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• NodeJs : How to pipe two streams into one spawned process stdin (i.e. ffmpeg) resulting in a single output

  20 juin 2018, par Keyne Viana

  In order to convert PCM audio to MP3 I’m using the following :

  function spawnFfmpeg() {
  
      var args = [
  
          '-f', 's16le',
  
          '-ar', '48000',
  
          '-ac', '1',
  
          '-i', 'pipe:0',
  
          '-acodec', 'libmp3lame',
  
          '-f', 'mp3',
  
          'pipe:1'
  
      ];
  
  
  
      var ffmpeg = spawn('ffmpeg', args);
  
  
  
      console.log('Spawning ffmpeg ' + args.join(' '));
  
  
  
      ffmpeg.on('exit', function (code) {
  
          console.log('FFMPEG child process exited with code ' + code);
  
      });
  
  
  
      ffmpeg.stderr.on('data', function (data) {
  
          console.log('Incoming data: ' + data);
  
      });
  
  
  
      return ffmpeg;
  
  }

  Then I pipe everything together :

  writeStream = fs.createWriteStream( "live.mp3" );
  
  var ffmpeg = spawnFfmpeg();
  
  stream.pipe(ffmpeg.stdin);
  
  ffmpeg.stdout.pipe(/* destination */); 

  The thing is... Now I want to merge (overlay) two streams into one. I already found how to do it with ffmpeg : How to overlay two audio files using ffmpeg

  But, the ffmpeg command expects two inputs and so far I’m only able to pipe one input stream into the pipe:0 argument. How do I pipe two streams in the spawned command ? Would something like ffmpeg -i pipe:0 -i pipe:0... work ? How would I pipe the two incoming streams with PCM data (since the command expects two inputs) ?

• FFmpeg Capture remote screen

  29 août 2018, par ricardo

  I am trying capture a remote screen via ffmpeg and x11grab, I run in my machine this command

  xpra start-desktop :20 --start-child=fluxbox

  this machine have the ip 192.168.1.15

  and in the remote capture I try run this

  /usr/local/bin/ffmpeg -f pulse -server 192.168.1.15 -i tarjeta01.monitor -f x11grab -framerate 25 -r 25 -i 192.168.1.15:20.0 -fflags nobuffer -f rtp -c:v h264_nvenc -preset llhp -profile:v baseline -level 4 -delay 0 -b:v 1500k -threads 4 -cbr 1 -r 25 -an udp://:5008 -f rtp -vn -c:a libopus -ar 48000 -ac 2 -ab 96k -application lowdelay -compression_level 0 -frame_duration 2.5 -cutoff 20000 -vbr constrained udp://localhost:5006

  I make xhost + and xhost + 192.168.1.16 in the machine where run xpra but always receive this error

  [x11grab @ 0x23e4ea0] Cannot open display 192.168.1.15:20, error 1.
  
  192.168.1.15:20: Input/output error

  I try xpra, Xephyr and xfvb but always get the same error

  Thanks for all best regards

• How to pass multiple RTP options to ffmpeg ?

  6 novembre 2017, par MSalters

  Building my own RTSP server for FFMPEG, so I’m executing ffmpeg as a child process.

  The problem I currently have is that I’m adding multicast support, and an RTSP client may add ttl to the RTSP Transport line. No problem so far, as ffmpeg supports that. But exactly how do I pass it ? The documented URL format is

   rtp://hostname[:port][?option=val...]

  That’s not the sort of definition you should write if you want to pass a Comp.Sci class. The ellipsis suggests you can pass more than one parameter, but not how. And I need not just ttl= but also localrtpport=.

  I suppose I could follow HTTP conventions and assume that they intended [?option=val[&option=val]*] but I can’t find an authoritative source for that.

  Asked elsewhere but unanswered there too.