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• Resize image by adding extra black pixels at borders

  25 juin 2020, par Sudheer Kumar

  I would like to resize an image(lower resolution to higher resolution) by adding black pixels at the borders. I have raw image data available in YUV420/RGB format. I want to add back pixels to this raw image data and change its resolution to desired state. Example before to after. I have all my code in CPP, and i am also using ffmpeg libraries to scale/convert data format.

  


• 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 ?

• 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 ?