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• Wrong video duration reported after concatenating video files in BASH script

  13 novembre 2012, par Benjen

  I am trying to merge three video files (each 16 seconds long) into one file using ffmpeg. Since they are in mpeg format I am simply trying to concatenate them into one file using cat command. The problem is that when I run the resulting file (video.mpg) it is reported as being 16 seconds long (same as the first concatenated video). Interestingly when I play the file in VLC, I can watch the whole 48 sec of video, even though the video progress bar also only reports up to 16 secs.

  It almost seems like the file "properties" (e.g. duration, etc) are not updated after the additional two videos are added using the cat command.

  Would appreciate any suggestions on how I might solve this.

  The following is the relevant section of the BASH script I have created :

  mkfifo intermediate1.mpg
  
  mkfifo intermediate2.mpg
  
  mkfifo intermediate3.mpg
  
  ffmpeg -i "./tmp/final01.mp4" -qscale 1 -y intermediate1.mpg < /dev/null &
  
  ffmpeg -i "./tmp/final02.mp4" -qscale 1 -y intermediate2.mpg < /dev/null &
  
  ffmpeg -i "./tmp/final03.mp4" -qscale 1 -y intermediate3.mpg < /dev/null &
  
  
  
  echo "[audioforge] Stitching files "
  
  cat intermediate1.mpg >> ./tmp/video.mpg
  
  cat intermediate2.mpg >> ./tmp/video.mpg
  
  cat intermediate3.mpg >> ./tmp/video.mpg
  
  
  
  # Convert back to mp4 format.
  
  ffmpeg -i "./tmp/video.mpg" -qscale 1 -y "./tmp/video.mp4"

• Using FFMPEG to stream from one computer to another on the same network

  23 juin 2021, par Andy B

  My problem

  


  I have a device with cameras, and I can access the video from those cameras via RTP over RTSP.

  


  I have an Ethernet cord going from the device to my computer, and I can see/record the video from the device using FFMPEG or VLC. I just use rtsp://<ip of="of" device="device">/path/of/stuff.extension?camera=<number></number></ip> like the user's manual says.

  


  This works great, but ultimately, I want to stream this video to another computer on the same network. I have tried many different things, but nothing seems to work.

  


  Theoretically, this FFMPEG command should work, but I'm messing up somewhere and I don't know why or where.

  


  ffmpeg -rtsp_transport tcp -i rtsp://<ip of="of" device="device">/path/thing.extension?camera=1 \ &#xA;-f mpegts udp://<ip of="of" computer="computer" i="i" want="want" to="to" send="send" it="it">:<some port="port">&#xA;</some></ip></ip>

  


  In VLC on the other computer, I want to be able to just go into VLC and start a network stream that looks like udp://@<ip address="address">:<port></port></ip>

  


  What I thought would work, but doesn't

  


  If the camera device has IP A.A.A.A, and the computer getting and streaming the video is B.B.B.B, and the computer I want to watch the streamed video on is C.C.C.C then is the following correct ? Because it does not work for me...

  


  Computer A :

  


  ffmpeg -rtsp_transport tcp -i rtsp://A.A.A.A/path.ext?camera=1 -f mpegts udp://B.B.B.B:10001


  


  Computer B (in VLC) : udp://@B.B.B.B:10001

  


• FFmpeg Negative Duration [migrated]

  22 septembre 2014, par filby

  i have a large number of small videos (parts of a larger) of the form :

  Metadata:
  
  major_brand     : isom
  
  minor_version   : 512
  
  compatible_brands: isomiso2avc1mp41
  
  encoder         : Lavf55.43.100
  
  Duration: 00:00:05.53, start: -1.831497, bitrate: 3355 kb/s
  
  Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 4760 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc (default)
  
  Metadata:
  
    handler_name    : VideoHandler
  
  Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 157 kb/s (default)
  
  Metadata:
  
    handler_name    : SoundHandler

  I want to completely discard the negative start, the 1.83 seconds, and keep only the 3.67 seconds in the positive ’axis’.

  I cut the videos with the correct duration however i believe due to some sync i did in sound (in the original), resulted in me having a video of 5.53 second, of which 1.83 is audio only, and the last 3.67 seconds are the ones i want to keep (and the ones i did cut).

  In a video player i can watch the 3.67 seconds i want to however if i extract the audio i get +1.83 seconds of audio at start from the original video (from which i cut the parts) which i didnt intend to cut. What can i do ;

  P.S.
  Example of the command i used to cut the part :

  ffmpeg -ss 818 -i input -t 3.67 -codec:v libx264 -profile:v high -preset slow -b:v 5000k -maxrate 5000k -threads 0 -codec:a copy output