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• FFmpeg script skips files

  15 avril 2014, par ucq52ose

  I wrote a shell script to convert many video files and save them with something appended to the file name. The script works, but it seems to randomly skip files, and a lot of them.

  When I re-run the script, it will convert files it skipped before. How can I get it to stop skipping files ?

  workingDir=/home/user/Videos
  
  
  
  # get list of files to convert
  
  find /video/folder -iname "*.mp4" > $workingDir/file_list
  
  
  
  # convert files
  
  cat $workingDir/file_list | while read LINE; do
  
      # FFmpeg often cuts off the beginning of this line
  
      echo "$(dirname "$LINE")/$(basename "$LINE")"
  
      if /usr/bin/ffmpeg -n -loglevel panic -v quiet -stats -i "$LINE" \
  
          -c:v libx264 -vf scale="trunc(oh*a/2)*2:320" \
  
          -pix_fmt yuv420p -preset:v slow -profile:v main -tune:v animation -crf 23 \
  
          "$(dirname "$LINE")/$(basename "$LINE" \.mp4)"_reencoded.mp4 2>/dev/null; then
  
              echo "Success: $(dirname "$LINE")/$(basename "$LINE")" >> $workingDir/results
  
      else
  
          echo "Failed:  $(dirname "$LINE")/$(basename "$LINE")" >> $workingDir/results
  
      fi
  
  done

  One problem seems to be that FFmpeg interferes with the script. The FFmpeg output often cuts off the beginning of the next command, even if the output is not shown. This is demonstrated by the echo line before the if statement, which is often cut off. But even for lines that aren't cut off, most of them will be skipped for no apparent reason.

• Does the incoming codec or audio-video sync matter when encoding from Xvfb using FFMPEG ?

  15 décembre 2022, par Nav

  How I'm capturing :
  
I'm using Xvfb on Linux, to capture a video and audio from an app that is also running on Linux. I'm using -f x11grab when capturing that video headlessly from Xvfb's frambuffer using FFMPEG, and encoding it using a few other parameters like -c:v libx264 -pix_fmt yuv420p.

  


  The questions :
  
Since I'm reading from Xvfb framebuffer :

  


  

  1. Would it matter that the app uses SVC to encode the video, and I'm using H.264 ?

  


  2. Would it matter if I use a different framerate than the app is using ?

  


  3. Would it matter if I use a different pix_fmt than what the app is using ?

  


  


  Reason for asking :

  


  
  
As shown in the image (blue is the app, red is FFMPEG, green is Xvfb) ;

  


  

  • The CPU percentage consumed by FFMPEG shoots up when the app's CPU percentage shoots up. I've also encountered audio being ahead of video for some participants, but I'm unable to figure out whether it's due to network lag or due to FFMPEG's encoding.

  


  • Also, the aim is to reduce CPU consumption, so I was looking to see if I could do FFMPEG encoding in the same format as the app.

  


  


• What does the summary output of the coding with ffmpeg means

  12 novembre 2015, par Jai

  I am working with video comparison using ffmpeg. By Using ffmpeg command I can find the difference between 2 videos. But i want to find the percentage different in 2 videos.
  From the below ffmpeg output how can i found the percentage difference in two videos. Which attribute denote the difference.?

  TaskList: video:530kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.266679%
  
  TaskList: [libx264 @ 0000000002750b00] frame I:2     Avg QP:23.92  size: 29796
  
  TaskList: [libx264 @ 0000000002750b00] frame P:97    Avg QP:22.97  size:  4477
  
  TaskList: [libx264 @ 0000000002750b00] frame B:9     Avg QP:28.16  size:  5338
  
  TaskList: [libx264 @ 0000000002750b00] consecutive B-frames: 83.3% 16.7%  0.0%  0.0%
  
  TaskList: [libx264 @ 0000000002750b00] mb I  I16..4: 25.7% 37.8% 36.5%
  
  TaskList: [libx264 @ 0000000002750b00] mb P  I16..4:  1.9%  4.5%  1.0%  P16..4: 26.7%  8.8%  3.8%  0.0%  0.0%    skip:53.3%
  
  TaskList: [libx264 @ 0000000002750b00] mb B  I16..4:  0.7%  2.4%  2.7%  B16..8: 19.9%  8.8%  2.6%  direct: 4.7%  skip:58.2%  L0:32.3% L1:53.2% BI:14.4%
  
  TaskList: [libx264 @ 0000000002750b00] 8x8 transform intra:55.1% inter:69.5%
  
  TaskList: [libx264 @ 0000000002750b00] coded y,uvDC,uvAC intra: 55.6% 70.0% 24.2% inter: 19.8% 26.7% 2.5%
  
  TaskList: [libx264 @ 0000000002750b00] i16 v,h,dc,p: 25% 44%  5% 27%
  
  TaskList: [libx264 @ 0000000002750b00] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 24% 26% 17%  5%  5%  6%  5%  6%  6%
  
  TaskList: [libx264 @ 0000000002750b00] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 26% 29% 13%  5%  5%  6%  5%  6%  5%
  
  TaskList: [libx264 @ 0000000002750b00] i8c dc,h,v,p: 44% 30% 20%  5%
  
  TaskList: [libx264 @ 0000000002750b00] Weighted P-Frames: Y:6.2% UV:4.1%
  
  TaskList: [libx264 @ 0000000002750b00] ref P L0: 64.2% 28.5%  5.8%  1.3%  0.1%
  
  TaskList: [libx264 @ 0000000002750b00] ref B L0: 88.4% 11.6%
  
  TaskList: [libx264 @ 0000000002750b00] kb/s:1204.25