Failing to lock exposure on Logitech C270

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Hi all,

Go easy on me I'm from the python world and only recently started needing to compile outside of the Arduino IDE!

I'm trying to lock the auto exposure. I've found & modified a simple python test script that runs, but fails to lock the exposure:

import cv2
cap = cv2.VideoCapture(1)
print("before setting CAP_PROP_AUTO_EXPOSURE = %s" % cap.get(cv2.CAP_PROP_AUTO_EXPOSURE))
cap.set(cv2.CAP_PROP_AUTO_EXPOSURE, 0)
print("after setting CAP_PROP_AUTO_EXPOSURE = %s" % cap.get(cv2.CAP_PROP_AUTO_EXPOSURE))
print("before setting CAP_PROP_EXPOSURE = %s" % cap.get(cv2.CAP_PROP_AUTO_EXPOSURE))
cap.set(cv2.CAP_PROP_EXPOSURE,-4)
print("after setting CAP_PROP_EXPOSURE = %s" % cap.get(cv2.CAP_PROP_AUTO_EXPOSURE))
while(True):
    ret, frame = cap.read()
    cv2.imshow('frame',frame)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
cap.release()
cv2.destroyAllWindows()

That doesn't work. I see the following warnings:

[ WARN:0] global /home/wesbrooks/horus3/opencv/modules/videoio/src/cap_gstreamer.cpp (924) open OpenCV | GStreamer warning: Cannot query video position: status=0, value=-1, duration=-1
[ WARN:0] global /home/wesbrooks/horus3/opencv/modules/videoio/src/cap_gstreamer.cpp (1175) setProperty OpenCV | GStreamer warning: GStreamer: unhandled property
[ WARN:0] global /home/wesbrooks/horus3/opencv/modules/videoio/src/cap_gstreamer.cpp (1025) getProperty OpenCV | GStreamer warning: unhandled property: 21
[ WARN:0] global /home/wesbrooks/horus3/opencv/modules/videoio/src/cap_gstreamer.cpp (1025) getProperty OpenCV | GStreamer warning: unhandled property: 15

I can run this on the command prompt before it and the exposure is locked:

v4l2-ctl -d /dev/video1 -c exposure_auto=1 -c exposure_auto_priority=0 -c exposure_absolute=10

The cmake options are:

cmake -D CMAKE_BUILD_TYPE=RELEASE \
            -D CMAKE_INSTALL_PREFIX=$cwd/installation/OpenCV-"$cvVersion" \
            -D INSTALL_C_EXAMPLES=ON \
            -D INSTALL_PYTHON_EXAMPLES=ON \
            -D WITH_TBB=ON \
            -D WITH_V4L=ON \
            -D OPENCV_PYTHON3_INSTALL_PATH=$cwd/OpenCV-$cvVersion-py3/lib/python3.6/site-packages \
            -D WITH_QT=ON \
            -D WITH_OPENGL=ON \
            -D BUILD_EXAMPLES=ON ..

My compile at the moment has the following errors or test failures:

-- Performing Test HAVE_CXX_WMISSING_PROTOTYPES - Failed
-- Performing Test HAVE_CXX_WSTRICT_PROTOTYPES - Failed
-- Performing Test HAVE_C_WSIGN_PROMO - Failed
-- Performing Test HAVE_C_WSUGGEST_OVERRIDE - Failed
-- Performing Test HAVE_C_WNO_DELETE_NON_VIRTUAL_DTOR - Failed
-- Performing Test HAVE_CXX_WNO_UNNAMED_TYPE_TEMPLATE_ARGS - Failed
-- Performing Test HAVE_C_WNO_UNNAMED_TYPE_TEMPLATE_ARGS - Failed
-- Performing Test HAVE_C_FVISIBILITY_INLINES_HIDDEN - Failed
-- Performing Test HAVE_CXX_WNO_INCONSISTENT_MISSING_OVERRIDE - Failed
-- Performing Test HAVE_CXX_WNO_MISSING_PROTOTYPES - Failed
-- Could not find OpenBLAS include. Turning OpenBLAS_FOUND off
-- Could not find OpenBLAS lib. Turning OpenBLAS_FOUND off
-- Could NOT find Atlas (missing: Atlas_CLAPACK_INCLUDE_DIR) 
-- Performing Test HAVE_CXX_WNO_TAUTOLOGICAL_UNDEFINED_COMPARE - Failed
-- Performing Test HAVE_CXX_WNO_SHORTEN_64_TO_32 - Failed
-- Performing Test HAVE_CXX_WNO_ENUM_COMPARE_SWITCH - Failed
-- Could NOT find Flake8 (missing: FLAKE8_EXECUTABLE) 
-- VTK is not found. Please set -DVTK_DIR in CMake to VTK build directory, or to VTK install subdirectory with VTKConfig.cmake file
-- Caffe:   NO
-- Protobuf:   NO
-- Could NOT find HDF5 (missing: HDF5_LIBRARIES HDF5_INCLUDE_DIRS) (found version "")
-- Module opencv_ovis disabled because OGRE3D was not found
-- No preference for use of exported gflags CMake configuration set, and no hints for include/library directories provided. Defaulting to preferring an installed/exported gflags CMake configuration if available.
--   No package 'tesseract' found
-- Tesseract:   NO
-- Performing Test HAVE_CXX_WNO_UNUSED_PRIVATE_FIELD - Failed

The general configuration output is:

-- General configuration for OpenCV 4.1.1-pre =====================================
--   Version control:               4.1.0-473-g453466eb1
-- 
--   Extra modules:
--     Location (extra):            /home/wesbrooks/horus3/opencv_contrib/modules
--     Version control (extra):     4.1.0-65-g3830f186
-- 
--   Platform ...