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• How to convert natural language to structural description like FFmpeg filter graph strings

  11 juillet 2022, par 张无敌

  I'm working on a program that takes natural language as input, and outputs valid FFmpeg filter graph description, for example :

  


  Input string :

  


  rotate 1.mp4 90deg clockwise, downscale to 480p, output 2.mpeg


  


  Output description :

  


  rotate=a=90,scale=640*480


  


  It seems impractical with complete natural language, especially in the case of complex filter graphs, but still doable with slightly formatted input.

  


  I am new to NLP, wondering which areas or methods could help implement this.

  


• App engine php flex env exec("ffmpeg...") - Unable to open logfile : /dev/stderr

  15 octobre 2018, par dan

  I’m trying to run FFMPEG on the app engine flex env for php.

  I’ve whitelisted the exec() function in my app.yaml and installed FFMPEG using the docker file - so far so good.

  When I’m running a exec("usr/bin/ffmpeg [args]...") I get an error that ffmpeg can’t access the dev/stderr and the function shuts down. see ref :

  WARNING : [pool app] child 44 said into stderr : "NOTICE : PHP message : ALERT - Unable to open logfile : /dev/stderr (attacker ’’, file ’/app/index.php’, line 49)"

  WARNING : [pool app] child 44 said into stderr : "NOTICE : PHP message : PHP Warning : exec() has been disabled for security reasons in /app/index.php on line 49"

  My configuration files are as follows :

  APP.YAML :

  runtime: custom
  
  env: flex
  
  runtime_config:
  
    document_root: .

  COMPOSER.JSON :

  {
  
      "require": {
  
          "php": "5.6.*",
  
          "google/cloud-storage": "^1.0",
  
      }
  
  }

  DOCKERFILE :

  FROM gcr.io/google-appengine/php:latest
  
  ENV DOCUMENT_ROOT /app
  
  RUN apt-get -y update && apt-get install -y ffmpeg

  INDEX.PHP :

  <?php
  
  //downloaded images into /tmp folder
  
  $cmd = "/usr/bin/ffmpeg -r 24 -i /tmp/frame_%05d.png -r 24 -vcodec libx264 -pix_fmt yuv420p -b 50M -s 1920x1080 -y /tmp/export.mp4";
  
  exec($cmd);
  
  ?>

  I’ve tried using all the other shell function - system(), exec_shell(),proc_open()
  With the same result.

  Any help ?

  Thank you

• How to programmatically start/stop FFMPEG stream transcoding

  3 février 2014, par Paul Wieland

  I have an ip webcam which provides an MJPEG stream. I can successfully transcode and save that stream with ffmpeg under OSX. The following gives me pretty much what I want :

  ffmpeg -f mjpeg -i "http://user:pass@10.0.1.200/nphMotionJpeg?Resolution=640x480&Quality=Standard" -b:v 1500k -vcodec libx264 /tmp/test.mp4

  That will start an FFMPEG session and begin saving the live stream to my test.mp4 file. pressing q will quit ffmpeg and save the file.

  I would like to programmatically start & stop the recording using a PHP or Bash shell script. I have tried the following :

  <?php
  
  
  
  $pid = pcntl_fork();
  
  
  
  if($pid == -1){
  
      die("could not fork"); 
  
  }elseif($pid){
  
      // we are the parent...
  
      print $pid.' started recording. waiting 10 seconds...';
  
      sleep(10); // Wait 10 seconds
  
  
  
      print_r(shell_exec("kill ".$pid)); // Kill the child recording process
  
  
  
      echo 'done';
  
      exit(); 
  
  }else{
  
      // we are the child process. call ffmpeg.
  
      exec('../lib/ffmpeg -f mjpeg -i "http://user:pass@10.0.1.200/nphMotionJpeg?Resolution=640x480&Quality=Standard" -b:v 1500k -vcodec libx264 /tmp/test.mp4');
  
  }

  But there are two problems :

  1. The ffmpeg process does not end/die (probably because its forked again)
  2. When I manually kill the ffmpeg process, the video file is not readable