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• How to convert H264 RTP stream from PCAP to a playable video file

  21 août 2014, par yoosha

  I have captured stream of H264 in PCAP files and trying to create media files from the data. The container is not important (avi,mp4,mkv,…).
  When I’m using videosnarf or rtpbreak (combined with python code that adds 00 00 00 01 before each packet) and then ffmpeg, the result is OK only if the input frame rate is constant (or near constant). However, when the input is vfr, the result plays too fast (and on same rare cases too slow).
  For example :

  videosnarf -i captured.pcap –c
  ffmpeg -i H264-media-1.264 output.avi

  After doing some investigation of the issue I believe now that since the videosnarf (and rtpbreak) are removing the RTP header from the packets, the timestamp is lost and ffmpeg is referring to the input data as cbr.

  1. I would like to know if there is a way to pass (on a separate file ?)
     the timestamps vector or any other information to ffmpeg so the
     result will be created correctly ?
  2. Is there any other way I can take the data out of the PCAP file and play it or convert it and then play it ?
  3. Since all work is done in Python, any suggestion of libraries/modules that can help with the work (even if requires some codding) is welcome as well.

  Note : All work is done offline, no limitations on the output. It can be cbr/vbr, any playable container and transcoding. The only "limitation" I have : it should all run on linux…

  Thanks
  Y

  Some additional information :
  Since the nothing provides the FFMPEG with the timestamp data, i decided to try a different approach : skip videosnarf and use Python code to pipe the packets directly to ffmpeg (using the "-f -i -" options) but then it refuses to accept it unless I provide an SDP file...
  How do I provide the SDP file ? is it an additional input file ? ("-i config.sdp")

  The following code is an unsuccessful try doing the above :

  import time  
  
  import sys  
  
  import shutil  
  
  import subprocess  
  
  import os  
  
  import dpkt  
  
  
  
  if len(sys.argv) < 2:  
  
      print "argument required!"  
  
      print "txpcap <pcap file="file">"  
  
      sys.exit(2)  
  
  pcap_full_path = sys.argv[1]  
  
  
  
  ffmp_cmd = ['ffmpeg','-loglevel','debug','-y','-i','109c.sdp','-f','rtp','-i','-','-na','-vcodec','copy','p.mp4']  
  
  
  
  ffmpeg_proc = subprocess.Popen(ffmp_cmd,stdout = subprocess.PIPE,stdin = subprocess.PIPE)  
  
  
  
  with open(pcap_full_path, "rb") as pcap_file:  
  
      pcapReader = dpkt.pcap.Reader(pcap_file)  
  
      for ts, data in pcapReader:  
  
          if len(data) &lt; 49:  
  
              continue  
  
          ffmpeg_proc.stdin.write(data[42:])
  
  
  
  sout, err = ffmpeg_proc.communicate()  
  
  print "stdout ---------------------------------------"  
  
  print sout  
  
  print "stderr ---------------------------------------"  
  
  print err  
  
  </pcap>

  In general this will pipe the packets from the PCAP file to the following command :

  ffmpeg -loglevel debug -y -i 109c.sdp -f rtp -i - -na -vcodec copy p.mp4

  SDP file : [RTP includes dynamic payload type # 109, H264]

  v=0
  o=- 0 0 IN IP4 ::1
  s=No Name
  c=IN IP4 ::1
  t=0 0
  a=tool:libavformat 53.32.100
  m=video 0 RTP/AVP 109
  a=rtpmap:109 H264/90000
  a=fmtp:109
  packetization-mode=1 ;profile-level-id=64000c ;sprop-parameter-sets=Z2QADKwkpAeCP6wEQAAAAwBAAAAFI8UKkg==,aMvMsiw= ;
  b=AS:200

  Results :

  ffmpeg version 0.10.2 Copyright (c) 2000-2012 the FFmpeg developers
  built on Mar 20 2012 04:34:50 with gcc 4.4.6 20110731 (Red Hat
  4.4.6-3) configuration : —prefix=/usr —libdir=/usr/lib64 —shlibdir=/usr/lib64 —mandir=/usr/share/man —enable-shared —enable-runtime-cpudetect —enable-gpl —enable-version3 —enable-postproc —enable-avfilter —enable-pthreads —enable-x11grab —enable-vdpau —disable-avisynth —enable-frei0r —enable-libopencv —enable-libdc1394 —enable-libdirac —enable-libgsm —enable-libmp3lame —enable-libnut —enable-libopencore-amrnb —enable-libopencore-amrwb —enable-libopenjpeg —enable-librtmp —enable-libschroedinger —enable-libspeex —enable-libtheora —enable-libvorbis —enable-libvpx —enable-libx264 —enable-libxavs —enable-libxvid —extra-cflags=’-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector —param=ssp-buffer-size=4 -m64 -mtune=generic -fPIC’ —disable-stripping libavutil 51. 35.100 / 51. 35.100 libavcodec 53. 61.100 / 53. 61.100 libavformat 53. 32.100
  / 53. 32.100 libavdevice 53. 4.100 / 53. 4.100
  libavfilter 2. 61.100 / 2. 61.100 libswscale 2. 1.100
  / 2. 1.100 libswresample 0. 6.100 / 0. 6.100
  libpostproc 52. 0.100 / 52. 0.100 [sdp @ 0x15c0c00] Format sdp
  probed with size=2048 and score=50 [sdp @ 0x15c0c00] video codec set
  to : h264 [NULL @ 0x15c7240] RTP Packetization Mode : 1 [NULL @
  0x15c7240] RTP Profile IDC : 64 Profile IOP : 0 Level : c [NULL @
  0x15c7240] Extradata set to 0x15c78e0 (size : 36) !error,_recognition
  separate : 1 ; 1 [h264 @ 0x15c7240] error,_recognition combined : 1 ;
  10001 [sdp @ 0x15c0c00] decoding for stream 0 failed [sdp @
  0x15c0c00] Could not find codec parameters (Video : h264) [sdp @
  0x15c0c00] Estimating duration from bitrate, this may be inaccurate
  109c.sdp : could not find codec parameters Traceback (most recent
  call last) : File "./ffpipe.py", line 26, in
  ffmpeg_proc.stdin.write(data[42 :]) IOError : [Errno 32] Broken pipe

  (forgive the mass above, the editor keep on complaining about code that is not indented OK ??)

  I’m working on this issue for days... any help/suggestion/hint will be appreciated.

• Create a video with audio only on one channel

  6 février 2018, par Jude Osborn

  I’m trying to create 5 videos that each play audio only in one channel. So, for example, one video only plays audio in the right front, another only in the back left, another only in the center, etc.

  The videos are currently stereo. Can I use ffmpeg to accomplish this ?

• Best way of playing mkv video that is being recorded with ffmpeg in web browser

  17 juin 2017, par martin49

  I’m looking for a way to play a video that is being recorded with ffmpeg in a web browser preferably using HTML5 video tag.

  I have this code in my page, the URL is pointing to a video file (example.mkv) that is being recorded by ffmpeg.

  <video class="video-player" controls="controls" loop="loop">          
  
              <source src="{{asset('example.mkv')}}" type="video/mp4">
  
              <p>Your browser does not support H.264/MP4.</p>
  
  </source></video>

  Google Chrome/Chromium can play mkv video in HTML5, but only plays the part that was loaded when page was loaded. Is it possible to continue to load the video while it is being recorded ?