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• lavc/libopenjpegenc : move opj_setup_encoder to libopenjpeg_encode_frame

  23 janvier 2015, par Jean First

  lavc/libopenjpegenc : move opj_setup_encoder to libopenjpeg_encode_frame
  if the openjpeg parameter tcp_rates is not 0 ( using the ffmpeg compression_level option )
  
  every 2nd image per thread is badly encoded. By moving the opj_setup_encoder function from
  
  libopenjpeg_encode_init to libopenjpeg_encode_frame this can be prevented.
  This fixes ticket #3754.
  Signed-off-by : Jean First <jeanfirst@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/libopenjpegenc.c

• avfilter/vf_delogo : Use AVPixFmtDescriptor.nb_components

  10 décembre 2015, par Jean Delvare

  avfilter/vf_delogo : Use AVPixFmtDescriptor.nb_components
  Relying on AVPixFmtDescriptor.nb_components is cleaner and faster than
  
  checking data and linesize for every possible plane.
  Signed-off-by : Jean Delvare <jdelvare@suse.de>
  
  Reviewed-by : Paul B Mahol <onemda@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavfilter/vf_delogo.c

• A 'clean' way to cut an MP4 movie into two sections using FFMPEG ?

  30 août 2020, par Peter in Japan

  I am attempting to use FFMPEG to make a script that can easily split a short MP4 movie with sound into two pieces at a certain point. I've searched through what feels like hundreds of posts to try to find "the" answer, but most of my attempts end up with poor results, broken video files that cause my video play to freeze, and so on. I am attempting to make a script that allows me to easily cut a short anime movie (something grabbed from Twitter or some other short source) and cut it into two sections, so it can be under the 2:20 Twitter time limit, or to cut out some scene I don't want to show my followers.

  


  The issue is that FFMPEG is good at cutting videos into segments, but bad at know where keyframes are, so most videos have two seconds of blank video at the front before some keyframe appears, which looks terrible.

  


  One example I found that works well is below, which cuts any mp4 into a bunch of chunks of n second size (six seconds in the example below). Source and documentation for this is https://moe.vg/3b8eNTs

  


  ffmpeg -i seitokai.mp4 -c:v libx264 -crf 22 -map 0 -segment_time 6 -reset_timestamps 1 -g 30 -sc_threshold 0 -force_key_frames "expr:gte(t,n_forced*1)" -f segment output%03d.mp4

  


  This code works great, at least allowing me to access the "left" side of a video that I want, in this case a six-second segment I want. Can anyone tell me how to accomplish the above, but starting at the 13-second period in said video, so I could get right "right" (not starting from 00:00:00) video cut cleanly ?

  


  Alternately, a single, unified and elegant way to split (re-encode) an MP4 into two segments that forces keyframes from the very beginning of the cut pieces would be wonderful. I can't believe how hard this seems to be.

  


  Thanks in advance for any help you can give ! Greetings from rural Japan !