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• Watch multi-stream video file while being recorded by ffmpeg

  20 janvier 2020, par Luke Gorrie

  I am using ffmpeg to record four 1080p video streams simultaneously and I would like to view these streams in real time while they are being recorded. Ideally I would like to view them from a separate machine, using some convenient Linux data sharing method like ssh/sshfs/..., but that is a nice-to-have. Is there a practical way to accomplish this ?

  The ffmpeg recording command that I currently use is like this :

  ffmpeg \
  
    -f v4l2 -i $cam0 \
  
    -f v4l2 -i $cam1 \
  
    -f v4l2 -i $cam2 \
  
    -f v4l2 -i $cam3 \
  
    -f matroska \
  
    -map 0 \
  
    -map 1 \
  
    -map 2 \
  
    -map 3 \
  
    -c copy \
  
    $output.mkv

  My problem would be solved if I could use a command like ffplay or vlc to play one or more of the video streams, always tracking close to the end of the stream, playing more as data becomes available. I haven’t found such an option though.

  One alternative might be to have the recording ffmpeg process also tile the four 1080p videos into one 4K grid and pipe that to ffplay. Then I could at least preview on the same machine that is recording. I have not been able to work out the right ffmpeg command to do the tiling though and would appreciate an example.

• FFmpeg vidstab generates jerky wiggling video

  27 mars 2022, par praet0ri4n

  I run Kdenlive 21.12.3 on Ubuntu 20.04.
Recently I stared editing footage from my Nikon D3100 DSLR. Source videos are 1920:1080 24fps in MOV format (camera set to PAL system).

  


  After trying to stabilize a video where I am walking I noticed that the result is kind of stabilized but the image is distorted and contains some strange wiggling effect. Changing the stabilization settings doesn't have any impact on this effect. I haven't seen this before. Previously I stabilized footage from other cameras without problems. This is the first time I use that DSLR.

  


  To me it looks like stabilization is doing some strange interpolation and it is stretching and skewing the image or pixel aspect ratio.
For convenience I tried the vidstab filter with ffmpeg, played around with the interpol option too, but the result ist exactly the same.

  


  Here the source MOV and stabilized mp4 file for comparison
https://nc.p1p0.eu/index.php/s/tTQgPj9rDbmReYn

  


  Thank you !

  


• bash while loop and ffmpeg

  17 juin 2013, par Larry_b

  Sorry for this questions I imagine the answer is pretty straightforward however I have had a search and I haven't found anything that answers it.

  I have written the following :

  while read p                        # reads in each line of the text
  
  do                                  # file- folder_list.txt each iteration.
  
      echo "$p"                       # print out current line
  
      if [ -f  $p/frame_number1.jpg ] # checks if the image exists in the specific folder
  
      then
  
          echo "$p"                   #prints specific folder name
  
          sleep 1                     #pause for 1 second
  
          ffmpeg -f image2 -r 10 -i $p/frame_number%01d.jpg -r 30 $p/out.mp4  #create video
  
       fi                             # end if statement
  
  done code>

  The script is supposed to read a text file which contains the folder tree structure, then check if the folder contains the specified JPEG if it does then the code should create a video from the images contained within the specified folder.

  However what appears to be happening is the script skips whole folders that definitely contain images. I was wondering if the while loop is continuing to iterate whilst the video is being created or if something else is happening ?

  Any help would be greatly appreciated.

  Many thanks in advance

  Laurence