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• using ffmpeg to automate splitting video into quarters and stacking

  14 novembre 2017, par user3297049

  I need to create a quick FFMPEG batch file that takes a very wide video file and splits it into quarters (dimension wise not time wise), then outputting a file where each quarter is under the previous.

  E.g.

  A B C D

  Would become :

  A
  B
  C
  D

  I know this should be possible with crop and pad commands, and through research I’ve found that someone divided into quarters and put the top left and bottom right next to each other horizontally using :

  "%~dp0\ffmpeg.exe" -i %1 -filter_complex "[0:0]crop=iw/2:ih/2:0:0,pad=iw*2:ih:0:0[tl];[0:0]crop=iw/2:ih:iw/2:ih/2[br];[tl][br]overlay=W/2" -b:v 32000k -b:a 128k %1_2.avi

  Can anyone help as the command line is beyond me ?

• node-fluent-ffmpeg doesn't resize videos correctly when given specific size

  8 décembre 2019, par Yagiz

  Version information

  • fluent-ffmpeg version : 2.1.2
  • ffmpeg version : ffmpeg version 4.1.3
  • OS : mac os x mojave 10.14.3

  Code to reproduce

  First cut the videos using this command :

  const cutVideo = async (currentWord) => {
  
      return new Promise((resolve, reject) => {
  
          console.log('cutting video', currentWord.file)
  
          ffmpeg(currentWord.file)
  
              .videoCodec('libx264')
  
              // .addOptions('-vf "setdar=ratio=16/9:max=1000"')
  
              .on('start', command => console.log('command', command))
  
              .on('error', reject)
  
              .on('end', resolve)
  
              .withSize('640x360')
  
              .withAspect('16:9')
  
              .applyAutopadding(true, 'black')
  
              .saveToFile(currentWord.file.replace('-unfinished', ''), './')
  
      })
  
  }

  Later merge them together using .mergeToFile() command :

  const mergeFilesAsync = async function(files, folder, filename)
  
  {
  
      return new Promise((resolve, reject) => {
  
          console.log('merging files', files)
  
          var cmd = ffmpeg({ logger: console })
  
              .videoCodec('libx264')
  
              .on('start', command => console.log('command', command))
  
              .on('error', reject)
  
              .on('end', resolve)
  
  
  
          for (var i = 0; i < files.length; i++)
  
          {
  
              const currentWord = files[i]
  
              cmd.input(currentWord.file.replace('-unfinished', ''))
  
          }
  
  
  
          cmd.mergeToFile(folder + "/" + filename, folder);
  
      });
  
  }

  Expected results

  The videos resized in cutVideo function should have 640x360 size with 16:9 aspect ratio.

  Observed results

  The first video processed had a dimension of : 850 × 480, the output after processing it is : 642 × 360 (It should be 640x360)

  The second video processed had a dimension of : 1152 × 480, the output after processing it is : 638 × 360

  The third video processed had a dimension of 853 × 480, the output after processing it is : 642 × 360

  FFmpeg command produced by fluent-ffmpeg :

  ffmpeg -i /Users/yagiz/Desktop/video-creator/what's-unfinished.mp4 -y -vcodec libx264 -filter:v scale=w='if(gt(a,1.7777777777777777),640,trunc(360*a/2)*2)':h='if(lt(a,1.7777777777777777),360,trunc(640/a/2)*2)',pad=w=640:h=360:x='if(gt(a,1.7777777777777777),0,(640-iw)/2)':y='if(lt(a,1.7777777777777777),0,(360-ih)/2)':color=black /Users/yagiz/Desktop/video-creator/what's.mp4
  
  cutting video /Users/yagiz/Desktop/video-creator/up?-unfinished.mp4

  and

  ffmpeg -i /Users/yagiz/Desktop/video-creator/up?-unfinished.mp4 -y -vcodec libx264 -filter:v scale=w='if(gt(a,1.7777777777777777),640,trunc(360*a/2)*2)':h='if(lt(a,1.7777777777777777),360,trunc(640/a/2)*2)',pad=w=640:h=360:x='if(gt(a,1.7777777777777777),0,(640-iw)/2)':y='if(lt(a,1.7777777777777777),0,(360-ih)/2)':color=black /Users/yagiz/Desktop/video-creator/up?.mp4

  I think that 1.77777 value in this command produces a lower bound or an upper bound of the actual item.

  Any idea where the issue lies ?

  Thanks !

• Frame Accurate Seeking in WebM

  11 janvier 2016, par SapphireSun

  I’m trying to do a somewhat tricky thing with WebM. I am trying to encode a stack of 256 biological images as a WebM. The time dimension of motion is very similar to the space dimension of the image stack so the compression ratios are insanely good. However, I am having trouble decoding the movie frames. I know that WebM uses an IPB predictive coding scheme, but I was reading several blog posts and discussion groups from WHATWG from 2011, and they said that frame accurate seeking was working in Chrome at that time.

  When I do video.currentTime = 0, I correctly get this :

  

  However, if I do video.currentTime = 0.34 (for example) I get something that looks like this :

  

  It looks like I’m getting a random poorly predicted frame. Am I just encoding the video wrong ? When I play it normally it looks fine.

  I encoded the video using 256 pngs using ffmpeg compiled with libvpx using the VP8 codec.

  ffmpeg -y -framerate 60 -start_number 0 -pattern_type glob -i '*.png' -qmin 10 -qmax 42 out.webm

  References to the WHATWG and some other info from 2011 :

  WHATWG discusses frame accuracy :

  https://lists.w3.org/Archives/Public/public-whatwg-archive/2011Jan/0372.html

  BBC Tech Director talking about frame accuracy :

  http://www.bbc.co.uk/blogs/bbcinternet/2011/02/frame_accurate_video_in_html5.html