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• How do dcraw and stdin work together ?

  25 juillet 2018, par Metin Akkın

  I want to use this :

  dcraw -a -q 3 -6 -v -I < a.nef

  but the picture becomes a dark image. I changed draw.c library but it doesnt work. I want to use stdin and I use this link : https://blog.mclemon.io/dcraw-and-stdin. Please help me.

• Why does mp3lame conversion from mp3float not work for rtmp ?

  12 avril 2020, par SquirrelSenpai

  I am creating a rtmp stream using FFMPEG and sending the data to local NGINX server with the RTMP module.

  



  The originally stream is mp3float, however the conversion to Mp3lame did not work while flv did , how comes ?

  



  Doesn't work but no errors

  



  fmpeg -hide_banner -loglevel warning -i http://x.x.x.x:8138 -f mp3 rtmp://localhost/live


  



  Works with no errors

  



  fmpeg -hide_banner -loglevel warning -i http://x.x.x.x:8138 -f flv rtmp://localhost/live


  


• 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