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• Unable to open mp4 video file with VideoCapture with OpenCV 3.0 before and after recompiling with ffmpeg

  19 août 2015, par ricardo_8990

  When running

  VideoCapture cap;
  
  cap.open("GOPR3252.mp4");
  
  
  
  if(!cap.isOpened())
  
  {
  
      return -1;
  
  }

  I couldn’t open the video, even though I tried to manually add the codec CV_FOURCC(’A’, ’V’, ’C’, ’1’). I read that this may be due to the link with ffmpeg. So I compiled and installed ffmpeg using this guide and this one.

  Later, I uninstalled OpenCV, downloaded and compiled using CMake as :

  cmake -D CMAKE_SHARED_LINKER_FLAGS=-Wl,-Bsymbolic -D WITH_FFMPEG=ON -D WITH_QT=ON -D BUILD_EXAMPLES=ON CMAKE_BUILD_TYPE=Release /route_to_software/opencv/

  However, all the time I get this in the resume at the video section :

  --   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:                    NO/YES
  
  --     XIMEA:                       NO
  
  --     Xine:                        NO
  
  --     gPhoto2:                     NO
  
  --

  I have no problem making and installing OpenCV, but I still can’t open that video.

  Then, I tried to convert the video from mp4 to avi and got this error when reading the video file :

  Unexpected list type. Expected : hdrl. Got : movi.

  I tried with different formats as 3gp, wmv with any luck.

  I am running out of ideas. Any clue what I am doing wrong ?

  EDIT
  After uninstalling again ffmpeg and OpenCV. Then I installed ffmpeg from the packman repositories with libffmpeg-dev, compile and install OpenCV. I can play the video in the avi format but I still get this message :

  Unexpected list type. Expected : hdrl. Got : movi.

  I am using OpenSUSE 13.2

  Thanks in advance,

• After using ffmpeg to remove some streams in mkv file, it takes much longer to open the media file in potplayer in Windows

  31 mars 2024, par r ne

  It is well known that ffmpeg command line can be used to remove some streams in mkv or mp4 files, and I have no problem in doing so.

  


  ffmpeg -i input.mp4 -map 0 -map -0:a:3 -map -0:a:6 -c copy output.mp4


  


  The only issue I meet sometimes is, the result media files in mkv or mp4 are much much slower to be opened by player. I cannot figure out the real reason and bypass it.

  


  Any hint or help on solving this issue ? Thanks !

  


• Python - second subprocess won't open if sys.argv containts "&" character

  3 juin 2015, par Hyperion

  I’ve got a Python script which download a video using youtube-dl and then extract frames from it using ffmpeg. This is the code :

  def DownloadVideo():
  
      output_file = "/Users/francesco/Desktop/SOURCE/%(title)s-%(id)s.%(ext)s"
  
      check_call(["youtube-dl","--output", output_file, "--restrict-filenames", "-f", "best", sys.argv[1]])
  
  
  
  def ConvertVideo(video):
  
      DEST = "/Users/francesco/Desktop/OUTPUT"
  
      SOURCE = "/Users/francesco/Desktop/SOURCE"
  
      ffmpeg_path = "/Users/francesco/Desktop/ffmpeg/ffmpeg"
  
      video_path = SOURCE + "/" + video
  
      dest_path = DEST + "/" + os.path.splitext(video)[0] + "-%d.png"
  
      check_call([ffmpeg_path, "-v", "0", "-i", video_path, "-f", "image2", dest_path])
  
  
  
  def Main():
  
      DownloadVideo()
  
      for video in os.listdir("/Users/francesco/Desktop/SOURCE"):
  
         ConvertVideo(video)

  I run the command python myscript.py myvideolink and everything goes fine in the download process, but the ConvertVideo doesn’t start, it just get frozen for a couple of seconds and then the program exits.

  If I try to run the same command skipping the DownloadVideo() (with the video already downloaded in the folder) it doens’t work too, but if I use python myscript.py without the argv[1], the ffmpeg process works ! Why this happens ?

  Update : I’ve tried to remove the -v 0 option in ffmpeg to see what actually happens, ffmpeg process starts, but get frozen like this :

  ffmpeg version 2.6.2 Copyright (c) 2000-2015 the FFmpeg developers
  
    built with llvm-gcc 4.2.1 (LLVM build 2336.11.00)
  
    configuration: --prefix=/Volumes/Ramdisk/sw --enable-gpl --enable-pthreads --enable-version3 --enable-libspeex --enable-libvpx --disable-decoder=libvpx --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libx264 --enable-avfilter --enable-libopencore_amrwb --enable-libopencore_amrnb --enable-filters --enable-libgsm --enable-libvidstab --enable-libx265 --disable-doc --arch=x86_64 --enable-runtime-cpudetect
  
    libavutil      54. 20.100 / 54. 20.100
  
    libavcodec     56. 26.100 / 56. 26.100
  
    libavformat    56. 25.101 / 56. 25.101
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 11.102 /  5. 11.102
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  1.100 /  1.  1.100
  
    libpostproc    53.  3.100 / 53.  3.100

  Update 2 : Turns out that this happens only when the argument (which is a link) contains the character "&". Anyone knows why this is a problem for ffmpeg ? He’s not neither using the arg variable...