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• OpenCV : Cannot open camera with CAP_FFMPEG even though ffmpeg is installed

  24 février 2021, par cildiracagim

  Initializing a camera video capture using CAP_FFMPEG fails even though I have ffmpeg installed :

  


  cv::VideoCapture vcap;
vcap.open(0, cv::CAP_FFMPEG);

// After these, vcap.isOpened() returns false.


  


  However, it works perfectly when I open a file in the same way :

  


  cv::VideoCapture vcap;
vcap.open(argv[1], cv::CAP_FFMPEG);

/* Correctly opens the video file at path argv[1],
vcap.isOpened() returns true. */


  


  The problem occurs in both OpenCV versions installed in my system : 4.5.1 and 3.2.0. Version 3.2.0 came installed in my Linux distribution but I have compiled 4.5.1 myself. During compilation, I have verified that CMake succesfully recognized the ffmpeg installation in my system. I guess the problem is not related to OpenCV not recognizing ffmpeg since I can open and work on video files without any problems on both OpenCV versions.

  


  Any help is greatly appreciated.

  


• I have installed FFMPEG and can't find it inside a PHP script

  14 novembre 2019, par Antop

  I have installed FFMPeg in CentOS. It works perfectly.
  It’s inside /usr/bin directory. Also, I have PHP 7.2.24 that comes with Plesk 18.0.20.

  I want to use FFMPeg inside a PHP script, but that script can’t find the executable of FFMpeg. I have tried giving the exact route (/usr/bin/ffmpeg) but doesn’t work.

  It’s a production server. The same script, in my development server (macOS) works perfectly.

  I tried using :

  var_dump(getenv('PATH'));
  
  var_dump(exec('which ffmpeg'));
  
  var_dump(ini_get('open_basedir'));
  
  var_dump(is_file(exec('which ffmpeg')));
  
  var_dump(is_executable(exec('which ffmpeg')));

  And it returns me :

  string(49) "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin"
  
  string(0) ""
  
  string(44) "/var/www/vhosts/name-of-the-domain.com/:/tmp/"
  
  bool(false)
  
  bool(false)
  
  NULL

  ¿What could be happening ?

  A very strange thing I’ve noticed is that I can’t access any command via php :
  I tried using it with echo

  var_dump(exec('which echo'));
  
  var_dump(is_file(exec('which echo')));
  
  var_dump(is_executable(exec('which echo')));

  And it returns me :

  string(0) ""
  
  bool(false)
  
  bool(false)
  
  NULL

  And the permissions are right :

  [root@vps bin]# ls -lha echo
  
  -rwxr-xr-x 1 root root 33K ago 20 08:25 echo
  
  
  
  [root@vps bin]# ls -lha ffmpeg
  
  -rwxr-xr-x 1 root root 217K abr  4  2019 ffmpeg

  But if I make a

  var_dump(exec('echo "HELLO"'))

  it returns me

  string(5) "HELLO"

• Trying to fetch all audio streams with FFmpeg Python

  27 juillet 2022, par Apollo

  I'm using ffmpeg-python to fetch streams from a video and write some parameters (codec_name, resolution, etc.) for each stream into csv.

  


  video = 'test.mkv'
probe = ffmpeg.probe(video)
video_stream = next((stream for stream in probe['streams'] if stream['codec_type'] == 'video'), None)
print(video_stream['codec_long_name'])
audio_stream = next((stream for stream in probe['streams'] if stream['codec_type'] == 'audio'), None)
...


  


  My problem is that it works well for a video stream, but not for multiple audio (or subtitles) streams. If the video has several audio streams it returns only one audio stream.

  


  I've tried another approach, but it returns some streams 2-3 times and I get duplicates. So if the video sample has 4 audio tracks, I end up with 9 audio streams instread of 4.

  


  audio_streams = []
for audio in (probe['streams']):
    if (audio['codec_type'] == 'audio'):
        audio_streams.append(audio)
        pprint(audio_streams)


  


  All other ideas I tried don't work, I'm new to programming and I'm stuck with it.
How can I get all audio streams from a file without duplicates ?