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• openCV doesn't play video on Fedora 28

  2 octobre 2018, par Enes

  I have just started learn opencv and i encountered a problem about playing video. I use qt-creator for opencv and my os is fedora 28.

  My code :

  cv::VideoCapture vCap;
  
  vCap.open("/home/enes/sample.mp4");
  
  if(vCap.isOpened()){
  
      cv::Mat frame;
  
      cv::namedWindow("Video");
  
      for(;;){
  
          if(!vCap.read(frame)) break;
  
          cv::imshow("Video", frame);
  
      }
  
  }

  My problem is below.

  Failed to query video capabilities: Inappropriate ioctl for device
  
  libv4l2: error getting capabilities: Inappropriate ioctl for device
  
  VIDEOIO ERROR: V4L: device /home/enes/sample.mp4: Unable to query number of channels
  
  OpenCV(3.4.1) Error: Unspecified error (GStreamer: your gstreamer installation is missing a required plugin
  
  ) in handlemessage, file /builddir/build/BUILD/opencv-3.4.1/modules/videoio/src/cap_gstreamer.cpp, line 1869
  
  VIDEOIO(cvCreateCapture_GStreamer (CV_CAP_GSTREAMER_FILE, filename)): raised OpenCV exception:
  
  
  
  OpenCV(3.4.1) /builddir/build/BUILD/opencv-3.4.1/modules/videoio/src/cap_gstreamer.cpp:1869: error: (-2) GStreamer: your gstreamer installation is missing a required plugin
  
   in function handlemessage
  
  
  
  CvCapture_OpenNI::CvCapture_OpenNI : Failed to open input file (/home/enes/sample.mp4): Bad file extension

  What should I do to solve this problem ? Thanks.

• How to ffmpeg - encode a video for the web ?

  23 août 2014, par Michael Heuberger

  the videos I currently encode with ffmpeg for the web have a problem : I cannot repeat these in a loop nor jump to a scene. They only can be played once and that’s it !

  Maybe I have to add some more parameters ? Not sure which ones.

  I am encoding the videos into MP4 and WebM both so that they can be played in all browsers within the <video></video> element. This with the nodejs module ttps ://github.com/fluent-ffmpeg/node-fluent-ffmpeg. Here an example of the command for the WebM version only :

  ffmpeg -r 14.713847936548586 -f image2 -pix_fmt yuv420p -i /home/michael.heuberger/binarykitchen/code/videomail.io/var/local/tmp/clients/11e4-2a94-058ed290-9c13-4572b2c7aa99/frames/%d.webp -y -an -vcodec libvpx -b:v 386k -deadline realtime -cpu-used 5 -crf 4 /home/michael.heuberger/binarykitchen/code/videomail.io/var/local/tmp/clients/11e4-2a94-058ed290-9c13-4572b2c7aa99/videomail_preview.webm

  Any clues are very welcome !

• how to use FFMPEG to transcode h264 to h265 on Ubuntu 12.04 ?

  13 avril 2021, par ching

  I am ching.

  


  I use the following command to transcode h264 to h265.

  


  ffmpeg -i input.mp4 -c:v libx265 -crf 26 -preset fast -c:a aac -b:a 128k output.mp4


  


  But the result is

  


  


  Unknown encoder 'libx265'

  


  


  But I have compiled h265 by the following command before using the above command.

  


  sudo apt-get install cmake mercurial
cd ~/ffmpeg_sources
hg clone https://bitbucket.org/multicoreware/x265
cd ~/ffmpeg_sources/x265/build/linux
PATH="$HOME/bin:$PATH" cmake -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX="$HOME/ffmpeg_build" -DENABLE_SHARED:bool=off ../../source
make
make install


  


  Then, I use ffmpeg -codecs to check if it supports to encode h265.

  


  The result is

  


  


  D.V.L. hevc H.265 / HEVC (High Efficiency Video Coding)

  


  


  It seems that ffmpeg does not support h265.

  


  How can I solve this problem ?