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• How to process single segment from fragmented mp4 container ?

  14 septembre 2020, par user14258924

  I have fragmented mp4 that I stream. First the mp4 header and then individual segments that are each one GOP. It is h264 and aac encoded video that I am getting from RTMP server.

  


  I would like to process these individual segments with ffmpeg(I doubt there are other tools available). Either adjust resolution or bitrate or even transcode to vp8/9 or avi1 if needed.

  


  But it seems that ffmpeg cannot handle this because the segment has no header. So I wodner if there is a flag or set of flags for ffmpeg to be able to process these segments without the header ? I could possibly just take the raw h264 and aac packets from the RTMP and not pack it into MP4 container beforehand, if that helps - would ffmpeg be able to process these ?

  


• Faster frame extraction than ffmpeg

  23 janvier 2013, par Ben Ford

  I have a video analytics program that processes assorted frames from a video. (Several hours long)
  The video is likely going to be an MP4 but may be other formats going forwards.

  At the moment, I have a C# wrapper around an ffmpeg call to extract an individual frame at the requested time. (I'm using the ffmpeg.exe binary. Not the libraries directly)
  At the moment, this all works. But it's slow. Very slow.

  I've found ways to improve the speed by storing the extracted frames in a ramdisk while they're being processed. Changing the stored image format etc...

  I just wanted to check if anyone could think of any way to pull individual frames out. At split-second accuracy.
  I know this is probably possible with DShow etc... I went straight to FFMPEG as I've used it before. But if DShow is likely to be faster I'll gladly change !

• ffmpeg Sound going out of sync with -concat or -ss

  6 août 2012, par Jared Glass

  I have a tool that spits out video from a 3D application and then concats the individual videos to make a sequence. But the sound seems to go out of sync in the sequence (the inividual files are fine) and it stutters in VLC and Quicktime. Windows media player seems to handle it bes to my supprise, yet it still goes out of sync. I have two senarios, one works and one doesn't but i need both working :

  Working :
  get already created out movs...

  convert to avi :
  os.system( ffmpeg + " -i C:\clip.mov -sameq -r 24 -y C:\clip.avi")

  concat to avi sequence :
  os.system( ffmpeg + ''' -i concat: C:\clip.avi|C:\clip1.avi|C:\clip2.avi -sameq -r 24 -y C:\sequence.avi''' )

  convert sequence to mov :
  os.system( ffmpeg + " -i C:\sequence.avi -sameq -r 24 -y C:\sequence.mov")

  Not Working :
  create individual avi's from 3D program...

  cut down to correct length :
  os.system(ffmpeg + " -i C:\clip.avi -sameq -r 24 -ss " + startTime + " -vframes " + totalFrames + " -y C:\clip.avi" )

  concat to avi sequence :
  os.system( ffmpeg + ''' -i concat: C:\clip.avi|C:\clip1.avi|C:\clip2.avi -sameq -r 24 -y C:\sequence.avi''' )

  convert sequence to mov :
  os.system( ffmpeg + " -i C:\sequence.avi -sameq -r 24 -y C:\sequence.mov")

  convert individual avi's to mov :
  os.system( ffmpeg + " -i C:\clip.avi-sameq -r 24 -y C:\clip.mov")

  Please let me know where I've gone wrong ?