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• 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

• How to remove 6 seconds of both video and audio every 20 seconds with ffmpeg

  15 juillet 2018, par Adam Estel

  I tried to figure a way to to remove 6 seconds of both video and audio every 20 seconds.This is my code :

    ffmpeg -y -i "input.mp4" -vf "select='not(lt(mod(t,20),6))',setpts=N/FRAME_RATE/TB,setpts=PTS-STARTPTS" -af "aselect='not(lt(mod(t,20),6))',asetpts=N/SR/TB,asetpts=PTS-STARTPTS" -preset superfast out.mp4

  But it resulted not that I want,the wrong timings being selected.
  I don’t know what did i do wrong here ?
  Sorry for my bad english.Thank you

• Out of memory on ffmpeg when converting to H265

  18 août 2017, par Lion

  I’ve a bunch of video files, mostly H264. To save storage, I wrote a batch script, that converts all of them to H265 using ffmpeg. Problem : Some files cause ffmpeg to use ALL my memory (24 GB). Then it crashes (cause it try to allocate even more RAM), which stops the converting process.

  I think that these files are corrupt in some kind. Because with other files, it works well with low memory consumption. Now I want to reject those broken ones, so that unattended converting is possible.

  How is it possible to detect such corruption ? Can ffmpeg do this, or is a third party tool required ?

  My ffmpeg call

  set crf=20
  
  set codec=265
  
  
  
  ffmpeg -hide_banner -i "!fullSourcePath!" -c:v libx%codec% -crf %crf% "%targetPath%\!targetFileName!"

  mkvalidator can’t help

  mkvalidator says that a corrupt file is valid :

  mkvalidator.exe "V:\Filme\_LegacyFormat\22 Jump Street.mkv"
  
  ........................................................................................................................
  
  WRN0D0: There are 5306 bytes of void data..
  
  
  
  mkvalidator 0.5.0: the file appears to be valid
  
          file created with libebml v1.3.0 + libmatroska v1.4.1 / mkvmerge v6.9.1 ('Blue Panther') 64bit built on Apr 18 2014 18:23:38

  eac3to331 can’t help, too

  I found the tool eac3to331, which has a check flag. But it gave me no errors, although the tested file seems corrupt (cause my PC to crash after several minutes running ffmpeg)

  eac3to.exe -check "V:\Filme\_LegacyFormat\22 Jump Street.mkv"
  
  MKV, 1 video track, 2 audio tracks, 1 subtitle track, 1:51:57, 24p /1.001
  
  1: h264/AVC, English, 1920x808 24p /1.001 (240:101)
  
  2: DTS, German, 5.1 channels, 1509kbps, 48kHz
  
  3: DTS, English, 5.1 channels, 1509kbps, 48kHz
  
  4: Subtitle (SRT), German
  
  v01 Extracting video track number 1...
  
  a02 Extracting audio track number 2...
  
  a03 Extracting audio track number 3...
  
  s04 Extracting subtitle track number 4...
  
  Video track 1 contains 161039 frames.
  
  eac3to processing took 1 minute, 26 seconds.
  
  Done.