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• unable to stream video using ffmpeg

  24 septembre 2015, par AGS

  I’ve grabbed an Image from the video capture card with opencv. I want to process each frame and send it back as a video stream. so, to do this I’ve written that video to a location using videowriter class in opencv and I’ve tried to stream that video using ffmpeg but the output isn’t satisfactory(gives stuttering effect), I’ve used mjpeg stream method to stream the video but that was a failure too.

• VideoReader decodes different Frame counts on different computers

  7 février 2014, par vishal

  I have a large video clip of .avi format(approx 1 hour in length). I read the file using VideoReader in Matlab. Surprisingly the number of frames I get on two different computers vary. Below are my system details along with the number of frames I get.

  System 1 :
  OS : Windows 8.1 (x64)
  Matlab Version : 2013b
  Media Package installed : (default, didn't install anything separately. VLC Player is also there on the PC)
  Number of frames decoded in Video : 119391

  System 2 :
  OS : Windows 7 (x64)
  Matlab Version : 2013b
  Media Package installed : ffMpeg
  Number of frames decoded in Video : 119653

  It appears the difference in frame counts is because of different codecs being used in the two cases ?

  How can I align the H264 decoder versions in the two cases ? In case I install ffmpeg on System 1, how do I configure Matlab to use that particular decoding library.

  And also I would like to know why two different codecs should yield different number of frames on decoding the same video clip !!

• How to avoid stopping or record all dynamic videos in the process of capturing screen video with ffmpeg from a python program ?

  3 décembre 2020, par fengnix

  I have many robotframework test cases and in the first case, a ffmpeg command like the following is invoked to record the whole running process :

  


  ffmpeg -framerate 30 -f gdigrab -i desktop -c:v libx264rgb -crf 0 -preset ultrafast output.mkv


  


  Whenever I firstly run all cases and then manuually run the above command from an addition command console, the recorded video always looks fine, it looks like all contents on the screen can be correctly captured.

  


  However, once I execute the command the same as the above one in the first case by call the following code :

  


  p=subprocess.Popen(cmd, shell=True, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)


  


  and then in the final test case the record process is stopped by calling the following code to tell ffmpeg that we want to stop the recording :

  


  p.stdin.write(bytes("q",'UTF-8'))  


  


  the final result video only contain correct contents of the "start" and the "end" of the whole process, but all other contents no longer changed and seemd just a static image, which means all the dynamic effects on the screen cannot be captured.

  


  Could anyone be so kind as to let me know what the matter is and how to solve it ?