Author: Jakub Wlodek
Corresponding Author: Kazimierz Gofron
Created: July 19, 2018
Last Updated: January 18, 2019
Copyright (c): 2018-2019 Brookhaven National Laboratory

Release versions of this driver are available on Github. Release notes are available on https://jwlodek.github.io/ADUVC. Please report any problems or feature requests on the issues page on https://github.com/epicsNSLS2-areaDetector/ADUVC.

Note - ADUVC has only been tested on linux-x86_64

Prior to installing the ADUVC area detector driver, there are several dependencies that must be met. First, libusb, libjpeg, and cmake and their development packages must be installed. On a debian based linux machine, this can be done with the following command:

sudo apt install libusb-dev libusub-1.0-0-dev libjpeg-dev cmake

If you wish to use the libjpeg version included with ADSupport, it is important to specifiy that during the build of libuvc, because otherwise there will be a conflict when building ADUVC. The simplest solution is to set JPEG_EXTERNAL=YES in the CONFIG_SITE.local file in the configure directory at the top level of areaDetector.

After libusb and the other dependencies have been installed, libuvc, the library for connecting to USB Video Class (UVC) devices must be installed. The easiest way to do this is to enter the adUVCSupport directory, and run the installlibuvc.sh script:

./installlibuvc.sh

This script will start by cloning the github repository for the libuvc library, and then build it with cmake. The resulting library and include files are then placed in the appropriate locations in the epics build path, as well as in the /usr/local directory, so that libuvc can be accessed in the other support functions. Once libuvc is installed, and epics-base, epics-modules, ADCore, and ADSupport have all been built as well, enter the top ADUVC directory, and simply run:

make

The driver is now installed.

Libuvc can also be built from source at: https://github.com/libuvc/libuvc.git
Documentation for the library can be found at: https://int80k.com/libuvc/doc/

Once the driver is installed, the UVC camera must be set up. There are some important things to keep in mind when using ADUVC:

• Every UVC camera has either a serial number or a product ID. Either can be used to connect to the camera
  • The UVC serial number is locked behind root privelages. Connecting with it will require running the IOC as root or with sudo access
  • The product ID will allow ioc connection without root privelages. (Note not all cameras have a product ID)
• ADUVC requires sole access to the camera. I.E. each camera can only run one IOC and cannot be connected to any external software
• UVC cameras generally don't have many acquisition modes, Usually sticking to 8-bit RGB in the form of MJPEG streams. The ADUVC driver also has support for Uncompressed formats and also YUYV, Grayscale, and RGB color modes in 8 or 16 bit. If an illegal combination of color mode, data type, and/or image size is selected that is not supported by the camera, acquisition will fail to start.

To begin the ADUVC setup process, there are two included helper .cpp programs included in the adUVCSupport directory: cameraDetector, and imageCaptureTest. The first of these two, will use libuvc to detect all UVC cameras connected to the system, while the second will use OpenCV highgui with libuvc to test image acquisition. It is recommended to run both programs prior to using the ADUVC driver to make sure that the camera is detected correctly.

The cameraDetector program lists device information for each of the UVC cameras connected to the system, including their serial number and/or product number if they exist. One of these two values is necessary to connect to the camera. Note that the serial number is actually passed as a const char* to the IOC, so should be placed in quotation marks, while the product number is an integer. More information on running the cameraDetector program can be found in the README file in the appropriate directory.

Once a serial number or a product number has been discovered using the Camera Detector program, you may want to test image acquisition. Installation and run instructions are found in the appropriate README file. Make sure to compile and run as root as required. You should see 200 frames captured by the camera displayed in an OpenCV highgui window.

To set up the ADUVC ioc, you will need either the device product ID or the serial number. In the st.cmd file in the iocs/adUVCIOC/iocBoot/iocADUVC directory, locate the ADUVCConfig function call. There are two options for this function, one where the serial number is passed and product ID is set 0, and one where the productID is passed and the serial number is an empty string "". Simply uncomment the way you wish to connect to the device, and place the serial or productID in the appropriate parameter spot. From here the driver IOC is ready to be started with:

sudo ./startEPICS.sh

Note that running as sudo is not required if connecting via product ID.

