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• How would I dynamically link FFmpeg in a C# Project for use with FFMpegCore ?

  15 octobre 2024, par liamliam

  So far, I have FFMpegCore working in my project with a ffmpeg.exe dropped into the project directory. This works, but for LGPL license compliance FFmpeg requires dynamic linking :
  
Use dynamic linking (on windows, this means linking to dlls) for linking with FFmpeg libraries..

  


  While I understand the basic concept of dynamic vs static linking, my problem is likely a misunderstanding of how .dlls work and how they apply to C# and .NET.
  
Would it be possible to compile ffmpeg into a single .dll that could be accessed by FFMpegCore cross-platform ? From what I can gather in the source, FFMpegCore looks for an ffmpeg or ffmpeg.exe file in its configuration path.

  


  Is it possible to have .NET dynamically link FFmpeg and expose it to libraries for use or is that a complete misunderstanding and would I then need a wrapper library with different capabilities ?

  


  I've attempted to find the answer in the relevant documentation, but I found none for this specific use of either library. I suspect my problem might be a fundamental misunderstanding of how these tools work and work together.
My ideal result would be using FFMpegCore with an FFmpeg.dll that works cross-platform instead of the .exe.

  


  Edit 1 : @taratect's answer and graphic sent me down a path that cleared up quite a bit about exes and dlls. .Net compiles source code down to platform agnostic Intermediate Language in the form of a .dll or .exe(completely different to C++ variants of these files), which is executed by the Common Language Runtime using a Just In Time compiler to convert that Intermediate Language to Machine Code that can be run on the specific platform .Net is installed on. C++(FFmpeg) compiles directly to platform specific Machine Code (as shown in the graphic), confusingly in the form of a .dll or .exe (on Windows). .Net can indeed load and run machine code unmanaged by Common Language Runtime, since everything is run as Machine Code by the end, however memory and other complexities must then be managed by me, which seems to be what FFMpegCore does in wrapping the executable. I might still be confused/incorrect on some of this, unmanaged code is beyond my understanding so far.
This does more or less confirm that FFMpegCore probably can't be expected to use FFmpeg in the way I hoped and a better workaround might be having the user just supply an FFmpeg source or implement a downloader as part of installation so that I don't have to redistribute it at all.

  


• How to convert images to video using FFMpeg for embedded applications ?

  19 avril 2019, par zthatch56

  I’m encoding images as video using FFmpeg using custom C code rather than linux commands because I am developing the code for an embedded system.

  I am currently following through the first dranger tutorial and the code provided in the following question.

  How to encode a video from several images generated in a C++ program without writing the separate frame images to disk ?

  I have found some "less abstract" code in the following github location.

  https://github.com/FFmpeg/FFmpeg/blob/master/doc/examples/encode_video.c

  And I plan to use it as well.

  My end goal is simply to save video on an embedded system using embedded C source code, and I am coming up the curve too slowly. So in summary my question is, Does it seem like I am following the correct path here ? I know that my system does not come with hardware for video codec conversion, which means I need to do it with software, but I am unsure if FFmpeg is even a feasible option for embedded work because I am yet to compile.

  The biggest red flag for me thus far is that FFmpeg uses dynamic memory allocation. I am unfamiliar with how to assess the amount of dynamic memory that it uses. This is very important information to me, and if anyone is familiar with the amount of memory used or how to assess it before compiling, I would greatly appreciate the input.

• FFmpeg : java.lang.UnsatisfiedLinkError while calling Runnable class

  12 mars 2013, par Yuliya Tarasenko

  I need to take a picture file and an audio file and create a video.
  I know that it's possible to do with the help of

  Runtime.getRuntime().exec("ffmpeg -i image.jpeg -i audio.mp3 out.avi") 

  but only for rooted devices, so I've tried to create JNI wrapper for main() from ffmpeg.c and call it from my Activity like here : http://demo860.blogspot.com/2010/07/android-ffmpeg-dynamic-module-jni.html

  1.This code is in ffmpeg.c :

  int m_argc = 0;
  
  char *m_pargv [30];
  
  
  
  int dynamic_ffpmeg_main (int argc, char **argv);
  
  jint JNICALL Java_com_ccmedia_codec_ffmpeg_mod_1run ( JNIEnv *, jclass, jstring,     jstring );
  
  
  
  jint JNICALL Java_com_ccmedia_codec_ffmpeg_mod_1run ( JNIEnv *env, jclass class, jstring pj1, jstring pj2)
  
  {
  
      // as in http://demo860.blogspot.com/2010/07/android-ffmpeg-dynamic-module-jni.html
  
  }
  
  
  
  int dynamic_ffpmeg_main(int argc, char **argv)
  
  {
  
  // as in http://demo860.blogspot.com/2010/07/android-ffmpeg-dynamic-module-jni.html
  
  }
  
  
  
  int main(int argc, char **argv)
  
  {
  
      dynamic_ffpmeg_main ( argc, argv );
  
      return 0;
  
  }

  2.This code is in my .java :

  public class FFmpegCreator implements Runnable {
  
  
  
      static boolean m_bret = false;
  
  static String m_szconfig = " -i /sdcard/file.mpg -vcodec mpeg4 aaa.mpg";
  
  
  
  //public native String unimplementedStringFromJNI();
  
  
  
  static {
  
      try {
  
  
  
          System.out.println("[AdDBCache] Module load try ffmpeg : "
  
                  + System.getProperty("java.library.path"));
  
  
  
          // System.load("/sdcard/arm_and/bin/libffmpeg.so");
  
  
  
          System.loadLibrary("ffmpeg");
  
  
  
          System.out.println("[AdDBCache] Module load success");
  
  
  
      }
  
  
  
      catch (Exception e) {
  
  
  
          System.out.println("[AdDBCache] Module load err : "
  
                  + System.getProperty("java.library.path"));
  
  
  
      }
  
  
  
  }
  
  
  
  private static synchronized final native int Java_com_ccmedia_codec_ffmpeg_mod_1run(String name, String sztoken);
  
  
  
  public void set_config(String sz_config) {
  
  
  
      m_szconfig = sz_config;
  
  
  
  }
  
  
  
  public void run_core(String sz_file, String sz_token) {
  
  
  
      int n_stat;
  
      m_bret = false;
  
      n_stat = Java_com_ccmedia_codec_ffmpeg_mod_1run(m_szconfig, sz_token);
  
      m_bret = true;
  
  
  
  }
  
  
  
  public void run() {
  
  
  
      run_core("", "");
  
  
  
  }
  
  }

  3.And this in my Activity :

  FFmpegCreator f = new FFmpegCreator ();
  
  new Thread(f).start();

  But I have

  E/AndroidRuntime(25682): java.lang.UnsatisfiedLinkError: Java_com_ccmedia_codec_ffmpeg_mod_1run .

  And I can't understand why... FFmpeg build was successful...
  Could anyone help me, please ? I'll really appreciate if you could help me. Thank you.