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• The `Process` does not start with the special characters in the process argument

  21 septembre 2015, par Mitra M

  I can run FFmpeg.exe -i test.flv -f flv - | ffplay -i - in the cmd, But I can’t run it in the c# codes when "|" is in argument.

  This code works :

    Process process = new Process();
  
    process process .StartInfo.FileName = "FFmpeg.exe";
  
    process process .StartInfo.Arguments =" -i test.flv "
  
    process .Start();

  But this code is not working :

    Process process = new Process();
  
    process process .StartInfo.FileName = "FFmpeg.exe";
  
    process process .StartInfo.Arguments =" -i test.flv -f flv - | ffplay -i -"
  
    process .Start();

  I tried this codes but did not effect :

     process process .StartInfo.Arguments =" -i test.flv -f flv - \| ffplay -i -"
  
  
  
     process process .StartInfo.Arguments =" -i test.flv -f flv - \\| ffplay -i -"
  
  
  
     process process .StartInfo.Arguments =@" -i test.flv -f flv - | ffplay -i -"
  
  
  
     process process .StartInfo.Arguments ="\" -i test.flv -f flv - \| ffplay -i -\""

  Please tell me how can I run FFmpeg.exe -i test.flv -f flv - | ffplay -i - in the C# codes.

• Video ; Zoom to different points with a single render (?)

  31 mai 2021, par RewossKy

  Based on 16 seconds, I want the codes to zoom to the top left for the first 4 seconds, to the bottom left for the next 4 seconds, to the top right for the next 4 seconds, and then to the bottom right for 4 seconds.

  


  Structurally, the codes are ready, but I need small details, I want to render them in one go (without rendering 4 times) and focus every 4 seconds elsewhere.

  


  If you can help me I would be very happy. I couldn't figure it out for days.

  


  'Top left
ffmpeg -y -i input.mp4 -vf "zoompan=z='if(lte(mod(time,16),4),2,1.05)':d=1:x=iw/3-(iw/zoom/2):y=ih/3-(ih/zoom/2):fps=29.97" output.mp4

  


  Top right
ffmpeg -y -i input.mp4 -vf "zoompan=z='if(lte(mod(time,16),4),2,1.05)':d=1:x=iw/1-(iw/zoom/2):y=ih/3-(ih/zoom/2):fps=29.97" output.mp4

  


  Bottom left
ffmpeg -y -i input.mp4 -vf "zoompan=z='if(lte(mod(time,16),4),2,1.05)':d=1:x=iw/2-(iw/zoom/1):y=ih/1-(ih/zoom/1):fps=29.97" output.mp4

  


  Bottom right
ffmpeg -y -i input.mp4 -vf "zoompan=z='if(lte(mod(time,16),4),2,1.05)':d=1:x=iw/1-(iw/zoom/2):y=ih/1-(ih/zoom/2):fps=29.97" output.mp4'

  


• Precise cut of remote video file

  20 août 2014, par Nicolas Goy

  I have hours long video files living on a server, and I need to be able to cut segments in them in an accurate and fast way.

  I tried :

  ffmpeg -ss 10:00 -i http://server/input.mp4 -t 5:00 -vcodec copy -acodec copy out.mp4

  This works and is fast, but it’s not precise as ffmpeg seeks backward until it finds a keyframe. The resulting video file ends up with a negative start time which is not working nice with browsers.

  I know I can re-encode the video for accurate seeking, but this would be slow and lose quality.

  I came up with the following idea :

  For example, let’s say we have a 20 seconds video, with keyframes every 5 secs, at 0,5,10,15,20.

  If I want a segment from sec 2 to sec 17, I would re-encode from sec 2 to 5, vcopy from sec 5 to 15, re-encode from sec 15 to 17 and concat the three files.

  This is the general problem and my idea, now the requirements are :

  • Source files must be accessed over HTTP
  • There must be no or very few quality loss
  • It must be fast, cutting 10 minutes in a 2h video should take around 1-2 sec
  • It must be accurate
  • It must work for webm and mp4

  It doesn’t have to be a ffmpeg command, I’m quite sure I’ll have to write a C wrapper around libav.

  Source file can be pre-processed in any necessary way to make it work.

  UPDATE : After getting more info, it seems my "idea" of gluing re-encoded extremities parts with a stream copied middle part won’t work because of different encoding settings. But I could extract a longuer part (keyframe -> keyframe) and extract timecodes I could add in an HTTP header, like Time-Range: 0.25,15.14 which would mean "play from sec 0.25 to 15.14 and discard the rest".