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• OpenCV linux how to install FFMPEG

  19 janvier 2017, par Thandi Ngamu

  Can someone please help me with a working method on how to install FFMPEG on linux, I have followed several tutorials and they seem to work except after everything FFMPEG is never found in the system, even after several system reboots my last try was from this link Compile FFmpeg on Ubuntu, Debian, or Mint

  I did everything in the tutorial but when i run the man ffmpeg it tells me no manual found and OpenCV too does not detect it, I tried calling the Core.getBuildInformation() and the output was :

  GUI: 
  
  QT:                          NO
  
  GTK+:                        NO
  
  GThread :                    NO
  
  GtkGlExt:                    NO
  
  OpenGL support:              NO
  
  VTK support:                 NO
  
  
  
  Media I/O: 
  
  ZLib:                        zlib (ver 1.2.8)
  
  JPEG:                        libjpeg (ver 90)
  
  WEBP:                        build (ver 0.3.1)
  
  PNG:                         build (ver 1.6.24)
  
  TIFF:                        build (ver 42 - 4.0.2)
  
  JPEG 2000:                   build (ver 1.900.1)
  
  OpenEXR:                     build (ver 1.7.1)
  
  GDAL:                        NO
  
  GDCM:                        NO
  
  
  
  Video I/O:
  
  DC1394 1.x:                  NO
  
  DC1394 2.x:                  NO
  
  FFMPEG:                      NO
  
    avcodec:                   NO
  
    avformat:                  NO
  
    avutil:                    NO
  
    swscale:                   NO
  
    avresample:                NO
  
  GStreamer:                   NO
  
  OpenNI:                      NO
  
  OpenNI PrimeSensor Modules:  NO
  
  OpenNI2:                     NO
  
  PvAPI:                       NO
  
  GigEVisionSDK:               NO
  
  Aravis SDK:                  NO
  
  UniCap:                      NO
  
  UniCap ucil:                 NO
  
  V4L/V4L2:                    NO/YES
  
  XIMEA:                       NO
  
  Xine:                        NO
  
  gPhoto2:                     NO
  
  
  
  Parallel framework:            pthreads
  
  
  
  Other third-party libraries:
  
  Use IPP:                     9.0.1 [9.0.1]
  
       at:                     /home/daddy/opencv-3.2.0/build/3rdparty/ippicv/ippicv_lnx
  
  Use IPP Async:               NO
  
  Use VA:                      NO
  
  Use Intel VA-API/OpenCL:     NO
  
  Use Lapack:                  NO
  
  Use Eigen:                   NO
  
  Use Cuda:                    NO
  
  Use OpenCL:                  YES
  
  Use OpenVX:                  NO
  
  Use custom HAL:              NO
  
  
  
  OpenCL:                        <dynamic loading="loading" of="of" opencl="opencl" library="library">
  
  Include path:                /home/daddy/opencv-3.2.0/3rdparty/include/opencl/1.2
  
  Use AMDFFT:                  NO
  
  Use AMDBLAS:                 NO
  
  
  
  Python 2:
  
  Interpreter:                 /usr/bin/python2.7 (ver 2.7.12)
  
  
  
  Python 3:
  
  Interpreter:                 /usr/bin/python3 (ver 3.5.2)
  
  
  
  Python (for build):            /usr/bin/python2.7
  
  
  
  Java:
  
  ant:                         /usr/bin/ant (ver 1.9.6)
  
  JNI:                         /usr/lib/jvm/java-8-oracle/include /usr/lib/jvm/java-8-oracle/include/linux /usr/lib/jvm/java-8-oracle/include
  
  Java wrappers:               YES
  
  Java tests:                  YES
  
  
  
  Matlab:                        Matlab not found or implicitly disabled
  
  
  
  Documentation:
  
  Doxygen:                     NO
  
  
  
  Tests and samples:
  
  Tests:                       YES
  
  Performance tests:           YES
  
  C/C++ Examples:              NO
  
  
  
  Install path:                  /usr/loca
  
  cvconfig.h is in:              /home/user/opencv-3.2.0/build
  
  </dynamic>

• PHP readfile on a file which is increasing in size

  13 février 2013, par Sathiya Sundaram

  Is it possible to use PHP readfile function on a remote file whose size is unknown and is increasing in size ? Here is the scenario :

  I'm developing a script which downloads a video from a third party website and simultaneously trans-codes the video into MP3 format. This MP3 is then transferred to the user via readfile.

  The query used for the above process is like this :

  wget -q -O- "VideoURLHere" | ffmpeg -i - "Output.mp3" > /dev/null 2>&1 &

  So the file is fetched and encoded at the same time.
  Now when the above process is in progress I begin sending the output mp3 to the user via readfile. The problem is that the encoding process takes some time and therefore depending on the users download speed readfile reaches an assumed EoF before the whole file is encoded, resulting in the user receiving partial content/incomplete files.

  My first attempt to fix this was to apply a speed limit on the users download, but this is not foolproof as the encoding time and speed vary with load and this still led to partial downloads.

