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• cutting multiple segments with ffmpeg [duplicate]

  13 juin 2018, par B Pulsart

  This question already has an answer here :

  • Every 30 seconds is to cut a video 3s
    
    1 answer
    

  So there is a 10 min long .mp4 and I have to cut it in 2 seconds long segments every 10 seconds, then concatenate all 2 sec segments together to get a 2 min long film.

  I manage to do that with a loop in python that subprocep ffmpeg, but it’s long and ugly (cut, cut cut... and then glue)

  Is it a way to do that with just a line in ffmpeg ?

  my code in python for cutting sequences :

  import subprocess# as sp
  
  
  
  ffmpeg = file on disk # on Windows
  
  film_in =  a file name
  
  
  
  t_total = 10#min
  
  t_sec = t_total*60
  
  
  
  def c_cut(time) :
  
      cmd = [ffmpeg  , '-i' ,film_in ,'-b:v', '800k' ,'-ss', str(time) , '-t','2' , '-an', film_out]
  
      return cmd
  
  
  
  
  
  for tps in range(0, t_sec, 10) :
  
      film_out = a file name unique for each segment
  
      command = c_cut(tps)
  
      subprocess.call(command)

• How to stabilize inverse 360 video using stabilization algorithms ?

  11 août 2020, par Jimmy Leahy

  We have a 12-foot circular ring with about 50 cameras spaced evenly around the perimeter of the circle. These cameras are pointed at the exact center of the circle and are manually aligned. Our application snaps an image from all cameras simultaneously and makes a video from these images creating a matrix-like effect. I believe the effect is called Bullet Time.

  



  This process works well and does a great job of snapping a moment in time from all angles. The problem is that every camera is not perfectly aligned and the video ends up being slightly jerky due to the slightest differences in camera alignments.

  



  We need to stabilize the video. We are using FFmpeg's vidstabdetect and vidstabtransform to do this right now but the results are not desirable. From what I understand, these libraries are meant to be used with a video where the camera angle is static.

  



  Here are the exact commands :

  



  ffmpeg -i "input.mp4" -vf vidstabdetect=stepsize=32:shakiness=5:accuracy=15:result=transform_vectors.trf -f null - 
ffmpeg -i "input.mp4" -y -vf vidstabtransform=input=transform_vectors.trf:zoom=0:relative=1:interpol=bicubic:smoothing=10,unsharp=5:5:0.8:3:3:0.4 -b:v 100M -vcodec hevc_nvenc -tune film -an stabilized.mp4


  



  Are there any algorithms out there for these inverse or negative 260 videos ?

  


• avformat/movenc : use enum values directly for colr atom

  31 mars 2020, par Michael Bradshaw

  avformat/movenc : use enum values directly for colr atom
  The switch cases were missing :
    - Primaries : bt470m, film, smpte428, and ebu3213.
  
    - TRCs : gamma22, gamma28, linear, log, log_sqrt, iec61966_2_4, bt1361,
  
      iec61966_2_1, bt2020_10bit, and bt2020_12bit.
  
    - Space : rgb, fcc, ycgco, bt2020_cl, smpte2085, chroma-derived-nc,
  
      chroma-derived-c, and ictcp.
  They also annoyingly remapped the following (which are functionally
  
  equivalent but can be treated differently by clients) :
    - smpte240m primaries to smpte170m.
  
    - smpte170m TRC to bt709.
  
    - bt470bg color space to smpte170m.
  The enum values in FFmpeg are the same values as ITU-T H.273 and
  
  ISO/IEC 23001-8 so we can just use them directly, which is both simpler
  
  and preserves the user intent.
  Signed-off-by : Michael Bradshaw <mjbshaw@google.com>
  

  • [DH] libavformat/movenc.c