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• How fade-in and fade-out an overlay image on a video and repeat after every 15s

  20 juin 2018, par Adam Estel

  I have code that fade-in 2s and fade-out 3s and overlay image on a video :

  ffmpeg -f lavfi -i video.mp4 -loop 1 -i logo.png -filter_complex "[1:0] format=rgba,fade=in:st=0:d=2:alpha=1,fade=out:st=6:d=3:alpha=1 [ovr];[0:0][ovr] overlay=0:0" -t 10 -y out.mp4

  I want to repeat fade-in and fade-out effects after every 15 seconds.Is it possible with ffmpeg ?
  I tried variety methods but "Fade" filter only apply specific frame(or time) not variable.
  Sorry for my bad english.

• how av_freep in ffmpeg works ?

  11 août 2016, par Billy Bob

  I have some questions regarding void pointer in C. I found out the following code, part of ffmpeg that I couldn’t understand... Could someone explain to me how it works ?

  void av_freep(void *arg)
  
  {
  
          void *val;
  
  
  
          memcpy(&val, arg, sizeof(val));
  
          memcpy(arg, &(void *){ NULL }, sizeof(val));
  
          av_free(val);
  
  }

  and later it’s called like this :

  char *str;
  
  av_freep(&str);

  my questions :

  1. how passing address of str (&str) doesn’t trigger "incompatible type" warning when it’s compiled ? Shouldn’t &str type is become char** ?
  2. what’s the meaning of &(void *) NULL in one of memcpy parameter ?
  3. why it’s trying to free "val" which is not allocated ?

  Thanks !

• Deobfuscation Redux : JavaScript

  20 juin 2011, par Multimedia Mike — Reverse Engineering, deobfuscation, javascript, programming

  Google recently released version 12 of their Chrome browser. This version adds a new feature that automatically allows deobfuscating obfuscated JavaScript source code.

  Before :

  
  
  

  After :

  
  
  

  As a reverse engineering purist, I was a bit annoyed. Not at the feature, just the naming. This is clearly code beautification but not necessarily deobfuscation. The real obfuscation comes not from removing whitespace but from renaming variable and function names to terse 1- and 2-letter identifiers. True automated deobfuscation — which entails recovering the original variable and function identifiers as well as source code comments — is basically impossible.

  Still, it makes me wonder if there is any interest in a JavaScript deobfuscator that operates similar to my Java deobfuscator which was one of the first things I published on this blog. The general idea is automatically replace function names with random English verbs (since functions correspond to actions) and variable names with random animal names (I decided "English nouns" encompassed too broad a category of words). I suspect the day that someone releases a proprietary multimedia codec in a pure (though obfuscated) JavaScript format is that day that I will try to accomplish this, if it hasn’t been done already.

  See also :

  • Success on the Java De-obfuscation Front