  So is there a way to implement this system in such a way that I can serve the downloads simultaneously along with the encoding and also guarantee sending the complete file to the end user ?

  Any help is appreciated.

  EDIT :
  In response to Peter, I'm actually using fread(read readfile_chunked) :

   <?php
  
   function readfile_chunked($filename,$retbytes=true) {
  
              $chunksize = 1*(1024*1024); // how many bytes per chunk
  
              $totChunk = 0;
  
              $buffer = '';
  
              $cnt =0;
  
              $handle = fopen($filename, 'rb');
  
              if ($handle === false) {
  
                  return false;
  
              }
  
              while (!feof($handle)) {
  
                  //usleep(120000); //Used to impose an artificial speed limit
  
                  $buffer = fread($handle, $chunksize);
  
                  echo $buffer;
  
                  ob_flush();
  
                  flush();
  
                  if ($retbytes) {
  
                      $cnt += strlen($buffer);
  
                  }
  
              }
  
                  $status = fclose($handle);
  
              if ($retbytes && $status) {
  
                  return $cnt;        // return num. bytes delivered like readfile() does.
  
              }
  
              return $status;
  
          }
  
          readfile_chunked($linkToMp3);
  
      ?>

  This still does not guarantee complete downloads as depending on the users download speed and the encoding speed, the EOF() may be reached prematurely.

  Also in response to theJeztah's comment, I'm trying to achieve this without having to make the user wait..so that's not an option.

• Opencv Videocapture fails to read http url videos

  16 mars 2019, par Purav Zumkhawala

  I want to read HTTP URL videos in my Ubuntu system without downloading them. I can do this in windows OS but when I try to run the same code in Ubuntu using the same opencv VideoCapture method it fails to get any frames.

  Why is this so ?

  I have used same opencv version in both Ubuntu and Windows, can anyone guide me towards a workaround, a tutorial using which I can compile opencv and stream url videos or any other library that supports this functionality in Ubuntu ?

  I have tried almost everything but with no productive result which has led me to finally ask this as a question.

  opencv build information :
  
  
  
    OpenCV modules:
  
      To be built:                 calib3d core dnn features2d flann gapi highgui imgcodecs imgproc java_bindings_generator ml objdetect photo python3 python_bindings_generator stitching video videoio
  
      Disabled:                    world
  
      Disabled by dependency:      -
  
      Unavailable:                 java js python2 ts
  
      Applications:                -
  
      Documentation:               NO
  
      Non-free algorithms:         NO
  
  
  
    GUI: 
  
      QT:                          YES (ver 4.8.7 EDITION = OpenSource)
  
        QT OpenGL support:         NO
  
      GTK+:                        NO
  
      VTK support:                 NO
  
  
  
    Media I/O: 
  
      ZLib:                        /lib64/libz.so (ver 1.2.3)
  
      JPEG:                        /opt/libjpeg-turbo/lib64/libjpeg.a (ver 62)
  
      WEBP:                        build (ver encoder: 0x020e)
  
      PNG:                         build (ver 1.6.35)
  
      TIFF:                        build (ver 42 - 4.0.9)
  
      JPEG 2000:                   build (ver 1.900.1)
  
      OpenEXR:                     build (ver 1.7.1)
  
      HDR:                         YES
  
      SUNRASTER:                   YES
  
      PXM:                         YES
  
      PFM:                         YES
  
  
  
    Video I/O:
  
      DC1394:                      NO
  
      FFMPEG:                      YES
  
        avcodec:                   YES (ver 58.21.104)
  
        avformat:                  YES (ver 58.17.101)
  
        avutil:                    YES (ver 56.18.102)
  
        swscale:                   YES (ver 5.2.100)
  
        avresample:                NO
  
      GStreamer:                   NO
  
      v4l/v4l2:                    linux/videodev2.h
  
  
  
    Parallel framework:            pthreads
  
  
  
    Trace:                         YES (with Intel ITT)
  
  
  
    Other third-party libraries:
  
      Lapack:                      NO
  
      Eigen:                       NO
  
      Custom HAL:                  NO
  
      Protobuf:                    build (3.5.1)
  
  
  
    OpenCL:                        YES (no extra features)
  
      Include path:                /io/opencv/3rdparty/include/opencl/1.2
  
      Link libraries:              Dynamic load
  
  
  
    Python 3:
  
      Interpreter:                 /opt/python/cp36-cp36m/bin/python (ver 3.6.5)
  
      Libraries:                   libpython3.6m.a (ver 3.6.5)
  
      numpy:                       /opt/python/cp36-cp36m/lib/python3.6/site-packages/numpy/core/include (ver 1.11.3)
  
      packages path:               lib/python3.6/site-packages
  
  
  
    Python (for build):            /opt/python/cp36-cp36m/bin/python
  
  
  
    Java:                          
  
      ant:                         NO
  
      JNI:                         NO
  
      Java wrappers:               NO
  
      Java tests:                  NO
  
  
  
    Install to:                    /io/_skbuild/linux-x86_64-3.6/cmake-install