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• How would I create a radially offset mosaic of rtsp streams that transitions to a logo

  18 juillet 2018, par Jack

  I’m new to stack overflow, but I’ve been researching how to do this for a couple weeks to no avail. I’m hoping perhaps one of you has some knowledge I haven’t seen online yet.

  Here is a crude illustration of what I hope to accomplish. I have a video wall of eight monitors - four each of two different sizes. The way it’s set up now, all eight monitors are treated together as one big monitor displaying an oddly shaped cutout of a desktop.

  Eventually I need each individual monitor to display a separate RTSP stream for about thirty seconds, then have the entire display - all eight monitors in conjunction - to fade out into a large logo.

  My problem right now is that I don’t know of a way to mask an rtsp stream so it looks like this rather than this, let alone how to arrange them into a weirdly spaced, oddly angled, multiple aspect-ratio mosaic like in the original illustration.

  Thank you all for your time. I’m just an intern here without insane technical knowhow, but I’ll try to clarify as much as I can.

  -J

• FFMPEG -f segment and FFPROBE keyframes are different

  18 juillet 2019, par user2190197

  I have a online video editor. And i want fast strip and concat mp4 files. For this i use code like this :

  For get keyframes :

  exe_ffprobe("-select_streams v -skip_frame nokey -show_frames -show_entries frame=pkt_pts_time,pict_type $input_file");

  Sample Result :

  array (
  
    0 => '0.083417',
  
    1 => '2.085419',
  
    2 => '4.170838',
  
  ...
  
    12 => '24.149149',
  
    13 => '26.234568',
  
    14 => '27.569236',       < Why ffmpeg missed this keyframe?
  
    15 => '29.654655',
  
  ...
  
    230 => '466.966967',
  
    231 => '469.052386',
  
    232 => '471.137804',
  
    233 => '473.223223',
  
    234 => '475.308642',
  
    235 => '477.394061',
  
    236 => '479.479479',
  
  )
  
  ...

  For split video :

  exe_ffmpeg("-y -i $input_file -c copy -map 0 -segment_list segments.csv -f segment -reset_timestamps 1 path/to/%d.mp4");

  Sample result :

  0.mp4,0.000000
  
  1.mp4,2.085419
  
  2.mp4,4.170838
  
  ...
  
  12.mp4,24.149149
  
  13.mp4,26.234568
  
  14.mp4,29.654655
  
  15.mp4,31.740073
  
  ...
  
  230.mp4,475.308642
  
  231.mp4,477.394061
  
  232.mp4,479.479479
  
  end

  But count of keyframes from ffprobe, and count splitted videos are different.

  So how i can segment or get keyframes correctly, to match the count

  Also, keyframes and segments.csv are differently too, but more of keyframes has correct timestamps

• ffmpeg how to extract X frames every Y interval from url efficiently

  13 décembre 2018, par Luay Gharzeddine

  I’m trying to gather data for a datascience project, and am downloading frames from online videos using ffmpeg. I want to download a subset of the frames in the video, without needing to be precise about which, the only requirement is that they are reasonably spaced apart from each other.

  I have tried

  ffmpeg -i "http://www.somevideo.com" -r 1 -f image2 "image%06d.jpg"

  and

  ffmpeg -i "http://www.somevideo.com" -vf fps=1 "image%06d.jpg"

  and eventually found the following method

  ffmpeg -ss offset1 -i "http://www.somevideo.com" -ss offset2 -i "http://www.somevideo.com" -map 0:v -frames:v 10 -start_number 0 "image%06d.jpg" -map 1:v -frames:v 10 -start_number 10 "image%06d.jpg"

  and all work, but are slow. I have found a hack where I run the following command multiple times, at different offsets, and it seems to be the fastest (where each ffmpeg command is run in parallel multithreaded)

  ffmpeg -ss offset -i "http://www.somevideo.com" -vframes frames_per_fragment -an -start_number start_index "image%06d.jpg"

  this about 25% faster than the previous method

  Is there a faster way to do this ? The issue is that downloading over a network is a bottleneck, so I want to download only the frames I need. I’m looking to download videos/frames in bulk, so any speed improvement would be helpful.