Further documentation, including CSS screenshots and usage information, is available at the driver's website.

Most UVC cameras are cheap and easy to set up, making them perfect for a variety of use cases including:

• Plugin testing and development -> easy to set up, making them great test benches.
• Monitoring -> Cheap and small, so can be used as a monitoring device, especially paired up with small devices like Raspberry Pis, or Arduinos.
• Use in small confined areas -> UVC cameras are available in many configurations including tiny pencil cameras that can be used to view confined areas.

There are also several more traditional industrial cameras that use the UVC standard:

• https://www.theimagingsource.com/products/industrial-cameras/usb-3.0-color/
• https://www.e-consystems.com/8MP-AF-UVC-USB-Camera.asp
• https://www.framos.com/en/news/videology-introduces-super-speed-uvc-compliant-compact-usb-3.0-board-camera
• https://www.vision-systems.com/articles/2013/04/usb-30-cameras-are-uvc-compliant.html
• https://www.theimagingsource.com/products/industrial-cameras/usb-3.0-monochrome/

• When building libuvc, the system level jpeg library is used in cmake, but once ADSupport is compiled, a different version is used. This causes an error when converting mjpeg to rgb. The solution is to either compile libuvc with the jpeg lib in ADSupport, or to set JPEG_EXTERNAL = YES in the CONFIG_SITE.local file in the top level AD configuration directory.
• Certain cameras only support one framerate per frame size, so setting the framerate PV may not affect the actual image rate
• Most cameras have a limited selection of fixed acquisition modes (certain framerates with certain sizes). Use the cameraDetector helper program to identify these modes.
• In cheaper cameras framerate drops when there is lots of motion. This is due to image processing on the camera itself, not due to the driver.
• First frame in mjpeg stream can be corrupted, causing a UVC Error, however, the driver continues and each subsequent frame is uncorrupted.
• If using ADUVC with Virtualbox, you need to passthrough the hold of the camera to the guest OS. Instructions for doing so can be found on this website: https://scribles.net/using-webcam-in-virtualbox-guest-os-on-windows-host/

• The USB camera device is typically owned by root, which prevents EPICS IOC from running as softioc user, and automatic startup using procServer. To grant access to USB camera device by other users, such as softioc, we wrote udev rules.

kgofron@xf17bm-ioc2:/etc/udev/rules.d$ more usb-cams.rules
# cam1 f007
SUBSYSTEM=="usb", ATTRS{idVendor}=="f007", OWNER="softioc", GROUP="softioc", MODE="0666", SYMLINK="cam1"
# cam2 0c45
SUBSYSTEM=="usb", ATTRS{idVendor}=="0c45", OWNER="softioc", GROUP="softioc", MODE="0666", SYMLINK="cam2"
# cam3 2560
SUBSYSTEM=="usb", ATTRS{idVendor}=="2560", OWNER="softioc", GROUP="softioc", MODE="0666", SYMLINK="cam3"
# cam4 eb1a (not attached)
SUBSYSTEM=="usb", ATTRS{idVendor}=="eb1a", OWNER="softioc", GROUP="softioc", MODE="0666", SYMLINK="cam4"
# cam5 eb1a
SUBSYSTEM=="usb", ATTRS{idVendor}=="eb1a", OWNER="softioc", GROUP="softioc", MODE="0660", SYMLINK="cam5"

• Some inexpensive UVC cameras do not have Serial Numbers written to the device by vendors. Since ADUVC uses either product or serial number to start the IOC, we are currently not able to simultaneously run multiple camera IOCs from the same EPICS server. One could explore posibility of running the device by modifying rules and/or ADUVC driver to run it by SYMLINK generated by udev rules file, or KERNELS settings.

# maybe something like this to get the identical vendor/product/serial# cams working simultaneously
#SUBSYSTEM=="usb", ATTRS{idVendor}=="eb1a", KERNELS=="1-8:1.0", OWNER="softioc", GROUP="softioc", MODE="0660", SYMLINK="cam5"