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• Reducing frames with ffmpeg leads to massive video size reaction - what´s wrong ?

  9 juin 2023, par Katharina

  I am working on a project in which I need to

  


  -transform many videos from .h264 format to .mp4

  


  -cut them after 1 hour duration

  


  -reduce the framerate from 60 fps to 30 fps

  


  Up to now, I came up with following :

  


  Convert :

  


  for %a in ("*.h264") do ffmpeg -framerate 60 -fflags +genpts -i "%a" -vcodec copy -acodec copy "%~na_Conv.mp4


  


  Cut :

  


  for %a in ("*.mp4") do ffmpeg -ss 00:00:00 -i "%a" -to 01:00:00  -vcodec copy -acodec copy "%~na_cut.mp4


  


  Reduce framerate :

  


  for %a in ("*.mp4") do ffmpeg -i "%a" -filter:v fps=fps=30 "%~na_30fps.mp4


  


  It finally seems to work fine, but I am worried, because the original file has 2.6 GB, the converted and cut video file has 2.4 GB (which I find reasonable), but the video file with 30 fps has only 340 MB. It does not seem corect, that the files got so small. However, I used fprobe to determine the framerates and it shows that the fps should be as specified. Still, I find it puzzling that the video is now so small when only half the frames were dropped. Unfortunately, looking at the videos does not give hints if too many frames were dropped.

  


  I am grateful for any advice how to find the error or how to evaluate my result properly. Thank you for your help !

  


• avcodec/pthread_frame : Fix cleanup during init

  11 février 2021, par Andreas Rheinhardt

  avcodec/pthread_frame : Fix cleanup during init
  In case an error happened when setting up the child threads,
  
  ff_frame_thread_init() would up until now call ff_frame_thread_free()
  
  to clean up all threads set up so far, including the current, not
  
  properly initialized one.
  
  But a half-allocated context needs special handling which
  
  ff_frame_thread_frame_free() doesn't provide.
  
  Notably, if allocating the AVCodecInternal, the codec's private data
  
  or setting the options fails, the codec's close function will be
  
  called (if there is one) ; it will also be called if the codec's init
  
  function fails, regardless of whether the FF_CODEC_CAP_INIT_CLEANUP
  
  is set. This is not supported by all codecs ; in ticket #9099 it led
  
  to a crash.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/pthread_frame.c

• avcodec : export motion vectors in frame side data on demand

  16 juillet 2014, par Clément Bœsch

  avcodec : export motion vectors in frame side data on demand
  The reasoning behind this addition is that various third party
  
  applications are interested in getting some motion information out of a
  
  video "for free" when it is available.
  It was considered to export other information as well (such as the intra
  
  information about the block, or the quantization) but the structure
  
  might have ended up into a half full-generic, half full of codec
  
  specific cruft. If more information is necessary, it should either be
  
  added in the "flags" field of the AVMotionVector structure, or in
  
  another side-data.
  This commit also includes an example exporting them in a CSV stream.
  

  • [DH] .gitignore
  • [DH] configure
  • [DH] doc/APIchanges
  • [DH] doc/Makefile
  • [DH] doc/codecs.texi
  • [DH] doc/examples/Makefile
  • [DH] doc/examples/extract_mvs.c
  • [DH] libavcodec/avcodec.h
  • [DH] libavcodec/mpegvideo.c
  • [DH] libavcodec/options_table.h
  • [DH] libavutil/Makefile
  • [DH] libavutil/frame.c
  • [DH] libavutil/frame.h
  • [DH] libavutil/motion_vector.h
  • [DH] libavutil/version.h