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• 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 ?

  


• How to add subtitle in Video using Ffmpeg Command

  8 mai 2014, par Sanket990

  I m executing below command and getting Stream #0:0 : Subtitle : unknown_codec
  (codec unknown_codec) not found for output stream #0:0
  FFmpeg command :

  final String demoVideoPath =   "/sdcard/b.mp4";
  
  final String subTitlePath="/sdcard/srtf.srt";
  
  String ffmpegCommand[] = { "ffmpeg", "-i", demoVideoPath, "-i", subTitlePath,
  
                          "-map","1", "-c", "copy","-strict", "experimental","-c:v","mpeg","-crf","23","-preset","veryfast",
  
                            "/sdcard/output.avi" };

  LogCat

   Shellout[srt @ 0xc03930] Estimating duration from bitrate, this may be inaccurate
  
   ShelloutInput #1, srt, from '/sdcard/srtf.srt':
  
  Shellout  Duration: N/A, bitrate: N/A
  
   Shellout    Stream #1:0: Subtitle: srt
  
   ShelloutPlease use -b:a or -b:v, -b is ambiguous
  
   ShelloutOutput #0, avi, to '/sdcard/output.avi':
  
  Shellout  Metadata:
  
   Shellout    major_brand     : isom
  
  Shellout    minor_version   : 512
  
   Shellout    compatible_brands: isomiso2mp41
  
  
  
  Shellout    creation_time   : 2013-12-20 11:33:07
  
  Shellout    encoder         : Lavf51.12.1
  
   Shellout    Stream #0:0: Subtitle: unknown_codec
  
   ShelloutStream mapping:
  
  Shellout  Stream #1:0 -> #0:0 (srt -> ?)
  
  ShelloutEncoder (codec unknown_codec) not found for output stream #0:0

  How to handle unknown_codec error.

• ffmpeg crop with negative offset

  12 août 2020, par Ajouve

  I have a nodejs application which is cropping videos using ffmpeg

  


  From time to time I have an error because I am trying to crop out of the video, see attached image where the black is the video and in red the crop zone. My final video has to be a square.

  


  

  


  If I am replacing the negative offset with 0 the final result will not be a square.

  


  I just need to add a black background on the non-existing part

  


  This is my actual code

  


  const cropVideo = (buffer, width, height, x, y) => {

    const inputFile = tmp.fileSync();
    const outputFile = tmp.fileSync();

    fs.writeFileSync(inputFile.name, buffer);

    return new Promise((resolve, reject) => {
        ffmpeg(inputFile.name)
            .videoFilters(`crop=${width}:${height}:${x}:${y}`)
            .format('mp4')
            .on('error', reject)
            .on('end', () => resolve(fs.readFileSync(outputFile.name)))
            .save(outputFile.name);
    })
}