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• How do you generate a looping animated gif for Facebook with ffmpeg

  7 février 2020, par Alan W. Smith

  When I paste a giphy url (like this one) into a facebook post or comment, the gif plays immediately and loops indefinitely. When I upload ones I make from ffmpeg, neither of those things happen. You have to click a play button to start the animation and then it ends after one time through.

  I have a couple of ffmpeg commands I use to create the gifs. They are :

  ffmpeg -ss 10 -t 5  -i input.m4v -vf "fps=15,scale=800:-2:flags=lanczos,palettegen" -y palette.png

  and

  ffmpeg -ss 10.6 -t 5 -i input.m4v -i palette.png -filter_complex "fps=15,scale=800:-1:lanczos[video];[video][1:v]paletteuse" output.gif

  The first one generates a custom color pallet that’s used by the second one to create a high quality animated gif. I’ve also tried adding -loop 0 (i.e. ffmpeg -ss 10.6 -t 5 -i input.m4v -i palette.png -filter_complex "fps=15,scale=800:-1:lanczos[video];[video][1:v]paletteuse" -loop 0 output.gif) but that didn’t work either.

  I also tried uploading the ffmpeg generated images to a personal website and calling them from there but those didn’t load at all.

  In case it helps, here’s a copy of one of the gifs (which autostarts and loops on StackOverflow for me but not on FB)

  

  How does one go about creating a gif that will autostart and loop indefinitely for facebook ?

  (Note : I’ve got no problem if I need to do something with a personal website, but I don’t want to use Giphly or the other animated gif sites directly if at all possible. Also worth pointing out that I discovered if I download the image from giphly and upload it, it doesn’t autostart either. So, this may be something internal to FB, but I’d still like to figure that out.)

• Concatenating video clip with static image causes buffer errors

  16 février 2020, par jgaeb

  I’m trying to concatenate a 15 second clip of a video (MOVIE.mp4) with 5 seconds (no audio) of an image (IMAGE.jpg) using FFmpeg.

  Something seems to be wrong with my filtergraph, although I’m unable to determine what. The command I’ve put together is the following :

  ffmpeg \
  
  -loop 1 -t 5 -I IMAGE.jpg \
  
  -t 15 -I MOVIE.mp4 \
  
  -filter_complex "[0:v]scale=480:640[1_v];anullsrc[1_a];[1:v][1:a][1_v][1_a]concat=n=2:v=1:a=1[out]" \
  
  -map "[out]" \
  
  -strict experimental tst_full.mp4

  Unfortunately, this seems to be creating some strange results :

  1. On my personal computer (FFmpeg 4.2.1) it correctly concatenates the movie with the static image ; however, the static image lasts for an unbounded length of time. (After entering ctrl-C, the movie is still viewable, but is of an extremely long length—e.g., 35 min—depending on when I interrupt the process.)

  2. On a remote machine where I need to do the ultimate video processing (FFmpeg 2.8.15-0ubuntu0.16.04.1), the command does not terminate, and instead, I get cascading errors of the following form :

  Past duration 0.611458 too large
  
  ...
  
  [output stream 0:0 @ 0x21135a0] 100 buffers queued in output stream 0:0, something may be wrong.
  
  ...
  
  [output stream 0:0 @ 0x21135a0] 100000 buffers queued in output stream 0:0, something may be wrong.

  I haven’t been able to find much documentation that elucidates what these errors mean, so I don’t know what’s going wrong.

• FFmpeg truncates untrunc'ed video

  18 mars 2020, par petrpulc

  Background : Colleague's Panasonic consumer camera had issues with high-capacity SD card and yielded two different types of truncated files (mp4 and mdt) with both header and index corrupted. Both were "fixable" with following steps :

  



  

  1. Locate with hex editor the ascii sequence "mdat" in both a truncated and a corresponding known good file. In mp4 the "mdat" is quite deep in the file as it contains some (but bad) headers, the mdt type almost starts with it.

  


  2. Replace everything up to the "mdat" sequence with known good header. BUT this also means that metadata on length are copied over.

  


  3. Run https://github.com/ponchio/untrunc on the file with corrected header (it refused to run on original files).

  


  4. Profit ! VLC plays the file fine, ffprobe shows correct length. BUT ffmpeg encoding stops at the end timecode of the file I taken the known good header from in step 2.

  


  5. A somewhat ugly solution is to recode the file in VLC (video copy seems to be breaking file up again).

  


  



  I am wondering if I overlooked something ; big time. I guess I do, but simple timecode operations on input file do not seem to have any effect at all.

  



  Is there a way to persuade ffmpeg to encode the whole file that ffprobe and VLC see ?

  



  Files may be provided for analysis on personal basis only, sorry.