cap.isOpened()：在 CentOS 中为 Python 3 和 OpenCV 3.1.0 返回 false

Question

所以 opencv 3 的 cap 在 CentOS 中不起作用。我最初尝试过的 OSX 或 Windows 7 没有问题。 下面是示例代码：

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

我得到：

/usr/local/anaconda3/bin/python /home/grad3/jalal/PycharmProjects/hw4_cs585/test.py
not opened
frame empty

Process finished with exit code 0

我可以使用 ffplay vid_name 打开视频，这也是https://pastebin.com/YGk2DDCi 这里https://pastebin.com/HSyHSsEZ（ffmpeg 编解码器）的结果。我应该如何解决这个问题？

我有 opencv 3.1.0，这里有一些系统信息。

$ 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

和

$ 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
-----------------------------------------------------------------

更新：尝试了 .avi 和 .flv 格式，但同样的问题！

Answer 1

您需要 ffmpeg 支持，还需要使用提供的 python 模块而不是 pip 安装（pip repo 版本对我来说与 opencv 不兼容，我遇到了同样的错误）

一些选项：

-DOPENCV_EXTRA_MODULES_PATH=/path/to/opencv_contrib-3.2.0/modules
-DBUILD_PYTHON_SUPPORT=ON 
-DBUILD_opencv_python2=ON 
-DBUILD_opencv_python3=ON
-DPYTHON3_INCLUDE_DIRS=$(python3 -c "from distutils.sysconfig import get_python_inc; print(get_python_inc())") 
-DPYTHON3_PACKAGES_PATH=$(python3 -c "from distutils.sysconfig import get_python_lib; print(get_python_lib())") 
-DPYTHON3_LIBRARY=/usr/lib/x86_64-linux-gnu/libpython3.5m.so

贡献者：https://github.com/opencv/opencv_contrib/

如果您由于系统管理员政策而无法自行安装，也许您可​​以将其 dockerize