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• Ffmpeg gets aborted in an Electron sandboxed application

  6 décembre 2017, par YoannM

  I have an Electron app, published on the Mac AppStore, and sandboxed.

  I’m trying to add a new feature that will encode/decode videos on the fly so I can stream more video formats in an Electron context.

  I’m using fluent-ffmpeg and a static exec of ffmpeg.

  Everything works awesomely, I’ve uploaded the sandboxed app to Apple, and got rejected because ffmpeg is using by default a secure transport protocol which is using non-public API, this is what they’ve sent me with the rejection :

  Your app uses or references the following non-public API(s) :

  ’/System/Library/Frameworks/Security.framework/Versions/A/Security’

   : SecIdentityCreate

  Alright, after much investigation, it appears that I have to compile ffmpeg myself with a --disable-securetransport flag. Easy enough, I do it using the same config as the static build I’ve downloaded simply adding the new flag.

  I manage to install every dependencies needed, except libxavs, no big deal I guess and simply remove its flag from the configure command :

  ./configure \
  
  --cc=/usr/bin/clang \
  
  --prefix=/opt/ffmpeg \
  
  --extra-version=tessus \
  
  --enable-avisynth \
  
  --enable-fontconfig \
  
  --enable-gpl \
  
  --enable-libass \
  
  --enable-libbluray \
  
  --enable-libfreetype \
  
  --enable-libgsm \
  
  --enable-libmodplug \
  
  --enable-libmp3lame \
  
  --enable-libopencore-amrnb \
  
  --enable-libopencore-amrwb \
  
  --enable-libopus \
  
  --enable-libsnappy \
  
  --enable-libsoxr \
  
  --enable-libspeex \
  
  --enable-libtheora \
  
  --enable-libvidstab \
  
  --enable-libvo-amrwbenc \
  
  --enable-libvorbis \
  
  --enable-libvpx \
  
  --enable-libwavpack \
  
  --enable-libx264 \
  
  --enable-libx265 \
  
  --enable-libxvid \
  
  --enable-libzmq \
  
  --enable-libzvbi \
  
  --enable-version3 \
  
  --pkg-config-flags=--static \
  
  --disable-securetransport \
  
  --disable-ffplay

  With the new ffmpeg exec, everything still works as expected. But once I’m packaging, signing and sandboxing the app, ffmpeg stops working as soon as I try to launch it throwing this error :

  An error occurred ffmpeg was killed with signal SIGABRT Error: ffmpeg was killed with signal SIGABRT
  
      at ChildProcess.eval (webpack:///../node_modules/fluent-ffmpeg/lib/processor.js?:180:22)
  
      at emitTwo (events.js:125:13)
  
      at ChildProcess.emit (events.js:213:7)
  
      at Process.ChildProcess._handle.onexit (internal/child_process.js:200:12)

  I’ve tried to remove the --disable-securetransport flag, see if it could have messed with something, same result.

  I’ve tried to compile on a Linux machine, just to see if it could help, same thing.

  As soon as I’m using my custom compiled exec it doesn’t work in the sandbox, but when using the static one, everything is ok (after I xattr it, because it’s quarantined and blocked in sandbox).

  The only thing I’ve noticed that seems odd is that my custom compilation is only 20mo or so, when the static install I’ve downloaded is 43mo.

  I’m really stuck with this.

• Back porting ffmpeg.dll from electron for windows xp by disassembling

  28 juillet 2024, par Oosuke Ren

  I've recently gotten into a really interesting project of having a fully functional (and as futuristic as possible) physical retro gaming machine with windows xp. I had found One Core Api that successfully works to allow for some programs to work that otherwise wouldn't have. One of them is electron (5.0.13). Thanks to a vast testing between a VM with the kernel extender and a vanilla XP, I found out that the only thing stopping me from succeeding is because it's dependent on an EXTREMELY specific version/fork of ffmpeg (Chromium fork of ffmpeg 4.1) . Due to that being a relatively old fork/version, the build tools/links for some of the stuff are nonexistent right now, so even if I do have the fork locally with all the instructions, I can't build it. (and if I do I have to patch Win Vista+ Api functions, with one custom stub dll I have)

  


  AcquireSRWLockExclusive InitializeConditionVariable SleepConditionVariableSRW InitOnceBeginInitialize InitOnceComplete InitializeSRWLock ReleaseSRWLockExclusive WakeAllConditionVariable WakeConditionVariable

  


  Since I can't custom build ffmpeg I have to patch it's calls by redirecting them to my custom dll that includes these back ported functions and more.

  


  I tried many different ways => IDA Pro, Ghidra, objconv, currently am the closest with "DLL to C"

  


  Ida Pro and Ghidra seem to not be creating assembly code that I'd be able to assemble back after patching.

  


  objconv produces a really accurate disassembly, but the issue is it doesn't have an assembler. And the produced .asm won't assemble with Fasm, masm or nasm

  


  As for DLL to C-> successfully created a quite presentable VS project, the project successfully compiles with only one warning, the byte sizes is quite similar, the problem is => the functions are getting wrongly directed (towards wrong functions in my dll- and thus the ones needed are undefined) And this is too deep to be able to tell if it's a VS version issue, wrong code implementation or if just DLL to C has wrongly disassembled the logic.

  


  Question is, is my last option remaining to manually edit the HEXES of the Import Address Table and Import Names so they get redirected ? (the problem is my knowledge in Assembly isn't too good, so I'm not sure if that's all I'd have to do, and even if so, I have a feeling I'd mess up the Virtual Addresses or something.

  


• Get the second on which the thumbnail was generated

  24 juin 2018, par Suhail Gupta

  I am using the following command to generate thumbnails from a video every 5 seconds :

  ffmpeg -ss 3 -i input.mp4 -vf "select=gt(scene\,0.4),scale=640:360" 
  
     -vsync vfr -vf fps=fps=1/5 out%02d.jpg

  The thumbnails generated are formatted using 2 digits. So images are generated starting from out01.jpg, out02.jpg and goes on until out99.jpg. Is there a way I could get the seconds in the filename ? Like I want to know the number of seconds elapsed in the original video when any particular thumbnail was generated.

  For example, it could be in a format resembling :

  out01_23.jpg
  
  out02_28.jpg
  
  out03_33.jpg
  
  
  
  .  
  
  .

  So here 23,28 and 33 represent the number of seconds elapsed in the video. out01_33.jpg is a thumbnail that represents the 33rd second of the video.

  Is there a way to get this ?