Not able to get even basic gstreamer pipeline into python opencv

Python
,
1

I am trying to import a simple gstreamer pipeline into python opencv. The gst-launch-1.0 works but I have not been able to integrate to opencv python.

OS - Ubuntu 22.04

My basic code

import cv2

# didn't work - this also
## `works on bash` - gst-launch-1.0 filesrc location="${videosrc}" ! qtdemux ! avdec_h264 ! videoconvert ! autovideosink
## videosrc = "/mnt/D/software_projects/video resources/Big Buck Bunny 60fps 4K - Official Blender Foundation Short Film.mp4"
## pipeline = (f"filesrc location='{videosrc}' ! qtdemux ! avdec_h264 ! videoconvert ! appsink")


pipeline = "videotestsrc ! videoconvert ! appsink"
# pipeline = "videotestsrc ! video/x-raw,format=BGR ! videoconvert ! appsink"

cap = cv2.VideoCapture(pipeline, cv2.CAP_GSTREAMER)

if not cap.isOpened():
    print("Error: Could not open GStreamer pipeline.")
    exit()

while True:
    ret, frame = cap.read()
    if not ret:
        print("Error: Unable to read frame")
        break
    cv2.imshow("GStreamer OpenCV", frame)
    if cv2.waitKey(1) & 0xFF == ord("q"):
        break

cap.release()
cv2.destroyAllWindows()

Here is my cv2.getBuildInformation()

General configuration for OpenCV 4.8.0 =====================================
  Version control:               4.8.0-dirty

  Platform:
    Timestamp:                   2023-08-09T11:41:23Z
    Host:                        Linux 5.15.0-1042-azure x86_64
    CMake:                       3.27.1
    CMake generator:             Unix Makefiles
    CMake build tool:            /bin/gmake
    Configuration:               Release

  CPU/HW features:
    Baseline:                    SSE SSE2 SSE3
      requested:                 SSE3
    Dispatched code generation:  SSE4_1 SSE4_2 FP16 AVX AVX2 AVX512_SKX
      requested:                 SSE4_1 SSE4_2 AVX FP16 AVX2 AVX512_SKX
      SSE4_1 (16 files):         + SSSE3 SSE4_1
      SSE4_2 (1 files):          + SSSE3 SSE4_1 POPCNT SSE4_2
      FP16 (0 files):            + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 AVX
      AVX (7 files):             + SSSE3 SSE4_1 POPCNT SSE4_2 AVX
      AVX2 (35 files):           + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2
      AVX512_SKX (5 files):      + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2 AVX_512F AVX512_COMMON AVX512_SKX

  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 -Wreturn-type -Wnon-virtual-dtor -Waddress -Wsequence-point -Wformat -Wformat-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 -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -fvisibility=hidden -fvisibility-inlines-hidden -O3 -DNDEBUG  -DNDEBUG
    C++ flags (Debug):           -Wl,-strip-all   -fsigned-char -W -Wall -Wreturn-type -Wnon-virtual-dtor -Waddress -Wsequence-point -Wformat -Wformat-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 -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -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 -Wreturn-type -Waddress -Wsequence-point -Wformat -Wformat-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 -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -fvisibility=hidden -O3 -DNDEBUG  -DNDEBUG
    C flags (Debug):             -Wl,-strip-all   -fsigned-char -W -Wall -Wreturn-type -Waddress -Wsequence-point -Wformat -Wformat-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 -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections  -msse -msse2 -msse3 -fvisibility=hidden -g  -O0 -DDEBUG -D_DEBUG
    Linker flags (Release):      -Wl,--exclude-libs,libippicv.a -Wl,--exclude-libs,libippiw.a -L/ffmpeg_build/lib  -Wl,--gc-sections -Wl,--as-needed -Wl,--no-undefined  
    Linker flags (Debug):        -Wl,--exclude-libs,libippicv.a -Wl,--exclude-libs,libippiw.a -L/ffmpeg_build/lib  -Wl,--gc-sections -Wl,--as-needed -Wl,--no-undefined  
    ccache:                      YES
    Precompiled headers:         NO
    Extra dependencies:          /lib64/libopenblas.so Qt5::Core Qt5::Gui Qt5::Widgets Qt5::Test Qt5::Concurrent /usr/local/lib/libpng.so /lib64/libz.so dl m pthread rt
    3rdparty dependencies:       libprotobuf ade ittnotify libjpeg-turbo libwebp libtiff libopenjp2 IlmImf quirc ippiw ippicv

