I found that x264 produces different files for my sample file when using next options:
Code:
x264.exe -B 800 --8x8dct -A p8x8,i8x8,i4x4 --me umh --subme 6 --trellis 2 --threads 5 --quiet --no-psnr --no-ssim -o output.264 test.avi
I think that this bug somehow connected with use of multithreading. I suggest that it is somewhere in encoder\analyse.c x264_mb_analyse_init function but I am not sure. For testing I attached archive with my samle file and cmd-file for automation (it produces 100 files with my options).