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• VideoCapture always returns False in Python OPENCV [Linux]

  7 avril 2017, par Daniyal Shahrokhian

  Every time that I use VideoCapture trying to access the frames from a video file, the return value (ret) is false. See the sample code below :

  cap = cv2.VideoCapture('asd.mkv')
  
      vid = []
  
      while True:
  
          ret, img = cap.read()
  
          if not ret: # Always happens
  
              break
  
          vid.append(cv2.resize(img, (171, 128)))

  I have already tried absolutely everything I could find today by googling, including the OpenCV guide and this long issue on Github. Also, I read some solutions involving moving ffmpeg dll files, but that only was in the case of Windows.

  Any ideas ? Because I defenitely ran out of them.

• How do I include FFMpeg for development in a windows program ?

  4 août 2024, par Lama Mao

  I'm trying to follow a tutorial about using the FFMpeg libraries to extract frames from videos in C++ (by Bartholomew).

  


  In order to include the libraries, according to the tutorial, it is advised to use pkg-config to find the libraries and put them together so that CMake can include them. In the video he uses homebrew to install ffmpeg and somehow pkg-config is able to find the header files for ffmpeg (libavcodec, libavformat, libavdevice ...)

  


  The problem is I don't know how to get the ffmpeg libraries installed so that pkg-config can find them.

  


  On windows, I've tried installing the compiled windows binaries, and I've tried installing ffmpeg-full package using chocolatey. However, I fail to see where these header files are installed to.

  


  There's a ffmpeg folder in C:/ffmpeg/ but when I look in that there's no header files or libraries, just the binaries. Perhaps I need to clone the entire source project, but then how is pkg-config supposed to find them ? When I try and compile I get this output :

  


   Found PkgConfig: C:/Strawberry/perl/bin/pkg-config.bat (found version "0.26") 
 Checking for module 'libavcodec'
 Can't find libavcodec.pc in any of C:/Strawberry/c/lib/pkgconfig
 use the PKG_CONFIG_PATH environment variable, or
 specify extra search paths via 'search_paths'
 CMake Error at C:/Program Files/CMake/share/cmake-3.24/Modules/FindPkgConfig.cmake:607 (message):
 A required package was not found
 Call Stack (most recent call first):
 C:/Program Files/CMake/share/cmake-3.24/Modules/FindPkgConfig.cmake:829 (_pkg_check_modules_internal)
 lib/FFMpeg/CMakeLists.txt:5 (pkg_check_modules)
 Checking for module 'libavcodec'        <----- here
 Can't find libavcodec.pc in any of C:/Strawberry/c/lib/pkgconfig
 use the PKG_CONFIG_PATH environment variable, or
 specify extra search paths via 'search_paths'
 CMake Error at C:/Program Files/CMake/share/cmake-3.24/Modules/FindPkgConfig.cmake:607 (message):
 A required package was not found
 Call Stack (most recent call first):
 C:/Program Files/CMake/share/cmake-3.24/Modules/FindPkgConfig.cmake:829 (_pkg_check_modules_internal)
 lib/FFMpeg/CMakeLists.txt:5 (pkg_check_modules)


  


  The contents of C:/Strawberry/c/lib/pkgconfig seem to be a whole load of libraries none of which are from ffmpeg.

  


  In case the problem is in my CMakeLists file, here are the contents of the subdirectory file :

  


  cmake_minimum_required(VERSION 3.9)
project(FFMpeg)

find_package(PkgConfig REQUIRED)
pkg_check_modules(AVCODEC    REQUIRED    IMPORTED_TARGET libavcodec)
pkg_check_modules(AVFILTER   REQUIRED    IMPORTED_TARGET libavformat)
pkg_check_modules(AVDEVICE   REQUIRED    IMPORTED_TARGET libavdevice)
pkg_check_modules(AVUTIL     REQUIRED    IMPORTED_TARGET libavutil)
pkg_check_modules(SWRESAMPLE REQUIRED    IMPORTED_TARGET libswresample)
pkg_check_modules(SWSCALE    REQUIRED    IMPORTED_TARGET libswscale)

add_library(FFMpeg INTERFACE IMPORTED GLOBAL)

target_include_directories(
    FFmpeg INTERFACE
    ${AVCODEC_INCLUDE_DIRS}
    ${AVFILTER_INCLUDE_DIRS}
    ${AVDEVICE_INCLUDE_DIRS}
    ${AVUTIL_INCLUDE_DIRS}
    ${SWRESAMPLE_INCLUDE_DIRS}
    ${SWSCALE_INCLUDE_DIRS}
)

target_link_options(
    FFmpeg INTERFACE
    ${AVCODEC_LDFLAGS}
    ${AVFILTER_LDFLAGS}
    ${AVDEVICE_LDFLAGS}
    ${AVUTIL_LDFLAGS}
    ${SWRESAMPLE_LDFLAGS}
    ${SWSCALE_LDFLAGS}
)


  


  What have I done wrong/am not understanding ?

  


• Revision 926a6f63cb : sh tests : Add support for running tested programs within another program. Speci

  11 juillet 2014, par Tom Finegan

  Changed Paths :
   Modify /test/decode_to_md5.sh

  
   Modify /test/decode_with_drops.sh

  
   Modify /test/postproc.sh

  
   Modify /test/resize_util.sh

  
   Modify /test/simple_decoder.sh

  
   Modify /test/simple_encoder.sh

  
   Modify /test/tools_common.sh

  
   Modify /test/twopass_encoder.sh

  
   Modify /test/vp8cx_set_ref.sh

  
   Modify /test/vp9_spatial_svc_encoder.sh

  
   Modify /test/vpx_temporal_svc_encoder.sh

  
  
  sh tests : Add support for running tested programs within another program.

  Specifying the —prefix command line arg executes all test programs within the
  context of the prefix string, which is assigned to VPX_TEST_PREFIX.
  All test functions updated to include VPX_TEST_PREFIX in their eval command.

  Change-Id : I2e215cc8f216048edf3269db02a6b5660fe32318