Recherche avancée

Sur d’autres sites (8683)

• 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.)

• Script to cut video by silence part with FFMPEG

  11 février 2020, par fricadelle

  This is a question that is raised here How to split video or audio by silent parts or here How can I split an mp4 video with ffmpeg every time the volume is zero ?

  So I was able to come up with a straightforward bash script that works on my Mac.

  Here it is (only argument is the name of the video to be cut, it will generate a file start_timestamps.txt with the list of silence starts if the file does not exist and reuse it otherwise) :

  #!/bin/bash
  
  
  
  INPUT=$1
  
  
  
  filename=$(basename -- "$INPUT")
  
  extension="${filename##*.}"
  
  filename="${filename%.*}"
  
  
  
  SILENCE_DETECT="silence_detect_logs.txt"
  
  TIMESTAMPS="start_timestamps.txt"
  
  
  
  if [ ! -f $TIMESTAMPS ]; then
  
      echo "Probing start timestamps"
  
      ffmpeg -i "$INPUT" -af "silencedetect=n=-50dB:d=3" -f null - 2> "$SILENCE_DETECT"
  
      cat "$SILENCE_DETECT"| grep "silence_start: [0-9.]*" -o| grep -E '[0-9]+(?:\.[0-9]*)?' -o > "$TIMESTAMPS"
  
  fi
  
  
  
  PREV=0.0
  
  number=0
  
  
  
  cat "$TIMESTAMPS"| ( while read ts
  
  do
  
      printf -v fname -- "$filename-%02d.$extension" "$(( ++number ))"
  
      DURATION=$( bc <<< "$ts - $PREV")
  
      ffmpeg -y -ss "$PREV" -i "$INPUT" -t "$DURATION" -c copy "$fname"
  
      PREV=$ts
  
  done
  
  printf -v fname -- "$filename-%02d.$extension" "$(( ++number ))"
  
  ffmpeg -y -ss "$PREV" -i "$INPUT" -c copy "$fname" )

  Unfortunately it does not seem to work :

  I have a video that is basically a collection of clips, each clip being introduced by a 5 second silence with a static frame with a title on it. So I want to cut the original video so that each chunk is the 5 seconds "introduction" + video until the next introduction. Hope it’s clear.

  Anyway, in my script I first find all silence_start using ffmpeg silencedetect plugin. I get a start_timestamps.txt that read :

  141.126
  
  350.107
  
  1016.07
  
  etc.

  Then for example I would call (I don’t need to transcode again the video), knowing that (1016.07 - 350.107) = 665.963

  ffmpeg -ss 350.107 -i Some_video.mp4 -t 665.963 -c copy "Some_video02.mp4"

  The edge cases being the first chunk that has to go from 0 to 141.126 and the last chunk that has to go from last timestamp to end of the video.

  Anyway the start_timestamps seem legit. But my output chunks are completely wrong. Sometimes the video does not even play anymore in Quicktime. I don’t even have my static frame with the title in any of the videos...

  Hope someone can help. Thanks.

  EDIT Ok as explained in the comments, if I echo $PREV while commenting out the ffmpeg command I get a perfectly legit list of values :

  0.0
  
  141.126
  
  350.107
  
  1016.07
  
  etc.

  With the ffmpeg command I get :

  0.0
  
  141.126
  
  50.107
  
  016.07
  
  etc.

  bash variable changes in loop with ffmpeg shows why.

  I just need to append < /dev/null to the ffmpeg command or add -nostdin argument. Thanks everybody.

• avformat/http: split the fragment part from the HTTP URL before the request

  3 février 2020, par Marton Balint

  avformat/http: split the fragment part from the HTTP URL before the request
  RFC 3986 states that the fragment identifier is separated from the rest of the
  
  URI prior to a dereference, and thus the identifying information within the
  
  fragment itself is dereferenced solely by the user agent.
  Signed-off-by : Marton Balint <cus@passwd.hu>
  

  • [DH] libavformat/http.c