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• Why is ffmpeg cut setting the wrong duration on my output file

  9 mai 2023, par danielson317

  Setup

  


  I am trying to break a video up into parts using some basic commands I have seen available.

  


  I have tried :

  


  ffmpeg -ss 00:00:00 -t 00:11:42 -i 'original.m4v' -acodec copy -vcodec copy 'output.m4v'

  


  I also tried more generic (and much slower) :

  


  ffmpeg -ss 00:00:00 -t 00:11:42 -i 'original.m4v' 'output.m4v'

  


  I am on Ubuntu 20 with ffmpeg 4.2.7-0. I know it is a little outdated but this computer lost it's network card so I cannot update it at this time.

  


  The problem

  


  In both cases the video cuts correctly to only have the first 11:42. However the video properties state the video is 31 minutes long (the length of the original). This file size also reflects the reduced size I would expect from the cut. When I play the video in VLC it reports the video is 31 minutes long but scanning or playing past 11:42 "crashes" the playback.

  


  Question

  


  Why is the new video reporting the wrong length and how do I correct this ? Preferably in the conversion process not a secondary command.

  


• How to change stream metadata with ffmpeg ?

  13 juillet 2012, par Igor Grinfeld

  I have many video files and part of it have wrong size, or at least ffmpeg reports wrong size.
  For example, ffmpeg prints :

   Metadata:
  
      major_brand     : mp42
  
      minor_version   : 0
  
      compatible_brands: mp42isom
  
      creation_time   : 2009-10-11 15:04:33
  
      encoder         : HandBrake 0.9.3 2008112300
  
   Duration: 01:47:42.18, start: 0.000000, bitrate: 663 kb/s
  
      Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 720x464 [
  
  SAR 43:36 DAR 215:116], 499 kb/s, 25 fps, 25 tbr, 48k tbn, 50 tbc
  
   Metadata:
  
      creation_time   : 2009-10-11 15:04:33
  
      handler_name    :
  
   Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, s16, 159
  
  kb/s
  
   Metadata:
  
       creation_time   : 2009-10-11 15:04:33
  
       handler_name    :

  However, when I configure media player to play the file without resizing it has 860x464 size.

  I want to write scripts that will fix the files, but I don't know how to do that. I've updated to last ffmpeg version and tried to use -metadata:s:v:0 Video="...860x464...", as I read in ffmpegh doc, but it doesn't work.
  What is my mistake ?

• Fragmented MP4 has wrong duration in Windows Media Player

  3 février 2020, par Expressingx

  I’m streaming video from a camera to a file using ffmpeg. The case to use Fragmented MP4 is that there can be sudden power off and lose the video. I’ve configured the fragments to be at least 30 secs and this is how much the Windows Media Player reports for the duration even if its 2 hours long, after that it keeps streaming the video but is not seekable after the 30th second. How can be that fixed ?

  ffmpeg -c copy -movflags frag_keyframe+separate_moof+omit_tfhd_offset -min_frag_duration 30000000 -bsf:a aac_adtstoasc \ out.mp4

  If I use -movflags frag_keyframe+empty_moov then the video is not seekable at all and no duration reported.

  I aim for seekable video with correct duration both on VLC/Windows Media Player

  Version of ffmpeg : 3.3.4