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• Why does the video lose few seconds after FFMPEG xfade ?

  25 août 2023, par promaxdev

  I am having a use case where I need to add a few xfade transitions to an existing video at uniform intervals. I followed an approach almost similar to the one explained in the official document here and the SO reply here

  


  Here is the command that I use.

  


  ffmpeg 
-i clean_0.mp4 
-filter_complex "[0] split = 8[i1][i2][i3][i4][i5][i6][i7][i8]; 
    [i1]select='between(t\,0.0\,3.75)',setpts='PTS-STARTPTS'[i11]; 
    [i2]select='between(t\,3.75\,7.5)',setpts='PTS-STARTPTS'[i22]; 
    [i3]select='between(t\,7.5\,11.25)',setpts='PTS-STARTPTS'[i33]; 
    [i4]select='between(t\,11.25\,15.0)',setpts='PTS-STARTPTS'[i44]; 
    [i5]select='between(t\,15.0\,18.75)',setpts='PTS-STARTPTS'[i55]; 
    [i6]select='between(t\,18.75\,22.5)',setpts='PTS-STARTPTS'[i66]; 
    [i7]select='between(t\,22.5\,26.25)',setpts='PTS-STARTPTS'[i77]; 
    [i8]select='between(t\,26.25\,30.0)',setpts='PTS-STARTPTS'[i88]; 
    [i11][i22]xfade=duration=1:offset=2.75:transition=dissolve [c1]; 
    [i33][i44]xfade=duration=1:offset=2.75:transition=distance [c2]; 
    [i55][i66]xfade=duration=1:offset=2.75:transition=fadegrays [c3]; 
    [i77][i88]xfade=duration=1:offset=2.75:transition=pixelize [c4]; 
    [c1][c2][c3][c4]concat=n=4:v=1:a=0 " 
-pix_fmt yuv420p -y clean_out.mp4 


  


  (The above code is executed in a single line broken down for ease of understanding.)

  


  What this does is splits the input video in to parts of equal length in duration and and inserts xfade effects in between and the concats them. So the net effect would be the original video with xfade effects added.

  


  The input video is 30 seconds in length and has 25 fps. But the output video is 26 seconds.

  


  Here are my analysis so far.

  


  

  • the no. of seconds reduced with each added transition. i.e. when 5 transitions are provided, the output video reduces to 25 seconds

  


  • ffprobe at different stages below

    

    • i1, i2,... being copies of input video had 750 frames @ 25fps ie 30 seconds

    


    • i11, i22,... -> had 94 frames @ 25fps resulting in 3.76 seconds (3.76 X 8 = 30.08s)

    


    • c1, c2,.. -> had 163 frames @ 25fps resulting in 6.52 seconds (6.52 X 4 = 26.08s)

    


    


  


  • Enabling trace on ffmpeg showed different filters like 'Parsed_select_', 'Parsed_setpts_' and 'Parsed_xfade_', 'Parsed_concat_' corresponding to the 'select', 'setpts', 'xfade' and concat filters and there was another 'auto_scale_' auto inserted by ffmpeg. But details were found only for Parsed_select_ and Parsed_setpts_* filters in rest of the logs. There was no other trace of Parsed_xfade_* filters. So not much info from there

  


  


  End result is concat of all c* videos resulting in reduced duration

  


  So we can infer that xfade is causing some frames to be lost. (or I am doing it wrong) I need help to find the reason for the reduction in the duration of the final video and fix it.Also, Is there a way to log Xfade trace ?

  


• C program cannot find function which included in header file

  17 juin 2013, par Juneyoung Oh

  I made program like this.

    1 #include 
  
    2 #include 
  
    3 #include 
  
    4 #include "libavformat/avformat.h"
  
    5 
  
    6 int main (int argc, char* argv[]){
  
    7         av_register_all();
  
    8         return 0;
  
    9 }

  My header file located in

  root@ubuntu:/home/juneyoungoh/getDuration# find / -name "avformat.h"
  
  /root/ffmpeg/libavformat/avformat.h
  
  /usr/local/include/libavformat/avformat.h

  then I run with gcc getDuration.c , but I show message like below.

  root@ubuntu:/home/juneyoungoh/getDuration# gcc getDuration.c 
  
  /tmp/ccwjonqH.o: In function `main':
  
  getDuration.c:(.text+0x10): undefined reference to `av_register_all'
  
  collect2: ld returned 1 exit status

  Frankly, I do not have any idea what makes this.

  Thanks for your answers.

  ========================== edited #1 ===========================

  when I "ls /usr/local/lib", I get this.

  root@ubuntu:/home/juneyoungoh/getDuration# ls /usr/local/lib/
  
  libavcodec.a   libavutil.a    libopus.la       libvpx.a   python2.7
  
  libavdevice.a  libfdk-aac.a   libpostproc.a    libx264.a
  
  libavfilter.a  libfdk-aac.la  libswresample.a  libyasm.a
  
  libavformat.a  libopus.a      libswscale.a     pkgconfig

  you can see libavformat.a in the very first of the last line.

  so if I command like what you suggest, I get below.

  /root/ffmpeg/libavformat/vqf.c:244: undefined reference to `av_free_packet'
  
  /usr/local/lib//libavformat.a(vqf.o): In function `add_metadata':
  
  /root/ffmpeg/libavformat/vqf.c:58: undefined reference to `av_malloc'
  
  /root/ffmpeg/libavformat/vqf.c:64: undefined reference to `av_dict_set'
  
  /usr/local/lib//libavformat.a(vqf.o): In function `vqf_read_header':
  
  /root/ffmpeg/libavformat/vqf.c:148: undefined reference to `av_dict_set'
  
  /root/ffmpeg/libavformat/vqf.c:208: undefined reference to `av_log'
  
  /root/ffmpeg/libavformat/vqf.c:216: undefined reference to `av_malloc'
  
  /root/ffmpeg/libavformat/vqf.c:170: undefined reference to `av_log'
  
  /root/ffmpeg/libavformat/vqf.c:121: undefined reference to `av_log'
  
  /root/ffmpeg/libavformat/vqf.c:184: undefined reference to `av_log'
  
  /root/ffmpeg/libavformat/vqf.c:136: undefined reference to `av_log'
  
  /usr/local/lib//libavformat.a(wavenc.o): In function `wav_write_trailer':
  
  /root/ffmpeg/libavformat/wavenc.c:210: undefined reference to `av_rescale'
  
  /usr/local/lib//libavformat.a(wavenc.o): In function `wav_write_packet':
  
  /root/ffmpeg/libavformat/wavenc.c:181: undefined reference to `av_log'

  It is too long, so I just post little part of that.

  I think all link of libavformat has been broken, But I do not know

  what can I do to fix that link.

  I have installed that their official link said.

  https://ffmpeg.org/trac/ffmpeg/wiki/UbuntuCompilationGuideQuantal

• Anomalie #3776 (Fermé) : CVT Multi-étapes // Problème de gestion de tableaux avec l’utilisation `_...

  7 mai 2017, par cedric -

  Pour ce genre de cas difficile de proposer une solution automatique intégrée.
  La solution c’est d’ajouter un input hidden avec les checkbox, avec le meme name, qui ajoute une valeur vide au tableau, de façon à ce qu’il y ait toujours un post de la variable concernée. Il faut ensuite filtrer cette valeur vide dans le traitement du formulaire