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• Record audio from specific Xvfb session on Centos

  18 août 2017, par boygiandi

  I’m trying to record audio from firefox in a Xvfb session. I installed pulseaudio server and I can record audio. But when I have more than 1 Xvfb session, the audio get mixed. How can I start 2 ffmpeg process and record 2 Xvfb sessions separate ?

  The ffmpeg command look like this

  ffmpeg -f pulse -i default -r 30 -framerate 5 -f x11grab -i :xxx -c:v libx264 -x264-params keyint=60 -bufsize 500k -c:a aac -ar 44100 -b:a 128k -f flv ...

  Then I tried to create virtual audio device

  pacmd load-module module-null-sink sink_name=MySink

  pacmd load-module module-loopback sink=MySink

  Set this device as default input/output audio

  pacmd set-default-source "MySink.monitor"

  pacmd set-default-sink "MySink"

  I hope that when I start Xvfb session + firefox, it’ll play audio on this device as default and ffmpeg’ll also get audio from there. The ffmpeg command now become

  ffmpeg -f pulse -i MySink.monitor -r 30 -framerate 5 -f x11grab -i :xxx -c:v libx264 -x264-params keyint=60 -bufsize 500k -c:a aac -ar 44100 -b:a 128k -f flv ...

  But what I get is noise or ffmpeg error 100 buffers queued in out_0_1, something may be wrong. What did I do wrong ?

  And as I know, firefox 54 doesn’t support alsa anymore, so we only can use pulseaudio.

• Using ffmpeg to assemble images from S3 into a video

  10 juillet 2020, par Mass Dot Net

  I can easily assemble images from local disk into a video using ffmpeg and passing a %06d filespec. Here's what a typical (pseudocode) command would look like :

  


  ffmpeg.exe -hide_banner -y -r 60 -t 12 -i /JpgsToCombine/%06d.JPG <..etc..>


  


  However, I'm struggling to do the same with images stored in AWS S3, without using some third party software to mount a virtual drive (e.g. TNTDrive). The S3 folder containing our images is too large to download to the 20GB ephemeral storage provided for AWS containers, and we're trying to avoid EFS because we'd have to provision expensive bandwidth.

  


  Here's what the HTTP and S3 URLs to each of our JPGs looks like :

  


  # HTTP URL
https://massdotnet.s3.amazonaws.com/jpgs-to-combine/000000.JPG # frame 0
https://massdotnet.s3.amazonaws.com/jpgs-to-combine/000012.JPG # frame 12
https://massdotnet.s3.amazonaws.com/jpgs-to-combine/000123.JPG # frame 123
https://massdotnet.s3.amazonaws.com/jpgs-to-combine/456789.JPG # frame 456789

# S3 URL
s3://massdotnet/jpgs-to-combine/000000.JPG # frame 0
s3://massdotnet/jpgs-to-combine/000012.JPG # frame 12
s3://massdotnet/jpgs-to-combine/000123.JPG # frame 123
s3://massdotnet/jpgs-to-combine/456789.JPG # frame 456789


  


  Is there any way to get ffmpeg to assemble these ? We could generate a signed URL for each S3 file, and put several thousand of those URLs onto a command line with an FFMPEG concat filter. However, we'd run up into the command line input limit in Linux at some point using this approach. I'm hoping there's a better way...

  


• Increase resolution of captured image using avconv

  26 novembre 2014, par user3723711

  I am setting two virtual devices using gst-launch-0.10 :

  gst-launch-0.10 v4l2src device=/dev/video1 ! video/x-raw-rgb,framerate=30/1,width=640,height=480 ! ffmpegcolorspace ! tee name=t ! v4l2sink device=/dev/video2 t. ! queue ! v4l2sink device=/dev/video3

  then for /dev/video2 I am using ffmpeg to stream video and then I send this stream to browser :

  ffmpeg -s 640x480 -f video4linux2 -i /dev/video2 -f mpeg1video -b 800k -r 30 http://localhost:8082/pass/640/480/

  now on my browser when user clicks on "capture" button I am using this function to capture the frame from ffmpeg stream using avconv :

  function captureImage(res, path) {
  
      var ffmpeg_options = ['-s', '1280x720', '-f', 'video4linux2', '-i', '/dev/video3', '-ss', '0:0:0', '-frames', '1', path];
  
      avcov_capture = spawn('avconv', ffmpeg_options, null);
  
      var stream = false;
  
      avcov_capture.stdout.on('data', function(buf) {
  
          console.log('CAP OUT: ' + buf.toString());
  
      });
  
      avcov_capture.stderr.on('data', function(data) {
  
          if (data.toString().indexOf('frame') >= 0) {
  
              var ret = {
  
                  result : 'captured',
  
                  path : path
  
              };
  
              checkFile(res, ret, path);
  
          }
  
      });
  
  };

  My question is when I capture a frame using avconv (in captureImage function), how I can increase the resolution of that image and stop ffmpeg stream after I capture a frame ?

  Is it a better idea if I increase resolution of video stream sent to video2 in gst-launch pipeline ?If so how can I add that setting to my pipeline.