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• Python & OpenCV - VideoCapture.read() always returns false

  21 août 2017, par Julen

  I need to extract frames from a video at a given time, and I’m using OpenCV for it. I’m using Linux Mint 18.1, but it must also run on Ubuntu.

  This code example is not working for me :

  import cv2
  
  
  
  print('making screenshot from {0}'.format('/tmp/big_buck_bunny_720p_5mb.mp4'))
  
  
  
  cap = cv2.VideoCapture(video_path)
  
  cap.set(cv2.CAP_PROP_POS_MSEC,1000)
  
  ret,frame = cap.read()
  
  print(ret)                      # This is false
  
  cv2.imwrite("image.jpg", frame) # Creates an empty file

  (I’ve checked that the path of the video is correct and that the file is not corrupted).

  I have installed the Python OpenCV 3.3.0 version :

  >>> import cv2
  
  >>> cv2.__version__
  
  '3.3.0'

  I’ve compiled and installed the source for OpenCV (with the WITH_FFMPEG=ON option) :

  git clone https://github.com/Itseez/opencv.git /tmp/opencv-3                                                                                                                                                                                
  
  /tmp/opencv-3                                                                                                                                                                                                                            
  
  mkdir -p release                                                                                                                                                                                                                            
  
  cd release                                                                                                                                                                                                                                  
  
  cmake -D WITH_FFMPEG=ON -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local ..                                                                                                                                                   
  
  make                                                                                                                                                                                                                                        
  
  sudo make install     

  The output of ffmpeg -version is the following :

  ffmpeg version 2.8.11-0ubuntu0.16.04.1 Copyright (c) 2000-2017 the FFmpeg developers
  
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
  
  configuration: --prefix=/usr --extra-version=0ubuntu0.16.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-libx264 --enable-libopencv
  
  libavutil      54. 31.100 / 54. 31.100
  
  libavcodec     56. 60.100 / 56. 60.100
  
  libavformat    56. 40.101 / 56. 40.101
  
  libavdevice    56.  4.100 / 56.  4.100
  
  libavfilter     5. 40.101 /  5. 40.101
  
  libavresample   2.  1.  0 /  2.  1.  0
  
  libswscale      3.  1.101 /  3.  1.101
  
  libswresample   1.  2.101 /  1.  2.101
  
  libpostproc    53.  3.100 / 53.  3.100

  What am I missing ?

• Android version in Metadata

  26 août 2018, par ClassA

  I just ran this FFMPEG command and noticed that the android version is in the metadata :

  ffmpeg -i test.mp4 -f ffmetadata metadata.txt
  
  -->
  
  com.android.version=7.0

  This was very interesting because I’m currently trying to check if a video file was taken with a Android device or not.

  Can someone please tell me if all Android devices add this tag to the Metadata of a video and if I will be able to use MediaMetadataRetriever to check if this tag exists ?

• decode hevc on android

  27 mars 2015, par skipper

  I’m trying to make a video player on android using android-ffmpeg, it works fine with avc streams, but failed to decode hevc ones. Are there any special requirements for decoding hevc on android with android-ffmpeg ?