Is there a set of working P/Invoke declarations for FFMpeg, libavutil, libavformat and libavcodec in .NET?

Question

I\'m currently looking to access libavutil, libavformat and libavcodec (all part of FFMpeg) from .NET.

Currently, I\'m getting the libraries from the automated build

Answer 1

SharpFFmpeg imports c++ libraries. C++ code is an unmanaged code. It needs pointers to the unmanaged memory. "Marshal" class provides some method to allocate unmanaged memory. For example:

    IntPtr buffer = Marshal.AllocHGlobal(buf.Length + FFmpeg.FF_INPUT_BUFFER_PADDING_SIZE); //buf is a byte array

Also, if you want to send a managed variable (any C# variable) to the function, you have to marshal (copy) this variable to the unmanaged memory.

    for (int i = 0; i < buf.Length; i++)
        Marshal.StructureToPtr(buf[i], buffer + i, true);

Now you can send a pointer to the function.

    FFmpeg.avcodec_decode_video(codecContextUnmanaged, frame, ref success, buffer, buf.Length);

It's possible that you'll need to modify some unmanaged structures. To do this you have to copy structure to a managed memory (Marshal.PtrToStructure method), then modify it, and copy it to an unmanaged memory again.
I was tormented by the same problem a lot. I solved it, but I can't decode video anyway)) I hope my solution will help anybody.