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• Frames per second Conceptual Details

  25 février 2014, par Whoami

  i am a newbie and trying to understand the concepts behind ffmpeg/video.

  FPS means frame per second , for example

  25fps -> 25 frames captured in a second

  From the display perpective

  25 frames need to be displayed in a second.

  correct me if i am wrong ?

  Now i have written a simple video player in ffmpeg to display. i read
  frames by av_read_frame(), if fps is 25, then does

   av_read_frame()

  returns 25 frames per second ? how can i relate it ?

• exec function not working as expected

  6 mars 2016, par Albert

  I am running a shell function from php to convert a video file to flash once it is uploaded. The exec function is like this :

  exec("ffmpeg -i " . WWW_ROOT . "files" . DS . "videos" . DS . $id . $ext . " -ar 22050 -r 32 -f flv -s 640x480 " . WWW_ROOT . "files" . DS . "videos" . DS . $id . ".flv");
  
  
  
  // if I echo the string it returns:
  
  // ffmpeg -i /home/vceroot/public_html/example.com/test/intraweb/app/webroot/files/videos/516c1203-0484-417a-b047-5488c40293e9.mpg -ar 22050 -r 32 -f flv -s 640x480 /home/vceroot/public_html/example.com/test/intraweb/app/webroot/files/videos/516c1203-0484-417a-b047-5488c40293e9.flv
  
  // the locations are correct

  However, it does not convert the video.

  After it uploaded the file, it just goes back to the index action. There is no converted file although the uploaded file is there.

  My permissions on the folder is 755. And the folder owner is apache. I don’t know what else to do. Can anyone assist me ?

  UPDATE

  So I’ve changed my exec query a bit and echoed the output :

  exec("ffmpeg -i " . WWW_ROOT . "files" . DS . "videos" . DS . $id . $ext . " -ar 22050 -r 32 -f flv -s 640x480 " . WWW_ROOT . "files" . DS . "videos" . DS . $id . ".flv 2>&1", $output, $return);
  
  die(print_r($output));

  This returned the following error :

  Array ( [0] => sh: ffmpeg: command not found ) 1

  So I changed it a bit to this :

  exec("/usr/local/bin/ffmpeg -i " . WWW_ROOT . "files" . DS . "videos" . DS . $id . $ext . " -ar 22050 -r 32 -f flv -s 640x480 " . WWW_ROOT . "files" . DS . "videos" . DS . $id . ".flv 2>&1", $output, $return);
  
  die(print_r($output));

  And now it returns :

  Array ( [0] => /usr/local/bin/ffmpeg: error while loading shared libraries: libavdevice.so.55: cannot open shared object file: No such file or directory ) 1

  Where do I go from here ?

• ffmpeg in opencv 2.4

  27 août 2012, par Josh Elsdon

  I am using opencv, but it is very pick with video types that it will open. I have version 2.4 of opencv and it apparently has ffmpeg support built in, though it does not open any movie files correctly, obj.grab() returns false and retrieve(frame,0) return NULL. So it seems to me that FFmpeg is not working correctly, is there something I need to do to turn it on, from internet searches people seem to suggest that from 2.4 onward it is a non-issue(though apparently not). Any help, all the other threads seem to just aout stop short of the answer for me.

  (windows 7, Visual studio 2010, opencv 2.4)