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• ffmpeg - avoid duration approximation of generated files

  17 mai 2020, par Francesco

  I'm trying to generate videos with high precision durations, but all of the results always end up with their duration approximated leaving out milliseconds.

  



  E.g. ffmpeg -y -loop 1 -i "blank.png" -tune stillimage -t 9.983002003392 test.mkv

  



  This example is supposed to give the file a duration of 9 seconds and 983002003392 milliseconds, though those milliseconds get lost when I check the duration using ffbrobe ffprobe test.mkv -show_entries format=duration -v quiet -of csv="p=0", it shows 10.000000 instead.

  



  This doesn't happen when generating audio files instead, like ffmpeg -y -f lavfi -i anullsrc=sample_rate=48000 -t 9.983002003392 test.wav

  



  When I check its duration it shows 9.98, which is not the precision I asked but at least it's not approximated to just seconds.

  



  The duration is then further messed up by using concat on the videos and mixing audio files with the videos, but I suppose that's a problem related to the different settings of each file.

  



  My question is : How can I generate a video with a high precision duration without approximating it to just seconds ?

  


• Insert Random silence multiple times between Audios in ffmpeg

  23 septembre 2021, par Gracie williams

  suppose I have MP3 of around 1 minute duration and increase its duration longer.Duration can be any.

  


  I want to randomly add N seconds of silence to that audio.

  


  I can generate the silence like below

  


  ffmpeg -f lavfi -i anullsrc=r=44100:cl=mono -t <seconds> -q:a 9 -acodec libmp3lame out.mp3&#xA;</seconds>

  


  And I can insert silence to audio like below

  


  ffmpeg -i in.wav -filter_complex "anullsrc,atrim=0:4[s];[0]atrim=0:14[a];[0]atrim=14,asetpts=N/SR/TB[b];[a][s][b]concat=3:v=0:a=1" out.wav


  


  Is there anyway to insert silence at multiple areas.With php I can generate random time to insert based on 60 seconds audio like below.

  


  $arr = [];
$arr[3] = 2; //here 3 is original audio insert time and 2 is the duration of silence
$arr[6] = 3;  //here 6 is original audio insert time and 3 is the duration of silence
$arr[10] = 1;
$arr[12] = 3;


  


  Now I want to insert silence between seconds based on above array like

  


  2 seconds silence at 3rd second
3 seconds silence at 6th second
1 second silence at 10th second


  


  and son on..

  


• FFMPEG inside conda shell , running c++

  20 novembre 2018, par albert1905

  I’m trying to run a c++ program that depends on ffmpeg library.
  Important to mention, I’m working on a distance computer, so I don’t have the entire permissions.
  So I created a conda shell, download ffmpeg-dev, so far so good.
  I’m trying to run the c++ I want and he doesn’t recognize the "libav*" libraries (which are part of ffmpeg).
  I read that the libraries suppose to sit in "/usr/include" (or soemthing like that), in order that

  # include <>

  will recognize the library, but I don’t have permissions to write to this directory, so I had to think about something else, so I copied all the libav directories from "anconda3/include" to my dir and manually changed all the #includes to the realpath.

  But now I’m getting this error :

  g++ mpegflow.cpp -o mpegflow -O3 -D__STDC_CONSTANT_MACROS -lswscale
  -lavdevice -lavformat -lavcodec -lswresample -lavutil -lpthread -lbz2 -lz -lc -lrt -Idependencies/include -Ldependencies/lib /nfs/iil/itools/em64t_SLES11/pkgs/gcc/4.7.2/.bin/../lib64/gcc/x86_64-suse-linux/4.7.2/../../../../x86_64-suse-linux/bin/ld :
  cannot find -lavdevice collect2 : error : ld returned 1 exit status
  make : *** [mpegflow] Error 1

  I understand the problem, But I have no Idea how to solve it.
  I’ll be happy for your help.
  Thanks.