ffmpeg and UE4

Hi, i use ffmpeg together with the Unreal Engine 4 (UE4) to record audio/video. Setup of codecs, format, file, etc. seems to work fine until i write into the file with av_interleaved_write_frame, where i get an access violation. I currently have the latest stable version build with MYSY2/mingw for Winx64 + libx264. I use Win 8.1 with VS2013 for UE4 development.

Version:

ffmpeg version n2.6.3-1-g1f7343c Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 4.9.2 (Rev5, Built by MSYS2 project)
  configuration: --prefix=/usr/ffmpeg --enable-gpl --enable-pthreads --enable-li
bx264 --arch=x86_64 --target-os=mingw32 --enable-debug=1 --disable-optimizations
 --enable-extra-warnings --disable-stripping --disable-fast-unaligned --enable-m
emory-poisoning --enable-pic --enable-shared
  libavutil      54. 20.100 / 54. 20.100
  libavcodec     56. 26.100 / 56. 26.100
  libavformat    56. 25.101 / 56. 25.101
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 11.102 /  5. 11.102
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100

The recording uses an extra thread in my UE4 plugin; it does not seem like a race condition to me.

ret = av_interleaved_write_frame(oc, &pkt); // Unhandled exception at 0x000000006AE999FE (avformat-56.dll) in UE4Editor.exe: 0xC0000005: Access violation reading location 0x0000000000000070.

I already had to do that to prevent a divide by zero in av_interleaved_write_frame:

// this seems to fix a divide - by - zero error
if (st->pts.den == 0)
{
	st->pts.num = 0;
	st->pts.den = 1;
}

OpenCV does something similar, while doing its own interleaving (is this why i have the error?). I used OpenCV successfully, for the same purpose, but it does not support audio rec, which is why ffmpeg.