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• cap.isOpened() : returns false in CentOS for Python 3 and OpenCV 3.1.0

  29 octobre 2017, par Mona Jalal

  So cap from opencv 3 doesn’t work in CentOS. I had no problem in OSX or Windows 7 which I tried initially.
  Here is the example code :

  import cv2
  
  cap = cv2.VideoCapture('/home/grad3/jalal/PycharmProjects/hw4_cs58‌​5/Concession_LAN_8‌​‌​00‌​k.mp4',cv2.CAP_FFMPEG)
  
  
  
  if not cap.isOpened():
  
      print('not opened')
  
  
  
  while True:
  
      ret,frame = cap.read()
  
  
  
      if ret == False:
  
          print('frame empty')
  
          break
  
      cv2.imshow('frame', frame)
  
      if cv2.waitKey(1) == ord('q'):
  
          break

  And I get :

  /usr/local/anaconda3/bin/python /home/grad3/jalal/PycharmProjects/hw4_cs585/test.py
  
  not opened
  
  frame empty
  
  
  
  Process finished with exit code 0

  I can open the video using ffplay vid_name and also here is the result of https://pastebin.com/YGk2DDCi here https://pastebin.com/HSyHSsEZ (ffmpeg codecs). How should I fix this ?

  I have opencv 3.1.0 and here’s some sys info.

  $ uname -a
  
  Linux goku.bu.edu 3.10.0-693.5.2.el7.x86_64 #1 SMP Fri Oct 20 20:32:50 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

  and

  $ lsb_release -a
  
  LSB Version:    :core-4.1-amd64:core-4.1-noarch
  
  Distributor ID: CentOS
  
  Description:    CentOS Linux release 7.4.1708 (Core) 
  
  Release:    7.4.1708
  
  Codename:   Core
  
  
  
  cv2. getBuildInformation()
  
  General configuration for OpenCV 3.1.0 =====================================
  
    Version control:               unknown
  
  
  
    Platform:
  
      Host:                        Linux 4.8.0-46-generic x86_64
  
      CMake:                       3.6.3
  
      CMake generator:             Unix Makefiles
  
      CMake build tool:            /usr/bin/gmake
  
      Configuration:               Release
  
  
  
    C/C++:
  
      Built as dynamic libs?:      YES
  
      C++ Compiler:                /opt/rh/devtoolset-2/root/usr/bin/c++  (ver 4.8.2)
  
      C++ flags (Release):         -I/cs/software/anaconda3/include    -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 -Wno-narrowing -Wno-delete-non-virtual-dtor -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -mno-avx -msse3 -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -ffunction-sections -fvisibility=hidden -fvisibility-inlines-hidden -fopenmp -O3 -DNDEBUG  -DNDEBUG
  
      C++ flags (Debug):           -I/cs/software/anaconda3/include    -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 -Wno-narrowing -Wno-delete-non-virtual-dtor -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -mno-avx -msse3 -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -ffunction-sections -fvisibility=hidden -fvisibility-inlines-hidden -fopenmp -g  -O0 -DDEBUG -D_DEBUG
  
      C Compiler:                  /opt/rh/devtoolset-2/root/usr/bin/cc
  
      C flags (Release):           -I/cs/software/anaconda3/include    -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wno-narrowing -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -mno-avx -msse3 -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -ffunction-sections -fvisibility=hidden -fopenmp -O3 -DNDEBUG  -DNDEBUG
  
      C flags (Debug):             -I/cs/software/anaconda3/include    -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wno-narrowing -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -msse -msse2 -mno-avx -msse3 -mno-ssse3 -mno-sse4.1 -mno-sse4.2 -ffunction-sections -fvisibility=hidden -fopenmp -g  -O0 -DDEBUG -D_DEBUG
  
      Linker flags (Release):
  
      Linker flags (Debug):
  
      Precompiled headers:         YES
  
      Extra dependencies:          /cs/software/anaconda3/lib/libjpeg.so /cs/software/anaconda3/lib/libpng.so /cs/software/anaconda3/lib/libtiff.so /cs/software/anaconda3/lib/libhdf5.so /usr/lib64/librt.so /usr/lib64/libpthread.so /cs/software/anaconda3/lib/libz.so /usr/lib64/libdl.so /usr/lib64/libm.so dl m pthread rt
  
      3rdparty dependencies:       libwebp libjasper IlmImf libprotobuf
  
  
  
    OpenCV modules:
  
      To be built:                 core flann hdf imgproc ml photo reg surface_matching video dnn fuzzy imgcodecs shape videoio highgui objdetect plot superres xobjdetect xphoto bgsegm bioinspired dpm face features2d line_descriptor saliency text calib3d ccalib datasets rgbd stereo structured_light tracking videostab xfeatures2d ximgproc aruco optflow stitching python3
  
      Disabled:                    world contrib_world
  
      Disabled by dependency:      -
  
      Unavailable:                 cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev java python2 ts viz cvv matlab sfm
  
  
  
    GUI: 
  
      QT:                          NO
  
      GTK+:                        NO
  
      GThread :                    NO
  
      GtkGlExt:                    NO
  
      OpenGL support:              NO
  
      VTK support:                 NO
  
  
  
    Media I/O: 
  
