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• Cutting movie with ffmpeg result in audio/video desync

  15 mai 2020, par T4ng10r

  I've concate long ago set of movies taken during some lecture. Now I want to cut them for each question/answer.

  



  I do it like this.

  



  


  ffmpeg -ss 00:00:34.7 -t 00:10:44.6 -y -i input_movie.mp4 -vcodec copy -acodec copy output_1.mp4

  
 


  ffmpeg -ss 00:11:22.2 -y -i input_movie.mp4 -vcodec copy -acodec copy output_2.mp4

  


  



  Yet, for the second part I can't set proper starting point so audio and video would be in sync.
  
Usually I could fix it with small tweeks in cut start time (like .1, .2, and so on). For this case this doesn't work.
  
When I play second cut in mplayer video is few second behind audio (where audio is cut properly). When I jump forward and back - all is again in sync.

  



  Where's the problem ? How to fix it ?

  


• create only 5 thumbnail images (Independent of time) via ffmpeg

  17 janvier 2015, par ali raha

  This code will create one thumbnail image every second, named out1.png, out2.png, out3.png, ...

  ffmpeg -i input.flv -f image2 -vf fps=fps=1 out%d.png

  But how can create only 5 image also Independent of time !
  I do not know about Length movies...I want the movie to be divided into five equal parts.and create pic per each part !

  something like this :

  start video<====out1.png======out2.png======out3.png=====out4.png======out5.png======>end video

• ffmpeg video rendering command adding empty audio to end of video

  13 janvier 2020, par Martin

  I have an ffmpeg command which is supposed to take an mp3 file and image file as inputs, and render a music video with the image as the background and the video length is the exact length of the mp3 audio file input.

  I was using this command :

  ffmpeg -loop 1 -framerate 2 -i "front.jpg" -i "audioInput.mp3" -vf "scale=2*trunc(iw/2):2*trunc(ih/2),setsar=1,format=yuv420p" -c:v libx264 -preset medium -tune stillimage -crf 18 -c:a aac -b:a 320k -shortest -vf scale=1920:1080 -pix_fmt yuv420p "videoOutput.mp4"

  But the problem was that my audioInput.mp3 file is 1 minute 12 seconds long, and my output video was 1 minute 39 seconds, with an added couple seconds of silence at the end of the video.

  I asked a question on stackoverflow and it was closed/linked to this question. The accepted answer says that this command would not add extra seconds onto the end of the video :

  ffmpeg -y -loop 1 -framerate 2 -i "front.jpg" -i "maintheme.mp3" -c:v libx264 -tune stillimage -c:a aac -b:a 320k -pix_fmt yuv420p -shortest -fflags +shortest -max_interleave_delta 100M "result2.mp4"

  I tried using this command, and my output video was still 1.14 seconds long.
  I tried the command again with a different audio file (flac) and the video output had again 2 seconds of blank audio at the end. Is one of my flags causing extra space to be appended ? Can I cut the video’s length to be that of the audio file ?