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• ffmpeg frame perfect video splitting

  5 mai 2020, par aosborne

  I'm working on a project that needs to calculate some computer vision stuff (openCV with Python) on every frame of the video. I'm trying to speed this up by splitting the video into chunks and giving each chunk to a different processor to handle.

  



  This works- except I can't seem to break up the video right. I've been looking at FFMPEG and have read about -ss and -t, -segment, even re-encoding the video to add more key frames.

  



  No matter what I've tried, I cannot accomplish my goal : cut a video into segments, where the exact placement of the segment divide doesn't matter, but if I were to line up the segments back together there would be no lost frames and no added frames (duplicated).

  



  If I can't figure this out, I expect I will use FFMPEG to loosely segment the video and I will find where the video overlaps in my program code by comparing frames.

  


• avformat/mpegts : Fix for the DOVI video stream descriptor

  14 octobre 2021, par Limin Wang

  avformat/mpegts : Fix for the DOVI video stream descriptor
  By <<Dolby Vision Streams Within the MPEG-2 Transport Stream Format v1.2>>
  Signed-off-by : Limin Wang <lance.lmwang@gmail.com>
  

  • [DH] libavformat/mpegts.c

• How to add a Poster Frame to an MP4 video by timecode ?

  25 mai 2020, par Crissov

  The mvhd atom or box of the original Quicktime MOV format supports a poster time variable for a timecode to use as a poster frame that can be used in preview scenarios as a thumbnail image or cover picture. As far as I can tell, the ISOBMFF-based MP4 format (.m4v) has inherited this feature, but I cannot find a way to set it using FFmpeg or MP4box or similar cross-platform CLI software. Edit : Actually, neither ISOBMFF nor MP4 imports this feature from MOV. Is there any other way to achieve this, e.g. using something like HEIFʼs derived images with a thmb (see Amendment 2) role ?

  



  

  



  The original Apple Quicktime (Pro) editor did have a menu option for doing just that. (Apple Compressor and Photos could do it, too).

  



  

  



  To be clear, I do not want to attach a separate image file, which could possibly be a screenshot grabbed from a movie still, as a separate track to the multimedia container. I know how to do that :

  



  

  • Stackoverflow #54717175

  


  • Superuser #597945

  


  



  I also know that some people used to copy the designated poster frame from its original position to the very first frame, but many automatically generated previews use a later time index, e.g. from 10 seconds, 30 seconds, 10% or 50% into the video stream.