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• ffmpeg rtp streaming errors : RTP : dropping old packet received too late

  2 février 2019, par Андрей_RnD

  I start video transfer by means of ffmpeg like this :

  ffmpeg -f video4linux2 -i /dev/video0 -vcodec libx264 -preset ultrafast -crf 20 -tune zerolatency -s 800x600 -r 25 -b:v 0.9M -sdp_file video.sdp -f rtp rtp://192.168.10.24:5010    

  I reproduce this way :

  ffplay -protocol_whitelist file,udp,rtp video.sdp    

  Everything works just fine. Then I interrupt transmission and after a couple of seconds I resume. ffplay does not immediately start to reproduce but errors occur :

  ....
  
  [sdp @ 0x6ebf80] RTP: dropping old packet received too lateB f=1/1
  
      Last message repeated 14 times
  
  [sdp @ 0x6ebf80] RTP: dropping old packet received too lateB f=1/1
  
      Last message repeated 33 times
  
  [sdp @ 0x6ebf80] RTP: dropping old packet received too lateB f=1/1
  
      Last message repeated 41 times
  
  [sdp @ 0x6ebf80] RTP: dropping old packet received too lateB f=1/1
  
      Last message repeated 49 times
  
  [sdp @ 0x6ebf80] RTP: dropping old packet received too lateB f=1/1
  
      Last message repeated 33 times
  
  [sdp @ 0x6ebf80] RTP: dropping old packet received too lateB f=1/1
  
      Last message repeated 27 times
  
  [sdp @ 0x6ebf80] RTP: dropping old packet received too lateB f=1/1
  
      Last message repeated 14 times
  
  [sdp @ 0x6ebf80] RTP: dropping old packet received too lateB f=1/1
  
      Last message repeated 48 times
  
  [sdp @ 0x6ebf80] RTP: dropping old packet received too lateB f=1/1
  
      Last message repeated 34 times
  
  ......    

  After a some time, playback is restored, but it is too long. Is there a way to eliminate or minimize the occurrence of errors of this nature when the incoming stream is suspended, can options or something else ? Read the manual ffmpeg nothing worthwhile about this did not naryl .... ((((

• ffmpeg tile screenshot file with uniform distribution over video length

  23 octobre 2017, par Michael Yousef

  I’m trying to take a video and create a screenshot file for it. I want it to cover the entire duration of the video and be uniformly distributed over the video. I have a command right now that I found online, it can produce a screenshot file, but it doesn’t cover the entire duration

  ffmpeg -ss 00:05:00 -i video.mp4 -frames 1 -vf "select=not(mod(n\,8000)),scale=320:240,tile=4x8" out.png

  Instead of having it cap every 80 seconds, I want it to determine what the duration is use that. It should cap the first screen at my initial offset, then however far ahead as necessary.

  Also, if anyone knows how to add information to the outputted file at the top, like filename, duration, bitrate, etc., that’s also something I want to output.

• How to receive MPEGT-TS stream with Pro-MPEG FEC using ffmpeg ?

  1er février 2019, par Antoxic

  I have two Linux computers connected through internet transmitting MPEG-TS from one PC to the other. The connection is not perfect and sometimes the packets get lost. I want to transmit an MPEG-TS from one PC to another using PRO-MPEG in order to enable error correction (FEC). On one computer I’m running ffmpeg with :

  ffmpeg-i "http://1.2.3.4:1234 -map 0 -r 25 -c:v copy -f rtp_mpegts -fec prompeg=l=5:d=5 rtp://4.3.2.1:4321

  And now I need to receive that stream and I want to correct the transmission errors using the FEC info which comes on RTP port +1 and +2. How can I achieve that with ffmpeg ? If it is not possible wit ffmpeg, what other solution can I use ?

  I’m using an ffmpeg snapshot version N-87867-g0655810. I can’t find any information about how to receive it and use the FEC information to recover transmission errors.