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• FFmpeg : Issues for Transparent Background in WebM Video [closed]

  20 juillet 2024, par BlueSky

  I've encountered an issue while processing videos with FFmpeg. I want to convert a MOV video with an alpha channel to WebM format and overlay it onto a main video. Below are the steps I took and the problem I encountered.

  


  I used Adobe After Effects (AE) to remove the green screen background from a video and exported the MOV file with RGB+Alpha channels using the Animation codec. Additionally, I tried exporting in QuickTime format, both ensuring the alpha channel was included.

  


  When converting the MOV video to WebM format, I executed the following command :

  


  ffmpeg -i input.mov -c:v libvpx-vp9 overlay.webm


  


  Then, I attempted to overlay the converted WebM video onto the main video main.mp4 using the following command :

  


  ffmpeg -i main.mp4 -vf "movie=overlay.webm,scale=200x200[video_inner];[in][video_inner]overlay=x=10:y=10[out]" output.mp4


  


  However, in the final output.mp4 video, the background of the WebM video was not transparent as expected, but instead showed a black background after removing the green screen.

  


  Could there be an error in one of my steps ?

  


  I have tried different command parameters and options but have not been able to resolve this issue.

  


  I expected the WebM video to retain its transparent background when overlaid onto the main video. However, the resulting output.mp4 video showed the background of the WebM portion as black instead of transparent.

  


• Python convert audio files to MP3

  19 janvier 2015, par Fernando Retimo

  I’m trying to write a small utility that get as input an m4a/ogg file and converts it to a MP3 audio file.
  My main goal is not to use any third party binaries such as ’Lame’ or ’ffmpeg’.
  I read allot about PyMedia and such, but my knowledge on audio codecs is very poor.
  Can any one help me and give me an elegant cross platform solution ?
  Thanks !

  EDIT :
  meanwhile I know it is very basic but this is my code :

  import sys
  
  
  
  def convert2mp3(input_file):
  
      .....
  
      some magic...
  
      ...
  
      return mp3file
  
  
  
  if __name__ == "__main__":
  
      if len(sys.argv) != 2:
  
          print "%prog Usage: %s <input file="file" />"
  
          sys.exit()
  
  
  
      convert2mp3(sys.argv[1])

• How to "re-interlace" a video ? How to convert a naïvely deinterlaced 480p video back to 480i ? [closed]

  8 juillet 2021, par toughluck

  I have a 480p video that was naïvely created from a 480i original and had no deinterlacing applied. The resulting format is 480p25. Combing is visible and I would like to convert it back to 480i50, so sort of "re-interlace" the video back to its original state.

  


  I have tried the solution from this question : How to convert a 1080p to 1080i using FFMPEG but it did not create the expected output.

  


  I looked at ffmpeg reference here : https://www.ffmpeg.org/ffmpeg-all.html but I could not find a proper option. Tons of filters to deinterlace interlaced videos but nothing to "re-interlace" them.

  


  My expected output would be this :

  


   ------> time
Input:
Frame 1 (0 ms)        Frame 2 (40 ms)

11111                 33333
22222                 44444
11111                 33333
22222                 44444

Output 1:
Frame 1 (0 ms)  Frame 2 (20 ms) Frame 3 (40 ms) Frame 4 (60 ms)
11111           22222           33333           44444
11111           22222           33333           44444
11111           22222           33333           44444
11111           22222           33333           44444

(Alternative) Output 2:
Frame 1 (0 ms)  Frame 2 (20 ms) Frame 3 (40 ms) Frame 4 (60 ms)
22222           11111           44444           33333
22222           11111           44444           33333
22222           11111           44444           33333
22222           11111           44444           33333


  


  (I'm not sure whether it's top field first or bottom field first, so I'd like to have an option to try both.)

  


  Is this possible ?