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• using ffmpeg to resize video with black bars

  23 juillet 2018, par Jens S

  i have a video with resolution 720:576 and i want it to have the ratio 16:9, e.g. 1024:576 with black bars on the sides. don’t know if it matters, but i am working with ffmpeg for windows. After research i tried the solution i found on 2 related questions :

  -i .\video.mp4 -vf scale=1024:576:force_original_aspect_ratio=decrease,pad=1024:576:(ow-iw)/2:(oh-ih)/2,setsar=1 out.mp4

  but i get an output that "ow-iw" was not recognized. Here is the complete output. unfortunatly it is in german(as am i) if u tell me how to change the output language i will provide it in english :

  ow-iw : Die Benennung "ow-iw" wurde nicht als Name eines Cmdlet, einer Funktion, einer Skriptdatei oder eines ausführbaren Programms erkannt. Überprüfen Sie die Schreibweise des
  
  Namens, oder ob der Pfad korrekt ist (sofern enthalten), und wiederholen Sie den Vorgang.
  
  In Zeile:1 Zeichen:119
  
  + ... :576:force_original_aspect_ratio=decrease,pad=1024:576:(ow-iw)/2:(oh- ...
  
  +                                                             ~~~~~
  
      + CategoryInfo          : ObjectNotFound: (ow-iw:String) [], CommandNotFoundException
  
      + FullyQualifiedErrorId : CommandNotFoundException

• ffmpeg adds black line between stacked videos

  2 septembre 2020, par Adam Gosztolai

  I am using the following command to stack two videos.

  


  ffmpeg -i video_1.mp4 -i video_2.mp4 -filter_complex "[0:v]scale=-1:500,pad='iw+mod(iw\,2)':'ih+mod(ih\,2)'[v0];[v0][1:v]hstack=inputs=2" output.mp4


  


  Not sure if this matters, but video_1.mp4 is static, as I created it from a .png, and is much shorter than video_2.mp4. So when I execute the following command, ffmpeg duplicates frames, indicated by the "More than 1000 frames duplicated" message.

  


  My issue is that the resulting video has a vertical black line between the two videos (between the illustration on the left and the "joint angles" on the right).

  


  

  


  This vertical line is not there if I stack video_1.mp4 or video_2.mp4 to itself.

  


  I have no idea what is going on. Could someone help ?

  


• FFMPEG Replacing black color fragments with alpha channel transparency

  31 décembre 2017, par kostya572

  I have file.mov video. It has a lot of blank black color fragments that have different durations.

  I need to replace black color fragments that show up for more than 5 seconds with transparency. Is that possible to add some alpha channel for that purpose ?

  Comment to Mulvya’s answer :

  Amazing solution. With #2 section everything ok.

  With #1 section I created this code :

  output=$(ffprobe -f lavfi -i "movie=file.mov,blackdetect=d=3.5" -show_entries tags=lavfi.black_start,lavfi.black_end -of compact=p=0 -v 0|awk '!/^$/')
  
  echo $output

  using awk '!/^$/' to remove empty lines.

  Here is the output I get :

  

  tag:lavfi.black_start repeats with same value several times, not having right structure with closing tag:lavfi.black_end

  If I change blackdetect=d=3.5 to other value, for exaple d=10, it outputs the same result as d=3.5. How could I solve this issue having right tag:lavfi.black_start,tag:lavfi.black_end synthax with correct grepping d= value ?