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• 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 !

  


• How to generate pcm audio file by setting 20 bit depth ?

  6 juillet 2015, par vip007

  No option using ffmpeg

  I am using ffmpeg to generate audio data. I am using following command

  ffmpeg.exe -i in.wav -ar 44100  -acodec pcm_s16le  -ac 1 out.wav

  but there is no option to convert to 20 bit depth pcm audio. (something like pcm_s20le).

  I want to perform some operations on apple codec (e.g. encoding pcm audio data to alac).

  On ALAC source : http://alac.macosforge.org/trac/browser/trunk/ReadMe.txt , it has been mentioned like this ;

  Apple Lossless supports the following features
  1. Bit depths 16, 20, 24 and 32 bits.

  Media Foundation on windows throwing exception for 20 bit depth

  I tried sample encoding and transcoding application mentioned on MSDN https://code.msdn.microsoft.com/windowsapps/media-transcode-sample-f7ba5269

  with following configuration but it failed

  spTypeOut->SetUINT32(MF_MT_AUDIO_BITS_PER_SAMPLE, 20);  

  NOTE : but i put 16 instead of 20 ; it created smoothly.

  Is there any way to generate such 20 bit PCM audio ? What is so special about 20 bit depth that it is not being considered on ffmpeg and media foundation but on apple codec ?

• fate/all : add missing file protocol dependencies

  30 juin, par Nicolas Gaullier

  fate/all : add missing file protocol dependencies
  First, always require file protocol when FATE suite is used.
  
  Then, add missing dependencies while removing duplicates.
  Signed-off-by : Nicolas Gaullier <nicolas.gaullier@cji.paris>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] tests/Makefile
  • [DH] tests/fate/cbs.mak
  • [DH] tests/fate/cover-art.mak
  • [DH] tests/fate/demux.mak
  • [DH] tests/fate/filter-audio.mak
  • [DH] tests/fate/filter-video.mak
  • [DH] tests/fate/image.mak
  • [DH] tests/fate/microsoft.mak
  • [DH] tests/fate/mpc.mak
  • [DH] tests/fate/pcm.mak
  • [DH] tests/fate/pixfmt.mak
  • [DH] tests/fate/seek.mak
  • [DH] tests/fate/subtitles.mak
  • [DH] tests/fate/vpx.mak
  • [DH] tests/fate/wavpack.mak