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• Recording a webpage stream with multiple requests using PhantomJS & ffmpeg to /dev/stdout leads to ffmpeg error

  2 septembre 2016, par Allisson Ferreira

  First of all, sorry for my english.

  I’m in a quest for days. I’ve researched everywhere and I couldn’t find an answer to my problem.

  I’m using Nodejs, Phantomjs and ffmpeg in this scenary :

  • An user enters the site, login with facebook and he can ask for a video with his name and some random photos (gathered by /me/ & sent via JSON POST) ;
  • Node receive the user data, creates a child process (PhantomJS + ffmpeg) and awaits for a response to send the video URL to the user.

  When I run a single instance of this request, everything is working fine. BUT, when two or more users make the request, only one video is sent and the others process end up in a ffmpeg stream error.

  I think the reason is that all the ffmpeg processes are using the same place (/dev/stdout). Since one process is already using it, the others enters in a "can’t access" error. But it is a assumption, I don’t know how /dev/stdout really works.

  Here are my codes. (I have removed some lines and renamed some variables for better understanding, sorry for any mistake)

  index.js :

  var generateVideo = 'phantomjs phantom.js '+videoID+' '+userID+' | ffmpeg -vcodec png -f image2pipe -r 30 -i - -pix_fmt yuv420p public/videos/'+userID+'/'+videoID+'.mp4 -y';
  
  
  
  childProcess.exec(generateVideo, function(err, stdout, stderr) {
  
      var json    = {};
  
      json.video  = '/videos/'+userID+'/'+videoID+'.mp4';
  
      res.send(json);
  
  });

  phantom.js :

  var page            = require('webpage').create();
  
  page.viewportSize   = { width: 1366, height: 768 };
  
  page.settings.resourceTimeout = 10000;
  
  
  
  var args            = require('system').args;
  
  var videoID         = args[1];
  
  var userID          = args[2];
  
  
  
  page.open('http://localhost:3000/recordvideo/'+videoID, 'post', function(status){
  
      var frame       = 0;
  
      var target_fps  = 30;
  
      var maxframes   = page.evaluate(function () {
  
                          return getTotalDurationInSeconds();
  
                      }) * target_fps;
  
  
  
      setInterval(function(){
  
          page.render('/dev/stdout', { format: "png" });
  
          if( frame >= maxframes ){
  
              phantom.exit();
  
          }
  
          frame++;
  
      }, (1000 / target_fps));
  
  });

  And the error :

  [Error: Command failed: /bin/sh -c phantomjs phantom.js XXXXXXXX XXXXXXXX | ffmpeg -vcodec png -f image2pipe -r 30 -i - -pix_fmt yuv420p public/videos/XXXXXXXX/XXXXXXXX.mp4 -y
  
  www-0 ffmpeg version N-80901-gfebc862 Copyright (c) 2000-2016 the FFmpeg developers
  
  www-0   built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04.3)
  
  www-0   configuration: --extra-libs=-ldl --prefix=/opt/ffmpeg --mandir=/usr/share/man --enable-avresample --disable-debug --enable-nonfree --enable-gpl --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --disable-decoder=amrnb --disable-decoder=amrwb --enable-libpulse --enable-libfreetype --enable-gnutls --enable-libx264 --enable-libx265 --enable-libfdk-aac --enable-libvorbis --enable-libmp3lame --enable-libopus --enable-libvpx --enable-libspeex --enable-libass --enable-avisynth --enable-libsoxr --enable-libxvid --enable-libvidstab
  
  www-0   libavutil      55. 28.100 / 55. 28.100
  
  www-0   libavcodec     57. 48.101 / 57. 48.101
  
  www-0   libavformat    57. 41.100 / 57. 41.100
  
  www-0   libavdevice    57.  0.102 / 57.  0.102
  
  www-0   libavfilter     6. 47.100 /  6. 47.100
  
  www-0   libavresample   3.  0.  0 /  3.  0.  0
  
  www-0   libswscale      4.  1.100 /  4.  1.100
  
  www-0   libswresample   2.  1.100 /  2.  1.100
  
  www-0   libpostproc    54.  0.100 / 54.  0.100
  
  www-0 [png @ 0x3d7c4a0] Invalid PNG signature 0x46726F6D20506861.
  
  www-0 [image2pipe @ 0x3d72780] decoding for stream 0 failed
  
  www-0 [image2pipe @ 0x3d72780] Could not find codec parameters for stream 0 (Video: png, none(pc)): unspecified size
  
  www-0 Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  www-0 Input #0, image2pipe, from 'pipe:':
  
  www-0   Duration: N/A, bitrate: N/A
  
  www-0     Stream #0:0: Video: png, none(pc), 30 tbr, 30 tbn, 30 tbc
  
  www-0 [buffer @ 0x3d81540] Unable to parse option value "0x0" as image size
  
  www-0 [buffer @ 0x3d81540] Unable to parse option value "-1" as pixel format
  
  www-0 [buffer @ 0x3d81540] Unable to parse option value "0x0" as image size
  
  www-0 [buffer @ 0x3d81540] Error setting option video_size to value 0x0.
  
  www-0 [graph 0 input from stream 0:0 @ 0x3d72600] Error applying options to the filter.
  
  www-0 Error opening filters!
  
  www-0 ]

  I really hope that I can find an answer here !
  And sorry if there already is an answer for this. But I researched for days.

  Thank you in advance !

• lavfi/atempo : avoid asendcmd assertion failure

  13 mars 2024, par Rajiv Harlalka

  lavfi/atempo : avoid asendcmd assertion failure
  Check for zeros equal to the total samples early, because in
  
  that case we would already be leaving the first few frames out.
  Fixes trac ticket #10692
  

  • [DH] libavfilter/af_atempo.c

• lavf/http: fix incorrect warning in range requests

  19 octobre 2015, par Rodger Combs

  lavf/http: fix incorrect warning in range requests
  

  • [DH] libavformat/http.c