This sounds vaguely familiar...f it fails with libx264 but works well with the others, you may be running up against a threading issue we're trying to resolve in the zeranoe builds. Could you try with this build and see if it works? http://x32.elijst.nl/FFmpeg-20120622.7z I tried this, but the overlay filter did not work in it. However going along theses lines I worked my way down the previous builds and found one that works without a glitch. Which probably confirms what you suspected anyway. Believe it or not the mingw people have ported gdb to windows, and it works quite well. http://sourceforge.net/projects/mingw-w64/files/External%20binary%20packages... It can even attach to remote processes. You'll want to be running a debug version of ffmpeg, though even a non debug version of it might show some interesting material.
basically start gdb, then (gdb) attach<pidd> (gdb) thread apply all bt GL! I didn't have a need to do this in the end. I tested the build in most
likely scenarios off line. I also replaced the build on the live compression system and ran it all day yesterday - older build worked like a charm. However if you'd find the outcome of thread traces useful for your purposes I'm happy to do some testing for you. Once again, thank you for your help. Fewer late nights for me now! All the best, Luke