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• ffmpeg transcoding reset the start time of file

  12 août 2013, par diousk

  I use a segmenter to segment my MPEG 2 Ts file into a series of media segment for HTTP live streaming

  and each segment's start time following the previous one
  (ex:start time of segments : 00:00,00:10,00:20,00:30,...)

  (In Ubuntu)

  The Question is :

  When I use ffmpeg to transcode one of the media segment (ex 800k bps to 200k bps)

  the start time of transcoded media segment will be reset to 0

  ex:As I transcode the third segement,

  start time of segments changing to : 00:00,00:10,00:00,00:30,...

  It cause my player freezing once play the transcoded media segment

  Is there any solution to transcode media file with the same start time ?

  I guess it's the ffmpeg reset the PTS(presentation timestamp) of segment

  But I don't know how to fix it...

  here is my ffmpeg command (transcode to 250k bps)

  ============================

  ffmpeg -y -i sample-03.ts -f mpegts -acodec libfaac -ar 48000 -ab 64k -vcodec libx264 -b 250k -flags +loop -cmp +chroma \
  
   -partitions +parti4x4+partp8x8+partb8x8 -subq 7 -trellis 0 -refs 0 -coder 0 -me_range 16 -keyint_min 25 \
  
   -sc_threshold 40 -i_qfactor 0.71 -maxrate 250k -bufsize 250k -rc_eq 'blurCplx^(1-qComp)' -qcomp 0.6 \
  
   -qmin 10 -qmax 51 -qdiff 4 -level 30 -aspect 320:240 -g 30 -async 2 sample.ts

  ============================

  Help !

  thanks

• Cut videos and stack them with hstack in ffmpeg at the same time

  18 juillet 2018, par ekuusi

  I have two videos that I want to stack with hstack. The videos are not perfectly in sync so I would like to cut a bit from the beginning of one of the videos to get them to sync perfectly. Everything works fine using two concurrent commands :

  ffmpeg -ss 00:00:18 -i video1.mp4 -ss 00:00:02.000 -c:v libx264 left.mp4 

  followed by

  ffmpeg -i left.mp4 -i right.mp4 -filter_complex hstack output.mp4

  I’m wondering however if it is possible to do the trimming at the same time as stacking so that ffmpeg doesn’t have to encode the cut video twice. This would save a lot of time for me as I will be doing this cutting & merging multiple times.

  I tried various ways to achieve this in one single command, but to no avail so I have to turn to the community. Thank you for helping !

• ffmpeg time-lapse from raw .NEF photos

  14 juin 2020, par Emil Terman

  I have about 3000 .NEF photos on the server, each weighting about 80MB.
I need to make a time-lapse out of them. Since it's just for a demo, it's fine if I reduce the quality, so compressing is fine.

  



  I've tried different things, but I couldn't really find a way to make a time-lapse out of .nef files.
But I did find a way to make time-lapse out of .jpg files :

  



  ffmpeg -r 24 -f concat -i ordered_list_of_photos.txt -s hd1080 -vcodec libx264 out.mp4


  



  This works perfectly, but it only works with .jpgs it seems.

  



  -f concat -i ordered_list_of_photos.txt - means : read the files from ordered_list_of_photos.txt. That file contains lines like :

  



  file 'jpgs/file1.jpg'
file 'jpgs/file2.jpg'
...


  



  Do you have any suggestions on how to do this ? I'm pretty sure it has something to do with rawvideo demuxer, but I can't figure it out on my own.

  



  Converting the .nef files to .jpg seems like an option, but I can't get ufraw-batch to work, as it throws segmentation faults after the first conversion. And I also don't have Desktop access to the computer, I'm using ssh to do all of this (so GUI apps won't work I think).