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• movenc : Add a new flag for writing global sidx indexes for dash

  9 août 2015, par Martin Storsjö

  movenc : Add a new flag for writing global sidx indexes for dash
  The double meaning of the faststart flag (moving a moov atom
  
  to the start of files, making them streamable, for non-fragmented
  
  files, vs inserting a global sidx index at the start of files
  
  for fragmented files) is confusing - see 40ed1cbf1 for
  
  explanation of its origins.
  Since the second meaning of the flag hasn’t been part of any
  
  libav release yet, just rename it to get rid of the confusion
  
  without any extra deprecation (which wouldn’t get rid of the
  
  potential confusion, of users adding -movflags faststart
  
  even for fragmented files, where it isn’t needed for making
  
  them "streamable").
  This gets back the old behaviour, where -movflags faststart
  
  doesn’t have any effect for fragmented files.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavformat/movenc.c
  • [DBH] libavformat/movenc.h

• ffmpeg audio/video sync problems when uploading to WhatsApp

  11 janvier 2021, par Luke Collins

  (Note : I have looked at related questions such as this one, but the solutions there didn't work for me since presumably their output files wouldn't play correctly in mpv, whereas mine do.)

  


  I want to send a scene from a film to my friend on WhatsApp. I run

  


  


  ffmpeg -i film.mp4 -ss 00:25:30 -t 00:03:00 -c: copy out.mp4

  


  


  to extract the clip, which produces the file out.mp4 which plays fine when I play it with mpv.

  


  If instead, I play the file in my browser (firefox), the first frame is static for a couple of seconds while audio plays, until the video starts and the video and audio are both in sync. (In other words, it seems the file has additional unnecessary audio information appended to the beginning of the file, which starts before my desired clip when played in firefox).

  


  Diagrammatically, I suspect the video contains the following information :

  


  

  


  and firefox plays it in this way :

  


  

  


  What's worse is that when I upload it to WhatsApp, it misaligns the audio with the video, instead playing it this way :

  


  

  


  How can I fix this so that the video has no additional video/audio information ?

  


  I appreciate any help with this.

  


• Cannot retrieve duration of webm file using ffmpeg

  10 juin 2016, par maximus 69

  I am trying to retrieve the duration of a .webm video file that I recorded using the the video.js plugin (https://github.com/collab-project/videojs-record).

  I am using ffmpeg to get the duration but it always return N/A :

  ffprobe version 3.0.2-static http://johnvansickle.com/ffmpeg/  Copyright (c) 2007-2016 the FFmpeg developers
  
    built with gcc 5.3.1 (Debian 5.3.1-16) 20160424
  
    configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --enable-libmp3lame --enable-libx264 --enable-libx265 --enable-libwebp --enable-libspeex --enable-libvorbis --enable-libvpx --enable-libfreetype --enable-fontconfig --enable-libxvid --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libtheora --enable-libvo-amrwbenc --enable-gray --enable-libopenjpeg --enable-libopus --enable-libass --enable-gnutls --enable-libvidstab --enable-libsoxr --enable-frei0r --enable-libfribidi --disable-indev=sndio --disable-outdev=sndio --enable-librtmp --enable-libmfx --enable-libzimg --cc=gcc
  
    libavutil      55. 17.103 / 55. 17.103
  
    libavcodec     57. 24.102 / 57. 24.102
  
    libavformat    57. 25.100 / 57. 25.100
  
    libavdevice    57.  0.101 / 57.  0.101
  
    libavfilter     6. 31.100 /  6. 31.100
  
    libswscale      4.  0.100 /  4.  0.100
  
    libswresample   2.  0.101 /  2.  0.101
  
    libpostproc    54.  0.100 / 54.  0.100
  
  Input #0, matroska,webm, from '/home/demoss/public_html/source/bALRt9I697PVQh4zglou.webm':
  
    Metadata:
  
      encoder         : Chrome
  
    Duration: N/A, start: 0.000000, bitrate: N/A
  
      Stream #0:0(eng): Video: vp8, yuv420p, 640x480, SAR 1:1 DAR 4:3, 30 fps, 30 tbr, 1k tbn, 1k tbc (default)
  
      Stream #0:1(eng): Audio: opus, 48000 Hz, mono, fltp (default)
  
  duration=N/A

  I don’t think the video is corrupted as it played in my VideoJS player without issues.

  Any pointers as to why its not returning the duration would be greatly appreciated. I wouldn’t mind using an alternative library as well

  Thanks