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• FFmpeg : Combine video files with different start times

  4 juin 2019, par Fabian

  I have two webm files with audio and video recordings of a video conference session. Both files only contain one side of the conversation. They are not of the same length (someone has joined before the other one), but I have the unix timestamp in milliseconds of the start time of each video file.

  On a timeline they look like this :

  webm 1:   -----------------------------------------------
  
  webm 2:                 -----------------------------

  or like this :

  webm 1:   -----------------------------------------------
  
  webm 2:                          -----------------------------

  I would like to combine these two video files into one file so that :

  1. They appear next to each other (using the hstack option), and
  2. That they are mixed with taking the time stamps of the start times
     into account. The final video should then look like this :

  Target result : --------------===========================----

  The beginning and the end of the new video would show a black placeholder for the video file that has no data at this time of the mixed stream.

  At the moment I use this command :

  ffmpeg -i 1463408731413703.webm -i 1463408880317860.webm -filter_complex \
  
  "[0:v][1:v]hstack=inputs=2[v]; \
  
   [0:a][1:a]amerge[a]" \
  
  -map "[v]" -map "[a]" -ac 2  -c:v libvpx output.webm

  This creates a video like this :

  Not good result : =====================------------------

  i.e. the conversation is out of sync.

  How can I combine two video streams with different length and different start times using ffmpeg so that I will end up with "Target result" above ?

  Thanks a lot !

• avconv save 10 frames and update them in cycle

  12 août 2016, par Flash Thunder

  The way I am saving frames from camera is :

  avconv -f video4linux2 -i /dev/video0 -r 5 output_%04d.png

  Seems to be working fine... but... I need to save only 10 frames and overwrite the saved first saved all the time... any way to do that ? I need to be able to save frames and process them in other application... but process may take longer than record.

  Tried to save one frame and overwrite it, but the problem is that file is being used and it simply doesn’t work.

• FFMpeg extract frames and save to memory

  1er janvier 2016, par dacio

  How can I extract frames from movie and save it to memory ? I am using FFMpeg and I can extraxt frames to save in on disc but then I need to processing that files and load it to memory. Is there any way to save them directly into RAM ?