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• How do I get the last line of a popen() callback in every iteration ?

  29 mai 2017, par Mike

  I’m trying to create a progress bar with FFMPEG using php and AJAX. When a user uploads a video file I want to be able to display the current percent until completion. I have managed to get everything working but I have one issue.

  The data returns what I want, but it also returns all the data from the previous iterations... like it just keeps stacking everything on top rather than flushing out the data from previous iterations. I tried to work with tail thinking it would return only the last line, but it did not return anything.

  Here is the code I’m working with :

  encode.php

  $video_path = 'test.mp4';
  
  $cmd        = 'ffmpeg -i ' . $video_path .' -y -hide_banner output.mp4 2>&1';
  
  
  
  while (@ ob_end_flush());
  
  
  
  $proc = popen($cmd, 'r');
  
  
  
  while (!feof($proc))
  
  {
  
  
  
      $file = escapeshellarg(fread($proc, 4096));
  
      //$line = `tail -n 1 $file`; // <-tried this with no luck
  
      echo fread($file, 4096) . "\n";
  
      @ flush();
  
  }
  
  return 'complete';
  
  pclose($proc);

  The above code returns :

  // first iteration
  
  frame=   52 fps= 13 q=29.0 size=     279kB time=00:00:00.10 bitrate=22856.9kbits/s
  
  
  
  // second iteration
  
  frame=   52 fps= 13 q=29.0 size=     279kB time=00:00:00.10 bitrate=22856.9kbits/s    
  
  frame=   54 fps= 12 q=29.0 size=     329kB time=00:00:00.16 bitrate=16146.6kbits/s 
  
  
  
  // third iteration
  
  frame=   52 fps= 13 q=29.0 size=     279kB time=00:00:00.10 bitrate=22856.9kbits/s    
  
  frame=   54 fps= 12 q=29.0 size=     329kB time=00:00:00.16 bitrate=16146.6kbits/s    
  
  frame=   57 fps= 11 q=29.0 size=     464kB time=00:00:00.26 bitrate=14233.2kbits/s 

  As you can see the data stacks, I need only the new line of data, not the data stacking.

  ** EDIT ** this has been marked as a duplicate, rather than me explain how it’s different, I’d like to hear how this is the same thing ? I am not writing to a log file and, like most people, do not feel that’s a good solution.

• 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 ?

  


• 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.