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• How can I show that a frame has been duplicated to extend the video framerate using ffprobe ?

  14 juillet 2023, par Brandon J

  As the title suggests I have a video.mp4 which I know visually has been extended from 5fps to 20fps. I know this because there are 256 frames and when I run ffprobe it reports 20fps and the video is 12.8 sec long. I also run

  


  ffprobe -v 0 -select_streams v -show_entries stream=duration_ts,time_base,nb_frames video.mp4

  


  reports to me 256 frames, 1/20 timebase adn 256 duration. This matches the expected 12.8 s duration. When I manually sort through the extracted frames I can see the frames have been held for 4 ticks. So it should be 5fps.

  


  I then run the below to view the packets and the frames (cmd not typed)

  


  ffprobe -show_packets -select_streams v:0 video.mp4

  


  and the packets or frames don't seem to give me a huge indication that the frames have been duplicated.

  


  With the -show_packets cmd the only possible indication of duplication I can see is that every 0.2 seconds, (consistent with 5fps) the size of the packets go from a consistent 150-300 size to around 16000 or so. Is there a way I can better articulate what I am seeing with the packet size change ? Why has their compression or encoder (forgive any error in verbiage) decided to duplicate frames to achieve 20fps vs extending the pts to 0.2 seconds for each packet ? It seems like simply defining a longer pts would reduce overall file size anyways ?

  


  All that said, is there something within ffprobe or other tool I can use to more efficiently confirm what I am visually seeing to say yep these frames were just duplicated from another program ? Thanks !

  


• Multicast video captured via VLC show a gray background for first 1/2 second

  28 juillet 2014, par DavidG

  I am capturing multicast video using VLC.exe and performing some processing/converting using FFmpeg.exe. The resulting video starts with a gray background with some of the moving objects moving through the gray background. This seems to me that the video is not starting on an I-Frame, but on a B-Frame or a P-Frame. However, when I run ffprobe, it states the first frame is a key frame. After about 1/2 second, the video plays fine.

  Here is the command I’m using to capture the video :

  vlc.exe -I curses --run-time=10 "my.sdp" --sout=video.mp4

  I’m not using anything special when I convert to an mp4 file using FFmpeg :

  ffmpeg.exe -i video.mp4 -s 400x300 final.mp4

  I tried to post an image of the first frame or two, but Stackoverflow gave me an error stating I need at least 10 reputation to post images. Sorry about that, an image would have helped.

  I ran the command "ffprobe show_frames " and it looks like the first frame is a key frame. Of course I’m new to all this and I don’t know what I’m doing or seeing.

  Here is beginning of the output to the "ffprobe show_frames " command :

  [FRAME]
  
  media_type=video
  
  key_frame=1
  
  pkt_pts=0
  
  pkt_pts_time=0.000000
  
  pkt_dts=0
  
  pkt_dts_time=0.000000
  
  pkt_duration=1001
  
  pkt_duration_time=0.033367
  
  pkt_pos=48
  
  pkt_size=756
  
  width=400
  
  height=300
  
  pix_fmt=yuv420p
  
  sample_aspect_ratio=1:1
  
  pict_type=I
  
  coded_picture_number=0
  
  display_picture_number=0
  
  interlaced_frame=0
  
  top_field_first=0
  
  repeat_pict=0
  
  reference=3
  
  [/FRAME]

  Is there any way to either tell VLC.exe to start capturing on an I-Frame (This would be the best solution as I specify a duration to capture the video) or is there a way to tell FFmpeg.exe to start converting the input video starting at the first I-Frame encountered ?

  Thanks,
   David

• Révision 19231 : Complément à r19158 sur le calcul du Path d’un document faussement distant :

  10 avril 2012, par esj@rezo.net

  accepter les variations http/https pour que ça marche dans un espace privé protégé par https * tenir compte du paramètre $force (mais est-ce vraiment utile ?)