Using ffmpeg to encode a raw video to H.264 format
First of all, those commands you use look syntactically incorrect. In order to have ffmpeg use x264, you need to supply the -c:v libx264
argument.
Now, if you have a raw YUV file, you need to tell ffmpeg which pixel format, which size, etc. is used:
ffmpeg -f rawvideo -pix_fmt yuv420p -s:v 1920x1080 -r 25 -i input.yuv \
-c:v libx264 output.mp4
Change these according to your YUV file's specifications. Have a look at ffmpeg -pix_fmts
for a list of supported pixel formats. fourcc.org is also a good resource on that.
If you just want the raw H.264 bitstream in a .264
file:
ffmpeg -f rawvideo -pix_fmt yuv420p -s:v 1920x1080 -r 25 -i input.yuv \
-c:v libx264 -f rawvideo output.264