  OpenCV modules:
    To be built:                 calib3d core dnn features2d flann gapi highgui imgcodecs imgproc ml objdetect photo python3 stitching video videoio
    Disabled:                    world
    Disabled by dependency:      -
    Unavailable:                 java python2 ts
    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 2.1.3-62)
    WEBP:                        build (ver encoder: 0x020f)
    PNG:                         /usr/local/lib/libpng.so (ver 1.6.40)
    TIFF:                        build (ver 42 - 4.2.0)
    JPEG 2000:                   build (ver 2.5.0)
    OpenEXR:                     build (ver 2.3.0)
    HDR:                         YES
    SUNRASTER:                   YES
    PXM:                         YES
    PFM:                         YES

  Video I/O:
    DC1394:                      NO
    FFMPEG:                      YES
      avcodec:                   YES (59.37.100)
      avformat:                  YES (59.27.100)
      avutil:                    YES (57.28.100)
      swscale:                   YES (6.7.100)
      avresample:                NO
    GStreamer:                   NO
    v4l/v4l2:                    YES (linux/videodev2.h)

  Parallel framework:            pthreads

  Trace:                         YES (with Intel ITT)

  Other third-party libraries:
    Intel IPP:                   2021.8 [2021.8.0]
           at:                   /io/_skbuild/linux-x86_64-3.7/cmake-build/3rdparty/ippicv/ippicv_lnx/icv
    Intel IPP IW:                sources (2021.8.0)
              at:                /io/_skbuild/linux-x86_64-3.7/cmake-build/3rdparty/ippicv/ippicv_lnx/iw
    VA:                          NO
    Lapack:                      YES (/lib64/libopenblas.so)
    Eigen:                       NO
    Custom HAL:                  NO
    Protobuf:                    build (3.19.1)
    Flatbuffers:                 builtin/3rdparty (23.5.9)

  OpenCL:                        YES (no extra features)
    Include path:                /io/opencv/3rdparty/include/opencl/1.2
    Link libraries:              Dynamic load

  Python 3:
    Interpreter:                 /opt/python/cp37-cp37m/bin/python3.7 (ver 3.7.17)
    Libraries:                   libpython3.7m.a (ver 3.7.17)
    numpy:                       /home/ci/.local/lib/python3.7/site-packages/numpy/core/include (ver 1.17.0)
    install path:                python/cv2/python-3

  Python (for build):            /opt/python/cp37-cp37m/bin/python3.7

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

  Install to:                    /io/_skbuild/linux-x86_64-3.7/cmake-install
-----------------------------------------------------------------
2

your cv2 was built without gstreamer support. try to use the ffmpeg backend instead to play video files (and no, you cannot use gstreamer pipe syntax, then)

to actually use gstreamer from cv2, you need to build the opencv libs & cv2 from src, with gstreamer-dev libs installed

1 Like
3

Oh I see my mistake. Thank you for pointing it out.

I am looking into building it and it is pretty confusing. If possible, can you point me to a reference on how to build it.
Sorry for asking more help as I am having hard time understanding all moving parts.

Thank you

4

https://docs.opencv.org/4.x/d7/d9f/tutorial_linux_install.html

(this will also rebuild the cv2 python wrapper)

5

Thank you @berak for your help.

I did install opencv and opencv_contrib following Build with opencv_contrib. But instead of sudo make install, used sudo checkinstall for installation.

I faced an issue - ImportError: libopencv_intensity_transform.so.408: cannot open shared object file: No such file or directory when importing cv2 which was solved by running

sudo ldconfig

It was a first time working with cmake and building from raw code. Thank you for your help.

6

adding -DBUILD_SHARED_LIBS=OFF to the cmake flags will result in a fat, statically linked cv2, that no more depends on opencv_xxx.so’s