Jetson Nano Python cannot initialize camera

Python
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1

Hi all,
I have an issue with the NVIDIA Jetson Nano camera. In particular, C++ correctly opens the video stream, using the stream

nvarguscamerasrc ! video/x-raw(memory:NVMM), width=(int)1600, height=(int)900, format=(string)NV12, framerate=(fraction)21/1 ! nvvidconv flip-method=0! video/x-raw, width=(int)1600, height=(int)900, format=(string)BGRx ! videoconvert ! video/x-raw, format=(string)BGR ! appsink

And it works correctly. The troubles starts with Python 3.x. Indeed, using the exact code the program stops and cannot initialize the camera.

In particular, I need to use the opencv-contrib-python library in order to work with the Aruco markers. The camera can be initialized also in Python 2.7, but the contrib version of the library is not supported.

Does anyone have the same problem? Is there a solution?

Thank you for your answers!

2

print(cv.getBuildInformation()) and report back the output

3 
General configuration for OpenCV 4.5.4 =====================================
  Version control:               4.5.4-dirty

  Extra modules:
    Location (extra):            /tmp/pip-req-build-4twktqs_/opencv_contrib/modules
    Version control (extra):     4.5.4

  Platform:
    Timestamp:                   2021-11-20T10:33:59Z
    Host:                        Linux 4.9.140-tegra aarch64
    CMake:                       3.22.0
    CMake generator:             Unix Makefiles
    CMake build tool:            /bin/gmake
    Configuration:               Release

  CPU/HW features:
    Baseline:                    NEON FP16

  C/C++:
    Built as dynamic libs?:      NO
    C++ standard:                11
    C++ Compiler:                /opt/rh/devtoolset-10/root/usr/bin/c++  (ver 10.2.1)
    C++ flags (Release):         -Wl,-strip-all   -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Wsuggest-override -Wno-delete-non-virtual-dtor -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections    -fvisibility=hidden -fvisibility-inlines-hidden -O3 -DNDEBUG  -DNDEBUG
    C++ flags (Debug):           -Wl,-strip-all   -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Wsuggest-override -Wno-delete-non-virtual-dtor -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections    -fvisibility=hidden -fvisibility-inlines-hidden -g  -O0 -DDEBUG -D_DEBUG
    C Compiler:                  /opt/rh/devtoolset-10/root/usr/bin/cc
    C flags (Release):           -Wl,-strip-all   -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wuninitialized -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections    -fvisibility=hidden -O3 -DNDEBUG  -DNDEBUG
    C flags (Debug):             -Wl,-strip-all   -fsigned-char -W -Wall -Werror=return-type -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wuninitialized -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections    -fvisibility=hidden -g  -O0 -DDEBUG -D_DEBUG
    Linker flags (Release):      -L/root/ffmpeg_build/lib  -Wl,--gc-sections -Wl,--as-needed  
    Linker flags (Debug):        -L/root/ffmpeg_build/lib  -Wl,--gc-sections -Wl,--as-needed  
    ccache:                      YES
    Precompiled headers:         NO
    Extra dependencies:          /lib64/libopenblas.so Qt5::Core Qt5::Gui Qt5::Widgets Qt5::Test Qt5::Concurrent /lib64/libpng.so /lib64/libz.so Iconv::Iconv dl m pthread rt
    3rdparty dependencies:       libprotobuf ade ittnotify libjpeg-turbo libwebp libtiff libopenjp2 IlmImf quirc tegra_hal

  OpenCV modules:
    To be built:                 aruco barcode bgsegm bioinspired calib3d ccalib core datasets dnn dnn_objdetect dnn_superres dpm face features2d flann fuzzy gapi hfs highgui img_hash imgcodecs imgproc intensity_transform line_descriptor mcc ml objdetect optflow phase_unwrapping photo plot python3 quality rapid reg rgbd saliency shape stereo stitching structured_light superres surface_matching text tracking video videoio videostab wechat_qrcode xfeatures2d ximgproc xobjdetect xphoto
    Disabled:                    world
    Disabled by dependency:      -
    Unavailable:                 alphamat cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev cvv freetype hdf java julia matlab ovis python2 sfm ts viz
    Applications:                -
    Documentation:               NO
    Non-free algorithms:         NO

  GUI:                           QT5
    QT:                          YES (ver 5.15.0 )
      QT OpenGL support:         NO
    GTK+:                        NO
    VTK support:                 NO

  Media I/O: 
    ZLib:                        /lib64/libz.so (ver 1.2.7)
    JPEG:                        libjpeg-turbo (ver 2.1.0-62)
    WEBP:                        build (ver encoder: 0x020f)
    PNG:                         /lib64/libpng.so (ver 1.5.13)
    TIFF:                        build (ver 42 - 4.2.0)
    JPEG 2000:                   build (ver 2.4.0)
    OpenEXR:                     build (ver 2.3.0)
    HDR:                         YES
    SUNRASTER:                   YES
    PXM:                         YES
    PFM:                         YES

  Video I/O:
    DC1394:                      NO
    FFMPEG:                      YES
      avcodec:                   YES (58.91.100)
      avformat:                  YES (58.45.100)
      avutil:                    YES (56.51.100)
      swscale:                   YES (5.7.100)
      avresample:                NO
    GStreamer:                   NO
    v4l/v4l2:                    YES (linux/videodev2.h)

  Parallel framework:            pthreads

  Trace:                         YES (with Intel ITT)

  Other third-party libraries:
    Lapack:                      YES (/lib64/libopenblas.so)
    Eigen:                       NO
    Custom HAL:                  YES (carotene (ver 0.0.1))
    Protobuf:                    build (3.5.1)

  OpenCL:                        YES (no extra features)
    Include path:                /tmp/pip-req-build-4twktqs_/opencv/3rdparty/include/opencl/1.2
    Link libraries:              Dynamic load

  Python 3:
    Interpreter:                 /opt/_internal/cpython-3.6.15/bin/python (ver 3.6.15)
    Libraries:                   libpython3.6m.a (ver 3.6.15)
    numpy:                       /tmp/pip-build-env-xk_ri53o/overlay/lib/python3.6/site-packages/numpy/core/include (ver 1.19.3)
    install path:                python/cv2/python-3.6

  Python (for build):            /bin/python2.7

  Java:                          
    ant:                         NO
    JNI:                         NO
    Java wrappers:               NO
    Java tests:                  NO

  Install to:                    /tmp/pip-req-build-4twktqs_/_skbuild/linux-aarch64-3.6/cmake-install
-----------------------------------------------------------------
4

so, you cannot run a gstreamer pipeline from VideoCapture, if there was no such support builtin ;(

5

yes, and that’s the line that means “no support”.

you’re gonna need a different build, i.e. build OpenCV yourself, with support for gstreamer.

building OpenCV is generally messy/complicated but not impossible. my advice is to either start “small” (as few modules as possible, then grow) or to disable any module that gives any errors in the build process.

6

Thanks a lot to everyone, I will try your advice and let you know if the problem goes away