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• Black overlay appears when merging a transparent video to another video

  13 juin 2012, par RakeshS

  This is what I have done so far :

  Command to create a transparent PNG image :

  convert -size 640x480 -background transparent -fill blue \
  
  -gravity South label:ROCK image1-0.png

  Command to create a transparent video :

  ffmpeg -loop 1 -f image2 -i image1-0.png -r 20 -vframes 100 \
  
  -vcodec png -pix_fmt bgra mov-1.mov

  (as per this post) - I expect this video to be a transparent video.

  Command to overlay a video with another :

  ffmpeg -i final-video.mov -sameq -ar 44100 \
  
  -vf "movie=mov-1.mov [logo];[in][logo] overlay=0:0 [out]" \
  
  -strict experimental final-video.mov

  Above commands works perfect and I have not faced any problem, but I don't get what I expect which is kinda watermarking effect, I want mov-1.mov to be transparent with final-video.mov.

  Questions :

  1. Is there any way to verify if the generated video is transparent ? other than merging ?
  2. Not sure why the above mov-1.mov is not transparent when it is merged with final-video.mov, any info to solve this problem would be great.

  Please help.

• Is there a way to extract every nth frame from an online video without downloading the entire video ?

  13 avril 2018, par Arif

  I’m looking for a website or app that lets you to download individual frames from a video as jpg without downloading the full thing. If there is no such website or app, is it possible via ffmpeg ?

• Text Watermarking on video without loss of audio and video quality

  8 janvier 2021, par Aditya Kumar

  I am using following command to add text watermark on a video file(for mp4, mpg,m4v,flv,mov etc..) :

  


  ffmpeg -i input.mp4 -vf "drawtext=text='Opentext':x=(w-text_w)/2:y=(h-text_h)/2:fontsize=24:fontcolor=white" TextOutput.mp4


  


  For some of the file transformation the property of video file changes. for example- When I tried to add text watermark on a mkv file I got this message :

  


  


  [matroska @ 0000001867d36ec0] Non-monotonous DTS in output stream 0:1 ;
previous : 2273, current : 1596 ; changing to 2273. This may result in
incorrect timestamps in the output file.

  


  


  This is one of the issues, i have mentioned here. There are others as well, such as :

  


  

  • video quality is reduced

  


  • video file size is changed(increses/decreases drastically)

  


  • Audio lagging occurs etc...

  


  


  So, I want to preserve the quality of video after adding the text watermark. How can I do that ?