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• Exporting MPEG Transport Stream (.ts) keyframes to images in C/C++ ? Libavcodec / FFMPEG ?

  11 mai 2021, par CyberBully2003

  I have some buffers made up of 188 byte TS packets. When I write them to a file, I can successfully view these .ts files in a video player. MPEG-2/H.264 is the format of the Transport Streams.

  


  Now, I would like to export the keyframes from these Transport Streams buffers (or .ts files) as .jpeg or some other common image format in my C/C++ project.

  


  This is a trivial task from the command line using ffmpeg, where I just feed it the .ts file and some parameters.

  


  However, for the purpose of this project, I would like to accomplish this conversion/exporting of keyframes as images code-side in my current C/C++ directory because the raw bytes from these generated images will be put into another format.

  


  People online seem to recommend using libavcodec. There is an mpegets file in the ffmpeg source that seems like it might have some of the backend to do what I want.

  


  However, the steps needed to achieve this task using the library is not apparent.

  


  I know I could call ffmpeg from C++ and use stdin, but this isn't a preferred solution for this project.

  


  If someone could give me some guidance (and even better some example code) to accomplish this task, it would be greatly appreciated !

  


• 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