of the driver that has not yet been added to the Ubuntu repositories.

If the feature is not currently supported, is it something that I could implement in my own build of the driver? If so, how difficult would it be if I have no previous experience with driver development?

Thanks in advance for the help. I apologize for my naivete, but my background is in aeronautical engineering. (My thesis work has taken me on quite a detour.)


--
Michael Darling
Graduate Student | Aerospace Engineering
Cal Poly, San Luis Obispo
***@calpoly.edu

[Paulo Assis]

Hi,

Post by Michael B. Darling
Hello,
I am new to the UVC Developer's mailing list and have a question about support for auto exposure bias in the uvcvideo driver. For my master's thesis, which aims to demonstrate vision-based formation flight of two small robotic aircraft, it would be very helpful if I could bias the exposure to be slightly underexposed. (I am trying to detect very high intensity LEDs affixed to the lead aircraft. An underexposed image would prevent large areas of the image from becoming saturated and allow the LEDs to better stand out.)
Does the uvcvideo driver currently support the V4L2_CID_AUTO_EXPOSURE_BIAS control, or is support of that feature specific to the model of webcam I am using? Auto-exposure bias does not appear when I query the device capabilities, but I was wondering if there might be a newer version of the driver that has not yet been added to the Ubuntu repositories.

UVC controls are always device specific, but I don't think this
control is on the standard uvc controls list (
http://www.usb.org/developers/devclass_docs/USB_Video_Class_1_5.zip ),
see section 2.3.3 - Camera Terminal. The only exposure controls
defined there are:
- Auto-Exposure Mode
- Auto-Exposure Priority
- Exposure Time

so if any camera model actually supports this (and I don't know of
any) it would have to be through an extension control.
Another possibility is to implement that feacture in your software,
just select manual exposure and control the exposure time (in the
software) accordingly to your needs.

Post by Michael B. Darling
If the feature is not currently supported, is it something that I could implement in my own build of the driver? If so, how difficult would it be if I have no previous experience with driver development?

No need to do it in the driver, like I said you can achieve this with
your software.

Post by Michael B. Darling
Thanks in advance for the help. I apologize for my naivete, but my background is in aeronautical engineering. (My thesis work has taken me on quite a detour.)

Good luck,
Paulo

Post by Michael B. Darling
--
Michael Darling
Graduate Student | Aerospace Engineering
Cal Poly, San Luis Obispo
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