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• How to extract a video snippet from a video file that is being written in by ffmpeg in realtime

  31 juillet 2020, par alex.b

  At the moment i am recording a LIVE stream video from youtube with youtube-dl (https://github.com/rg3/youtube-dl)

  



  The command i use for this :

  



  youtube-dl --id -f 92 https://www.youtube.com/watch?v=VYlQJbsVs48


  



  92 is a format code that i got after executing a command to get the formats, that gave me this list :

  



  format code  extension  resolution note
140          m4a        audio only DASH audio  144k , m4a_dash container, aac  @128k (48000Hz)
141          m4a        audio only DASH audio  272k , m4a_dash container, aac  @256k (48000Hz)
160          mp4        256x144    DASH video  124k , 15fps, video only
133          mp4        426x240    DASH video  258k , 30fps, video only
134          mp4        640x360    DASH video  616k , 30fps, video only
135          mp4        854x480    DASH video 1116k , 30fps, video only
136          mp4        1280x720   DASH video 2216k , 30fps, video only
137          mp4        1920x1080  DASH video 4141k , 30fps, video only
151          mp4        72p        HLS
132          mp4        240p       HLS
92           mp4        240p       HLS
93           mp4        360p       HLS
94           mp4        480p       HLS
95           mp4        720p       HLS
96           mp4        1080p      HLS  (best)


  



  This is creating a file called VYlQJbsVs48.mp4.part that gets bigger and bigger of course.

  



  Is there a way to extract a video snippet from that live stream or form the part file ? Or maybe there is a better way of doing this ?

  



  What i have noticed is that if i force quit iTerm2 while youtube-dl is running the .part file it creates wont contain any index information (something to do with an moov atom not being present in the mp4 file - which is the information about the number of frames and other things - metadata i think), so it makes me think i cannot extract from the file.

  



  Maybe if there would be a way that youtube-dl can write the index information at all times or maybe another way that i can record the live stream and get video snippets while its recording.

  



  I forgot to mention i am doing this on OSX Yosemite. I have FFMPEG installed with homebrew and youtoube-dl

  



  I am more than happy to try stuff on UBUNTU if there is a solution.

  



  Any help would be greatly appreciated.

  



  Thank you.

  



  Alex

  


• Problem with processing FFMPEG video , the output video is totally black in first 3 seconds

  13 janvier 2021, par Trần Minh Tuấn

  I want to make a slideshow by using concat demuxer like this link :
https://trac.ffmpeg.org/wiki/Slideshow

  


  Here is the textfile preinputFiles.txt :

  


  file 'path a'
duration 2
file 'path b'
duration 2
file 'path c'
duration 2
file 'path c'


  


  and my command array is :

  


  String[] cmd = new String[]{
            "-f","concat","-i",
            textFile,
            "-vsync", "vfr", "-pix_fmt", "yuv420p",
            dest.getAbsolutePath()};


  


  the video has 3 seconds that it is totally black and run from 3s to 9s even the gallery shows that it is a 6 seconds long video .

  


  Thanks for the help !

  


• ffmpeg x11grab inputting improperly

  20 décembre 2017, par Not a superuser

  I have the stock ffmpeg install from the xbps repository. I’ve used it before, but am on a new system.

  Running "ffmpeg x11grab -video_size 1280x800 -framerate 60 -i $DISPLAY output.mkv" yeilds no errors, but when I watch the video it is a mess switching between workspaces and with only partly rendered programs.

  Taking other inputs such as webcam work fine, and different encoding methods don’t change anything (though webm flat out doesn’t work, but that’s not a problem for me).

  I’ve tried what’s here : https://wiki.archlinux.org/index.php/FFmpeg

  Only other thing to note is that I use i3 as a dm, which shouldn’t be a problem, but figured I’d state it just in case.

  EDIT :
  I was using compton for composite, and that was where my issue lied...
  https://github.com/chjj/compton/issues/381

  Thanks !