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• How to Speed Up Two-Pass Encoding ?

  27 juillet 2017, par Matt McManis

  I have a Video file with Audio, Subtitles, Chapters, and Metadata.

  I removed Audio and Subtitles with -an -sn from -pass 1 and then inlclude them in -pass 2.

  What about for Chapters and Metadata ? And how do you apply Turbo to -pass 1 ?

  Is there anything more that can be done ?

  ---

  I have a script that will convert mpg to mp4. I’ve sorted it with linebreaks so it’s easier to read.

  Pass 1

  "C:\Videos\example.mpg" 
  
  
  
  -vcodec libx264 
  
  -preset medium -b:v 2500K -pix_fmt yuv420p -qcomp 0.8 
  
  -vf scale="trunc(iw/2)*2:trunc(ih/2)*2" 
  
  -pass 1 
  
  
  
  -map 0:v:0? -an -sn
  
  
  
  -threads 8 
  
  
  
  "C:\Videos\example.mp4" 

  Pass 2

  ffmpeg -y -i 
  
  
  
  "C:\Videos\example.mpg" 
  
  
  
  -vcodec libx264 
  
  -preset medium -b:v 2500K -pix_fmt yuv420p -qcomp 0.8 
  
  -vf scale="trunc(iw/2)*2:trunc(ih/2)*2" 
  
  -pass 2 
  
  
  
  -acodec aac 
  
  -b:a 320k 
  
  -af volume=1.2 
  
  
  
  -map 0:v:0? -map 0:a:0? -map 0:s? -c:s copy -map_metadata 0 
  
  
  
  -threads 8 
  
  
  
  "C:\Videos\example.mp4"

• Are there any resources listing current codecs and formats not supported by FFmpeg ?

  4 mars 2020, par Alexander Swann

  We are building a service where we do not know what format/codec a video uploaded by a user is in. Due to the nature of the application, we expect input video formats to be very fragmented, diverse and niche. We are currently using FFmpeg to transcode input formats to a consistent output (e.g. mp4).

  Due to the above scenario, I would like to establish a general list of what formats and codecs are not currently supported by FFmpeg. This is so I can research other open source video transcoding tools which I can utilise to fill in the gaps and allow our service to be more reliable for the user.

  Are there resources online that can help at least get a general idea of what might not be supported by FFmpeg ?

• Advice with ffmpeg creating clips out of a video

  5 décembre 2016, par Janx from Venezuela

  First of all I’m pretty new at this of video transcoding. I’m trying to use ffmpeg to create a 10 second clip out of a much larger video source, all this in a Node.js application using fluent-ffmpeg. My code goes something like :

  var command = ffmpeg().input(<sourcepath>).native().seekInput(<desiredstartpoint>)
  
      .duration(10)
  
      .on('start', function(commandLine){ // do some database persistence 
  
      }).on('progress',function(e){ // refresh a kill timeout
  
      }).on('error',function(e){ // clean up the mess
  
      }).on('end',function(e){ // success 
  
      }).save(<clipdestinationpath>);
  
  </clipdestinationpath></desiredstartpoint></sourcepath>

  Which usually translates into something like :

    ffmpeg -re -ss <desiredstartpoint> -i <sourcepath> -y -t 10 <clipdestinationpath>
  
  </clipdestinationpath></sourcepath></desiredstartpoint>

  What’s happening is that sometimes the process seems to ’hang’ and I have to manually kill the ffmpeg process (a batch console that appears on windows) for the node process to continue and the ’error’ callback to trigger. Same happens if I run the ffmpeg command manually on a CMD. It usually starts to :

     frame= xxx fps= yy q=x.x size= xxxKb time=00:00:0x.xx bitrate=xx.xxkbits/s
  
     frame= xxx fps= yy q=x.x size= xxxKb time=00:00:0x.xx bitrate=xx.xxkbits/s
  
     frame= xxx fps= yy q=x.x size= xxxKb time=00:00:0x.xx bitrate=xx.xxkbits/s

  Until is suddenly does it no more, and its hanged.

  I do have some fail-overs :

  • On the progress callback, I keep track of a timeout kill action, for when it hangs up, if there’s more than N seconds without activity, I call the kill like

    command.kill();

  • The other thing that I do is to decrement the desiredStartPoint by one (1) second at the time for up to five (5) seconds (greater than zero of course), and try again. Eventually the clip generates right, but it is so random... Sometimes it works like a charm, on the very first (1st) try it creates the clip all is OK to go.

  So my question is :

  • Do you see anything here that I might be missing ? Do I have to consider other variables ? like keyframes, fps, advanced stuffs like that ?

  I’ve also noticed that this happens more frequently on video sources recorded at high bitrate frequencies... I really don’t know men.