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• Using ffmpeg to capture frames at intervals from a video

  25 octobre 2011, par TheShaggyBeard

  So here is what I am trying to do - I want to automate creating animated gif previews from a video file (in this case I know they will always be a specific format). Here is what I have :

  echo 'Make a folder named "filenamemp4"'
  
  folderName=$(find . -type f -name "*.mp4" | grep -o [[:alnum:]] | tr -d '\n' | cat)
  
  
  
  echo 'Grab the frame rate and total number of frames and put them into xaa and xab'
  
  qtinfo asa.mp4 | awk 'NR = 1 { print $2 }' | grep -o "^[0-9]*" | split -l 1
  
  
  
  echo 'Assign values to variable'
  
  frameRate=$(cat xaa)
  
  frameTotal=$(cat xab)
  
  videoLength=$(expr $frameTotal / $frameRate)
  
  
  
  echo 'Take a screenshot at 10% intervals - this is the part that gives me a bitrate error.  It says that the -r option has an invalid input being 1 / value of videoLength' 
  
  ffmpeg -i asa.mp4 -y -ss $videoLength -an -sameq -f image2 -s 'qcif' -r $(expr 1/$videoLength) preview%02d.jpg
  
  
  
  echo 'Take the jpgs and mash them into an animated gif'
  
  convert -delay 50 -loop 10 preview*.jpg preview.gif
  
  
  
  echo 'Move the gif to the specified folder'
  
  mv preview.gif $folderName/preview.gif
  
  
  
  echo 'Clean Up'
  
  find . -type f -name "*.jpg" -exec rm -rf {} \;

  So perhaps there is a better way of doing this, or I am understanding how to use the -r option of ffmpeg wrong. In the tutorial I read on ffmpeg for a similar scenario, they used -r 1/5 to produce frames with a 5 second interval. My assumption is that for the desired interval you want, you just slap it in the denominator for the -r option.

• Building ffmpeg on Windows

  27 février 2014, par Niranjan

  I've the source code of ffmpeg and would like to build it in my win7. I've minGW installed on my machine. I found a step by step instruction from this link :

  http://www.gooli.org/blog/building-ffmpeg-for-windows-with-msys-and-mingw/

  The link 'Download updated bash for MSYS' did not follow. It showed the file is not found. When I try to build the program the way explained in the site, it shows an error :

  Unknown option “–extra-cflags=-mno-cygwin”.
  See ./configure –help for available options.
  ./myconfig : –extra-ldflags=-Wl,–add-stdcall-alias : command not found
  ./myconfig : –target-os=mingw32 : command not found

  From a similar question posted here, I followed the link http://ffmpeg.arrozcru.org/ but the static build downloaded from the site was corrupted. Pls help.

• FFmpeg fourcc Avi codec support list ?

  5 décembre 2013, par Sugrue

  A couple of similar questions are on stackoverflow, but I haven't been able to figure this exact problem out.

  I want to get a list of the fourccs for the avi codecs that FFMpeg can decode.

  I know how to get all the formats ffmpeg -formats and codecs ffmpeg -codecs but neither list gives me an accessible list of fourccs. Neither does the documentation I can find.

  I need this list, so that my application can access the fourcc of an avi file and determine whether to use ffmpeg or VfW (or DirectX) to try decode the file.

  Is there some ffmpeg command that can give me this list ?