      ZLib:                        /cs/software/anaconda3/lib/libz.so (ver 1.2.8)
  
      JPEG:                        /cs/software/anaconda3/lib/libjpeg.so (ver 80)
  
      WEBP:                        build (ver 0.3.1)
  
      PNG:                         /cs/software/anaconda3/lib/libpng.so (ver 1.6.27)
  
      TIFF:                        /cs/software/anaconda3/lib/libtiff.so (ver 42 - 4.0.6)
  
      JPEG 2000:                   build (ver 1.900.1)
  
      OpenEXR:                     build (ver 1.7.1)
  
      GDAL:                        NO
  
  
  
    Video I/O:
  
      DC1394 1.x:                  NO
  
      DC1394 2.x:                  NO
  
      FFMPEG:                      NO
  
        codec:                     NO
  
        format:                    NO
  
        util:                      NO
  
        swscale:                   NO
  
        resample:                  NO
  
        gentoo-style:              NO
  
      GStreamer:                   NO
  
      OpenNI:                      NO
  
      OpenNI PrimeSensor Modules:  NO
  
      OpenNI2:                     NO
  
      PvAPI:                       NO
  
      GigEVisionSDK:               NO
  
      UniCap:                      NO
  
      UniCap ucil:                 NO
  
      V4L/V4L2:                    YES/YES
  
      XIMEA:                       NO
  
      Xine:                        NO
  
      gPhoto2:                     NO
  
  
  
    Parallel framework:            OpenMP
  
  
  
    Other third-party libraries:
  
      Use IPP:                     9.0.1 [9.0.1]
  
           at:                     /opt/conda/conda-bld/opencv_1491943704081/work/opencv-3.1.0/3rdparty/ippicv/unpack/ippicv_lnx
  
      Use IPP Async:               NO
  
      Use VA:                      NO
  
      Use Intel VA-API/OpenCL:     NO
  
      Use Eigen:                   YES (ver 3.2.8)
  
      Use Cuda:                    NO
  
      Use OpenCL:                  NO
  
      Use custom HAL:              NO
  
  
  
    Python 2:
  
      Interpreter:                 (ver 3.5.3)
  
  
  
    Python 3:
  
      Interpreter:                 /cs/software/anaconda3/bin/python (ver 3.5.3)
  
      Libraries:                   /cs/software/anaconda3/lib/libpython3.5m.so (ver 3.5.3)
  
      numpy:                       /cs/software/anaconda3/lib/python3.5/site-packages/numpy/core/include (ver 1.12.1)
  
      packages path:               /cs/software/anaconda3/lib/python3.5/site-packages
  
  
  
    Python (for build):            
  
  
  
    Java:
  
      ant:                         NO
  
      JNI:                         NO
  
      Java wrappers:               NO
  
      Java tests:                  NO
  
  
  
    Matlab:                        NO
  
  
  
    Tests and samples:
  
      Tests:                       NO
  
      Performance tests:           NO
  
      C/C++ Examples:              NO
  
  
  
    Install path:                  /cs/software/anaconda3
  
  
  
    cvconfig.h is in:              /opt/conda/conda-bld/opencv_1491943704081/work/opencv-3.1.0/build
  
  -----------------------------------------------------------------

  UPDATE : tried .avi and .flv formats and the same problem !

• ffmpeg configure always returns "not found" when using sysroot and cross-prefix options - how to use them correctly ?

  5 août 2014, par user2212461

  I try to build ffmpeg with a cross-compiler. When setting the configure flags I am getting the following errors :

  WARNING: Compiler does not indicate floating-point ABI, guessing soft.
  
  build_it.sh: 29: build_it.sh: --sysroot=/home/android/android-ndk-r9/platforms/
  
      android-9/arch-arm/: not found
  
  build_it.sh: 32: build_it.sh.sh: --cross-prefix=/home/android/android-ndk-r9/
  
      toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86/bin/arm-linux-and
  
      roideabi-: not found

  The error message "not found" sounds like the paths dont exist but they are all correct and existing. How can I resolve this error ?

  build_it.sh :

  NDK=/home/android/android-ndk-r9
  
  SYSROOT=$NDK/platforms/android-9/arch-arm/
  
  TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86
  
  CPU=arm
  
  PREFIX=test
  
  ADDI_CFLAGS="-marm"
  
  platform="android-9"
  
  
  
  ./configure \
  
      --disable-asm \
  
      --enable-shared \
  
      --target-os=linux \
  
      --arch=arm \
  
      --enable-cross-compile \
  
      --disable-static \
  
      --sysroot=$SYSROOT \
  
      --extra-cflags="-Os -fpic $ADDI_CFLAGS" \
  
      --extra-ldflags="$ADDI_LDFLAGS"
  
      --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \
  
      --prefix=$PREFIX \
  
  
  
  ##configure fails here
  
  ...

• #include file from library returns "file not found"

  16 juin 2015, par Yossi Tsafar

  I’m getting this error from multiple .a files

  'libavcodec/avcodec.h' file not found

  Even though I added the library to project and also to "Library Search Paths" :

  $(PROJECT_DIR)/Project/Custom/RTPlayer/3rd-party/ffmpeg/lib

  This is how I add it to project :

  #include "libavcodec/avcodec.h"

  Please someone help me what seems to be the problem ?

  Thanks in advance !