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• Improve ffmpeg CPU usage by compramising quality

  20 juin 2015, par Hardik Juneja

  I am using FFMpeg for screen capturing.
  I am looking for a screen capturing tool that will run on 1000 of VMs (windows and mac).The VMs have limited CPU (1 core) and 2GB ram and No GPU.

  Currently I invoke ffmpeg with

  ffmpeg  -y -framerate 8 -f dshow -f gdigrab -i "desktop"  -c:v libx264  -crf 0 -preset ultrafast -threads 0 temp.mkv

  I am using gdigrab to capture screen ? Is there any better options that might reduce cpu usage ? or changing the encoder or format ?

  I am aiming for 4-5% reduction in CPU usage.

  Thanks in advance

• Implementing '-async 1' in C code to correct out of sync audio

  25 septembre 2013, par Christian P.

  I have built a segmenter that takes as input a h264 / AAC video and segments according to the HLS specification. The source code for it can be seen here : https://gist.github.com/cpnielsen/f36729c371aac0fe535d

  It is implemented as a python extension, but the interesting parts are in the process_video() function. It makes use of the libav library (alternatively ffmpeg) to do the heavy lifting.

  It works 95% of the time, but we have come upon some videos where it produces segments with audio out of sync. If I was using the command-line tool, I could simply add -async 1 to fix it, but how do I implement the same functionality in my C code ?

  I found a snippet of code in avconv_filter.c (for libav, not sure what the ffmpeg equivalent is) where they initiate the filter, but without any documentation it is hard to figure out how to do this outside the whole modular setup.

  I just need to :

  1. Initiate the correct filter
  2. Apply it to the input (or output ? not sure)
  3. Know of any pitfalls when using the filter.

  Any help is welcome ; sample code, explanation of the filter, etc.

• Using Node.js module fluent-ffmpeg to convert video but my files end up corrupt

  19 septembre 2013, par El Guapo

  i am writing a node based media encoding tool and have found a few good node packages that will help me to do this, but the output files are either totally corrupt or it only encodes half the video.

  The main node package i am using is fluent-ffmpeg, and i am trying it with the following code :

  var ffmpeg = require('fluent-ffmpeg');
  
  
  
  var proc = new ffmpeg({ source: 'uploads/robocop-tlr1_h480p.mov', nolog: false})
  
    .withVideoCodec('libx264')
  
    .withVideoBitrate(800)
  
    .withAudioCodec('libvo_aacenc')
  
    .withAudioBitrate('128k')
  
    .withAudioChannels(2)
  
    .toFormat('mp4')
  
    .saveToFile('output/robocop.mp4',
  
      function(retcode, error){
  
          console.log('file has been converted succesfully');
  
  });

  There is not a problem with the source video as i encoded it just fine using FFmpeg normally with the following comand line string (i run it from a batch file) :

  "c:\ffmpeg\bin\ffmpeg.exe" -i %1 -acodec libvo_aacenc -b:a 128k -ac 2 -vcodec libx264 -b:v 800k -f mp4 "../output/robocop2.mp4"

  Any ideas what i am doing wrong here ?