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• ffmpeg - Is is possible to create a video from image tiles

  16 mars 2017, par Thomas

  With ffmpeg, you can :

  • create a video from a list of images
  • create an image with tiles representing frames of a video

  but, how is it possible to create a video from tiles, in a picture, representing frames of a video ?

  if I have this command line :

  ffmpeg -i test.mp4 -vf "scale=320:240,tile=12x25" out.png

  I will get an image (out.png) made of 12x25 tiles of 320x240 pixels each.

  I am trying to reverse the process and, from that image, generate a video.

  Is it possible ?

  Edit with more details :
  What am I really trying to achieve is to convert a video into a gif preview. But in order to make an acceptable gif, I need to build a common palette. So, either I scan the movie twice, but it would be very long since I have to do it for a large batch, or I make a tiled image with all the frames in a single image, then make a gif with a palette computed from all the frames, which would be significantly faster... if possible.

• ffmpeg merge 60fps and 30 fps mp4 into one file

  3 avril 2017, par TyLO

  I have been trying to merge some mp4 files with different frame rates without success. When I merge the files, there always seems to be a problem with the output. Most of the time the audio is not in sync with the video. I tried to modify the frame rate of the videos (30 to 60 or 60 to 30), but it reduces the quality too much.

  To merge the files i have been using all the solutions in this post

  when trying this method :

  :: Create File List
  
      echo file file1.mp4 >  mylist.txt 
  
      echo file file2.mp4 >> mylist.txt
  
      echo file file3.mp4 >> mylist.txt
  
  :: Concatenate Files
  
      ffmpeg -f concat -i mylist.txt -c copy output.mp4

  The audio and video aren’t synch anymore and the video sometimes freezes.

  When trying the "mp4 to mpg then merge" :

   ffmpeg -i 1.mp4 -qscale 0 1.mpg
  
   ffmpeg -i 2.mp4 -qscale 0 2.mpg
  
   cat 1.mpg 2.mpg | ffmpeg -f mpeg -i - -qscale 0 -vcodec mpeg4 output.mp4

  I loose the audio on the 60 FPS files, at this point i thought it was an audio problem so i tried to "unify" the audio codec of all mp4 files like this :

  ffmpeg -i input.mp4 -acodec SOME_AUDIO_TYPE -vcodec copy out.mp4

  the merge occur without any errors but the audio is unsynch

  So in my last attempt i tried to change the fps rate of my files like this :

  ffmpeg -y -i source.mp4 -r FPS -s RESOLUTION -c:v libx264 -b:v 3M -strict -2 -movflags faststart destination.mp4

  But the result reduces the quality too much.

  Is there any solution to this problem ?

• Crop video into a 4x4 grid/tiles/matrix efficiently via command-line ffmpeg ?

  22 avril 2017, par Dylan

  Hello Stackoverflow community !

  I dread having to ask questions, but there seems to be no efficient way to take a single input video and apply a matrix transformation/split the video into equal sized pieces, preferably 4x4=16 segments per input.

  I tried using all the libraries such as ffmpeg and mencoder, but having 16 outputs can be as slow as 0.15x. The goal of my project is the split the video into 16 segments, rearrange those segments and combine back into a final video ; later reversing the process in HTML5 canvas. Here is a picture to help you understand what I am talking about :
  the source but also the final destination after reorganizing the pieces

  after the segments are exported, I will recombine the pieces in a puzzle manner (they are also inverted and rotated but unrelated)

  I do not believe you can do this all in one command, so my goal is to crop into 16 mapped outputs quickly, then reassemble them in a different order. But I can do the other parts myself. Ideally there would be a way to move pixel blocks eg 100x100 and just move them around. My math is not strong enough..
  I really appreciate the work you guys do !

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