Recherche avancée

Sur d’autres sites (10263)

• Remove Static Pixels from a Video to Mimic a Green Screen Effect [closed]

  2 août 2021, par nKrkan

  I have a video that's 50 seconds in length, resolution of 480x480 and 16 frames per second.

  


  There is a person talking in it, with the background being static I thought if there's a way
  
to remove those static pixels (background) and just extract the moving pixels (foreground)
  
and possibly mimic a green screen effect ?

  


  I was thinking on writing a picture-by-picture comparison tool to do such thing but I don't
  
believe I'm up to the task, or maybe It's laziness.

  


  And now I know, some of you will point out that the video has compression artifacts and that
  
might cause some problems but It doesn't have to be Studio quality stuff.

  


  I tried the ffmpeg command from this question : Remove random background from video using ffmpeg or Python
  
And it does mask the person, but... I couldn't quite get it to work, apparently putting the
  
reference image in the input makes that image burned into the video, thus having no way to
  
remove it, but it did mask the background as black and the person as greenish, so still not a
  
viable way to do it.

  


  Have also tried some Python projects I've found on the GitHub but none of them worked as
  
I expected.

  


  So, what I thought to do is simply compare the first and the second frame of the video, check
  
all the pixels by comparing them with the two sources, and change those that stay within a
  
certain range of the initial pixel value.

  


  I should point out I'm not very knowledgeable with mathematics and the majority of the
  
methods used in these type of things, but perhaps someone could point me to an interesting
  
source to read and learn, or by providing an alternative to the methods aforementioned above.

  


• Monitoring ffmpeg two-passes encoding

  31 décembre 2024, par Hodol

  I'm new in FFMPEG.

  


  According to the official guide, https://trac.ffmpeg.org/wiki/Encode/VP9 I use the following command to convert a large h.264 file :

  


  ffmpeg -i input.mp4 -c:v libvpx-vp9 -b:v 0 -crf 30 -pass 1 -an -f null /dev/null
ffmpeg -i input.mp4 -c:v libvpx-vp9 -b:v 0 -crf 30 -pass 2 -c:a libopus output.webm


  


  However, the pass-1 takes too long time and it does not log progress. With -report option I can see something is in progress but I don't know how long I should wait.

  


  Here's questions :

  


  

  1. Is there any way to see the progress of 1-pass ?

  


  2. Is there any way to speed up the process ?

  


  


  Thank you,

  


• ffmpeg and grep not working to extract mean_volume value

  31 octobre 2019, par Json

  I have a list of mp3 files and i want to set all mean_volume to the same db value using a script, so I enter the command for detecting the value (https://trac.ffmpeg.org/wiki/AudioVolume) and I try to grep the value but it fails and instead prints all the output from the ffmpeg command. Any thoughts ?
  Also tried tr instead of grep. The command I used is :

  ffmpeg -i sample.mp3 -filter:a volumedetect -f null /dev/null | grep 'mean_volume'