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• avcodec/cfhd : Replace a few literal numbers by named constants

  29 août 2020, par Michael Niedermayer

  avcodec/cfhd : Replace a few literal numbers by named constants
  Reviewed-by : Paul B Mahol <onemda@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/cfhd.c
  • [DH] libavcodec/cfhd.h

• How to trim video by multiple frame numbers then concatenate using FFMPEG

  31 août 2020, par puneet18

  Using following code, I'm able to trim video by time :

  


  ffmpeg -i input.mp4 -filter_complex \
"[0:v]trim=60:65,setpts=PTS-STARTPTS[v0]; \
 [0:a]atrim=60:65,asetpts=PTS-STARTPTS[a0]; \
 [0:v]trim=120:125,setpts=PTS-STARTPTS[v1];
 [0:a]atrim=120:125,asetpts=PTS-STARTPTS[a1]; \
 [v0][a0][v1][a1]concat=n=2:v=1:a=1[out]" \
-map "[out]" output.mp4


  


  Above code trim video from 60-65 sec & 120-125sec then concatenate in output.mp4 file.

  


  Need to know how to trim video by using frame number and concatenate.

  


  ---

  


  Is it possible to get the time by using Frame Number and fps ?

  


  frame_1_start = 100 #Frame Number
frame_1_end   = 200 #Frame Number
frame_2_start = 450 #Frame Number
frame_3_end   = 700 #Frame Number
fps = 20 # Frame per second

time_x_1 = frame_1_start/fps
time_x_2 = frame_1_end/fps
time_y_1 = frame_2_start/fps
time_y_2 = frame_2_end/fps

ffmpeg -i input.mp4 -filter_complex \
"[0:v]trim=#{time_x_1}:#{time_x_2},setpts=PTS-STARTPTS[v0]; \
 [0:a]atrim=#{time_x_1}:#{time_x_2},asetpts=PTS-STARTPTS[a0]; \
 [0:v]trim=#{time_y_1}:#{time_y_2},setpts=PTS-STARTPTS[v1];
 [0:a]atrim=#{time_y_1}:#{time_y_2},asetpts=PTS-STARTPTS[a1]; \
 [v0][a0][v1][a1]concat=n=2:v=1:a=1[out]" \
-map "[out]" output.mp4


  


• Does FFMpeg random generates identical sequences of pseudo-random numbers for consecutive executions ?

  20 août 2020, par justew

  For example if I execute command twice :

  


  ffmpeg -i input.mp4 -vf geq=r='random(1)*255':g='random(1)*255':b='random(1)*255' -strict -2 output.mp4

  


  For the same source file, I have identical output files. Why ? I want to get different output files.

  


  Testing configuration :

  


  ffmpeg version 2.8.17-0ubuntu0.1 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.12) 20160609


  


  I suppose that's because randomizer start value is identical. Does ffmepg have function like srand ?

  


  More specifically I want to add random noise just like this : noise=alls=20:allf=p+t+u. But if I try do so I got the same noise for different executions on the same input file.